Add the first version of group performance code.

1 files changed, 5261 insertions, 0 deletions

diff --git a/test/vfd_swmr_gperf_writer.c b/test/vfd_swmr_gperf_writer.c
new file mode 100644
index 0000000..9996798
--- /dev/null
+++ b/test/vfd_swmr_gperf_writer.c
@@ -0,0 +1,5261 @@
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * Copyright by The HDF Group.                                               *
+ * All rights reserved.                                                      *
+ *                                                                           *
+ * This file is part of HDF5.  The full HDF5 copyright notice, including     *
+ * terms governing use, modification, and redistribution, is contained in    *
+ * the COPYING file, which can be found at the root of the source code       *
+ * distribution tree, or in https://www.hdfgroup.org/licenses.               *
+ * If you do not have access to either file, you may request a copy from     *
+ * help@hdfgroup.org.                                                        *
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+#define H5F_FRIEND /*suppress error about including H5Fpkg   */
+
+#include "hdf5.h"
+
+#include "H5Fpkg.h"
+#include "H5HGprivate.h"
+#include "H5VLprivate.h"
+
+#include "testhdf5.h"
+#include "vfd_swmr_common.h"
+
+#ifndef H5_HAVE_WIN32_API
+
+#define READER_WAIT_TICKS 3
+#define VS_ATTR_NAME_LEN  21
+
+#define TIME_PASSED(X,Y)        \
+             ((double)((Y.tv_sec - X.tv_sec) * 1000000000 + (Y.tv_nsec - X.tv_nsec))) / 1000000000.0
+
+typedef struct {
+    hid_t        file, filetype, one_by_one_sid;
+    char         filename[PATH_MAX];
+    char         progname[PATH_MAX];
+    unsigned int asteps;
+    unsigned int csteps;
+    unsigned int nsteps;
+    unsigned int update_interval;
+    bool         use_vfd_swmr;
+    bool         old_style_grp;
+    bool         use_named_pipes;
+    char         grp_op_pattern;
+    bool         grp_op_test;
+    char         at_pattern;
+    bool         attr_test;
+    uint32_t     max_lag;
+    uint32_t     tick_len;
+    int          np_fd_w_to_r;
+    int          np_fd_r_to_w;
+    int          np_notify;
+    int          np_verify;
+    bool         gperf;
+    double       min_time;
+    double       max_time;
+    double       mean_time;
+    double       total_time;
+    unsigned int num_attrs;
+} state_t;
+
+#define ALL_HID_INITIALIZER                                                                                  \
+    (state_t)                                                                                                \
+    {                                                                                                        \
+        .file = H5I_INVALID_HID, .one_by_one_sid = H5I_INVALID_HID, .filename = "",                          \
+        .filetype = H5T_NATIVE_UINT32, .asteps = 10, .csteps = 10, .nsteps = 100,                            \
+        .update_interval = READER_WAIT_TICKS, .use_vfd_swmr = true, .old_style_grp = false,                  \
+        .use_named_pipes = true, .grp_op_pattern = ' ', .grp_op_test = false, .at_pattern = ' ',             \
+        .attr_test = false, .tick_len = 4, .max_lag = 7, .np_fd_w_to_r = -1, .np_fd_r_to_w = -1,             \
+        .np_notify = 0, .np_verify = 0, .gperf = false, .min_time = 100., .max_time = 0.,.mean_time = 0., \
+        .total_time = 0.,.num_attrs = 1                                                                        \
+    }
+
+static void
+usage(const char *progname)
+{
+    fprintf(stderr,
+            "usage: %s [-S] [-G] [-a steps] [-b] [-c] [-n iterations]\n"
+            "    [-N] [-q] [-u numb_ticks] [-A at_pattern] [-O grp_op_pattern]\n"
+            "\n"
+            "-S:             do not use VFD SWMR\n"
+            "-G:             old-style type of group\n"
+            "-a steps:       `steps` between adding attributes\n"
+            "-b:             write data in big-endian byte order\n"
+            "-c steps:       `steps` between communication between the writer and reader\n"
+            "-n ngroups:     the number of groups\n"
+            "-N:             do not use named pipes, \n"
+            "                mainly for running the writer and reader seperately\n"
+            "-u numb_ticks:  `numb_ticks` for the reader to wait before verification\n"
+            "-A at_pattern:  `at_pattern' for different attribute tests\n"
+            "              The value of `at_pattern` is one of the following:\n"
+            "              `compact`              - Attributes added in compact storage\n"
+            "              `dense`                - An attribute added in dense storage\n"
+            "              `compact-del`          - Attributes added and then one\n"
+            "                                       attribute deleted, in compact \n"
+            "              `dense-del`            - Attributes added until the storage\n"
+            "                                       is dense then an attribute deleted\n"
+            "                                       the storge still in dense\n"
+            "              `compact-add-to-dense` - Attributes added first in compact\n"
+            "                                       then in dense storage\n"
+            "              `dense-del-to-compact` - Attributes added until the storage\n"
+            "                                       is dense, then several attributes \n"
+            "                                       deleted, the storage changed to\n"
+            "                                       compact\n"
+            "              `modify`               - An attribute added then modified\n"
+            "              `add-vstr`             - A VL string attribute added\n"
+            "              `remove-vstr`          - A VL string attribute added then\n"
+            "                                       deleted\n"
+            "              `modify-vstr`          - A VL string attribute added then \n"
+            "                                       modified \n"
+            "              `add-ohr-block`        - An attribute is added and this forces\n"
+            "                                       the creation of object header\n"
+            "                                       continuation block \n"
+            "              `del-ohr-block`        - An attribute is added and this forces\n"
+            "                                       the creation of object header\n"
+            "                                       continuation block and then this \n"
+            "                                       attribute is deleted so the \n"
+            "                                       object header continuation block is \n"
+            "                                       removed. \n"
+            "-O grp_op_pattern:  `grp_op_pattern' for different group operation tests\n"
+            "              The value of `grp_op_pattern` is one of the following:\n"
+            "              `grp-creation`         - A group is created.\n"
+            "              `grp-deletion`         - An existing group is deleted.\n"
+            "              `grp-move`             - A group is moved to become \n"
+            "                                       another group. \n"
+            "              `grp-ins-links`        - Links are inserted, including\n"
+            "                                       both hard and soft links. \n"
+            "              `grp-del-links`        - Links are deleted, including\n"
+            "                                       both hard ans soft links. \n"
+            "              `grp-compact-t-dense`  - Links are inserted to the group.\n"
+            "                                       The link storage of this group \n"
+            "                                       changed from compact to dense. \n"
+            "                                       The links include both hard and\n"
+            "                                       soft links.                    \n"
+            "              `grp-dense-t-compact`  - Links are inserted to the group\n"
+            "                                       The link storage of this group \n"
+            "                                       changed from compact to dense. \n"
+            "                                       Then several links are deleted.\n"
+            "                                       The link storage changed from  \n"
+            "                                       dense to compact again.        \n"
+            "                                       The links include both hard and\n"
+            "                                       soft links.                    \n"
+            "-q:             silence printouts, few messages\n"
+            "\n",
+            progname);
+    exit(EXIT_FAILURE);
+}
+
+static bool
+state_init(state_t *s, int argc, char **argv)
+{
+    unsigned long tmp;
+    int           ch;
+    const hsize_t dims  = 1;
+    char *        tfile = NULL;
+    char *        end;
+
+    *s = ALL_HID_INITIALIZER;
+
+    if (H5_basename(argv[0], &tfile) < 0) {
+        printf("H5_basename failed\n");
+        TEST_ERROR;
+    }
+
+    esnprintf(s->progname, sizeof(s->progname), "%s", tfile);
+
+    if (tfile)
+        HDfree(tfile);
+
+    while ((ch = getopt(argc, argv, "PSGa:bc:n:Nqu:A:O:")) != -1) {
+        switch (ch) {
+            case 'P':
+                s->gperf = true;
+                break;
+            case 'S':
+                s->use_vfd_swmr = false;
+                break;
+            case 'G':
+                s->old_style_grp = true;
+                break;
+            case 'a':
+            case 'c':
+            case 'n':
+            case 'u':
+                errno = 0;
+                tmp   = HDstrtoul(optarg, &end, 0);
+                if (end == optarg || *end != '\0') {
+                    printf("couldn't parse `-%c` argument `%s`\n", ch, optarg);
+                    TEST_ERROR;
+                }
+                else if (errno != 0) {
+                    printf("couldn't parse `-%c` argument `%s`\n", ch, optarg);
+                    TEST_ERROR;
+                }
+                else if (tmp > UINT_MAX) {
+                    printf("`-%c` argument `%lu` too large\n", ch, tmp);
+                    TEST_ERROR;
+                }
+
+                if (ch == 'a')
+                    s->asteps = (unsigned)tmp;
+                else if (ch == 'c')
+                    s->csteps = (unsigned)tmp;
+                else if (ch == 'n')
+                    s->nsteps = (unsigned)tmp;
+                else if (ch == 'u')
+                    s->update_interval = (unsigned)tmp;
+                break;
+            case 'b':
+                s->filetype = H5T_STD_U32BE;
+                break;
+            case 'N':
+                s->use_named_pipes = false;
+                break;
+            case 'O':
+                if (HDstrcmp(optarg, "grp-creation") == 0)
+                    s->grp_op_pattern = 'c';
+                else if (HDstrcmp(optarg, "grp-deletion") == 0)
+                    s->grp_op_pattern = 'd';
+                else if (HDstrcmp(optarg, "grp-move") == 0)
+                    s->grp_op_pattern = 'm';
+                else if (HDstrcmp(optarg, "grp-ins-links") == 0)
+                    s->grp_op_pattern = 'i';
+                else if (HDstrcmp(optarg, "grp-del-links") == 0)
+                    s->grp_op_pattern = 'D';
+                else if (HDstrcmp(optarg, "grp-compact-t-dense") == 0)
+                    s->grp_op_pattern = 't';
+                else if (HDstrcmp(optarg, "grp-dense-t-compact") == 0)
+                    s->grp_op_pattern = 'T';
+                else {
+                    printf("Invalid -O argument \"%s\"", optarg);
+                    TEST_ERROR;
+                }
+                break;
+            case 'A':
+                if (HDstrcmp(optarg, "compact") == 0)
+                    s->at_pattern = 'c';
+                else if (HDstrcmp(optarg, "dense") == 0)
+                    s->at_pattern = 'd';
+                else if (HDstrcmp(optarg, "compact-add-to-dense") == 0)
+                    s->at_pattern = 't';
+                else if (HDstrcmp(optarg, "compact-del") == 0)
+                    s->at_pattern = 'C';
+                else if (HDstrcmp(optarg, "dense-del") == 0)
+                    s->at_pattern = 'D';
+                else if (HDstrcmp(optarg, "dense-del-to-compact") == 0)
+                    s->at_pattern = 'T';
+                else if (HDstrcmp(optarg, "modify") == 0)
+                    s->at_pattern = 'M';
+                else if (HDstrcmp(optarg, "add-vstr") == 0)
+                    s->at_pattern = 'v';
+                else if (HDstrcmp(optarg, "remove-vstr") == 0)
+                    s->at_pattern = 'r';
+                else if (HDstrcmp(optarg, "modify-vstr") == 0)
+                    s->at_pattern = 'm';
+                else if (HDstrcmp(optarg, "add-ohr-block") == 0)
+                    s->at_pattern = 'a';
+                else if (HDstrcmp(optarg, "del-ohr-block") == 0)
+                    s->at_pattern = 'R';
+                else {
+                    printf("Invalid -A argument \"%s\"", optarg);
+                    TEST_ERROR;
+                }
+                break;
+            case 'q':
+                verbosity = 0;
+                break;
+            case '?':
+            default:
+                usage(s->progname);
+                break;
+        }
+    }
+    argc -= optind;
+    argv += optind;
+
+    if (s->grp_op_pattern != ' ')
+        s->grp_op_test = true;
+    if (s->at_pattern != ' ')
+        s->attr_test = true;
+
+    if (!s->grp_op_test) {
+        if (s->asteps < 1 || s->asteps > s->nsteps) {
+            printf("attribute interval is out of bounds\n");
+            TEST_ERROR;
+        }
+    }
+
+    if (s->grp_op_test && s->attr_test) {
+        printf("Cannot test both group operation and attribute tests!\n");
+        printf("Attribute tests are ignored.\n");
+    }
+
+    if (s->csteps < 1 || s->csteps > s->nsteps) {
+        printf("communication interval is out of bounds\n");
+        TEST_ERROR;
+    }
+
+    if (argc > 0) {
+        printf("unexpected command-line arguments\n");
+        TEST_ERROR;
+    }
+
+    /* space for attributes */
+    if ((s->one_by_one_sid = H5Screate_simple(1, &dims, &dims)) < 0) {
+        printf("H5Screate_simple failed\n");
+        TEST_ERROR;
+    }
+
+    esnprintf(s->filename, sizeof(s->filename), "vfd_swmr_group.h5");
+
+    return true;
+
+error:
+    if (tfile)
+        HDfree(tfile);
+    return false;
+}
+
+/* Named Pipe Subroutine: np_wr_send_receive
+ * Description:
+ *   The writer sends a message to the reader,
+ *   then waits for max_lag ticks,
+ *   then checks the returned message from the reader.
+ * Return:
+ *   True  if succeed
+ *   False if an error occurs in any step above.
+ *         An error is mostly caused by an unexpected
+ *         notification number from the message sent
+ *         by the reader.
+ */
+static bool
+np_wr_send_receive(state_t *s)
+{
+
+    unsigned int i;
+    /* Bump up the value of notify to notice the reader to start to read */
+    s->np_notify++;
+    if (HDwrite(s->np_fd_w_to_r, &(s->np_notify), sizeof(int)) < 0) {
+        printf("HDwrite failed\n");
+        TEST_ERROR;
+    }
+
+    /* During the wait, writer makes repeated HDF5 API calls
+     * to trigger EOT at approximately the correct time */
+    for (i = 0; i < s->max_lag + 1; i++) {
+        decisleep(s->tick_len);
+        H5E_BEGIN_TRY
+        {
+            H5Aexists(s->file, "nonexistent");
+        }
+        H5E_END_TRY;
+    }
+
+    /* Receive the same value from the reader and verify it before
+     * going to the next step */
+    (s->np_verify)++;
+    if (HDread(s->np_fd_r_to_w, &(s->np_notify), sizeof(int)) < 0) {
+        printf("HDread failed\n");
+        TEST_ERROR;
+    }
+
+    if (s->np_notify == -1) {
+        printf("reader failed to verify group or attribute operation.\n");
+        TEST_ERROR;
+    }
+
+    if (s->np_notify != s->np_verify) {
+        printf("received message %d, expecting %d\n", s->np_notify, s->np_verify);
+        TEST_ERROR;
+    }
+
+    return true;
+
+error:
+    return false;
+}
+
+/* Named Pipe Subroutine: np_rd_receive
+ * Description:
+ *   The reader receives a message from the writer,
+ *   then checks if the notification number from
+ *   the writer is expected.
+ * Return:
+ *   True  if succeed
+ *   False if an error occurs in any step above.
+ *         An error is mostly caused by an unexpected
+ *         notification number from the message sent
+ *         by the writer.
+ */
+static bool
+np_rd_receive(state_t *s)
+{
+
+    /* The writer should have bumped up the value of notify.
+     * Do the same with verify and confirm it */
+    s->np_verify++;
+
+    /* Receive the notify that the writer bumped up the value */
+    if (HDread(s->np_fd_w_to_r, &(s->np_notify), sizeof(int)) < 0) {
+        printf("HDread failed\n");
+        TEST_ERROR;
+    }
+
+    if (s->np_notify == -1) {
+        printf("writer failed to create group or carry out an attribute operation.\n");
+        TEST_ERROR;
+    }
+
+    if (s->np_notify != s->np_verify) {
+        printf("received message %d, expecting %d\n", s->np_notify, s->np_verify);
+        TEST_ERROR;
+    }
+
+    return true;
+
+error:
+    return false;
+}
+
+/* Named Pipe Subroutine: np_rd_send
+ * Description:
+ *   The reader sends an acknowledgement to the writer
+ * Return:
+ *   True  if succeed
+ *   False if an error occurs in sending the message.
+ */
+static bool
+np_rd_send(state_t *s)
+{
+
+    if (HDwrite(s->np_fd_r_to_w, &(s->np_notify), sizeof(int)) < 0) {
+        H5_FAILED();
+        AT();
+        printf("HDwrite failed\n");
+        return false;
+    }
+    else
+        return true;
+}
+
+/* Named Pipe Subroutine: np_send_error
+ * Description:
+ *   An error (notification number is 1) message is sent
+ *   either from the reader or the writer.
+ *   A boolean input parameter is used to choose
+ *   either reader or writer.
+ * Return:
+ *     None
+ */
+static void
+np_send_error(state_t *s, bool writer)
+{
+    s->np_notify = -1;
+    if (writer)
+        HDwrite(s->np_fd_w_to_r, &(s->np_notify), sizeof(int));
+    else
+        HDwrite(s->np_fd_r_to_w, &(s->np_notify), sizeof(int));
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    check_ohr_num_chunk
+ *
+ * Purpose:     Check if the number of object header chunks is as expected.
+ *
+ * Parameters:  hid_t oid
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              bool one_chunk_ohr
+ *              flag to indicate if the object header chunk is 1 or greater
+ *              1: true
+ *              greater than 1: false
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+check_ohr_num_chunk(hid_t g, bool one_chunk_ohr)
+{
+
+    H5O_native_info_t ninfo;
+
+    /* Get the object information */
+    if (H5Oget_native_info(g, &ninfo, H5O_NATIVE_INFO_HDR) < 0) {
+        printf("H5Oget_native_info failed\n");
+        TEST_ERROR;
+    }
+
+    if (true == one_chunk_ohr) {
+        if (ninfo.hdr.nchunks != 1) {
+            printf("Object header should have only one chunk,but it is not.\n");
+            TEST_ERROR;
+        }
+    }
+    else {
+        if (ninfo.hdr.nchunks <= 1) {
+            printf("Object header should have more than one chunk,but it is not.\n");
+            TEST_ERROR;
+        }
+    }
+
+    return true;
+
+error:
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    add_attr
+ *
+ * Purpose:     Add attributes to a group.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t oid
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation, use to generate
+ *              newly created group name. The group name is "group-which".
+ *
+ *              unsigned num_attrs
+ *              The number of attributes to be created
+ *
+ *              const char*aname_fmt
+ *              The attribute name template used to create unique attribute names.
+ *
+ *              unsigned int g_which
+ *              This parameter is used to generate correct group name in a key
+ *              debugging message.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+add_attr(state_t *s, hid_t oid, unsigned int which, unsigned num_attrs, const char *aname_fmt,
+         unsigned int g_which)
+{
+
+    char     attrname[VS_ATTR_NAME_LEN];
+    unsigned u;
+    unsigned attr_value;
+    hid_t    aid    = H5I_INVALID_HID;
+    hid_t    amtype = H5I_INVALID_HID;
+    hid_t    atype  = s->filetype;
+    hid_t    sid    = s->one_by_one_sid;
+
+    /* Need to obtain native datatype for H5Aread */
+    if ((amtype = H5Tget_native_type(atype, H5T_DIR_ASCEND)) < 0) {
+        printf("H5Tget_native_type failed\n");
+        TEST_ERROR;
+    }
+
+    for (u = 0; u < num_attrs; u++) {
+
+        /* Create attribute */
+        /* Construct attribute name like attr-0-0 */
+        HDsprintf(attrname, aname_fmt, which, u);
+        if ((aid = H5Acreate2(oid, attrname, atype, sid, H5P_DEFAULT, H5P_DEFAULT)) < 0) {
+            printf("H5Acreate2 failed\n");
+            TEST_ERROR;
+        }
+
+        attr_value = u + which;
+
+        dbgf(1, "setting attribute %s on group %u to %u\n", attrname, g_which, u + which);
+
+        /* Write data into the attribute */
+        if (H5Awrite(aid, amtype, &attr_value) < 0) {
+            printf("H5Awrite failed\n");
+            TEST_ERROR;
+        }
+
+        /* Close attribute */
+        if (H5Aclose(aid) < 0) {
+            printf("H5Aclose failed\n");
+            TEST_ERROR;
+        }
+
+        /* If coming to an "object header continuation block" test,
+         * we need to check if this test behaves as expected. */
+        if (s->at_pattern == 'a' || s->at_pattern == 'R') {
+            if (false == check_ohr_num_chunk(oid, false)) {
+                printf("An object header continuation block should be created. \n");
+                printf("But it is not.\n");
+                TEST_ERROR;
+            }
+        }
+
+        /* Writer sends a message to reader: an attribute is successfully generated.
+           then wait for the reader to verify and send an acknowledgement message back.*/
+        if (s->use_named_pipes && s->attr_test == true) {
+            dbgf(2, "writer: write attr - ready to send/receive message: %d\n", s->np_notify + 1);
+            if (np_wr_send_receive(s) == false) {
+                H5_FAILED();
+                AT();
+                dbgf(2, "writer: write attr - verification failed.\n");
+                /* Note: This is (mostly) because the verification failure message
+                 *       from the reader. So don't send the error message back to
+                 *       the reader. Just stop the test. */
+                goto error2;
+            }
+        }
+
+    } /* end for */
+
+    if (H5Tclose(amtype) < 0) {
+        TEST_ERROR;
+    }
+
+    return true;
+
+error:
+    /* Writer needs to send an error message to the reader to stop the test*/
+    if (s->use_named_pipes && s->attr_test == true)
+        np_send_error(s, true);
+
+error2:
+    H5E_BEGIN_TRY
+    {
+        H5Aclose(aid);
+        H5Tclose(amtype);
+    }
+    H5E_END_TRY;
+
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    add_default_group_attr
+ *
+ * Purpose:     Add an attribute to a group.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation, use to generate
+ *              newly created group and attribute names.
+ *              The group name is "group-which" and the attribute name
+ *              is "attr-which".
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This function is used for the "dense" storage test.
+ *              It is also used by the group-only, "add-ohr-block"
+ *              and "del-ohr-block" tests.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+add_default_group_attr(state_t *s, hid_t g, unsigned int which)
+{
+
+    const char *aname_format = "attr-%u";
+
+    /* Note: Since we only add one attribute, the parameter for
+     *        the number of attributes is 1. */
+    return add_attr(s, g, which, 1, aname_format, which);
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    add_vlstr_attr
+ *
+ * Purpose:     Add a variable length string  attribute to a group.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation, use to generate
+ *              newly created group and attribute names.
+ *              The group name is "group-which" and the attribute name
+ *              is "attr-which".
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is for the "vstr" test.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+add_vlstr_attr(state_t *s, hid_t g, unsigned int which)
+{
+
+    hid_t aid   = H5I_INVALID_HID;
+    hid_t atype = H5I_INVALID_HID;
+    char  name[VS_ATTR_NAME_LEN];
+    char *astr_val = NULL;
+    hid_t sid      = s->one_by_one_sid;
+
+    /* Allocate buffer for the VL string value */
+    astr_val = HDmalloc(VS_ATTR_NAME_LEN);
+    if (astr_val == NULL) {
+        printf("Allocate memory for VL string failed.\n");
+        TEST_ERROR;
+    }
+
+    /* Assign the VL string value and the attribute name.. */
+    HDsprintf(astr_val, "%u", which);
+    esnprintf(name, sizeof(name), "attr-%u", which);
+
+    dbgf(1, "setting attribute %s on group %u to %u\n", name, which, which);
+
+    /* Create a datatype to refer to. */
+    if ((atype = H5Tcopy(H5T_C_S1)) < 0) {
+        printf("Cannot create variable length datatype.\n");
+        TEST_ERROR;
+    }
+
+    if (H5Tset_size(atype, H5T_VARIABLE) < 0) {
+        printf("Cannot set variable length datatype.\n");
+        TEST_ERROR;
+    }
+
+    /* Generate the VL string attribute.*/
+    if ((aid = H5Acreate2(g, name, atype, sid, H5P_DEFAULT, H5P_DEFAULT)) < 0) {
+        printf("H5Acreate2 failed.\n");
+        TEST_ERROR;
+    }
+
+    if (H5Awrite(aid, atype, &astr_val) < 0) {
+        printf("H5Awrite failed.\n");
+        TEST_ERROR;
+    }
+
+    if (H5Tclose(atype) < 0) {
+        printf("H5Tclose() failed\n");
+        TEST_ERROR;
+    }
+    if (H5Aclose(aid) < 0) {
+        printf("H5Aclose() failed\n");
+        TEST_ERROR;
+    }
+
+    HDfree(astr_val);
+
+    /* Writer sends a message to reader: a VL string attribute is successfully generated.
+       then wait for the reader to verify and send an acknowledgement message back. */
+    if (s->use_named_pipes && s->attr_test == true) {
+        dbgf(2, "writer: write attr - ready to send the message: %d\n", s->np_notify + 1);
+        if (np_wr_send_receive(s) == false) {
+            H5_FAILED();
+            AT();
+            dbgf(2, "writer: write attr - verification failed.\n");
+            goto error2;
+        }
+    }
+
+    return true;
+
+error:
+    /* Writer needs to send an error message to the reader to stop the test*/
+    if (s->use_named_pipes && s->attr_test == true)
+        np_send_error(s, true);
+    H5E_BEGIN_TRY
+    {
+        H5Aclose(aid);
+        H5Tclose(atype);
+    }
+    H5E_END_TRY;
+
+    if (astr_val)
+        HDfree(astr_val);
+
+error2:
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    del_one_attr
+ *
+ * Purpose:     delete one attribute in a group.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t obj_id
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              bool is_dense
+ *              if the deleted attribute is for checking the dense storage
+ *
+ *              bool is_vl_or_ohrc
+ *              if the deleted attribute is a VL string or for object header
+ *              continuation check test
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation, use to generate
+ *              newly created group and attribute names.
+ *              The group name is "group-which" and the attribute names
+ *              according to if this attribute is a VL string or for checking
+ *              the dense storage or the storage transition from dense to
+ *              compact.
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+del_one_attr(state_t *s, hid_t obj_id, bool is_dense, bool is_vl_or_ohrc, unsigned int which)
+{
+
+    char attrname[VS_ATTR_NAME_LEN];
+
+    /*attribute name template for the dense storage related deletion operation */
+    const char *aname_format_d = "attr-d-%u-%u";
+
+    /*attribute name template used for general attribute deletion operation */
+    const char *aname_format = "attr-%u-%u";
+
+    /*attribute name template used for VL string attribute deletion
+     * or object header continuation check operations */
+    const char *aname_format_vl = "attr-%u";
+
+    dbgf(2, "writer: coming to delete the attribute.\n");
+
+    /* Construct the attribute name */
+    if (is_dense == true)
+        HDsprintf(attrname, aname_format_d, which, 0);
+    else if (is_vl_or_ohrc == true)
+        HDsprintf(attrname, aname_format_vl, which, 0);
+    else
+        HDsprintf(attrname, aname_format, which, 0);
+
+    /* Delete the attribute */
+    if (H5Adelete(obj_id, attrname) < 0) {
+        printf("H5Adelete() failed\n");
+        TEST_ERROR;
+    }
+
+    /* If coming to an "object header continuation block" test,
+     * we need to check if this test behaves as expected. */
+    if (s->at_pattern == 'R') {
+        if (false == check_ohr_num_chunk(obj_id, true)) {
+            printf("The object header chunk should not continue. \n");
+            TEST_ERROR;
+        }
+    }
+    /* Writer sends a message to reader: an attribute is successfully generated.
+       then wait for the reader to verify and send an acknowledgement message back. */
+    if (s->use_named_pipes && s->attr_test == true) {
+        dbgf(2, "writer: delete attr - ready to send the message: %d\n", s->np_notify + 1);
+        if (np_wr_send_receive(s) == false) {
+            H5_FAILED();
+            AT();
+            dbgf(2, "writer: delete attr - verification failed.\n");
+            goto error2;
+        }
+    }
+
+    return true;
+
+error:
+    if (s->use_named_pipes && s->attr_test == true)
+        np_send_error(s, true);
+
+error2:
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    add_del_vlstr_attr
+ *
+ * Purpose:     Add a variable length string attribute
+ *              then delete this attribute in this a group.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation, use to generate
+ *              newly created group and attribute names.
+ *              The group name is "group-which" and the attribute name
+ *              is "attr-which".
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is for the "remove-vstr" test.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+add_del_vlstr_attr(state_t *s, hid_t g, unsigned int which)
+{
+
+    bool ret_value = false;
+
+    /* Add a VL string attribute then delete it. */
+    ret_value = add_vlstr_attr(s, g, which);
+    if (ret_value == true)
+        ret_value = del_one_attr(s, g, false, true, which);
+
+    return ret_value;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    modify_attr
+ *
+ * Purpose:     Modify the value of an attribute in a group.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              const char*aname_fmt
+ *              The attribute name template used to create unique attribute names.
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation, use to generate
+ *              newly created group name. The group name is "group-which".
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+modify_attr(state_t *s, hid_t g, const char *aname_fmt, unsigned int which)
+{
+
+    char         attrname[VS_ATTR_NAME_LEN];
+    hid_t        aid    = H5I_INVALID_HID;
+    hid_t        amtype = H5I_INVALID_HID;
+    unsigned int modify_value;
+
+    HDsprintf(attrname, aname_fmt, which, 0);
+    if ((aid = H5Aopen(g, attrname, H5P_DEFAULT)) < 0) {
+        printf("H5Aopen failed\n");
+        TEST_ERROR;
+    }
+
+    if ((amtype = H5Tget_native_type(s->filetype, H5T_DIR_ASCEND)) < 0) {
+        printf("H5Tget_native_type failed\n");
+        TEST_ERROR;
+    }
+
+    /* Make a large number to verify the change easily */
+    modify_value = which + 10000;
+
+    if (H5Awrite(aid, amtype, &modify_value) < 0) {
+        printf("H5Awrite failed\n");
+        TEST_ERROR;
+    }
+    if (H5Tclose(amtype) < 0) {
+        printf("H5Tclose failed\n");
+        TEST_ERROR;
+    }
+    if (H5Aclose(aid) < 0) {
+        printf("H5Aclose failed\n");
+        TEST_ERROR;
+    }
+
+    /* Writer sends a message to reader: an attribute is successfully modified.
+           then wait for the reader to verify and send an acknowledgement message back.*/
+    if (s->use_named_pipes && s->attr_test == true) {
+        dbgf(2, "writer: modify attr - ready to send the message: %d\n", s->np_notify + 1);
+        if (np_wr_send_receive(s) == false) {
+            H5_FAILED();
+            AT();
+            dbgf(2, "writer: write attr - verification failed.\n");
+            /* Note: This is (mostly) because the verification failure message
+             *       from the reader. So don't send the error message back to
+             *       the reader. Just stop the test. */
+            goto error2;
+        }
+    }
+
+    return true;
+error:
+    /* Writer needs to send an error message to the reader to stop the test*/
+    if (s->use_named_pipes && s->attr_test == true)
+        np_send_error(s, true);
+    H5E_BEGIN_TRY
+    {
+        H5Aclose(aid);
+        H5Tclose(aid);
+    }
+    H5E_END_TRY;
+
+error2:
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    modify_vlstr_attr
+ *
+ * Purpose:     Modify the value of an VL string attribute in a group.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation, use to generate
+ *              newly created group name. The group name is "group-which".
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+modify_vlstr_attr(state_t *s, hid_t g, unsigned int which)
+{
+
+    hid_t aid   = H5I_INVALID_HID;
+    hid_t atype = H5I_INVALID_HID;
+    char  name[VS_ATTR_NAME_LEN];
+    char *astr_val = NULL;
+
+    astr_val = HDmalloc(VS_ATTR_NAME_LEN);
+    if (astr_val == NULL) {
+        printf("Allocate memory for VL string failed.\n");
+        TEST_ERROR;
+    }
+
+    /* Change the VL string value and create the attribute name. */
+    HDsprintf(astr_val, "%u%c", which, 'A');
+    esnprintf(name, sizeof(name), "attr-%u", which);
+
+    dbgf(1, "setting attribute %s on group %u to %u\n", name, which, which);
+
+    /* Create a datatype to refer to. */
+    if ((atype = H5Tcopy(H5T_C_S1)) < 0) {
+        printf("Cannot create variable length datatype.\n");
+        TEST_ERROR;
+    }
+
+    if (H5Tset_size(atype, H5T_VARIABLE) < 0) {
+        printf("Cannot set variable length datatype.\n");
+        TEST_ERROR;
+    }
+
+    /* Open this attribute. */
+    if ((aid = H5Aopen(g, name, H5P_DEFAULT)) < 0) {
+        printf("H5Aopen failed.\n");
+        TEST_ERROR;
+    }
+
+    dbgf(1, "The modified VL string value  is  %s \n", astr_val);
+
+    if (H5Awrite(aid, atype, &astr_val) < 0) {
+        printf("H5Awrite failed.\n");
+        TEST_ERROR;
+    }
+
+    if (H5Tclose(atype) < 0) {
+        printf("H5Tclose() failed\n");
+        TEST_ERROR;
+    }
+
+    if (H5Aclose(aid) < 0) {
+        printf("H5Aclose() failed\n");
+        TEST_ERROR;
+    }
+
+    HDfree(astr_val);
+
+    /* Writer sends a message to reader: a VL string attribute is successfully generated.
+       then wait for the reader to verify and send an acknowledgement message back. */
+    if (s->use_named_pipes && s->attr_test == true) {
+        dbgf(2, "writer: modify vl attr - ready to send the message: %d\n", s->np_notify + 1);
+        if (np_wr_send_receive(s) == false) {
+            H5_FAILED();
+            AT();
+            dbgf(2, "writer: write attr - verification failed.\n");
+            goto error2;
+        }
+    }
+
+    return true;
+
+error:
+    H5E_BEGIN_TRY
+    {
+        H5Aclose(aid);
+        H5Tclose(atype);
+    }
+    H5E_END_TRY;
+
+    if (astr_val)
+        HDfree(astr_val);
+
+    if (s->use_named_pipes && s->attr_test == true)
+        np_send_error(s, true);
+
+error2:
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    add_modify_vlstr_attr
+ *
+ * Purpose:     Add a variable length string attribute
+ *              then modify this attribute in this a group.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation, use to generate
+ *              newly created group and attribute names.
+ *              The group name is "group-which" and the attribute name
+ *              is "attr-which".
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is for the "modify-vstr" test.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+add_modify_vlstr_attr(state_t *s, hid_t g, unsigned int which)
+{
+
+    bool ret_value = false;
+    ret_value      = add_vlstr_attr(s, g, which);
+    if (true == ret_value)
+        ret_value = modify_vlstr_attr(s, g, which);
+
+    return ret_value;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    add_attrs_compact
+ *
+ * Purpose:     Add some attributes to the group.
+ *              the number of attributes should be the maximal number of
+ *              attributes that the compact storage can hold
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              hid_t gcpl
+ *              Object creation property list ID
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation, use to generate
+ *              newly created group and attribute names.
+ *              The group name is "group-which" and the attribute name
+ *              is "attr-which".
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is for the "modify-vstr" test.
+ *              For attribute compact/dense storage, check the reference
+ *              manual of H5Pget_attr_phase_change.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+add_attrs_compact(state_t *s, hid_t g, hid_t gcpl, unsigned int which)
+{
+
+    unsigned    max_compact  = 0;
+    unsigned    min_dense    = 0;
+    const char *aname_format = "attr-%u-%u";
+
+    if (s->old_style_grp)
+        max_compact = 2;
+    else {
+        /* Obtain the maximal number of attributes to be stored in compact
+         * storage and the minimal number of attributes to be stored in
+         * dense storage. */
+        if (H5Pget_attr_phase_change(gcpl, &max_compact, &min_dense) < 0) {
+            printf("H5Pget_attr_phase_change() failed\n");
+            TEST_ERROR;
+        }
+    }
+
+    /* Add max_compact attributes, these attributes are stored in
+     * compact storage. */
+    return add_attr(s, g, which, max_compact, aname_format, which);
+
+error:
+    if (s->use_named_pipes && s->attr_test == true)
+        np_send_error(s, true);
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    add_attrs_compact_dense
+ *
+ * Purpose:     Add some attributes to the group.
+ *              First, the number of attributes should be the maximal number
+ *              of attributes that the compact storage can hold.
+ *              Then,  add another atribute, the storage becomes dense.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              hid_t gcpl
+ *              Object creation property list ID
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation, use to generate
+ *              newly created group and attribute names.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is for the "compact-to-dense" test.
+ *              For attribute compact/dense storage, check the reference
+ *              manual of H5Pget_attr_phase_change.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+add_attrs_compact_dense(state_t *s, hid_t g, hid_t gcpl, unsigned int which)
+{
+
+    unsigned    max_compact  = 0;
+    unsigned    min_dense    = 0;
+    const char *aname_format = "attr-d-%u-%u";
+    bool        ret_value    = false;
+
+    if (H5Pget_attr_phase_change(gcpl, &max_compact, &min_dense) < 0) {
+        printf("H5Pget_attr_phase_change failed\n");
+        TEST_ERROR;
+    }
+
+    /* Add attributes, until just before converting to dense storage */
+    ret_value = add_attrs_compact(s, g, gcpl, which);
+
+    /* Add another attribute, the storage becomes dense. */
+    if (ret_value == true)
+        ret_value = add_attr(s, g, which + max_compact, 1, aname_format, which);
+
+    return ret_value;
+
+error:
+    if (s->use_named_pipes && s->attr_test == true)
+        np_send_error(s, true);
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    del_attrs_compact_dense_compact
+ *
+ * Purpose:     delete some attributes in the group.
+ *              The number of attributes are deleted in such a way
+ *              that the attribute storage changes from compact to
+ *              dense then to compact again.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              hid_t gcpl
+ *              Object creation property list ID
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation, use to generate
+ *              newly created group and attribute names.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is an internal function used by the
+ *              "dense-del-to-compact" test.
+ *              For attribute compact/dense storage, check the reference
+ *              manual of H5Pget_attr_phase_change.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+del_attrs_compact_dense_compact(state_t *s, hid_t obj_id, hid_t gcpl, unsigned int which)
+{
+
+    unsigned max_compact = 0;
+    unsigned min_dense   = 0;
+    unsigned u           = 0;
+
+    char        attrname[VS_ATTR_NAME_LEN];
+    const char *aname_format  = "attr-%u-%u";
+    const char *adname_format = "attr-d-%u-%u";
+
+    /* Obtain the maximal number of attributes to be stored in compact
+     * storage and the minimal number of attributes to be stored in
+     * dense storage. */
+    if (H5Pget_attr_phase_change(gcpl, &max_compact, &min_dense) < 0) {
+        printf("H5Pget_attr_phase_change failed\n");
+        TEST_ERROR;
+    }
+    u = max_compact + 1;
+
+    /* delete a number of attributes so that the attribute storage just becomes dense.*/
+    for (u--; u >= (min_dense - 1); u--) {
+        HDsprintf(attrname, aname_format, which, max_compact - u);
+        if (H5Adelete(obj_id, attrname) < 0) {
+            printf("H5Adelete failed\n");
+            TEST_ERROR;
+        }
+
+        /* For each attribute deletion, we want to ensure the verification
+         * from the reader.
+         * So writer sends a message to reader: an attribute is successfully deleted.
+           then wait for reader to verify and send an acknowledgement message back. */
+        if (s->use_named_pipes && s->attr_test == true) {
+            dbgf(2, "writer: delete attr - ready to send the message: %d\n", s->np_notify + 1);
+            if (np_wr_send_receive(s) == false) {
+                H5_FAILED();
+                AT();
+                dbgf(2, "writer: delete attr - verification failed.\n");
+                goto error2;
+            }
+        }
+    }
+
+    /* The writer deletes another attribute, the storage is
+     * still dense. However, the attribute to be deleted
+     * doesn't follow the previous for loop. It may be
+     * in different location in the object header. Just add
+     * a litter variation to check if this operation is successful.
+     * The attribute name to be deleted is attr-max_compact+which-0
+     */
+
+    HDsprintf(attrname, adname_format, max_compact + which, 0);
+    if (H5Adelete(obj_id, attrname) < 0) {
+        printf("H5Adelete failed\n");
+        TEST_ERROR;
+    }
+    /* Again we need to notify the reader via Named pipe. */
+    if (s->use_named_pipes && s->attr_test == true) {
+        dbgf(2, "writer: delete attr - ready to send the message: %d\n", s->np_notify + 1);
+        if (np_wr_send_receive(s) == false) {
+            H5_FAILED();
+            AT();
+            dbgf(2, "writer: delete attr - verification failed.\n");
+            goto error2;
+        }
+    }
+
+    /* The following comments are left here in case in the future we want to
+     * use HDF5 function to verify the attribute storage */
+#if 0   
+    // May H5Oget_info3 -- obtain the number of attributes. 
+    //Check the number of attributes >=min_dense. 
+    //We may use the internal function  
+    //is_dense = H5O__is_attr_dense_test(dataset) to check if it is dense in the future. 
+    //
+#endif
+
+    return true;
+
+error:
+    if (s->use_named_pipes && s->attr_test == true)
+        np_send_error(s, true);
+
+error2:
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    add_del_attrs_compact
+ *
+ * Purpose:     Add some attributes to the group and then delete one attribute.
+ *              First, the number of attributes to be added should be the
+ *              maximal number of attributes that the compact storage can hold.
+ *              Then,  delete one atribute, the storage is still compact.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              hid_t gcpl
+ *              Object creation property list ID
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation, use to generate
+ *              newly created group and attribute names.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is for the "compact-del" test.
+ *              For attribute compact/dense storage, check the reference
+ *              manual of H5Pget_attr_phase_change.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+add_del_attrs_compact(state_t *s, hid_t g, hid_t gcpl, unsigned int which)
+{
+
+    bool ret_value = false;
+    ret_value      = add_attrs_compact(s, g, gcpl, which);
+    if (ret_value == true) {
+        dbgf(2, "writer: before deleting the attribute.\n");
+        ret_value = del_one_attr(s, g, false, false, which);
+    }
+
+    return ret_value;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    add_del_attrs_compact_dense
+ *
+ * Purpose:     Add some attributes to the group and then delete one attribute.
+ *              First, the number of attributes to be added exceeds
+ *              the maximal number of attributes that the compact storage can hold.
+ *              The storage changes from compact to dense.
+ *              Then,  delete one atribute, the storage is still dense.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              hid_t gcpl
+ *              Object creation property list ID
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation, use to generate
+ *              newly created group and attribute names.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is for the "dense-del" test.
+ *              For attribute compact/dense storage, check the reference
+ *              manual of H5Pget_attr_phase_change.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+add_del_attrs_compact_dense(state_t *s, hid_t g, hid_t gcpl, unsigned int which)
+{
+
+    bool     ret_value   = false;
+    unsigned max_compact = 0;
+    unsigned min_dense   = 0;
+
+    if (H5Pget_attr_phase_change(gcpl, &max_compact, &min_dense) < 0) {
+        printf("H5Pget_attr_phase_change failed\n");
+        TEST_ERROR;
+    }
+
+    ret_value = add_attrs_compact_dense(s, g, gcpl, which);
+    if (ret_value == true)
+        ret_value = del_one_attr(s, g, true, false, which + max_compact);
+
+    return ret_value;
+
+error:
+    if (s->use_named_pipes && s->attr_test == true)
+        np_send_error(s, true);
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    add_del_attrs_compact_dense_compact
+ *
+ * Purpose:     Add attributes to the group and then delete some of them.
+ *              First, the number of attributes to be added exceeds
+ *              the maximal number of attributes that the compact storage can hold.
+ *              The storage changes from compact to dense.
+ *              Then,  delete some attributes, the storage changes from
+ *              dense to compact again.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              hid_t gcpl
+ *              Object creation property list ID
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation, use to generate
+ *              newly created group and attribute names.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is for the "dense-del-to-compact" test.
+ *              For attribute compact/dense storage, check the reference
+ *              manual of H5Pget_attr_phase_change.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+add_del_attrs_compact_dense_compact(state_t *s, hid_t g, hid_t gcpl, unsigned int which)
+{
+
+    bool ret_value = false;
+    ret_value      = add_attrs_compact_dense(s, g, gcpl, which);
+    if (ret_value == true)
+        ret_value = del_attrs_compact_dense_compact(s, g, gcpl, which);
+
+    return ret_value;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    add_modify_default_group_attr
+ *
+ * Purpose:     Add an attribute then modify the value to a group.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation, use to generate
+ *              newly created group and attribute names.
+ *              The group name is "group-which" and the attribute name
+ *              is "attr-which".
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This function is used for the "modify" test.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+add_modify_default_group_attr(state_t *s, hid_t g, unsigned int which)
+{
+
+    bool        ret_value    = false;
+    const char *aname_format = "attr-%u";
+    ret_value                = add_default_group_attr(s, g, which);
+    if (ret_value == true)
+        ret_value = modify_attr(s, g, aname_format, which);
+    return ret_value;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    del_ohr_block_attr
+ *
+ * Purpose:     Add an attribute to force creation of object header
+ *              continuation block and remove this attribute to delete
+ *              the object header continuation block
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation, use to generate
+ *              newly created group and attribute names.
+ *              The group name is "group-which" and the attribute name
+ *              is "attr-which".
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This function is used for the
+ *              "deletion of object header continuation block" test.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+del_ohr_block_attr(state_t *s, hid_t g, unsigned int which)
+{
+
+    bool ret_value = false;
+    ret_value      = add_default_group_attr(s, g, which);
+    if (ret_value == true)
+        ret_value = del_one_attr(s, g, false, true, which);
+    return ret_value;
+}
+/*-------------------------------------------------------------------------
+ * Function:    add_group_attribute
+ *
+ * Purpose:     Check the attribute test pattern and then call the
+ *              correponding test function..
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              hid_t gcpl
+ *              Object creation property list ID
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation, use to generate
+ *              newly created group and attribute names.
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the write_group() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+add_group_attribute(state_t *s, hid_t g, hid_t gcpl, unsigned int which)
+{
+
+    bool ret_value    = false;
+    char test_pattern = s->at_pattern;
+
+    switch (test_pattern) {
+        case 'c':
+            ret_value = add_attrs_compact(s, g, gcpl, which);
+            break;
+        case 't':
+            ret_value = add_attrs_compact_dense(s, g, gcpl, which);
+            break;
+        case 'C':
+            ret_value = add_del_attrs_compact(s, g, gcpl, which);
+            break;
+        case 'D':
+            ret_value = add_del_attrs_compact_dense(s, g, gcpl, which);
+            break;
+        case 'T':
+            ret_value = add_del_attrs_compact_dense_compact(s, g, gcpl, which);
+            break;
+        case 'M':
+            ret_value = add_modify_default_group_attr(s, g, which);
+            break;
+        case 'v':
+            ret_value = add_vlstr_attr(s, g, which);
+            break;
+        case 'r':
+            ret_value = add_del_vlstr_attr(s, g, which);
+            break;
+        case 'm':
+            ret_value = add_modify_vlstr_attr(s, g, which);
+            break;
+        case 'R':
+            ret_value = del_ohr_block_attr(s, g, which);
+            break;
+        case 'a':
+        case 'd':
+        case ' ':
+        default:
+            ret_value = add_default_group_attr(s, g, which);
+            break;
+    }
+    return ret_value;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    write_group
+ *
+ * Purpose:     Create a group and carry out attribute operations(add,delete etc.)
+ *              according to the attribute test pattern.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the main() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+write_group(state_t *s, unsigned int which)
+{
+    char       name[sizeof("/group-9999999999")];
+    hid_t      g       = H5I_INVALID_HID;
+    hid_t      dummy_d = H5I_INVALID_HID;
+    hid_t      gcpl    = H5I_INVALID_HID;
+    bool       result  = true;
+    H5G_info_t group_info;
+    struct timespec start_time, end_time;
+    double temp_time;
+
+    if (which >= s->nsteps) {
+        printf("Number of created groups is out of bounds\n");
+        TEST_ERROR;
+    }
+
+    esnprintf(name, sizeof(name), "/group-%u", which);
+
+#if 0
+    if (s->old_style_grp)
+        gcpl = H5P_DEFAULT;
+    else {
+        gcpl = H5Pcreate(H5P_GROUP_CREATE);
+        if (gcpl < 0) {
+            printf("H5Pcreate failed\n");
+            TEST_ERROR;
+        }
+
+        /* If we test the dense storage, change the attribute phase. */
+        if (s->at_pattern == 'd') {
+            if (H5Pset_attr_phase_change(gcpl, 0, 0) < 0) {
+                printf("H5Pset_attr_phase_change failed for the dense storage.\n");
+                TEST_ERROR;
+            }
+        }
+    }
+#endif
+
+    if(s->gperf) {
+
+       if (HDclock_gettime(CLOCK_MONOTONIC, &start_time) == -1) {
+
+                fprintf(stderr, "HDclock_gettime failed");
+
+                TEST_ERROR;
+
+            }    
+
+
+    }
+    if ((g = H5Gcreate2(s->file, name, H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT)) < 0) {
+        printf("H5Gcreate2 failed\n");
+        TEST_ERROR;
+    }
+
+    if(s->gperf) {
+
+       if (HDclock_gettime(CLOCK_MONOTONIC, &end_time) == -1) {
+
+                fprintf(stderr, "HDclock_gettime failed");
+
+                TEST_ERROR;
+
+            }    
+
+
+       temp_time = TIME_PASSED(start_time,end_time);
+       if(temp_time < s->min_time)
+            s->min_time = temp_time;
+       if(temp_time > s->max_time)
+            s->max_time = temp_time;
+       s->total_time += temp_time;      
+    }
+    
+
+#if 0
+    /* We need to create a dummy dataset for the object header continuation block test. */
+    if (s->at_pattern == 'a' || s->at_pattern == 'R') {
+        if ((dummy_d = H5Dcreate2(g, "Dataset", H5T_NATIVE_INT, s->one_by_one_sid, H5P_DEFAULT, H5P_DEFAULT,
+                                  H5P_DEFAULT)) < 0) {
+            printf("H5Dcreate2 failed\n");
+            TEST_ERROR;
+        }
+    }
+    if (H5Gget_info(g, &group_info) < 0) {
+        printf("H5Gget_info failed\n");
+        TEST_ERROR;
+    }
+
+    if (s->old_style_grp) {
+        if (group_info.storage_type != H5G_STORAGE_TYPE_SYMBOL_TABLE) {
+            printf("Old-styled group test: but the group is not in old-style. \n");
+            TEST_ERROR;
+        }
+        dbgf(2, "Writer: group is created with the old-style.\n");
+    }
+    else {
+        if (group_info.storage_type == H5G_STORAGE_TYPE_SYMBOL_TABLE) {
+            printf("The created group should NOT be in old-style . \n");
+            TEST_ERROR;
+        }
+        dbgf(2, "Writer: group is created with the new-style.\n");
+    }
+
+    /* If coming to an "object header continuation block" test,
+     * we need to check if this test behaves as expected. */
+    if (s->at_pattern == 'a' || s->at_pattern == 'R') {
+        if (false == check_ohr_num_chunk(g, true)) {
+            printf("An object header continuation block should NOT be created. \n");
+            printf("But it is created.\n");
+            TEST_ERROR;
+        }
+    }
+
+    /* If an attribute test is turned on and named pipes are used,
+     * the writer should send and receive messages after the group creation.
+     * This will distinguish an attribute operation error from an
+     * group creation error.
+     * Writer sends a message to reader: an attribute is successfully generated.
+     * then wait for the reader to verify and send an acknowledgement message back.*/
+    if (s->use_named_pipes && s->attr_test == true) {
+        dbgf(2, "writer: ready to send the message: %d\n", s->np_notify + 1);
+        if (np_wr_send_receive(s) == false) {
+            H5_FAILED();
+            AT();
+            /* Note: This is (mostly) because the verification failure message
+             *       from the reader. So don't send the error message back to
+             *       the reader. Just stop the test. */
+            goto error2;
+        }
+    }
+
+    /* Then carry out the attribute operation. */
+    if (s->asteps != 0 && which % s->asteps == 0)
+        result = add_group_attribute(s, g, gcpl, which);
+
+    if (s->at_pattern == 'a' || s->at_pattern == 'R') {
+        if (H5Dclose(dummy_d) < 0) {
+            printf("H5Dclose failed\n");
+            TEST_ERROR;
+        }
+    }
+#endif
+    if (H5Gclose(g) < 0) {
+        printf("H5Gclose failed\n");
+        TEST_ERROR;
+    }
+
+
+    return result;
+
+error:
+
+
+    H5E_BEGIN_TRY {
+        H5Gclose(g);
+    }
+    H5E_END_TRY;
+
+    return false;
+}
+/*-------------------------------------------------------------------------
+ * Function:    check_attr_storage_type
+ *
+ * Purpose:     Check if the attribute storage type is correct
+ *
+ * Parameters:  hid_t oid
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              bool is_compact
+ *              true if the attribute is stored in compact storage
+ *              false if the attribute is stored in dense storage
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+check_attr_storage_type(hid_t g, bool is_compact)
+{
+
+    H5O_native_info_t ninfo;
+
+    /* Get the object information */
+    if (H5Oget_native_info(g, &ninfo, H5O_NATIVE_INFO_HDR | H5O_NATIVE_INFO_META_SIZE) < 0) {
+        printf("H5Oget_native_info failed\n");
+        TEST_ERROR;
+    }
+
+    if (is_compact) {
+        if (ninfo.meta_size.attr.index_size != 0 || ninfo.meta_size.attr.heap_size != 0) {
+            printf("Should be in compact storage,but it is not.\n");
+            TEST_ERROR;
+        }
+    }
+    else {
+        if (ninfo.meta_size.attr.index_size == 0 || ninfo.meta_size.attr.heap_size == 0) {
+            printf("Should be in dense storage,but it is not.\n");
+            TEST_ERROR;
+        }
+    }
+
+    return true;
+
+error:
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    vrfy_attr
+ *
+ * Purpose:     Verify is a group attribute value is as expected.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t oid
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation, use to generate
+ *              newly created group name. The group name is "group-which".
+ *
+ *              const char*aname
+ *              The attribute name
+ *
+ *              unsigned int g_which
+ *              This parameter is used to generate correct group name in a key
+ *              debugging message.
+ *
+ *              bool check_storage
+ *              a flag to indicate if the storage check is on
+ *
+ *              bool is_compact
+ *              true if the attribute storage should be in compact
+ *              false if the attribute storage should be in dense
+ *              Note: this parameter is not used if the check_storage
+ *              is set to false.
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+vrfy_attr(state_t *s, hid_t g, unsigned int which, const char *aname, unsigned int g_which,
+          bool check_storage, bool is_compact)
+{
+
+    unsigned int read_which;
+    hid_t        aid    = H5I_INVALID_HID;
+    hid_t        amtype = H5I_INVALID_HID;
+
+    /* The reader receives a message from the writer.Then sleep
+     * for a few ticks or stop the test if receiving an error
+     * message.
+     */
+    if (s->use_named_pipes && true == s->attr_test) {
+        if (false == np_rd_receive(s)) {
+            H5_FAILED();
+            AT();
+            /* Since receiving the error message from the writer,
+             * just stop the test. */
+            goto error2;
+        }
+        decisleep(s->tick_len * s->update_interval);
+        dbgf(1, "Reader: finish reading the message: %d\n", s->np_notify);
+    }
+
+    /* Go ahead to read the attribute. */
+    dbgf(1, "verifying attribute %s on group %u equals %u\n", aname, g_which, which);
+
+    if ((amtype = H5Tget_native_type(s->filetype, H5T_DIR_ASCEND)) < 0) {
+        printf("H5Tget_native_type failed\n");
+        TEST_ERROR;
+    }
+
+    if ((aid = H5Aopen(g, aname, H5P_DEFAULT)) < 0) {
+        printf("H5Aopen failed\n");
+        TEST_ERROR;
+    }
+
+    if (H5Aread(aid, amtype, &read_which) < 0) {
+        printf("H5Aread failed\n");
+        TEST_ERROR;
+    }
+
+    if (H5Aclose(aid) < 0) {
+        printf("H5Aclose failed\n");
+        TEST_ERROR;
+    }
+
+    if (read_which != which) {
+        printf("reader: the add_attribute verfication failed,expected value is  %d\n", which);
+        printf("reader: the add_attribute verfication failed, the value is %d\n", read_which);
+        printf("The add_attribute verification failed\n");
+        TEST_ERROR;
+    }
+
+    if (!s->old_style_grp && check_storage == true) {
+        if (false == check_attr_storage_type(g, is_compact)) {
+            printf("The attribute storage type is wrong. \n");
+            TEST_ERROR;
+        }
+        dbgf(2, "reader: finish checking the storage type: %d\n", s->np_notify);
+    }
+
+    /* If coming to an "object header continuation block" test,
+     * we need to check if this test behaves as expected. */
+    if (s->at_pattern == 'a' || s->at_pattern == 'R') {
+        if (false == check_ohr_num_chunk(g, false)) {
+            printf("An object header continuation block should be created. \n");
+            printf("But it is not.\n");
+            printf("Verification of 'object header continuation block test' failed.\n");
+            TEST_ERROR;
+        }
+    }
+
+    /* If the read value is expected, send back an OK message to the writer. */
+    if (s->use_named_pipes && s->attr_test == true) {
+        if (np_rd_send(s) == false) {
+            printf("named pipe reader send message error\n");
+            TEST_ERROR;
+        }
+        dbgf(2, "reader: finish sending back the message: %d\n", s->np_notify);
+    }
+    return true;
+
+error:
+    H5E_BEGIN_TRY
+    {
+        H5Tclose(amtype);
+        H5Aclose(aid);
+    }
+    H5E_END_TRY;
+
+    /* Send back an error message to the writer so that the writer can stop. */
+    if (s->use_named_pipes && s->attr_test == true)
+        np_send_error(s, false);
+error2:
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    verify_default_group_attr
+ *
+ * Purpose:     Check if the reader can retrieve the correct value of a
+ *              group attribute corrected by the writer.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigned int which
+ *              The expected attribute value. It is also used to construct the
+ *              group name.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This function is used for the "dense" storage test.
+ *              It is also used by the group-only, "add-ohr-block"
+ *              and "del-ohr-block" tests.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+verify_default_group_attr(state_t *s, hid_t g, unsigned int which)
+{
+    char        attrname[VS_ATTR_NAME_LEN];
+    const char *aname_format = "attr-%u";
+    HDsprintf(attrname, aname_format, which);
+    return vrfy_attr(s, g, which, attrname, which, false, true);
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    verify_modify_attr
+ *
+ * Purpose:     Check if the reader can retrieve the correct value of
+ *              an attribute in a group, first the original value then
+ *              the modified value.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigned int which
+ *              The expected attribute value. It is also used to construct the
+ *              group name. The modified attribute value can be derived from
+ *              the expected attribute value.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This function is used for the "modified" test.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+verify_modify_attr(state_t *s, hid_t g, unsigned int which)
+{
+
+    bool         ret       = false;
+    const char * aname_fmt = "attr-%u";
+    unsigned int read_which;
+    hid_t        aid    = H5I_INVALID_HID;
+    hid_t        amtype = H5I_INVALID_HID;
+    char         attrname[VS_ATTR_NAME_LEN];
+
+    /* First verify the original attribute value */
+    ret = verify_default_group_attr(s, g, which);
+
+    /* Then the modified value */
+    if (ret == true) {
+
+        /* The reader receives a message from the writer.Then sleep
+         * for a few ticks or stop the test if receiving an error
+         * message.
+         */
+        if (s->use_named_pipes && true == s->attr_test) {
+            if (false == np_rd_receive(s)) {
+                H5_FAILED();
+                AT();
+                goto error2;
+            }
+            decisleep(s->tick_len * s->update_interval);
+            dbgf(1, "Reader: finish reading the message: %d\n", s->np_notify);
+        }
+
+        /* Go ahead to read the attribute. */
+        esnprintf(attrname, sizeof(attrname), aname_fmt, which);
+        if ((amtype = H5Tget_native_type(s->filetype, H5T_DIR_ASCEND)) < 0) {
+            printf("H5Tget_native_type failed\n");
+            TEST_ERROR;
+        }
+
+        if ((aid = H5Aopen(g, attrname, H5P_DEFAULT)) < 0) {
+            printf("H5Aopen failed\n");
+            TEST_ERROR;
+        }
+
+        if (H5Aread(aid, amtype, &read_which) < 0) {
+            printf("H5Aread failed\n");
+            TEST_ERROR;
+        }
+
+        if (H5Tclose(amtype) < 0) {
+            printf("H5Tclose failed.\n");
+            TEST_ERROR;
+        }
+
+        if (H5Aclose(aid) < 0) {
+            printf("H5Aclose failed\n");
+            TEST_ERROR;
+        }
+
+        /* verify the modified value */
+        if (read_which != (which + 10000)) {
+            printf("reader: the modified_attr() expected value is  %d\n", which + 10000);
+            printf("reader: the modified_attr() actual value is %d\n", read_which);
+            printf("The modify_attribute verification failed.\n");
+            TEST_ERROR;
+        }
+
+        /* The reader sends an OK message back to the writer. */
+        if (s->use_named_pipes && s->attr_test == true) {
+            if (np_rd_send(s) == false)
+                goto error2;
+            dbgf(2, "reader: modify_attr finish sending back the message: %d\n", s->np_notify);
+        }
+        return true;
+    }
+    return false;
+
+error:
+    H5E_BEGIN_TRY
+    {
+        H5Aclose(aid);
+        H5Tclose(amtype);
+    }
+    H5E_END_TRY;
+
+    /* The reader needs to send an error message back to the writer to stop the test.*/
+    if (s->use_named_pipes && s->attr_test == true)
+        np_send_error(s, false);
+
+error2:
+
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    verify_group_vlstr_attr
+ *
+ * Purpose:     Check if the reader can retrieve the correct value of
+ *              a variable length string attribute created by the writer.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigned int which
+ *              Use to derieve the expected attribute value. It is also used
+ *              to construct the group name.
+ *
+ *              bool vrfy_mod
+ *              true if this function is used for the modified VL string test.
+ *              false if this function is just used for the VL string test.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This function is an internal function used by
+ *              both the "vlstr" and the "modify-vstr" tests.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+verify_group_vlstr_attr(state_t *s, hid_t g, unsigned int which, bool vrfy_mod)
+{
+    hid_t aid   = H5I_INVALID_HID;
+    hid_t atype = H5I_INVALID_HID;
+    char  name[VS_ATTR_NAME_LEN];
+
+    char *astr_val_exp;
+    char *astr_val;
+
+    /* The reader receives a message from the writer.Then sleep
+     * for a few ticks or stop the test if the received message
+     * is an error message.
+     */
+    if (s->use_named_pipes && true == s->attr_test) {
+        if (false == np_rd_receive(s)) {
+            H5_FAILED();
+            AT();
+            goto error2;
+        }
+        decisleep(s->tick_len * s->update_interval);
+        dbgf(1, "Reader: finish reading the message: %d\n", s->np_notify);
+    }
+
+    /* Go ahead to read the VL string attribute. */
+    astr_val_exp = HDmalloc(VS_ATTR_NAME_LEN);
+    if (astr_val_exp == NULL) {
+        printf("Allocate memory for expected buffer failed.\n");
+        TEST_ERROR;
+    }
+
+    esnprintf(name, sizeof(name), "attr-%u", which);
+
+    /* Construct the expected VL string value,depending if
+     * it is the modified value or the original value. */
+    if (vrfy_mod == true)
+        HDsprintf(astr_val_exp, "%u%c", which, 'A');
+    else
+        HDsprintf(astr_val_exp, "%u", which);
+
+    dbgf(1, "verifying attribute %s on group %u equals %u\n", name, which, which);
+
+    dbgf(1, "expected vl attr is= %s\n", astr_val_exp);
+
+    if ((aid = H5Aopen(g, name, H5P_DEFAULT)) < 0) {
+        printf("H5Aopen failed\n");
+        TEST_ERROR;
+    }
+
+    /* Create a VL string datatype  */
+    if ((atype = H5Tcopy(H5T_C_S1)) < 0) {
+        printf("Cannot create variable length datatype.\n");
+        TEST_ERROR;
+    }
+
+    if (H5Tset_size(atype, H5T_VARIABLE) < 0) {
+        printf("Cannot set variable length datatype.\n");
+        TEST_ERROR;
+    }
+
+    if (H5Aread(aid, atype, &astr_val) < 0) {
+        printf("Cannot read the attribute.\n");
+        TEST_ERROR;
+    }
+
+    dbgf(1, "read attr is= %s\n", astr_val);
+    if (HDstrcmp(astr_val, astr_val_exp) != 0) {
+        printf("reader: the vl add_attribute verfication failed,expected value is  %s\n", astr_val_exp);
+        printf("reader: the vl add_attribute verfication failed, the value is %s\n", astr_val);
+        printf("The vl add_attribute verification failed\n");
+        TEST_ERROR;
+    }
+
+    if (H5Tclose(atype) < 0) {
+        printf("H5Tclose failed.\n");
+        TEST_ERROR;
+    }
+
+    if (H5Aclose(aid) < 0) {
+        printf("H5Aclose failed.\n");
+        TEST_ERROR;
+    }
+
+    H5free_memory(astr_val);
+    HDfree(astr_val_exp);
+
+    /* Reader sends an OK message back to the reader */
+    if (s->use_named_pipes && s->attr_test == true) {
+        if (np_rd_send(s) == false)
+            goto error2;
+        dbgf(2, "reader: finish sending back the message: %d\n", s->np_notify);
+    }
+
+    return true;
+
+error:
+    H5E_BEGIN_TRY
+    {
+        H5Aclose(aid);
+        H5Tclose(atype);
+    }
+    H5E_END_TRY;
+    if (astr_val)
+        H5free_memory(astr_val);
+    if (astr_val_exp)
+        HDfree(astr_val_exp);
+
+    /* The reader sends an error message to the writer to stop the test.*/
+    if (s->use_named_pipes && s->attr_test == true)
+        np_send_error(s, false);
+
+error2:
+
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    verify_del_one_attr
+ *
+ * Purpose:     Verify if an attribute is successfully deleted.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              const char* aname
+ *              The name of the attribute to be deleted.
+ *
+ *              bool check_storage
+ *              a flag to indicate if the storage check is on
+ *
+ *              bool is_compact
+ *              true if after this attribute is deleted,
+ *              the storage should still be in compact, false
+ *              if the storage should be in dense.
+ *              Note: this parameter is not used if the check_storage
+ *              is set to false.
+
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is an internal function used by "remove-vlstr",
+ *              "compact-del","dense-del",dense-del-to-compact"  tests.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+verify_del_one_attr(state_t *s, hid_t g, const char *aname, bool check_storage, bool is_compact)
+{
+
+    htri_t attr_exists = FALSE;
+
+    /* The reader receives a message from the writer.Then sleep
+     * for a few ticks or stop the test if the received message
+     * is an error message.
+     */
+    if (s->use_named_pipes && true == s->attr_test) {
+        if (false == np_rd_receive(s)) {
+            H5_FAILED();
+            AT();
+            goto error2;
+        }
+        decisleep(s->tick_len * s->update_interval);
+        dbgf(1, "Reader: finish reading the message: %d\n", s->np_notify);
+    }
+
+    /* Check if the deleted attribute still exists. */
+    attr_exists = H5Aexists_by_name(g, ".", aname, H5P_DEFAULT);
+    if (attr_exists == FALSE) {
+        dbgf(1, "verify_del_attrs_compact() test: \n");
+        dbgf(1, "  attribute %s is successfully deleted. \n", aname);
+    }
+    else if (attr_exists == TRUE) {
+        printf("The supposed deleted attribute %s still exists \n", aname);
+        printf("verify_del_attrs_compact() test failed \n");
+        TEST_ERROR;
+    }
+    else {
+        printf("H5Aexists_by_name failed \n");
+        TEST_ERROR;
+    }
+
+    if (!s->old_style_grp && check_storage == true) {
+        if (false == check_attr_storage_type(g, is_compact)) {
+            printf("The attribute storage type is wrong. \n");
+            TEST_ERROR;
+        }
+        dbgf(2, "reader: finish checking the storage type: %d\n", s->np_notify);
+    }
+
+    /* If coming to an "object header continuation block" test,
+     * we need to check if this test behaves as expected. */
+    if (s->at_pattern == 'R') {
+        if (false == check_ohr_num_chunk(g, true)) {
+            printf("An object header continuation block should be removed. \n");
+            printf("But it is NOT.\n");
+            printf("Verification of an 'object header continuation block test' failed.\n");
+            TEST_ERROR;
+        }
+    }
+
+    /* Reader sends an OK message back to the reader */
+    if (s->use_named_pipes && s->attr_test == true) {
+        if (np_rd_send(s) == false)
+            TEST_ERROR;
+        dbgf(2, "reader: finish sending back the message: %d\n", s->np_notify);
+    }
+
+    return true;
+error:
+    /* The reader sends an error message to the writer to stop the test.*/
+    if (s->use_named_pipes && s->attr_test == true)
+        np_send_error(s, false);
+
+error2:
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    verify_remove_vlstr_attr
+ *
+ * Purpose:     Verify if an variable length string attribute is
+ *              successfully deleted by the writer.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigned int which
+ *              Use to derieve the expected attribute value added
+ *              by the writer. It is also used to construct
+ *              the attribute name.
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This function is for the "remove-vstr" test.
+ *              Also note this function first verifies if
+ *              a variable length attribute is added then
+ *              it verifies if it is deleted successfully.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+verify_remove_vlstr_attr(state_t *s, hid_t g, unsigned int which)
+{
+    bool        ret = false;
+    char        attrname[VS_ATTR_NAME_LEN];
+    const char *aname_format = "attr-%u";
+
+    ret = verify_group_vlstr_attr(s, g, which, false);
+    if (ret == true) {
+        HDsprintf(attrname, aname_format, which);
+        ret = verify_del_one_attr(s, g, attrname, false, false);
+    }
+    return ret;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    verify_modify_vlstr_attr
+ *
+ * Purpose:     Verify if an variable length string attribute is
+ *              successfully modified by the writer.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigned int which
+ *              Use to derieve the expected attribute value added
+ *              by the writer. It is also used to construct
+ *              the attribute name.
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This function is for the "modify-vstr" test.
+ *              Also note this function first verifies if
+ *              a variable length attribute is added then
+ *              it verifies if it is modified successfully.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+verify_modify_vlstr_attr(state_t *s, hid_t g, unsigned int which)
+{
+
+    bool ret = false;
+
+    ret = verify_group_vlstr_attr(s, g, which, false);
+    if (ret == true)
+        ret = verify_group_vlstr_attr(s, g, which, true);
+    return ret;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    verify_attrs_compact
+ *
+ * Purpose:     Verify if attributes are successfully added for the compact
+ *              storage.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigend max_c
+ *              The maximal number of attributes the compact storage
+ *              can hold
+ *
+ *              unsigned int which
+ *              Use to derieve the expected attribute value added
+ *              by the writer. It is also used to construct the
+ *              attribute names.
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This function is used by the "compact" test.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+verify_attrs_compact(state_t *s, hid_t g, unsigned max_c, unsigned int which)
+{
+
+    unsigned    u;
+    bool        ret          = true;
+    const char *aname_format = "attr-%u-%u";
+    char        attrname[VS_ATTR_NAME_LEN];
+
+    /* Need to verify the added attribute one by one. */
+    for (u = 0; u < max_c; u++) {
+
+        HDsprintf(attrname, aname_format, which, u);
+        if (false == vrfy_attr(s, g, u + which, attrname, which, true, true)) {
+            ret = false;
+            break;
+        }
+    }
+    return ret;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    verify_attrs_compact_dense
+ *
+ * Purpose:     Verify if attributes are successfully added first in the
+ *              compact storage then in the dense storage.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigend max_c
+ *              The maximal number of attributes the compact storage
+ *              can hold
+ *
+ *              unsigned int which
+ *              Use to derieve the expected attribute value added
+ *              by the writer. It is also used to construct
+ *              attribute names.
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This function is used by the "compact-dense" test.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+verify_attrs_compact_dense(state_t *s, hid_t g, unsigned max_c, unsigned int which)
+{
+
+    const char *aname_format = "attr-d-%u-%u";
+    char        attrname[VS_ATTR_NAME_LEN];
+
+    bool ret = verify_attrs_compact(s, g, max_c, which);
+
+    if (ret == true) {
+
+        /* Now the storage is in dense. Verify if the
+         * retrieved value is correct. */
+        HDsprintf(attrname, aname_format, max_c + which, 0);
+        ret = vrfy_attr(s, g, which + max_c, attrname, which, true, false);
+    }
+    return ret;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    verify_del_attrs_compact
+ *
+ * Purpose:     Verify if an attribute in compact storage is successfully
+ *              deleted.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigend max_c
+ *              The maximal number of attributes the compact storage
+ *              can hold
+ *
+ *              unsigned int which
+ *              Use to derieve the expected attribute value added
+ *              by the writer. It is also used to construct
+ *              attribute names.
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This function is used by the "compact-del" test.
+ *              Also note this function first verifies if
+ *              attributes are successfully added in compact storage then
+ *              it verifies if one added attribute is deleted  successfully.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+verify_del_attrs_compact(state_t *s, hid_t g, unsigned max_c, unsigned int which)
+{
+
+    const char *aname_format = "attr-%u-%u";
+    char        attrname[VS_ATTR_NAME_LEN];
+
+    bool ret = verify_attrs_compact(s, g, max_c, which);
+
+    if (ret == true) {
+        /* The writer only deletes the attribute attr-which-0 */
+        HDsprintf(attrname, aname_format, which, 0);
+        ret = verify_del_one_attr(s, g, attrname, true, true);
+    }
+
+    return ret;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    verify_del_attrs_compact_dense
+ *
+ * Purpose:     Verify if an attribute in dense storage is successfully
+ *              deleted.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigend max_c
+ *              The maximal number of attributes the compact storage
+ *              can hold
+ *
+ *              unsigned int which
+ *              Use to derieve the expected attribute value added
+ *              by the writer. It is also used to construct
+ *              attribute names.
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This function is used by the "dense-del" test.
+ *              Also note this function first verifies if
+ *              attributes are successfully added in compact storage then
+ *              in dense storage. Afterwards,
+ *              it verifies if one added attribute is deleted successfully.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+verify_del_attrs_compact_dense(state_t *s, hid_t g, unsigned max_c, unsigned int which)
+{
+
+    const char *aname_format = "attr-d-%u-%u";
+    char        attrname[VS_ATTR_NAME_LEN];
+
+    bool ret = verify_attrs_compact_dense(s, g, max_c, which);
+
+    if (ret == true) {
+        /* The writer only deletes the attribute attr-d-which-0 */
+        HDsprintf(attrname, aname_format, max_c + which, 0);
+        ret = verify_del_one_attr(s, g, attrname, true, false);
+    }
+
+    return ret;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    verify_del_attrs_compact_dense_compact
+ *
+ * Purpose:     verify that the attributes are deleted successfully
+ *              even the attribute storage changes from dense to
+ *              compact.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigend max_c
+ *              The maximal number of attributes the compact storage
+ *              can hold
+ *
+ *              unsigend min_d
+ *              The minimal number of attributes to be stored in
+ *              dense storage
+ *
+ *              unsigned int which
+ *              Use to derieve the expected attribute value added
+ *              by the writer. It is also used to construct
+ *              attribute names.
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This function is used by the "dense-del-to-compact" test.
+ *              Also note this function first verifies if
+ *              attributes are successfully added in compact storage then
+ *              in dense storage. Afterwards,
+ *              it verifies if some added attributes are deleted successfully
+ *              until the storage changes from dense to compact.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+verify_del_attrs_compact_dense_compact(state_t *s, hid_t g, unsigned max_c, unsigned min_d,
+                                       unsigned int which)
+{
+
+    unsigned    u;
+    const char *aname_format = "attr-%u-%u";
+    char        attrname[VS_ATTR_NAME_LEN];
+
+    /* Verify the attributes are added correctly from
+     * compact to dense storage*/
+    bool ret = verify_attrs_compact_dense(s, g, max_c, which);
+
+    if (ret == true) {
+
+        /* Then verify the deletion of attributes
+         * from dense to compact.
+         */
+        u = max_c + 1;
+        for (u--; u >= (min_d - 1); u--) {
+            HDsprintf(attrname, aname_format, which, max_c - u);
+            if (u == (min_d - 1))
+                ret = verify_del_one_attr(s, g, attrname, true, true);
+            else
+                ret = verify_del_one_attr(s, g, attrname, true, false);
+        }
+
+        /* Just verify one more deleted attribute by the writer.
+           The storage is still compact. */
+        HDsprintf(attrname, aname_format, max_c + which, 0);
+        ret = verify_del_one_attr(s, g, attrname, true, true);
+    }
+
+    return ret;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    verify_del_ohr_block_attr
+ *
+ * Purpose:     Verify that an attribute is added to force creation of
+ *              object header continuation block and remove this attribute
+ *              to delete the object header continuation block
+
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation, use to generate
+ *              group and attribute names.
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the verify_group() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+verify_del_ohr_block_attr(state_t *s, hid_t g, unsigned int which)
+{
+
+    bool        ret_value = false;
+    char        attrname[VS_ATTR_NAME_LEN];
+    const char *aname_format = "attr-%u";
+
+    ret_value = verify_default_group_attr(s, g, which);
+    if (ret_value == true) {
+        HDsprintf(attrname, aname_format, which);
+        ret_value = verify_del_one_attr(s, g, attrname, false, true);
+    }
+    return ret_value;
+}
+/*-------------------------------------------------------------------------
+ * Function:    verify_group_attribute
+ *
+ * Purpose:     Check the attribute test pattern and then call the
+ *              correponding verification function.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              HDF5 object ID (in this file: means group ID)
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation, use to generate
+ *              group and attribute names.
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the verify_group() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+verify_group_attribute(state_t *s, hid_t g, unsigned int which)
+{
+    char     test_pattern = s->at_pattern;
+    bool     ret          = false;
+    unsigned max_compact  = 0;
+    unsigned min_dense    = 0;
+    hid_t    gcpl         = H5I_INVALID_HID;
+
+    /* For tests "compact","compact-to-dense","compact-del",
+     *           "dense-del", "dense-del-to-compact",
+     *     the maximal number of attributes for the compact storage
+     *     and the minimal number of attributes for the dense storage
+     *     are needed. So obtain them here
+     * When testing the old-style group creation case, only max_compact
+     * matters. To reduce the testing time, we set max_compact to 2.*/
+    switch (test_pattern) {
+        case 'c':
+        case 't':
+        case 'C':
+        case 'D':
+        case 'T':
+            if (s->old_style_grp)
+                max_compact = 2;
+            else {
+                if ((gcpl = H5Gget_create_plist(g)) < 0) {
+                    printf("H5Gget_create_plist failed\n");
+                    TEST_ERROR;
+                }
+                if (H5Pget_attr_phase_change(gcpl, &max_compact, &min_dense) < 0) {
+                    printf("H5Pget_attr_phase_change failed\n");
+                    TEST_ERROR;
+                }
+                if (H5Pclose(gcpl) < 0) {
+                    printf("H5Pclose failed\n");
+                    TEST_ERROR;
+                }
+            }
+            break;
+        case 'v':
+        case 'd':
+        case 'M':
+        case 'm':
+        case 'r':
+        case 'a':
+        case 'R':
+        case ' ':
+        default:
+            break;
+    }
+
+    /* Distribute the verification test. */
+    switch (test_pattern) {
+        case 'c':
+            ret = verify_attrs_compact(s, g, max_compact, which);
+            break;
+        case 't':
+            ret = verify_attrs_compact_dense(s, g, max_compact, which);
+            break;
+        case 'C':
+            ret = verify_del_attrs_compact(s, g, max_compact, which);
+            break;
+        case 'D':
+            ret = verify_del_attrs_compact_dense(s, g, max_compact, which);
+            break;
+        case 'T':
+            ret = verify_del_attrs_compact_dense_compact(s, g, max_compact, min_dense, which);
+            break;
+        case 'M':
+            ret = verify_modify_attr(s, g, which);
+            break;
+        case 'v':
+            ret = verify_group_vlstr_attr(s, g, which, false);
+            break;
+        case 'r':
+            ret = verify_remove_vlstr_attr(s, g, which);
+            break;
+        case 'm':
+            ret = verify_modify_vlstr_attr(s, g, which);
+            break;
+        case 'R':
+            ret = verify_del_ohr_block_attr(s, g, which);
+            break;
+        case 'a':
+        case 'd':
+        case ' ':
+        default:
+            ret = verify_default_group_attr(s, g, which);
+            break;
+    }
+
+    return ret;
+
+error:
+    /* Still to finish the handshaking */
+    if (s->use_named_pipes && s->attr_test == true) {
+        np_rd_receive(s);
+        np_send_error(s, false);
+    }
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    verify_group
+ *
+ * Purpose:     verify the success of group creation and
+ *              carry out the test for attribute operations(add,delete etc.)
+ *              according to the attribute test pattern.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the main() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+verify_group(state_t *s, unsigned int which)
+{
+    char       name[sizeof("/group-9999999999")];
+    hid_t      g      = H5I_INVALID_HID;
+    bool       result = true;
+    H5G_info_t group_info;
+
+    /* The reader receives a message from the writer.Then sleep
+     * for a few ticks or stop the test if the received message
+     * is an error message.
+     */
+    if (s->use_named_pipes && true == s->attr_test) {
+
+        if (false == np_rd_receive(s)) {
+            H5_FAILED();
+            AT();
+            goto error2;
+        }
+        decisleep(s->tick_len * s->update_interval);
+        dbgf(1, "reader: finish reading the message: %d\n", s->np_notify);
+    }
+
+    if (which >= s->nsteps) {
+        printf("Number of created groups is out of bounds\n");
+        TEST_ERROR;
+    }
+
+    esnprintf(name, sizeof(name), "/group-%u", which);
+
+    if ((g = H5Gopen(s->file, name, H5P_DEFAULT)) < 0) {
+        printf("H5Gopen failed\n");
+        TEST_ERROR;
+    }
+
+    if (H5Gget_info(g, &group_info) < 0) {
+        printf("H5Gget_info failed\n");
+        TEST_ERROR;
+    }
+
+    dbgf(2, "Storage info is %d\n", group_info.storage_type);
+    if (s->old_style_grp) {
+        if (group_info.storage_type != H5G_STORAGE_TYPE_SYMBOL_TABLE) {
+            printf("Reader - Old-styled group: but the group is not in old-style. \n");
+            TEST_ERROR;
+        }
+        dbgf(2, "Reader: verify that the group is created with the old-style.\n");
+    }
+    else {
+        if (group_info.storage_type == H5G_STORAGE_TYPE_SYMBOL_TABLE) {
+            printf("Reader - The created group should NOT be in old-style . \n");
+            TEST_ERROR;
+        }
+        dbgf(2, "Reader: verify that the group is created with the new-style.\n");
+    }
+
+    /* If coming to an "object header continuation block" test,
+     * we need to check if this test behaves as expected. */
+    if (s->at_pattern == 'a' || s->at_pattern == 'R') {
+        if (false == check_ohr_num_chunk(g, true)) {
+            printf("An object header continuation block should NOT be created. \n");
+            printf("But it is created.\n");
+            printf("Verification of an 'object header continuation block test' failed.\n");
+            TEST_ERROR;
+        }
+    }
+
+    /* Reader sends an OK message back to the writer */
+    if (s->use_named_pipes && s->attr_test == true) {
+
+        if (np_rd_send(s) == false)
+            TEST_ERROR;
+        dbgf(1, "Reader: finish sending back the message: %d\n", s->np_notify);
+    }
+
+    /* Check if we need to skip the attribute test for this group. */
+    if (s->asteps != 0 && which % s->asteps == 0)
+        result = verify_group_attribute(s, g, which);
+    else
+        result = true;
+
+    if (H5Gclose(g) < 0) {
+        printf("H5Gclose failed\n");
+        TEST_ERROR;
+    }
+
+    return result;
+
+error:
+
+    H5E_BEGIN_TRY
+    {
+        H5Gclose(g);
+    }
+    H5E_END_TRY;
+
+    /* The reader sends an error message to the writer to stop the test.*/
+    if (s->use_named_pipes && s->attr_test == true)
+        np_send_error(s, false);
+
+error2:
+
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    create_group_id
+ *
+ * Purpose:     Create a group and return the group ID.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation
+ *              This is used to generate the group name.
+ *
+ *              bool dense_to_compact
+ *              true if this function is used to test the transition from dense to
+ *              compact, false if the test is from compact to dense.
+ *
+ * Return:      Success:    the group ID
+ *              Failure:    -1
+ *
+ * Note:        Only used by testing the link storage transit functions.
+ *-------------------------------------------------------------------------
+ */
+
+static hid_t
+create_group_id(state_t *s, unsigned int which, bool dense_to_compact)
+{
+
+    char       name[sizeof("/group-9999999999")];
+    hid_t      g    = H5I_INVALID_HID;
+    hid_t      gcpl = H5I_INVALID_HID;
+    H5G_info_t group_info;
+
+    if (which >= s->nsteps) {
+        printf("Number of created groups is out of bounds\n");
+        TEST_ERROR;
+    }
+
+    gcpl = H5Pcreate(H5P_GROUP_CREATE);
+    if (gcpl < 0) {
+        printf("H5Pcreate failed\n");
+        TEST_ERROR;
+    }
+
+    if (dense_to_compact) {
+        if (H5Pset_link_phase_change(gcpl, 2, 2) < 0) {
+            printf("H5Pset_link_phase_change failed for dense to compact.\n");
+            TEST_ERROR;
+        }
+    }
+    else {
+        if (H5Pset_link_phase_change(gcpl, 1, 1) < 0) {
+            printf("H5Pset_attr_phase_change failed for compact to dense.\n");
+            TEST_ERROR;
+        }
+    }
+
+    esnprintf(name, sizeof(name), "/group-%u", which);
+    if ((g = H5Gcreate2(s->file, name, H5P_DEFAULT, gcpl, H5P_DEFAULT)) < 0) {
+        printf("H5Gcreate2 failed\n");
+        TEST_ERROR;
+    }
+
+    if (H5Gget_info(g, &group_info) < 0) {
+        printf("H5Gget_info failed\n");
+        TEST_ERROR;
+    }
+
+    /* The storage type should always be compact when a group is created. */
+    if (group_info.storage_type != H5G_STORAGE_TYPE_COMPACT) {
+        printf("New-style group link storage test:. \n");
+        printf("    still be compact after group creation. \n");
+        TEST_ERROR;
+    }
+
+    if (H5Pclose(gcpl) < 0) {
+        printf("H5Pclose failed\n");
+        TEST_ERROR;
+    }
+
+    /* If a grp_op_test is turned on and named pipes are used,
+     * the writer should send and receive messages after the group creation.
+     * Writer sends a message to reader: a group is successfully created.
+     * then wait for the reader to verify and send an acknowledgement message back.*/
+    if (s->use_named_pipes && s->grp_op_test == true) {
+        dbgf(2, "Writer: ready to send the message: %d\n", s->np_notify + 1);
+        if (np_wr_send_receive(s) == false) {
+            H5_FAILED();
+            AT();
+            /* Note: This is (mostly) because the verification failure message
+             *       from the reader. So don't send the error message back to
+             *       the reader. Just stop the test. */
+            goto error2;
+        }
+    }
+
+    return g;
+
+error:
+    /* Writer needs to send an error message to the reader to stop the test*/
+    if (s->use_named_pipes && s->grp_op_test == true)
+        np_send_error(s, true);
+
+error2:
+
+    H5E_BEGIN_TRY
+    {
+        H5Pclose(gcpl);
+    }
+    H5E_END_TRY;
+
+    return -1;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    close_group_id
+ *
+ * Purpose:     Verify is a group is closed successfully.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              The ID of the group to be closed.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is used by the link storage transit functions.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+close_group_id(state_t *s, hid_t g)
+{
+
+    if (H5Gclose(g) < 0) {
+        printf("H5Gclose failed\n");
+        TEST_ERROR;
+    }
+
+    /* If a grp_op_test is turned on and named pipes are used, for
+     * link storage test,
+     * Writer sends a message to reader: the group is successfully closed.
+     * then wait for the reader to verify and send an acknowledgement message back.*/
+    if (s->use_named_pipes && s->grp_op_test == true) {
+        dbgf(2, "Writer: ready to send the message: %d\n", s->np_notify + 1);
+        if (np_wr_send_receive(s) == false) {
+            H5_FAILED();
+            AT();
+            goto error2;
+        }
+    }
+
+    return true;
+
+error:
+    /* Writer needs to send an error message to the reader to stop the test*/
+    if (s->use_named_pipes && s->grp_op_test == true)
+        np_send_error(s, true);
+
+error2:
+
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    create_group
+ *
+ * Purpose:     Create a group
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation
+ *              This is used to generate the group name.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the main() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+create_group(state_t *s, unsigned int which)
+{
+
+    char       name[sizeof("/group-9999999999")];
+    hid_t      g = H5I_INVALID_HID;
+    H5G_info_t group_info;
+
+    if (which >= s->nsteps) {
+        printf("Number of created groups is out of bounds\n");
+        TEST_ERROR;
+    }
+
+    esnprintf(name, sizeof(name), "/group-%u", which);
+    if ((g = H5Gcreate2(s->file, name, H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT)) < 0) {
+        printf("H5Gcreate2 failed\n");
+        TEST_ERROR;
+    }
+
+    if (H5Gget_info(g, &group_info) < 0) {
+        printf("H5Gget_info failed\n");
+        TEST_ERROR;
+    }
+
+    if (s->old_style_grp) {
+        if (group_info.storage_type != H5G_STORAGE_TYPE_SYMBOL_TABLE) {
+            printf("Old-styled group test: but the group is not in old-style. \n");
+            TEST_ERROR;
+        }
+        dbgf(2, "Writer: group is created with the old-style.\n");
+    }
+    else {
+        if (group_info.storage_type == H5G_STORAGE_TYPE_SYMBOL_TABLE) {
+            printf("The created group should NOT be in old-style . \n");
+            TEST_ERROR;
+        }
+        dbgf(2, "Writer: group is created with the new-style.\n");
+    }
+
+    if (H5Gclose(g) < 0) {
+        printf("H5Gclose failed\n");
+        TEST_ERROR;
+    }
+
+    /* Writer sends a message to reader,
+     * then wait for the reader to verify and send an acknowledgement message back.*/
+    if (s->use_named_pipes && s->grp_op_test == true) {
+        dbgf(2, "Writer: ready to send the message: %d\n", s->np_notify + 1);
+        if (np_wr_send_receive(s) == false) {
+            H5_FAILED();
+            AT();
+            goto error2;
+        }
+    }
+
+    return true;
+
+error:
+    /* Writer needs to send an error message to the reader to stop the test*/
+    if (s->use_named_pipes && s->grp_op_test == true)
+        np_send_error(s, true);
+
+error2:
+
+    H5E_BEGIN_TRY
+    {
+        H5Gclose(g);
+    }
+    H5E_END_TRY;
+
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    delete_one_link
+ *
+ * Purpose:     Delete a link(either hard/soft) in group operation tests.
+ *              according to the group test pattern.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t obj_id
+ *              The HDF5 object ID that the deleted link is attached to.
+ *
+ *              const char *name
+ *              The name of the link to be deleted.
+ *
+ *              short link_storage
+ *              <=0: link storage is ignored.
+ *              1: link storage should be compact after link deletion..
+ *              >1: link storage should be dense after link deletion.
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is used by delete_groups() and delete_links() functions.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+delete_one_link(state_t *s, hid_t obj_id, const char *name, short link_storage, unsigned int which)
+{
+
+    H5G_info_t group_info;
+
+    if (which >= s->nsteps) {
+        printf("Number of created groups is out of bounds\n");
+        TEST_ERROR;
+    }
+
+    if (H5Ldelete(obj_id, name, H5P_DEFAULT) < 0) {
+        printf("H5Ldelete failed\n");
+        TEST_ERROR;
+    }
+
+    if (link_storage > 0) {
+
+        if (s->old_style_grp) {
+            printf("Old style group doesn't support the indexed storage.\n");
+            TEST_ERROR;
+        }
+
+        if (H5Gget_info(obj_id, &group_info) < 0) {
+            printf("H5Gget_info failed\n");
+            TEST_ERROR;
+        }
+
+        if (link_storage == 1) {
+
+            if (group_info.storage_type != H5G_STORAGE_TYPE_COMPACT) {
+                printf("The group link storage should be compact. \n");
+                TEST_ERROR;
+            }
+        }
+        else {
+
+            if (group_info.storage_type != H5G_STORAGE_TYPE_DENSE) {
+                printf("The group link storage should be dense. \n");
+                TEST_ERROR;
+            }
+        }
+    }
+
+    /* Writer sends a message to reader:
+     * then wait for the reader to verify and send an acknowledgement message back.*/
+    if (s->use_named_pipes && s->grp_op_test == true) {
+        dbgf(2, "writer: ready to send the message: %d\n", s->np_notify + 1);
+        if (np_wr_send_receive(s) == false) {
+            H5_FAILED();
+            AT();
+            goto error2;
+        }
+    }
+
+    return true;
+
+error:
+    /* Writer needs to send an error message to the reader to stop the test*/
+    if (s->use_named_pipes && s->grp_op_test == true)
+        np_send_error(s, true);
+
+error2:
+
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    delete_group
+ *
+ * Purpose:     Delete a group and carry out group operations(add,delete etc.)
+ *              according to the group operation test pattern.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation
+ *              This is used to generate the group name
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the group_operations() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+delete_group(state_t *s, unsigned int which)
+{
+
+    char name[sizeof("/group-9999999999")];
+    bool ret_value = create_group(s, which);
+    if (ret_value == true) {
+        esnprintf(name, sizeof(name), "/group-%u", which);
+        ret_value = delete_one_link(s, s->file, name, 0, which);
+    }
+
+    return ret_value;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    move_one_group
+ *
+ * Purpose:     A helper function used by the move_group operation.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t obj_id
+ *              ID of the object this group is attached to
+ *
+ *              const char *name
+ *              The original group name
+ *
+ *              const char *newname
+ *              The new group name
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the move_group() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+move_one_group(state_t *s, hid_t obj_id, const char *name, const char *newname, unsigned int which)
+{
+
+    if (which >= s->nsteps) {
+        printf("Number of created groups is out of bounds\n");
+        TEST_ERROR;
+    }
+
+    if (H5Lmove(obj_id, name, obj_id, newname, H5P_DEFAULT, H5P_DEFAULT) < 0) {
+        printf("H5Ldelete failed\n");
+        TEST_ERROR;
+    }
+
+    /* Writer sends a message to reader:
+     * then wait for the reader to verify and send an acknowledgement message back.*/
+    if (s->use_named_pipes && s->grp_op_test == true) {
+        dbgf(2, "writer: ready to send the message: %d\n", s->np_notify + 1);
+        if (np_wr_send_receive(s) == false) {
+            H5_FAILED();
+            AT();
+            goto error2;
+        }
+    }
+
+    return true;
+
+error:
+    /* Writer needs to send an error message to the reader to stop the test*/
+    if (s->use_named_pipes && s->grp_op_test == true)
+        np_send_error(s, true);
+
+error2:
+
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    move_group
+ *
+ * Purpose:     Move a group to another group.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation
+ *              used to generate the group name.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the group_operations() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+move_group(state_t *s, unsigned int which)
+{
+
+    char name[sizeof("/group-9999999999")];
+    char new_name[sizeof("/new-group-9999999999")];
+    bool ret_value = create_group(s, which);
+    if (ret_value == true) {
+        esnprintf(name, sizeof(name), "/group-%u", which);
+        esnprintf(new_name, sizeof(new_name), "/new-group-%u", which);
+        ret_value = move_one_group(s, s->file, name, new_name, which);
+    }
+
+    return ret_value;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    insert_one_link
+ *
+ * Purpose:     A helper function used to attach a link to a group.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t obj_id
+ *              ID of the object this link is attached to
+ *
+ *              const char *name
+ *              The name of the target object used by creating links
+ *
+ *              const char *newname
+ *              The name of the linked objects
+ *
+ *              bool is_hard
+ *              true if inserting a hard link
+ *              false if inserting a soft link
+ *
+ *              short link_storage
+ *              <=0: link storage is ignored.
+ *              1: link storage should be compact.
+ *              >1: link storage should be dense.
+
+ *              unsigned int which
+ *              The number of iterations for group creation
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the insert_links and link storage transit functions.
+ *              For link storage, we test at both the writer and the reader.
+ *-------------------------------------------------------------------------
+*/
+
+static bool
+insert_one_link(state_t *s, hid_t obj_id, const char *name, const char *newname, bool is_hard,
+                short link_storage, unsigned int which)
+{
+
+    H5G_info_t group_info;
+
+    if (which >= s->nsteps) {
+        printf("Number of created groups is out of bounds\n");
+        TEST_ERROR;
+    }
+
+    /* For storage transit and insert_links cases, we
+     * create links in different style, just add a little
+     * variation of the tests.*/
+    if (is_hard) {
+        if (link_storage > 0) {
+            if (H5Lcreate_hard(s->file, name, obj_id, newname, H5P_DEFAULT, H5P_DEFAULT) < 0) {
+                printf("H5Lcreate_hard failed\n");
+                TEST_ERROR;
+            }
+        }
+        else {
+            if (H5Lcreate_hard(obj_id, name, obj_id, newname, H5P_DEFAULT, H5P_DEFAULT) < 0) {
+                printf("H5Lcreate_hard failed\n");
+                TEST_ERROR;
+            }
+        }
+    }
+    else {
+        if (link_storage > 0) {
+            if (H5Lcreate_soft("/", obj_id, newname, H5P_DEFAULT, H5P_DEFAULT) < 0) {
+                printf("H5Lcreate_soft failed\n");
+                TEST_ERROR;
+            }
+        }
+        else {
+            if (H5Lcreate_soft(name, obj_id, newname, H5P_DEFAULT, H5P_DEFAULT) < 0) {
+                printf("H5Lcreate_soft failed.\n");
+                TEST_ERROR;
+            }
+        }
+    }
+
+    if (link_storage > 0) {
+
+        if (s->old_style_grp) {
+            printf("Old style group doesn't support dense or compact storage.\n");
+            TEST_ERROR;
+        }
+
+        if (H5Gget_info(obj_id, &group_info) < 0) {
+            printf("H5Gget_info failed\n");
+            TEST_ERROR;
+        }
+
+        if (link_storage == 1) {
+            if (group_info.storage_type != H5G_STORAGE_TYPE_COMPACT) {
+                printf("The group link storage should be compact. \n");
+                TEST_ERROR;
+            }
+        }
+        else {
+            if (group_info.storage_type != H5G_STORAGE_TYPE_DENSE) {
+                printf("The group link storage should be dense. \n");
+                TEST_ERROR;
+            }
+        }
+    }
+
+    /* Writer sends a message to reader,
+     * then wait for the reader to verify and send an acknowledgement message back.*/
+    if (s->use_named_pipes && s->grp_op_test == true) {
+        dbgf(2, "writer: ready to send the message: %d\n", s->np_notify + 1);
+        if (np_wr_send_receive(s) == false) {
+            H5_FAILED();
+            AT();
+            goto error2;
+        }
+    }
+
+    return true;
+
+error:
+    /* Writer needs to send an error message to the reader to stop the test*/
+    if (s->use_named_pipes && s->grp_op_test == true)
+        np_send_error(s, true);
+
+error2:
+
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    insert_links
+ *
+ * Purpose:     create links with a group.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int which
+ *              The number of iterations
+ *              used to generate the group name.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the group_operations() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+insert_links(state_t *s, unsigned int which)
+{
+
+    char name[sizeof("/group-9999999999")];
+    char hd_name[sizeof("/hd-group-9999999999")];
+    char st_name[sizeof("/st-group-9999999999")];
+
+    bool ret_value = create_group(s, which);
+    if (ret_value == true) {
+        esnprintf(name, sizeof(name), "/group-%u", which);
+        esnprintf(hd_name, sizeof(hd_name), "/hd-group-%u", which);
+        esnprintf(st_name, sizeof(st_name), "/st-group-%u", which);
+        ret_value = insert_one_link(s, s->file, name, hd_name, true, 0, which);
+        if (ret_value == true)
+            ret_value = insert_one_link(s, s->file, name, st_name, false, 0, which);
+    }
+
+    return ret_value;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    delete_links
+ *
+ * Purpose:     create links with a group and then delete them successfully.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int which
+ *              The number of iterations
+ *              used to generate the group name.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the group_operations() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+delete_links(state_t *s, unsigned int which)
+{
+
+    char name[sizeof("/group-9999999999")];
+    char hd_name[sizeof("/hd-group-9999999999")];
+    char st_name[sizeof("/st-group-9999999999")];
+
+    bool ret_value = insert_links(s, which);
+    if (ret_value == true) {
+        esnprintf(name, sizeof(name), "/group-%u", which);
+        esnprintf(hd_name, sizeof(hd_name), "/hd-group-%u", which);
+        esnprintf(st_name, sizeof(st_name), "/st-group-%u", which);
+        ret_value = delete_one_link(s, s->file, hd_name, 0, which);
+        if (ret_value == true)
+            ret_value = delete_one_link(s, s->file, st_name, 0, which);
+    }
+
+    return ret_value;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    transit_storage_compact_to_dense
+ *
+ * Purpose:     Add links so that the link storage transits from
+ *              compact to dense.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int which
+ *              The number of iterations used to generate the group name.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the group_operations() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+transit_storage_compact_to_dense(state_t *s, unsigned int which)
+{
+
+    char name[sizeof("/group-9999999999")];
+    char hd_name[sizeof("/hd-group-9999999999")];
+    char st_name[sizeof("/st-group-9999999999")];
+
+    hid_t g = create_group_id(s, which, false);
+    if (g < 0) {
+        printf("create_group_id failed\n");
+        TEST_ERROR;
+    }
+
+    /* First insert a hard link, compact storage. */
+    esnprintf(name, sizeof(name), "/group-%u", which);
+    esnprintf(hd_name, sizeof(hd_name), "hd-group-%u", which);
+    if (insert_one_link(s, g, name, hd_name, true, 1, which) == false) {
+        printf("insert_one_link for compact storage failed\n");
+        TEST_ERROR;
+    }
+
+    /* Then insert a soft link, the storage becomes dense. */
+    esnprintf(st_name, sizeof(st_name), "st-group-%u", which);
+    if (insert_one_link(s, g, name, st_name, false, 2, which) == false) {
+        printf("insert_one_link for dense storage failed\n");
+        TEST_ERROR;
+    }
+
+    if (close_group_id(s, g) == false) {
+        printf("insert_one_link for dense storage failed\n");
+        TEST_ERROR;
+    }
+
+    return true;
+
+error:
+    H5E_BEGIN_TRY
+    {
+        H5Gclose(g);
+    }
+    H5E_END_TRY;
+
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    transit_storage_dense_to_compact
+ *
+ * Purpose:     Add or delete links so that the link storage transits from
+ *              compact to dense then to compact.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int which
+ *              The number of iterations used to generate the group name.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the group_operations() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+transit_storage_dense_to_compact(state_t *s, unsigned int which)
+{
+
+    char name[sizeof("/group-9999999999")];
+    char hd_name[sizeof("/hd-group-9999999999")];
+    char st_name[sizeof("st-group-9999999999")];
+    char st2_name[sizeof("st2-group-9999999999")];
+
+    hid_t g = create_group_id(s, which, true);
+    if (g < 0) {
+        printf("create_group_id failed\n");
+        TEST_ERROR;
+    }
+
+    /* Insert a link, storage is compact. */
+    esnprintf(name, sizeof(name), "/group-%u", which);
+    esnprintf(hd_name, sizeof(hd_name), "hd-group-%u", which);
+    if (insert_one_link(s, g, name, hd_name, true, 1, which) == false) {
+        printf("insert_one_link for compact storage failed\n");
+        TEST_ERROR;
+    }
+
+    /* Insert a link, storage is still compact. */
+    esnprintf(st_name, sizeof(st_name), "st-group-%u", which);
+    if (insert_one_link(s, g, name, st_name, false, 1, which) == false) {
+        printf("insert_one_link for compact storage failed\n");
+        TEST_ERROR;
+    }
+
+    /* Insert a link, storage becomes dense. */
+    esnprintf(st2_name, sizeof(st2_name), "st2-group-%u", which);
+    if (insert_one_link(s, g, name, st2_name, false, 2, which) == false) {
+        printf("insert_one_link for dense storage failed\n");
+        TEST_ERROR;
+    }
+
+    /* Delete a link, storage is still dense */
+    if (delete_one_link(s, g, st_name, 2, which) == false) {
+        printf("delete_one_link for dense storage failed\n");
+        TEST_ERROR;
+    }
+
+    /* Delete another link, storage becomes compact */
+    if (delete_one_link(s, g, st2_name, 1, which) == false) {
+        printf("delete_one_link for compact storage failed\n");
+        TEST_ERROR;
+    }
+
+    if (close_group_id(s, g) == false) {
+        printf("insert_one_link for dense storage failed\n");
+        TEST_ERROR;
+    }
+
+    return true;
+
+error:
+    H5E_BEGIN_TRY
+    {
+        H5Gclose(g);
+    }
+    H5E_END_TRY;
+
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    group_operations
+ *
+ * Purpose:     Carry out group and attribute operations(add,delete etc.)
+ *              according to the group operation and attribute test patterns.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the main() function. The check of attribute
+ *              operations is inside the write_group() function.
+ *-------------------------------------------------------------------------
+ */
+static bool
+group_operations(state_t *s, unsigned int which)
+{
+
+    bool ret_value    = false;
+    char test_pattern = s->grp_op_pattern;
+
+    switch (test_pattern) {
+        case 'c':
+            ret_value = create_group(s, which);
+            break;
+        case 'd':
+            ret_value = delete_group(s, which);
+            break;
+        case 'm':
+            ret_value = move_group(s, which);
+            break;
+        case 'i':
+            ret_value = insert_links(s, which);
+            break;
+        case 'D':
+            ret_value = delete_links(s, which);
+            break;
+        case 't':
+            ret_value = transit_storage_compact_to_dense(s, which);
+            break;
+        case 'T':
+            ret_value = transit_storage_dense_to_compact(s, which);
+            break;
+        case ' ':
+        default:
+            ret_value = write_group(s, which);
+            break;
+    }
+    return ret_value;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    vrfy_create_group
+ *
+ * Purpose:     Verify if a group can be created successfully.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation
+ *              used to generate the group name.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the verify_group_operations() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+vrfy_create_group(state_t *s, unsigned int which)
+{
+
+    char       name[sizeof("/group-9999999999")];
+    hid_t      g = H5I_INVALID_HID;
+    H5G_info_t group_info;
+
+    dbgf(2, "reader: ready to send the message: \n");
+
+    /* The reader receives a message from the writer.Then sleep
+     * for a few ticks or stop the test if the received message
+     * is an error message.
+     */
+    if (s->use_named_pipes && true == s->grp_op_test) {
+
+        if (false == np_rd_receive(s)) {
+            H5_FAILED();
+            AT();
+            goto error2;
+        }
+        decisleep(s->tick_len * s->update_interval);
+        dbgf(1, "reader: finish reading the message: %d\n", s->np_notify);
+    }
+
+    if (which >= s->nsteps) {
+        printf("Number of created groups is out of bounds\n");
+        TEST_ERROR;
+    }
+
+    esnprintf(name, sizeof(name), "/group-%u", which);
+
+    if ((g = H5Gopen(s->file, name, H5P_DEFAULT)) < 0) {
+        printf("H5Gopen failed\n");
+        TEST_ERROR;
+    }
+
+    if (H5Gget_info(g, &group_info) < 0) {
+        printf("H5Gget_info failed\n");
+        TEST_ERROR;
+    }
+
+    dbgf(2, "Storage info is %d\n", group_info.storage_type);
+    if (s->old_style_grp) {
+        if (group_info.storage_type != H5G_STORAGE_TYPE_SYMBOL_TABLE) {
+            printf("Reader - Old-styled group: but the group is not in old-style. \n");
+            TEST_ERROR;
+        }
+        dbgf(2, "Reader: verify that the group is created with the old-style.\n");
+    }
+    else {
+        if (group_info.storage_type == H5G_STORAGE_TYPE_SYMBOL_TABLE) {
+            printf("Reader - The created group should NOT be in old-style . \n");
+            TEST_ERROR;
+        }
+        dbgf(2, "Reader: verify that the group is created with the new-style.\n");
+    }
+
+    if (H5Gclose(g) < 0) {
+        printf("H5Gclose failed\n");
+        TEST_ERROR;
+    }
+
+    /* Reader sends an OK message back to the writer */
+    if (s->use_named_pipes && s->grp_op_test == true) {
+
+        if (np_rd_send(s) == false)
+            TEST_ERROR;
+        dbgf(1, "Reader: finish sending back the message: %d\n", s->np_notify);
+    }
+
+    return true;
+
+error:
+
+    H5E_BEGIN_TRY
+    {
+        H5Gclose(g);
+    }
+    H5E_END_TRY;
+
+    /* The reader sends an error message to the writer to stop the test.*/
+    if (s->use_named_pipes && s->grp_op_test == true)
+        np_send_error(s, false);
+
+error2:
+
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    vrfy_create_group_id
+ *
+ * Purpose:     Verify if a group is created successfully and return the group
+ *              ID.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation
+ *              used to generate the group name.
+ *
+ *              bool dense_to_compact
+ *              true if this function is used to test the transition from dense to
+ *              compact, false if the test is from compact to dense.
+ *
+ * Return:      Success:    the group ID
+ *              Failure:    -1
+ *
+ * Note:        This function is used by the link storage transit functions.
+ *-------------------------------------------------------------------------
+ */
+
+static hid_t
+vrfy_create_group_id(state_t *s, unsigned int which, bool dense_to_compact)
+{
+
+    char       name[sizeof("/group-9999999999")];
+    hid_t      g    = H5I_INVALID_HID;
+    hid_t      gcpl = H5I_INVALID_HID;
+    H5G_info_t group_info;
+    unsigned   max_compact = 0;
+    unsigned   min_dense   = 0;
+
+    dbgf(2, "reader: ready to receive a message: \n");
+    /* The reader receives a message from the writer.Then sleep
+     * for a few ticks or stop the test if the received message
+     * is an error message.
+     */
+    if (s->use_named_pipes && true == s->grp_op_test) {
+
+        if (false == np_rd_receive(s)) {
+            H5_FAILED();
+            AT();
+            goto error2;
+        }
+        decisleep(s->tick_len * s->update_interval);
+        dbgf(1, "reader: finish reading the message: %d\n", s->np_notify);
+    }
+
+    if (which >= s->nsteps) {
+        printf("Number of the created groups is out of bounds\n");
+        TEST_ERROR;
+    }
+
+    esnprintf(name, sizeof(name), "/group-%u", which);
+
+    if ((g = H5Gopen(s->file, name, H5P_DEFAULT)) < 0) {
+        printf("H5Gopen failed\n");
+        TEST_ERROR;
+    }
+
+    if ((gcpl = H5Gget_create_plist(g)) < 0) {
+        printf("H5Gget_create_plist failed\n");
+        TEST_ERROR;
+    }
+
+    if (H5Pget_link_phase_change(gcpl, &max_compact, &min_dense) < 0) {
+        printf("H5Pget_link_phase_change failed\n");
+        TEST_ERROR;
+    }
+
+    if (dense_to_compact) {
+        if (max_compact != 2) {
+            printf("For storage check from dense to compact:\n");
+            printf("    The max_compact should be 2.\n");
+            printf("    But the actual value is %d.\n", max_compact);
+            TEST_ERROR;
+        }
+        else if (min_dense != 2) {
+            printf("For storage check from dense to compact:\n");
+            printf("    The min_dense should be 2.\n");
+            printf("    But the actual value is %d.\n", min_dense);
+            TEST_ERROR;
+        }
+    }
+    else {
+        if (max_compact != 1) {
+            printf("For storage check from dense to compact:\n");
+            printf("    The max_compact should be 1.\n");
+            printf("    But the actual value is %d.\n", max_compact);
+            TEST_ERROR;
+        }
+        else if (min_dense != 1) {
+            printf("For storage check from dense to compact:\n");
+            printf("    The min_dense should be 1.\n");
+            printf("    But the actual value is %d.\n", min_dense);
+            TEST_ERROR;
+        }
+    }
+
+    if (H5Pclose(gcpl) < 0) {
+        printf("H5Pclose failed\n");
+        TEST_ERROR;
+    }
+
+    if (H5Gget_info(g, &group_info) < 0) {
+        printf("H5Gget_info failed\n");
+        TEST_ERROR;
+    }
+
+    /* When the group is created, the storage type is always compact. */
+    if (group_info.storage_type != H5G_STORAGE_TYPE_COMPACT) {
+        printf("Old-styled group test: but the group is not in old-style. \n");
+        TEST_ERROR;
+    }
+
+    dbgf(2, "Storage info is %d\n", group_info.storage_type);
+
+    /* Reader sends an OK message back to the reader */
+    if (s->use_named_pipes && s->grp_op_test == true) {
+
+        if (np_rd_send(s) == false)
+            TEST_ERROR;
+        dbgf(1, "Reader: finish sending back the message: %d\n", s->np_notify);
+    }
+
+    return g;
+
+error:
+
+    H5E_BEGIN_TRY
+    {
+        H5Gclose(g);
+        H5Pclose(gcpl);
+    }
+    H5E_END_TRY;
+
+    /* The reader sends an error message to the writer to stop the test.*/
+    if (s->use_named_pipes && s->grp_op_test == true)
+        np_send_error(s, false);
+
+error2:
+
+    return -1;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    vrfy_close_group_id
+ *
+ * Purpose:     Verify if a group is closed successfully.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t g
+ *              The ID of the group to be closed.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is used by the link storage transit functions.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+vrfy_close_group_id(state_t *s, hid_t g)
+{
+
+    /* The reader receives a message from the writer.Then sleep
+     * for a few ticks or stop the test if the received message
+     * is an error message.
+     */
+    if (s->use_named_pipes && true == s->grp_op_test) {
+
+        if (false == np_rd_receive(s)) {
+            H5_FAILED();
+            AT();
+            goto error2;
+        }
+        decisleep(s->tick_len * s->update_interval);
+        dbgf(1, "reader: finish reading the message: %d\n", s->np_notify);
+    }
+
+    if (H5Gclose(g) < 0) {
+        printf("H5Gclose failed\n");
+        TEST_ERROR;
+    }
+
+    /* Reader sends an OK message back to the reader */
+    if (s->use_named_pipes && s->grp_op_test == true) {
+
+        if (np_rd_send(s) == false)
+            TEST_ERROR;
+        dbgf(1, "Reader: finish sending back the message: %d\n", s->np_notify);
+    }
+
+    return true;
+
+error:
+
+    /* The reader sends an error message to the writer to stop the test.*/
+    if (s->use_named_pipes && s->grp_op_test == true)
+        np_send_error(s, false);
+
+error2:
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    vrfy_one_link_exist
+ *
+ * Purpose:     Verify if a link exists or not. The link storage is
+ *              also checked.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t obj_id
+ *              The ID of the object the link is attached to
+ *
+ *              bool expect_exist
+ *              A flag that indicates if this link is expected to exist
+ *
+ *              short link_storage
+ *              <=0: link storage check is ignored.
+ *              1: link storage is expected to be compact.
+ *              >1: link storage is expected to be dense.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        Helper function to check if links are inserted or deleted.
+ *              The link storage is also checked.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+vrfy_one_link_exist(state_t *s, hid_t obj_id, const char *name, bool expect_exist, short link_storage)
+{
+
+    int        link_exists = 0;
+    H5G_info_t group_info;
+
+    dbgf(2, "reader: ready to send the message: \n");
+    /* The reader receives a message from the writer.Then sleep
+     * for a few ticks or stop the test if the received message
+     * is an error message.
+     */
+    if (s->use_named_pipes && true == s->grp_op_test) {
+
+        if (false == np_rd_receive(s)) {
+            H5_FAILED();
+            AT();
+            goto error2;
+        }
+        decisleep(s->tick_len * s->update_interval);
+        dbgf(1, "reader: finish reading the message: %d\n", s->np_notify);
+    }
+
+    link_exists = H5Lexists(obj_id, name, H5P_DEFAULT);
+
+    if (link_exists < 0) {
+        printf("H5Lexists error\n");
+        TEST_ERROR;
+    }
+    else if (link_exists == 1) {
+        if (expect_exist == false) {
+            printf("This link should be moved or deleted but it still exists.\n");
+            TEST_ERROR;
+        }
+    }
+    else if (link_exists == 0) {
+        if (expect_exist == true) {
+            printf("This link should exist but it is moved or deleted.\n");
+            TEST_ERROR;
+        }
+    }
+
+    if (link_storage > 0) {
+
+        if (s->old_style_grp) {
+            printf("Old style group doesn't support the indexed storage.\n");
+            TEST_ERROR;
+        }
+
+        if (H5Gget_info(obj_id, &group_info) < 0) {
+            printf("H5Gget_info failed\n");
+            TEST_ERROR;
+        }
+
+        if (link_storage == 1) {
+            if (group_info.storage_type != H5G_STORAGE_TYPE_COMPACT) {
+                printf("The group link storage should be compact. \n");
+                TEST_ERROR;
+            }
+        }
+        else {
+            if (group_info.storage_type != H5G_STORAGE_TYPE_DENSE) {
+                printf("The group link storage should be dense. \n");
+                TEST_ERROR;
+            }
+        }
+    }
+
+    /* Reader sends an OK message back to the reader */
+    if (s->use_named_pipes && s->grp_op_test == true) {
+        if (np_rd_send(s) == false) {
+            TEST_ERROR;
+        }
+        dbgf(1, "Reader: finish sending back the message: %d\n", s->np_notify);
+    }
+
+    return true;
+
+error:
+
+    /* The reader sends an error message to the writer to stop the test.*/
+    if (s->use_named_pipes && s->grp_op_test == true)
+        np_send_error(s, false);
+
+error2:
+
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    vrfy_delete_group
+ *
+ * Purpose:     Verify if a group can be deleted successfully.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation
+ *              used to generate the group name.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the verify_group_operations() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+vrfy_delete_group(state_t *s, unsigned int which)
+{
+
+    bool ret_value = false;
+    char name[sizeof("/group-9999999999")];
+
+    ret_value = vrfy_create_group(s, which);
+    if (ret_value == true) {
+        esnprintf(name, sizeof(name), "/group-%u", which);
+        ret_value = vrfy_one_link_exist(s, s->file, name, false, 0);
+    }
+
+    return ret_value;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    vrfy_move_one_group
+ *
+ * Purpose:     A helper function to verify the move_group operation successfully.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              hid_t obj_id
+ *              ID of the object this group is attached to
+ *
+ *              const char *name
+ *              The original group name
+ *
+ *              const char *newname
+ *              The new group name
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the verify_move_group() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+vrfy_move_one_group(state_t *s, hid_t obj_id, const char *name, const char *newname, unsigned int which)
+{
+
+    hid_t      g = H5I_INVALID_HID;
+    H5G_info_t group_info;
+    int        link_exists = 0;
+
+    dbgf(2, "reader: ready to send the message: \n");
+    /* The reader receives a message from the writer.Then sleep
+     * for a few ticks or stop the test if the received message
+     * is an error message.
+     */
+    if (s->use_named_pipes && true == s->grp_op_test) {
+
+        if (false == np_rd_receive(s)) {
+            H5_FAILED();
+            AT();
+            goto error2;
+        }
+        decisleep(s->tick_len * s->update_interval);
+        dbgf(1, "reader: finish reading the message: %d\n", s->np_notify);
+    }
+
+    if (which >= s->nsteps) {
+        printf("Number of created groups is out of bounds\n");
+        TEST_ERROR;
+    }
+
+    link_exists = H5Lexists(obj_id, name, H5P_DEFAULT);
+    if (link_exists < 0) {
+        printf("H5Lexists error\n");
+        TEST_ERROR;
+    }
+    else if (link_exists == 1) {
+        printf("This link should be moved but it still exists.\n");
+        TEST_ERROR;
+    }
+
+    if ((g = H5Gopen(obj_id, newname, H5P_DEFAULT)) < 0) {
+        printf("H5Gopen failed\n");
+        TEST_ERROR;
+    }
+
+    if (H5Gget_info(g, &group_info) < 0) {
+        printf("H5Gget_info failed\n");
+        TEST_ERROR;
+    }
+
+    dbgf(2, "Storage info is %d\n", group_info.storage_type);
+    if (s->old_style_grp) {
+        if (group_info.storage_type != H5G_STORAGE_TYPE_SYMBOL_TABLE) {
+            printf("Reader - Old-styled group: but the group is not in old-style. \n");
+            TEST_ERROR;
+        }
+        dbgf(2, "Reader: verify that the group is created with the old-style.\n");
+    }
+    else {
+        if (group_info.storage_type == H5G_STORAGE_TYPE_SYMBOL_TABLE) {
+            printf("Reader - The created group should NOT be in old-style . \n");
+            TEST_ERROR;
+        }
+        dbgf(2, "Reader: verify that the group is created with the new-style.\n");
+    }
+
+    if (H5Gclose(g) < 0) {
+        printf("H5Gclose failed\n");
+        TEST_ERROR;
+    }
+
+    /* Reader sends an OK message back to the reader */
+    if (s->use_named_pipes && s->grp_op_test == true) {
+
+        if (np_rd_send(s) == false) {
+            TEST_ERROR;
+        }
+        dbgf(1, "Reader: finish sending back the message: %d\n", s->np_notify);
+    }
+
+    return true;
+
+error:
+
+    H5E_BEGIN_TRY
+    {
+        H5Gclose(g);
+    }
+    H5E_END_TRY;
+
+    /* The reader sends an error message to the writer to stop the test.*/
+    if (s->use_named_pipes && s->grp_op_test == true)
+        np_send_error(s, false);
+
+error2:
+
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    vrfy_move_group
+ *
+ * Purpose:     Verify if a group can be moved successfully.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation
+ *              used to generate the group name.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the verify_group_operations() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+vrfy_move_group(state_t *s, unsigned int which)
+{
+
+    char name[sizeof("/group-9999999999")];
+    char new_name[sizeof("/new-group-9999999999")];
+    bool ret_value = vrfy_create_group(s, which);
+    if (ret_value == true) {
+        esnprintf(name, sizeof(name), "/group-%u", which);
+        esnprintf(new_name, sizeof(new_name), "/new-group-%u", which);
+        ret_value = vrfy_move_one_group(s, s->file, name, new_name, which);
+    }
+
+    return ret_value;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    vrfy_insert_links
+ *
+ * Purpose:     Verify if the links are inserted successfully.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation
+ *              used to generate the group name.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the verify_group_operations() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+vrfy_insert_links(state_t *s, unsigned int which)
+{
+
+    bool ret_value = false;
+    char hd_name[sizeof("/hd-group-9999999999")];
+    char st_name[sizeof("/st-group-9999999999")];
+
+    ret_value = vrfy_create_group(s, which);
+
+    if (ret_value == true) {
+        esnprintf(hd_name, sizeof(hd_name), "/hd-group-%u", which);
+        esnprintf(st_name, sizeof(st_name), "/st-group-%u", which);
+        ret_value = vrfy_one_link_exist(s, s->file, hd_name, true, 0);
+        if (ret_value == true)
+            ret_value = vrfy_one_link_exist(s, s->file, st_name, true, 0);
+    }
+
+    return ret_value;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    vrfy_delete_links
+ *
+ * Purpose:     Verify if the links created with a group are deleted successfully.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation
+ *              used to generate the group name.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the verify_group_operations() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+vrfy_delete_links(state_t *s, unsigned int which)
+{
+
+    bool ret_value = false;
+    char hd_name[sizeof("/hd-group-9999999999")];
+    char st_name[sizeof("/st-group-9999999999")];
+
+    /* First verify if the links are inserted correctly */
+    ret_value = vrfy_insert_links(s, which);
+
+    /* Then if these links are deleted correctly. */
+    if (ret_value == true) {
+        esnprintf(hd_name, sizeof(hd_name), "/hd-group-%u", which);
+        esnprintf(st_name, sizeof(st_name), "/st-group-%u", which);
+        ret_value = vrfy_one_link_exist(s, s->file, hd_name, false, 0);
+        if (ret_value == true)
+            ret_value = vrfy_one_link_exist(s, s->file, st_name, false, 0);
+    }
+
+    return ret_value;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    vrfy_transit_storage_compact_to_dense
+ *
+ * Purpose:     Verify if the link storage successfully transits from
+ *              compact to dense.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation
+ *              used to generate the group name.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the verify_group_operations() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+vrfy_transit_storage_compact_to_dense(state_t *s, unsigned int which)
+{
+
+    hid_t g = H5I_INVALID_HID;
+    char  hd_name[sizeof("hd-group-9999999999")];
+    char  st_name[sizeof("st-group-9999999999")];
+
+    g = vrfy_create_group_id(s, which, false);
+    if (g < 0) {
+        printf("verify create_group_id failed\n");
+        TEST_ERROR;
+    }
+
+    esnprintf(hd_name, sizeof(hd_name), "hd-group-%u", which);
+    if (vrfy_one_link_exist(s, g, hd_name, true, 1) == false) {
+        printf("verify the compact storage failed for 'link compact to dense' test\n");
+        TEST_ERROR;
+    }
+
+    esnprintf(st_name, sizeof(st_name), "st-group-%u", which);
+    if (vrfy_one_link_exist(s, g, st_name, true, 2) == false) {
+        printf("verify the dense link storage failed for 'link compact to dense' test\n");
+        TEST_ERROR;
+    }
+
+    if (vrfy_close_group_id(s, g) == false) {
+        printf("verify the group close for 'link compact to dense' test\n");
+        TEST_ERROR;
+    }
+    return true;
+
+error:
+    H5E_BEGIN_TRY
+    {
+        H5Gclose(g);
+    }
+    H5E_END_TRY;
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    vrfy_transit_storage_dense_to_compact
+ *
+ * Purpose:     Verify if the link storage successfully transits from
+ *              compact to dense then to compact.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation
+ *              used to generate the group name.
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the verify_group_operations() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+vrfy_transit_storage_dense_to_compact(state_t *s, unsigned int which)
+{
+
+    hid_t g = H5I_INVALID_HID;
+    char  hd_name[sizeof("hd-group-9999999999")];
+    char  st_name[sizeof("st-group-9999999999")];
+    char  st2_name[sizeof("st2-group-9999999999")];
+
+    g = vrfy_create_group_id(s, which, true);
+    if (g < 0) {
+        printf("verify create_group_id failed\n");
+        TEST_ERROR;
+    }
+
+    /* Add a link, verify it is still the compact storage */
+    esnprintf(hd_name, sizeof(hd_name), "hd-group-%u", which);
+    if (vrfy_one_link_exist(s, g, hd_name, true, 1) == false) {
+        printf("verify the compact storage failed for 'link compact to dense' test\n");
+        TEST_ERROR;
+    }
+
+    /* Add another link, verify it is still the compact storage */
+    esnprintf(st_name, sizeof(st_name), "st-group-%u", which);
+    if (vrfy_one_link_exist(s, g, st_name, true, 1) == false) {
+        printf("verify the compact link storage failed for 'link compact to dense' test\n");
+        TEST_ERROR;
+    }
+
+    /* Add the third link, verify it becomes the dense storage */
+    esnprintf(st2_name, sizeof(st2_name), "st2-group-%u", which);
+    if (vrfy_one_link_exist(s, g, st2_name, true, 2) == false) {
+        printf("verify the dense link storage failed for 'link compact to dense' test\n");
+        TEST_ERROR;
+    }
+
+    /* Remove a link, verify the link doesn't exist and still dense storage */
+    if (vrfy_one_link_exist(s, g, st_name, false, 2) == false) {
+        printf("verify the dense link storage failed for 'link compact to dense' test\n");
+        TEST_ERROR;
+    }
+
+    /* Remove a link, verify the link doesn't exist and it becomes compact storage */
+    if (vrfy_one_link_exist(s, g, st2_name, false, 1) == false) {
+        printf("verify the compact link storage failed for 'link compact to dense' test\n");
+        TEST_ERROR;
+    }
+
+    if (vrfy_close_group_id(s, g) == false) {
+        printf("verify the group close for 'link compact to dense' test\n");
+        TEST_ERROR;
+    }
+    return true;
+
+error:
+    H5E_BEGIN_TRY
+    {
+        H5Gclose(g);
+    }
+    H5E_END_TRY;
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    verify_group_operations
+ *
+ * Purpose:     verify the success of group creation and
+ *              carry out the test for attribute operations(add,delete etc.)
+ *              according to the attribute test pattern.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file, named pipe
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int which
+ *              The number of iterations for group creation
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is called by the main() function.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+verify_group_operations(state_t *s, unsigned int which)
+{
+    bool ret_value    = false;
+    char test_pattern = s->grp_op_pattern;
+
+    switch (test_pattern) {
+        case 'c':
+            ret_value = vrfy_create_group(s, which);
+            break;
+        case 'd':
+            ret_value = vrfy_delete_group(s, which);
+            break;
+        case 'm':
+            ret_value = vrfy_move_group(s, which);
+            break;
+        case 'i':
+            ret_value = vrfy_insert_links(s, which);
+            break;
+        case 'D':
+            ret_value = vrfy_delete_links(s, which);
+            break;
+        case 't':
+            ret_value = vrfy_transit_storage_compact_to_dense(s, which);
+            break;
+        case 'T':
+            ret_value = vrfy_transit_storage_dense_to_compact(s, which);
+            break;
+        case ' ':
+        default:
+            ret_value = verify_group(s, which);
+            break;
+    }
+    return ret_value;
+}
+
+int
+main(int argc, char **argv)
+{
+    hid_t                 fapl = H5I_INVALID_HID, fcpl = H5I_INVALID_HID;
+    unsigned              step;
+    bool                  writer = false;
+    state_t               s;
+    const char *          personality;
+    H5F_vfd_swmr_config_t config;
+    const char *          fifo_writer_to_reader = "./fifo_group_writer_to_reader";
+    const char *          fifo_reader_to_writer = "./fifo_group_reader_to_writer";
+    int                   fd_writer_to_reader = -1, fd_reader_to_writer = -1;
+    int                   notify = 0, verify = 0;
+    bool                  wg_ret = false;
+    bool                  vg_ret = false;
+
+    if (!state_init(&s, argc, argv)) {
+        printf("state_init failed\n");
+        TEST_ERROR;
+    }
+
+    personality = HDstrstr(s.progname, "vfd_swmr_gperf_");
+
+    if (personality != NULL && HDstrcmp(personality, "vfd_swmr_gperf_writer") == 0)
+        writer = true;
+    else if (personality != NULL && HDstrcmp(personality, "vfd_swmr_gperf_reader") == 0)
+        writer = false;
+    else {
+        printf("unknown personality, expected vfd_swmr_gperf_{reader,writer}\n");
+        TEST_ERROR;
+    }
+
+    /* config, tick_len, max_lag, writer, flush_raw_data, md_pages_reserved, md_file_path */
+    init_vfd_swmr_config(&config, 4, 7, writer, FALSE, 128, "./group-shadow");
+
+    /* If old-style option is chosen, use the earliest file format(H5F_LIBVER_EARLIEST)
+     * as the second parameter of H5Pset_libver_bound() that is called by
+     * vfd_swmr_create_fapl. Otherwise, the latest file format(H5F_LIBVER_LATEST)
+     * should be used as the second parameter of H5Pset_libver_bound().
+     * Also pass the use_vfd_swmr, only_meta_page, config to vfd_swmr_create_fapl().*/
+    if ((fapl = vfd_swmr_create_fapl(!s.old_style_grp, s.use_vfd_swmr, true, &config)) < 0) {
+        printf("vfd_swmr_create_fapl failed\n");
+        TEST_ERROR;
+    }
+
+    if ((fcpl = H5Pcreate(H5P_FILE_CREATE)) < 0) {
+        printf("H5Pcreate failed\n");
+        TEST_ERROR;
+    }
+
+    if (H5Pset_file_space_strategy(fcpl, H5F_FSPACE_STRATEGY_PAGE, false, 1) < 0) {
+        printf("H5Pset_file_space_strategy failed\n");
+        TEST_ERROR;
+    }
+
+    if (writer)
+        s.file = H5Fcreate(s.filename, H5F_ACC_TRUNC, fcpl, fapl);
+    else
+        s.file = H5Fopen(s.filename, H5F_ACC_RDONLY, fapl);
+
+    if (s.file < 0) {
+        printf("H5Fcreate/open failed\n");
+        TEST_ERROR;
+    }
+
+    /* Use two named pipes(FIFO) to coordinate the writer and reader for
+     * two-way communication so that the two sides can move forward together.
+     * One is for the writer to write to the reader.
+     * The other one is for the reader to signal the writer.  */
+    if (s.use_named_pipes && writer) {
+        /* Writer creates two named pipes(FIFO) */
+        if (HDmkfifo(fifo_writer_to_reader, 0600) < 0) {
+            printf("HDmkfifo failed\n");
+            TEST_ERROR;
+        }
+
+        if (HDmkfifo(fifo_reader_to_writer, 0600) < 0) {
+            printf("HDmkfifo failed\n");
+            TEST_ERROR;
+        }
+    }
+
+    /* Both the writer and reader open the pipes */
+    if (s.use_named_pipes && (fd_writer_to_reader = HDopen(fifo_writer_to_reader, O_RDWR)) < 0) {
+        printf("HDopen failed\n");
+        TEST_ERROR;
+    }
+
+    if (s.use_named_pipes && (fd_reader_to_writer = HDopen(fifo_reader_to_writer, O_RDWR)) < 0) {
+        printf("HDopen failed\n");
+        TEST_ERROR;
+    }
+
+    /* Pass the named pipe information to the struct of state_t s, for attribute tests.*/
+    if (s.use_named_pipes) {
+        s.np_fd_w_to_r = fd_writer_to_reader;
+        s.np_fd_r_to_w = fd_reader_to_writer;
+        s.np_notify    = notify;
+        s.np_verify    = verify;
+        s.tick_len     = config.tick_len;
+        s.max_lag      = config.max_lag;
+    }
+
+    /* For attribute test, force the named pipe to communicate in every step.
+     * This will avoid the fake verification error from the reader when using the named pipe.
+     * If the named pipe is not forced to communicate in every step, the reader may go ahead
+     * to verify the group and the attribute operations before the writer has a chance to
+     * carry out the corresponding operations. */
+    if (s.attr_test && s.use_named_pipes)
+        s.csteps = 1;
+
+    /* For group operation test, force the named pipe to communicate in every step. */
+    if (s.grp_op_test && s.use_named_pipes)
+        s.csteps = 1;
+
+    if (writer) {
+        for (step = 0; step < s.nsteps; step++) {
+            dbgf(2, "writer: step %d\n", step);
+
+            wg_ret = group_operations(&s, step);
+
+            if (wg_ret == false) {
+
+                /* At communication interval, notifies the reader about the failure and quit */
+                if (s.use_named_pipes && s.attr_test != true && s.grp_op_test != true && step % s.csteps == 0)
+                    np_send_error(&s, true);
+                printf("write_group failed at step %d\n", step);
+                TEST_ERROR;
+            }
+            else {
+
+                /* At communication interval, notifies the reader and waits for its response */
+                if (s.use_named_pipes && s.attr_test != true && s.grp_op_test != true &&
+                    step % s.csteps == 0) {
+
+                    if (np_wr_send_receive(&s) == false) {
+                        printf("writer: write group - verification failed.\n");
+                        TEST_ERROR;
+                    }
+                }
+            }
+        }
+        s.mean_time = s.total_time/s.nsteps;
+         fprintf(stdout, "group creation min. time = %lf\n", s.min_time);
+         fprintf(stdout, "group creation max. time = %lf\n", s.max_time);
+         fprintf(stdout, "group creation mean time = %lf\n", s.mean_time);
+         fprintf(stdout, "group creation total time = %lf\n", s.total_time);
+    }
+    else {
+        for (step = 0; step < s.nsteps; step++) {
+            dbgf(1, "reader: step %d\n", step);
+
+            /* At communication interval, waits for the writer to finish creation before starting verification
+             */
+            if (s.use_named_pipes && s.attr_test != true && s.grp_op_test != true && step % s.csteps == 0) {
+                if (false == np_rd_receive(&s)) {
+                    TEST_ERROR;
+                }
+            }
+
+            /* For the default test, wait for a few ticks for the update to happen */
+            if (s.use_named_pipes && s.attr_test == false)
+                decisleep(config.tick_len * s.update_interval);
+
+            vg_ret = verify_group_operations(&s, step);
+
+            if (vg_ret == false) {
+
+                printf("verify_group_operations failed\n");
+
+                /* At communication interval, tell the writer about the failure and exit */
+                if (s.use_named_pipes && s.attr_test != true && s.grp_op_test != true && step % s.csteps == 0)
+                    np_send_error(&s, false);
+                TEST_ERROR;
+            }
+            else {
+
+                /* Send back the same nofity value for acknowledgement to tell the writer
+                 * move to the next step. */
+                if (s.use_named_pipes && s.attr_test != true && s.grp_op_test != true &&
+                    step % s.csteps == 0) {
+                    if (np_rd_send(&s) == false) {
+                        TEST_ERROR;
+                    }
+                }
+            }
+        }
+    }
+
+    if (H5Pclose(fapl) < 0) {
+        printf("H5Pclose failed\n");
+        TEST_ERROR;
+    }
+
+    if (H5Pclose(fcpl) < 0) {
+        printf("H5Pclose failed\n");
+        TEST_ERROR;
+    }
+
+    if (H5Sclose(s.one_by_one_sid) < 0) {
+        printf("H5Sclose failed\n");
+        TEST_ERROR;
+    }
+
+    if (H5Fclose(s.file) < 0) {
+        printf("H5Fclose failed\n");
+        TEST_ERROR;
+    }
+
+    /* Both the writer and reader close the named pipes */
+    if (s.use_named_pipes && HDclose(fd_writer_to_reader) < 0) {
+        printf("HDclose failed\n");
+        TEST_ERROR;
+    }
+
+    if (s.use_named_pipes && HDclose(fd_reader_to_writer) < 0) {
+        printf("HDclose failed\n");
+        TEST_ERROR;
+    }
+
+    /* Reader finishes last and deletes the named pipes */
+    if (s.use_named_pipes && !writer) {
+        if (HDremove(fifo_writer_to_reader) != 0) {
+            printf("HDremove failed\n");
+            TEST_ERROR;
+        }
+
+        if (HDremove(fifo_reader_to_writer) != 0) {
+            printf("HDremove failed\n");
+            TEST_ERROR;
+        }
+    }
+
+    return EXIT_SUCCESS;
+
+error:
+    H5E_BEGIN_TRY
+    {
+        H5Pclose(fapl);
+        H5Pclose(fcpl);
+        H5Sclose(s.one_by_one_sid);
+        H5Fclose(s.file);
+    }
+    H5E_END_TRY;
+
+    if (s.use_named_pipes && fd_writer_to_reader >= 0)
+        HDclose(fd_writer_to_reader);
+
+    if (s.use_named_pipes && fd_reader_to_writer >= 0)
+        HDclose(fd_reader_to_writer);
+
+    if (s.use_named_pipes && !writer) {
+        HDremove(fifo_writer_to_reader);
+        HDremove(fifo_reader_to_writer);
+    }
+
+    return EXIT_FAILURE;
+}
+
+#else /* H5_HAVE_WIN32_API */
+
+int
+main(void)
+{
+    HDfprintf(stderr, "Non-POSIX platform. Skipping.\n");
+    return EXIT_SUCCESS;
+} /* end main() */
+
+#endif /* H5_HAVE_WIN32_API */