Merge branch 'vfd_swmr_log' into feature/vfd_swmr

9 files changed, 3140 insertions, 2 deletions

diff --git a/src/H5FDvfd_swmr_private.h b/src/H5FDvfd_swmr_private.h
index 12fd2e2..a2c29cd 100644
--- a/src/H5FDvfd_swmr_private.h
+++ b/src/H5FDvfd_swmr_private.h
@@ -84,4 +84,13 @@ H5_DLL herr_t H5F_vfd_swmr_insert_entry_eot(struct H5F_t *f);
 H5_DLL void   H5F_vfd_swmr_update_entry_eot(eot_queue_entry_t *);
 H5_DLL herr_t H5F_dump_eot_queue(void);
 
+/***************************************/
+/* Log Macros and Functions            */
+/***************************************/
+
+/* VFD SWMR Helper macros to calcuate the elapsed time */
+/* The total time is in seconds */
+#define TOTAL_TIME_PASSED(X, Y)                                                                              \
+    ((double)((Y.tv_sec - X.tv_sec) * 1000000000 + (Y.tv_nsec - X.tv_nsec))) / 1000000000.0
+
 #endif /* H5FDvfd_swmr_private_H */
diff --git a/src/H5Fint.c b/src/H5Fint.c
index e650878..6827158 100644
--- a/src/H5Fint.c
+++ b/src/H5Fint.c
@@ -2013,7 +2013,23 @@ H5F_open(const char *name, unsigned flags, hid_t fcpl_id, hid_t fapl_id)
 
     /* Short cuts */
     shared = file->shared;
-    lf     = shared->lf;
+
+    /* Set up the VFD SWMR LOG file */
+    /* Kent*/
+    if (vfd_swmr_config_ptr->version) {
+        if (HDstrlen(vfd_swmr_config_ptr->log_file_path) > 0)
+            shared->vfd_swmr_log_on = TRUE;
+        if (TRUE == shared->vfd_swmr_log_on) {
+            /* Create the log file */
+            if ((shared->vfd_swmr_log_file_ptr = HDfopen(vfd_swmr_config_ptr->log_file_path, "w")) == NULL)
+                HGOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, NULL, "unable to create the log file")
+            if (HDclock_gettime(CLOCK_MONOTONIC, &(shared->vfd_swmr_log_start_time)) < 0)
+                HGOTO_ERROR(H5E_FILE, H5E_CANTGET, NULL, "can't get time via clock_gettime");
+        }
+    }
+    /* End of Kent */
+
+    lf = shared->lf;
 
     /* Set the file locking flag. If the file is already open, the file
      * requested file locking flag must match that of the open file.
@@ -2210,6 +2226,9 @@ H5F_open(const char *name, unsigned flags, hid_t fcpl_id, hid_t fapl_id)
     /* Success */
     ret_value = file;
 
+#if 1 /*Kent: write to the log file when H5F_open ends. Tested, can be commented out if necessary.*/
+    H5F_POST_VFD_SWMR_LOG_ENTRY(file, 1, "File open ends");
+#endif
 done:
     if ((NULL == ret_value) && file) {
         if (file->shared->root_grp && file->shared->nrefs == 1) {
diff --git a/src/H5Fpkg.h b/src/H5Fpkg.h
index c94c5af..578c6ab 100644
--- a/src/H5Fpkg.h
+++ b/src/H5Fpkg.h
@@ -469,6 +469,10 @@ struct H5F_shared_t {
                                  * manager
                                  */
 
+    FILE *          vfd_swmr_log_file_ptr;
+    hbool_t         vfd_swmr_log_on;
+    struct timespec vfd_swmr_log_start_time;
+
     /* Delayed free space release doubly linked list */
     shadow_defree_queue_t shadow_defrees;
 
@@ -608,4 +612,52 @@ H5_DLL htri_t H5F__same_file_test(hid_t file_id1, hid_t file_id2);
 H5_DLL herr_t H5F__reparse_file_lock_variable_test(void);
 #endif /* H5F_TESTING */
 
+/* VFD SMWR LOG REPORTING MACROS */
+
+/* H5F_POST_VFD_SWMR_LOG_ENTRY is the macro that needs to be used by the developers.
+ * It calls an internal reporting function H5F_post_vfd_swmr_log_entry() that receives
+ * the log entry_type_code,  which generates the log tag,  and the message log_info, which
+ * the library developer wants to save into the log file.
+ *
+ * The macro H5F_POST_VFD_SWMR_LOG_ENTRY_RELEASE(f, c, number_entry_production, m) is
+ * called by H5F_POST_VFD_SWMR_LOG_ENTRY when the HDF5 library is built with the
+ * production mode. Number_entry_production will control the number of entry tags that
+ * applications can receive. Currently this number is set to 1 and is subject to change
+ * when more tags are useful to be present to applications.
+ *
+ * The first argument of the macro is the HDF5 file pointer(H5F_t *).
+ * Its value needs to be checked to avoid a failure caused by "Low-Level File I/O "
+ * in the testhdf5 program, which involves the test of a non-existing HDF5 file.
+ */
+
+H5_DLL void H5F_post_vfd_swmr_log_entry(H5F_t *f, int entry_type_code, char *log_info);
+
+#define H5F_POST_VFD_SWMR_LOG_ENTRY_INTERNAL(fp, entry_type_code, log_info)                                  \
+    do {                                                                                                     \
+        if (fp != NULL) {                                                                                    \
+            if (fp->shared != NULL) {                                                                        \
+                if (fp->shared->vfd_swmr_log_on == TRUE) {                                                   \
+                    H5F_post_vfd_swmr_log_entry(fp, entry_type_code, log_info);                              \
+                }                                                                                            \
+            }                                                                                                \
+        }                                                                                                    \
+    } while (0)
+
+#define H5F_POST_VFD_SWMR_LOG_ENTRY_RELEASE(fp, entry_type_code, max_code, log_info)                         \
+    do {                                                                                                     \
+        if (entry_type_code < max_code) {                                                                    \
+            H5F_POST_VFD_SWMR_LOG_ENTRY_INTERNAL(fp, entry_type_code, log_info);                             \
+        }                                                                                                    \
+    } while (0)
+
+/* Note: change H5F_POST_VFD_SWMR_LOG_ENTRY_RELEASE(f, c, 1, m) on the following lines to
+ *       H5F_POST_VFD_SWMR_LOG_ENTRY_RELEASE(f, c, your_number_entry_production, m)
+ *       as necessary.
+ */
+#ifndef NDEBUG
+#define H5F_POST_VFD_SWMR_LOG_ENTRY(f, c, m) H5F_POST_VFD_SWMR_LOG_ENTRY_INTERNAL(f, c, m)
+#else
+#define H5F_POST_VFD_SWMR_LOG_ENTRY(f, c, m) H5F_POST_VFD_SWMR_LOG_ENTRY_RELEASE(f, c, 1, m)
+#endif
+
 #endif /* H5Fpkg_H */
diff --git a/src/H5Fvfd_swmr.c b/src/H5Fvfd_swmr.c
index 69e03a0..12c8905 100644
--- a/src/H5Fvfd_swmr.c
+++ b/src/H5Fvfd_swmr.c
@@ -54,6 +54,38 @@
 #define nanosecs_per_second    1000000000 /* nanoseconds per second */
 #define nanosecs_per_tenth_sec 100000000  /* nanoseconds per 0.1 second */
 
+/* Declare an array of string to identify the VFD SMWR Log tags.
+ * Note this array is used to generate the entry tag by the log reporting macro
+ * H5F_POST_VFD_SWMR_LOG_ENTRY.
+ *
+ * The following is the first version. Developers can add/modify the tags as necessary.
+ *
+ * If the entry code is 0, H5Fvfd_swmr_log_tags[0] is used to report the entry tag.
+ * H5F_POST_VFD_SWMR_LOG_ENTRY(f, 0, log_msg) will put the log_msg attached to
+ * the entry tag "EOT_PROCESSING_TIME".
+ * The entry code number is listed in the comment for convenience.
+ * Currently for the production mode, only the "EOT_PROCESSING_TIME" is present.
+ */
+
+/* clang-format off */
+static const char *H5Fvfd_swmr_log_tags[] = {
+                                             "EOT_PROCESSING_TIME",         /* 0 */
+                                             "FILE_OPEN",                   /* 1 */                        
+                                             "FILE_CLOSE",                  /* 2 */
+                                             "EOT_TRIGGER_TIME",            /* 3 */
+                                             "EOT_META_FILE_INDEX"          /* 4 */
+                                            };
+/* clang-format on */
+
+/* This string defines the format of the VFD SWMR log file.
+ * The current maximum length of entry tag string is set to 26.
+ * One can enlarge or reduce this number as necessary.
+ * For example, to enlarge the maximum length of entry tag string to 30,
+ * Just change 26 to 30 in the following line, like
+ * const char *log_fmt_str="%-30s: %.3lf s: %s\n";
+ */
+const char *log_fmt_str = "%-26s: %.3lf s: %s\n";
+
 /********************/
 /* Local Prototypes */
 /********************/
@@ -157,7 +189,6 @@ H5F_vfd_swmr_init(H5F_t *f, hbool_t file_create)
         /* Create the metadata file */
         if (((shared->vfd_swmr_md_fd = HDopen(shared->vfd_swmr_config.md_file_path, O_CREAT | O_RDWR,
                                               H5_POSIX_CREATE_MODE_RW))) < 0)
-
             HGOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL, "unable to create the metadata file")
 
         md_size = (hsize_t)shared->vfd_swmr_config.md_pages_reserved * shared->fs_page_size;
@@ -319,7 +350,16 @@ H5F_vfd_swmr_close_or_flush(H5F_t *f, hbool_t closing)
         if (H5F__vfd_swmr_update_end_of_tick_and_tick_num(shared, TRUE) < 0)
             HDONE_ERROR(H5E_FILE, H5E_CANTSET, FAIL, "unable to update end of tick");
     }
+#if 1 /*Kent  Save the end of close or flush info. to the log file, subject to comment out. */
+    H5F_POST_VFD_SWMR_LOG_ENTRY(f, 2, "VFD SWMR File close or flush ends");
+#endif
 done:
+
+    /* Kent: close the VFD SWMR log file if it is turned on */
+    if (shared->vfd_swmr_log_on) {
+        HDfclose(shared->vfd_swmr_log_file_ptr);
+    }
+    /* Kent */
     FUNC_LEAVE_NOAPI(ret_value)
 }
 
@@ -755,12 +795,24 @@ H5F_vfd_swmr_writer_end_of_tick(H5F_t *f, hbool_t wait_for_reader)
     herr_t        ret_value                 = SUCCEED; /* Return value */
     hbool_t       incr_tick                 = FALSE;
 
+    struct timespec start_time, end_time;
+    unsigned int    temp_time;
+    char *          log_msg;
+
     FUNC_ENTER_NOAPI(FAIL)
 
     HDassert(shared);
     HDassert(shared->page_buf);
     HDassert(shared->vfd_swmr_writer);
 
+    /* Kent */
+    /* Obtain the starting time for the logging info: the processing time of this function. */
+    if (shared->vfd_swmr_log_on == true) {
+        if (HDclock_gettime(CLOCK_MONOTONIC, &start_time) < 0)
+            HGOTO_ERROR(H5E_FILE, H5E_CANTGET, FAIL, "can't get time via clock_gettime");
+    }
+    /* Kent */
+
     if (!vfd_swmr_writer_may_increase_tick_to(shared->tick_num + 1, wait_for_reader))
         goto update_eot;
 
@@ -883,6 +935,17 @@ update_eot:
         HGOTO_ERROR(H5E_FILE, H5E_CANTSET, FAIL, "unable to insert entry into the EOT queue")
 
 done:
+    /* Kent: Calcuate the processing time and write the time info to the log file */
+    if (shared->vfd_swmr_log_on == true) {
+        if (HDclock_gettime(CLOCK_MONOTONIC, &end_time) < 0)
+            HGOTO_ERROR(H5E_FILE, H5E_CANTGET, FAIL, "can't get time via clock_gettime");
+        log_msg   = HDmalloc(48);
+        temp_time = (unsigned int)(TOTAL_TIME_PASSED(start_time, end_time) * 1000);
+        HDsprintf(log_msg, "Writer time is %u milliseconds", temp_time);
+        H5F_POST_VFD_SWMR_LOG_ENTRY(f, 0, log_msg);
+        HDfree(log_msg);
+    }
+    /* Kent */
     FUNC_LEAVE_NOAPI(ret_value)
 }
 
@@ -1886,3 +1949,46 @@ H5F_vfd_swmr_process_eot_queue(hbool_t entering_api)
 done:
     FUNC_LEAVE_NOAPI(ret_value)
 }
+
+/*-------------------------------------------------------------------------
+ *
+ * Function:    H5F_post_vfd_swmr_log_entry
+ *
+ * Purpose:     Write the log information to the log file.
+ *
+ * Parameters:
+ *              H5F_t *f                IN: HDF5 file pointer
+ *              int entry_type_code     IN: The entry type code to identify the
+ *                                          log entry tag.
+ *              char *log_info          IN: The information to be stored in the
+ *                                          log file.
+ * Return:   None
+ *
+ *-------------------------------------------------------------------------
+ */
+
+void
+H5F_post_vfd_swmr_log_entry(H5F_t *f, int entry_type_code, char *log_info)
+{
+    double          temp_time;
+    struct timespec current_time;
+    char *          gettime_error;
+
+    /* Obtain the current time.
+       If   failed, write an error message to the log file.
+       else calcluate the elapsed time in seconds since the log file
+            was created and wirte the time to the log file. */
+    if (HDclock_gettime(CLOCK_MONOTONIC, &current_time) < 0) {
+        gettime_error = HDmalloc(14);
+        HDsprintf(gettime_error, "gettime_error");
+        HDfprintf(f->shared->vfd_swmr_log_file_ptr, "%-26s:  %s\n", H5Fvfd_swmr_log_tags[entry_type_code],
+                  gettime_error);
+        HDfree(gettime_error);
+    }
+    else {
+        temp_time = TOTAL_TIME_PASSED(f->shared->vfd_swmr_log_start_time, current_time);
+        HDfprintf(f->shared->vfd_swmr_log_file_ptr, log_fmt_str, H5Fvfd_swmr_log_tags[entry_type_code],
+                  temp_time, log_info);
+    }
+    return;
+}
diff --git a/src/H5Pfapl.c b/src/H5Pfapl.c
index d20503f..3b39f12 100644
--- a/src/H5Pfapl.c
+++ b/src/H5Pfapl.c
@@ -5710,6 +5710,10 @@ H5Pset_vfd_swmr_config(hid_t plist_id, H5F_vfd_swmr_config_t *config_ptr)
     else if (name_len > H5F__MAX_VFD_SWMR_FILE_NAME_LEN)
         HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "md_file_path is too long")
 
+    name_len = HDstrlen(config_ptr->log_file_path);
+    if (name_len > H5F__MAX_VFD_SWMR_FILE_NAME_LEN)
+        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "log_file_path is too long")
+
     /* Set the modified config */
     if (H5P_set(plist, H5F_ACS_VFD_SWMR_CONFIG_NAME, config_ptr) < 0)
         HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set metadata cache initial config")
diff --git a/test/Makefile.am b/test/Makefile.am
index 87b2925..a97e968 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -56,6 +56,7 @@ SCRIPT_DEPEND = error_test$(EXEEXT) err_compat$(EXEEXT) links_env$(EXEEXT) \
     vfd_swmr_zoo_reader$(EXEEXT) vfd_swmr_zoo_writer$(EXEEXT) \
     vfd_swmr_gperf_reader$(EXEEXT) vfd_swmr_gperf_writer$(EXEEXT) \
     vfd_swmr_gfail_reader$(EXEEXT) vfd_swmr_gfail_writer$(EXEEXT) \
+    vfd_swmr_log_reader$(EXEEXT) vfd_swmr_log_writer$(EXEEXT) \
     vds_env$(EXEEXT) \
     vds_swmr_gen$(EXEEXT) vds_swmr_reader$(EXEEXT) vds_swmr_writer$(EXEEXT)
 if HAVE_SHARED_CONDITIONAL
@@ -115,6 +116,7 @@ check_PROGRAMS=$(TEST_PROG) error_test err_compat tcheck_version \
     vfd_swmr_attrdset_reader vfd_swmr_attrdset_writer \
     vfd_swmr_gperf_reader vfd_swmr_gperf_writer \
     vfd_swmr_gfail_reader vfd_swmr_gfail_writer \
+    vfd_swmr_log_reader vfd_swmr_log_writer \
 	vfd_swmr_check_compat \
     vfd_swmr_dsetchks_reader vfd_swmr_dsetchks_writer \
     swmr_check_compat_vfd vds_env vds_swmr_gen vds_swmr_reader vds_swmr_writer \
@@ -184,6 +186,7 @@ vfd_swmr_bigset_reader_SOURCES=vfd_swmr_bigset_writer.c
 vfd_swmr_group_reader_SOURCES=vfd_swmr_group_writer.c
 vfd_swmr_gperf_reader_SOURCES=vfd_swmr_gperf_writer.c
 vfd_swmr_gfail_reader_SOURCES=vfd_swmr_gfail_writer.c
+vfd_swmr_log_reader_SOURCES=vfd_swmr_log_writer.c
 vfd_swmr_dsetops_reader_SOURCES=vfd_swmr_dsetops_writer.c
 
 vfd_swmr_attrdset_writer_SOURCES=vfd_swmr_attrdset_writer.c
diff --git a/test/vfd_swmr_common.c b/test/vfd_swmr_common.c
index f57f39a..cfe93aa 100644
--- a/test/vfd_swmr_common.c
+++ b/test/vfd_swmr_common.c
@@ -369,6 +369,19 @@ init_vfd_swmr_config(H5F_vfd_swmr_config_t *config, uint32_t tick_len, uint32_t
 
 } /* init_vfd_swmr_config() */
 
+/* Initialize the log file path in config, this function should be called after init_vfd_swmr_config.  */
+void
+init_vfd_swmr_log(H5F_vfd_swmr_config_t *config, const char *log_file_fmtstr, ...)
+
+{
+    va_list ap;
+
+    HDva_start(ap, log_file_fmtstr);
+    evsnprintf(config->log_file_path, sizeof(config->log_file_path), log_file_fmtstr, ap);
+    HDva_end(ap);
+
+} /* init_vfd_swmr_log() */
+
 /* Perform common VFD SWMR configuration on the file-access property list:
  * configure page buffering, set reasonable VFD SWMR defaults.
  */
diff --git a/test/vfd_swmr_common.h b/test/vfd_swmr_common.h
index b2fbbbd..f5981a5 100644
--- a/test/vfd_swmr_common.h
+++ b/test/vfd_swmr_common.h
@@ -77,6 +77,9 @@ H5TEST_DLL void init_vfd_swmr_config(H5F_vfd_swmr_config_t *config, uint32_t tic
                                      hbool_t writer, hbool_t flush_raw_data, uint32_t md_pages_reserved,
                                      const char *md_file_fmtstr, ...) H5_ATTR_FORMAT(printf, 7, 8);
 
+H5TEST_DLL void init_vfd_swmr_log(H5F_vfd_swmr_config_t *config, const char *log_file_fmtstr, ...)
+    H5_ATTR_FORMAT(printf, 2, 3);
+
 H5TEST_DLL hid_t vfd_swmr_create_fcpl(H5F_fspace_strategy_t fs_strategy, hsize_t fs_page_size);
 
 H5TEST_DLL void dbgf(int, const char *, ...) H5_ATTR_FORMAT(printf, 2, 3);
diff --git a/test/vfd_swmr_log_writer.c b/test/vfd_swmr_log_writer.c
new file mode 100644
index 0000000..95f89f0
--- /dev/null
+++ b/test/vfd_swmr_log_writer.c
@@ -0,0 +1,2929 @@
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * 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.                                                        *
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+/* Description of this program:
+ * This program shows an example on how a VFD log file can be written.
+ * It is adapted from the group performence test. Most options of the
+ * group performance test are still kept.
+ * To turn on the log feature, one just needs to provide the log file path as
+ * indicated by the line init_vfd_swmr_log(&config, "./log-test") in the main
+ * function. The init_vfd_swmr_log is defined inside the vfd_swmr_common.c.
+ * For the demo of the log feature,
+ * one just needs to do te following:
+ * After compiling the program, just run the following line
+ *     ./vfd_swmr_log_writer -n 100000 -P -q
+ * A VFD SWMR log file log-test is generated.
+ * The log-test should include something like:
+ * 'EOT_PROCESSING_TIME       : 0.040 s: Writer time is 1 milliseconds'
+ * This program also checks the performance of group creations for VFD SWMR.
+ * Currently the group creation time, H5Fopen and H5Fclose time are measured.
+ * The output can help check the contents in the log-test.
+ *
+ */
+#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 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 nsteps;
+    bool         use_vfd_swmr;
+    bool         old_style_grp;
+    char         grp_op_pattern;
+    bool         grp_op_test;
+    char         at_pattern;
+    bool         attr_test;
+    uint32_t     max_lag;
+    uint32_t     tick_len;
+    bool         gperf;
+    double       min_gc_time;
+    double       max_gc_time;
+    double       mean_gc_time;
+    double       total_gc_time;
+    double       total_time;
+    double       mean_time;
+    double       fo_total_time;
+    double       fc_total_time;
+    unsigned int num_attrs;
+    bool         vlstr_test;
+    unsigned int ps;
+    unsigned int pbs;
+    unsigned int nglevels;
+} 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 = 1, .nsteps = 100, .use_vfd_swmr = true,                     \
+        .old_style_grp = false, .grp_op_pattern = ' ', .grp_op_test = false, .at_pattern = ' ',              \
+        .attr_test = false, .tick_len = 4, .max_lag = 7, .gperf = false, .min_gc_time = 100.,                \
+        .max_gc_time = 0., .mean_gc_time = 0., .total_gc_time = 0., .total_time = 0., .mean_time = 0.,       \
+        .fo_total_time = 0., .fc_total_time = 0., .num_attrs = 1, .vlstr_test = false, .ps = 4096,           \
+        .pbs = 4096, .nglevels = 0                                                                           \
+    }
+
+static void
+usage(const char *progname)
+{
+    fprintf(stderr,
+            "usage: ./%s -P -n 1000 -N 5 -q (create 1000 groups, each group has 5 attributes)\n"
+            "Options: \n"
+            " [-P] [-S] [-G] [-t tick_len] [-m max_lag][-B pbs] [-s ps]\n"
+            " [-n ngroups] [-l ng_levels] [-O grp_op_pattern]\n"
+            " [-N num_attrs] [-V] [-b] [-A at_pattern] [-a steps] [-q]\n"
+            "\n"
+            "-P:             carry out the performance test\n"
+            "-S:             do not use VFD SWMR\n"
+            "-G:             old-style type of group\n"
+            "-t tick_len:    length of a tick in tenths of a second.\n"
+            "-m max_lag:     maximum expected lag(in ticks) between writer and readers\n"
+            "-B pbs:         page Buffer Size in bytes:\n"
+            "                The default value is 4K(4096).\n"
+            "-s ps:          page size used by page aggregation, page buffer and \n"
+            "                the metadata file. \n"
+            "-n ngroups:     the number of groups\n"
+            "-l ng_levels:   the number of level of nested groups.  \n"
+            "                If all the groups are under the root group,  \n"
+            "                this number should be 0.\n"
+            "-N num_attrs:   the number of attributes \n"
+            "-V              use variable length string attributes for performance test\n"
+            "-b:             write data in big-endian byte order\n"
+            "                (For the performance test, -V overwrites -b)\n"
+            "-A at_pattern:  `at_pattern' for different attribute tests\n"
+            "-O grp_op_pattern:  `grp_op_pattern' for different group operation tests\n"
+            "-a steps:      `steps` between adding attributes\n"
+            "              (Don't recommend to use this option for performance test.)\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);
+        tfile = NULL;
+    }
+
+    if (argc == 1)
+        usage(s->progname);
+    while ((ch = getopt(argc, argv, "PSGa:bVt:m:B:s:n:qA:N:l: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 'n':
+            case 'N':
+            case 'l':
+            case 't':
+            case 'm':
+            case 'B':
+            case 's':
+                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 == 'n')
+                    s->nsteps = (unsigned)tmp;
+                else if (ch == 'N')
+                    s->num_attrs = (unsigned)tmp;
+                else if (ch == 'l')
+                    s->nglevels = (unsigned)tmp;
+                else if (ch == 't')
+                    s->tick_len = (unsigned)tmp;
+                else if (ch == 'm')
+                    s->max_lag = (unsigned)tmp;
+                else if (ch == 's')
+                    s->ps = (unsigned)tmp;
+                else if (ch == 'B')
+                    s->pbs = (unsigned)tmp;
+                break;
+            case 'b':
+                s->filetype = H5T_STD_U32BE;
+                break;
+            case 'V':
+                s->vlstr_test = true;
+                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 (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;
+}
+
+/*-------------------------------------------------------------------------
+ * 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
+ *              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;
+            }
+        }
+
+    } /* end for */
+
+    if (H5Tclose(amtype) < 0) {
+        TEST_ERROR;
+    }
+
+    return true;
+
+error:
+    H5E_BEGIN_TRY
+    {
+        H5Aclose(aid);
+        H5Tclose(amtype);
+    }
+    H5E_END_TRY;
+
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * 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
+ *              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);
+
+    return true;
+
+error:
+    H5E_BEGIN_TRY
+    {
+        H5Aclose(aid);
+        H5Tclose(atype);
+    }
+    H5E_END_TRY;
+
+    if (astr_val)
+        HDfree(astr_val);
+
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    add_vlstr_attrs
+ *
+ * Purpose:     Add variable length string attributes to a group.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file
+ *              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".  The attribute names
+ *              are "attr-which","attr-which+1"....
+ *
+ *
+ * Return:      Success:    true
+ *              Failure:    false
+ *
+ * Note:        This is for the performance test that has the VL string type.
+ *-------------------------------------------------------------------------
+ */
+
+static bool
+add_vlstr_attrs(state_t *s, hid_t g, unsigned int which, unsigned int num_attrs)
+{
+    unsigned u;
+    bool     ret_value = true;
+    for (u = 0; u < num_attrs; u++) {
+        ret_value = add_vlstr_attr(s, g, u + which);
+        if (ret_value == false)
+            break;
+    }
+
+    return ret_value;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    add_default_group_attr
+ *
+ * Purpose:     Add an attribute to a group.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file
+ *              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-%u";
+
+    /* Note: the number of attributes can be configurable,
+     * the default number of attribute is 1.
+     */
+    /* If the vl string attribute type is chosen. */
+    if (s->vlstr_test == true)
+        return add_vlstr_attrs(s, g, which, s->num_attrs);
+    else
+        return add_attr(s, g, which, s->num_attrs, aname_format, which);
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    del_one_attr
+ *
+ * Purpose:     delete one attribute in a group.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file
+ *              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;
+        }
+    }
+    return true;
+
+error:
+    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
+ *              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
+ *              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;
+    }
+
+    return true;
+error:
+    H5E_BEGIN_TRY
+    {
+        H5Aclose(aid);
+        H5Tclose(aid);
+    }
+    H5E_END_TRY;
+
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    modify_vlstr_attr
+ *
+ * Purpose:     Modify the value of an VL string attribute in a group.
+ *
+ * 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(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);
+
+    return true;
+
+error:
+    H5E_BEGIN_TRY
+    {
+        H5Aclose(aid);
+        H5Tclose(atype);
+    }
+    H5E_END_TRY;
+
+    if (astr_val)
+        HDfree(astr_val);
+
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    add_modify_vlstr_attr
+ *
+ * Purpose:     Add a variable length string attribute
+ *              then modify this attribute in the group.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file
+ *              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(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
+ *              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:
+    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
+ *              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:
+    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:  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(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;
+        }
+    }
+
+    /* 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;
+    }
+
+    return true;
+
+error:
+    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
+ *              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
+ *              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:
+    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
+ *              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(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
+ *              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
+ *              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
+ *              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
+ *              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 (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;
+            }
+        }
+    }
+
+    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, gcpl, 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_gc_time)
+            s->min_gc_time = temp_time;
+        if (temp_time > s->max_gc_time)
+            s->max_gc_time = temp_time;
+        s->total_gc_time += temp_time;
+    }
+
+    /* 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;
+        }
+    }
+    /* We only need to check the first group */
+    if (which == 0) {
+        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;
+        }
+    }
+
+    /* 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;
+        }
+    }
+
+    if (H5Gclose(g) < 0) {
+        printf("H5Gclose failed\n");
+        TEST_ERROR;
+    }
+
+    if (!s->old_style_grp && H5Pclose(gcpl) < 0) {
+        printf("H5Pclose failed\n");
+        TEST_ERROR;
+    }
+
+    return result;
+
+error:
+
+    H5E_BEGIN_TRY
+    {
+        H5Gclose(g);
+        if (s->at_pattern == 'a' || s->at_pattern == 'R')
+            H5Dclose(dummy_d);
+        if (!s->old_style_grp)
+            H5Pclose(gcpl);
+    }
+    H5E_END_TRY;
+
+    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
+ *              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;
+    }
+
+    return g;
+
+error:
+
+    H5E_BEGIN_TRY
+    {
+        H5Pclose(gcpl);
+    }
+    H5E_END_TRY;
+
+    return -1;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    close_group_id
+ *
+ * Purpose:     Verify is a group is closed successfully.
+ *
+ * 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(hid_t g)
+{
+
+    if (H5Gclose(g) < 0) {
+        printf("H5Gclose failed\n");
+        TEST_ERROR;
+    }
+
+    return true;
+
+error:
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    create_group
+ *
+ * Purpose:     Create a group
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file
+ *              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;
+    }
+
+    return true;
+
+error:
+
+    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
+ *              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;
+            }
+        }
+    }
+
+    return true;
+
+error:
+    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
+ *              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
+ *              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;
+    }
+
+    return true;
+
+error:
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    move_group
+ *
+ * Purpose:     Move a group to another group.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file
+ *              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
+ *              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;
+            }
+        }
+    }
+
+    return true;
+
+error:
+    return false;
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    insert_links
+ *
+ * Purpose:     create links with a group.
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file
+ *              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
+ *              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
+ *              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(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
+ *              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(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
+ *              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;
+}
+
+static unsigned int grp_counter = 0;
+
+/*-------------------------------------------------------------------------
+ * Function:    UI_Pow
+ *
+ * Purpose:     Helper function to obtain the power 'n' of
+ *              an unsigned integer 'x'
+ *              Similar to pow(x,y) but for an unsigned integer.
+ *
+ * Parameters:  unsigned int x
+ *              unsigned int n
+ *
+ * Return:      Return an unsigned integer of value of pow(x,n)
+ * Note:        If the returned value is > 2^32-1, an overflow
+ *              may occur. For our testing purpose, this may never happen.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+static unsigned int
+UI_Pow(unsigned int x, unsigned int n)
+{
+    unsigned int i; /* Variable used in loop grp_counter */
+    unsigned int number = 1;
+
+    for (i = 0; i < n; ++i)
+        number *= x;
+
+    return (number);
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    obtain_tree_level_elems
+ *
+ * Purpose:     Helper function to obtain the maximum number of elements
+ *              at one level.
+ *
+ * Parameters:  unsigned int total_ele
+ *              The total number of elements of a tree(excluding the root)
+ *
+ *              unsigned int level
+ *              The number of nested levels
+ *              (If every element of the tree is under the root,
+ *                  the level is 0.)
+ *
+ * Return:      Return the maximum number of elements at one level
+ *
+ * Example:     If the total number of elements is 6 and level is 1,
+ *                 the maximum number of elements is 2.The tree is
+ *                 a perfectly balanced tree.
+ *              Such as:
+ *                   0
+ *                1     2
+ *              3  4  5   6
+ *
+ *              If the total number of elements is 5 and level is 1,
+ *                 the maximum number of elements is still 2. The
+ *                 tree is not balanced, there is no element on the
+ *                 right-most leaf but the level is still 1.
+ *              Such as:
+ *                   0
+ *                1     2
+ *              3  4  5
+ *
+ *-------------------------------------------------------------------------
+ */
+
+static unsigned int
+obtain_tree_level_elems(unsigned int total_ele, unsigned int level)
+{
+
+    assert(level <= total_ele);
+    /* if every element is under the root, just return the total number of elements. */
+    if (level == 0)
+        return total_ele;
+    else {
+        unsigned int test_elems_level = 0;
+        unsigned     total            = 0;
+        unsigned int i                = 1;
+        /* Obtain the maximum number of elements for a level with the brutal force way. */
+        while (total < total_ele) {
+            test_elems_level++;
+            total = 0;
+            for (i = 1; i <= level + 1; i++)
+                total += UI_Pow(test_elems_level, i);
+        }
+        if (total == total_ele)
+            dbgf(2, "Perfectly match: Number of elements per level is %u\n", test_elems_level);
+        return test_elems_level;
+    }
+}
+
+/*-------------------------------------------------------------------------
+ * Function:    gen_tree_struct
+ *
+ * Purpose:     Generate the nested groups
+ *
+ * Parameters:  state_t *s
+ *              The struct that stores information of HDF5 file
+ *              and some VFD SWMR configuration parameters
+ *
+ *              unsigned int level
+ *              The number of nested levels +1
+ *              (Note: If every element of the tree is under the root,
+ *                     the level is 1 in this function.)
+ *              unsigned num_elems_per_level
+ *              The maximum number of element in a level
+ *              hid_t group_id
+ *              The ID of the parent group
+ *
+ * Return:      Success: true
+ *              Failure: false
+ */
+static bool
+gen_tree_struct(state_t *s, unsigned int level, unsigned ne_per_level, hid_t pgrp_id)
+{
+
+    char            name[sizeof("group-9999999999")];
+    unsigned int    i;
+    hid_t           grp_id;
+    bool            result = true;
+    H5G_info_t      group_info;
+    struct timespec start_time, end_time;
+    double          temp_time;
+
+    if (level > 0 && grp_counter < s->nsteps) {
+
+        for (i = 0; i < ne_per_level; i++) {
+
+            /* For each i a group is created.
+               Use grp_counter to generate the group name.
+            printf("id: %u,level: %u, index: %u\n",id,level,i);
+            */
+            esnprintf(name, sizeof(name), "group-%u", grp_counter);
+            if (grp_counter == s->nsteps)
+                break;
+
+            dbgf(2, "writer in nested group: step %d\n", grp_counter);
+            if (s->gperf) {
+
+                if (HDclock_gettime(CLOCK_MONOTONIC, &start_time) == -1) {
+                    fprintf(stderr, "HDclock_gettime failed");
+                    TEST_ERROR;
+                }
+            }
+
+            if ((grp_id = H5Gcreate2(pgrp_id, 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_gc_time)
+                    s->min_gc_time = temp_time;
+                if (temp_time > s->max_gc_time)
+                    s->max_gc_time = temp_time;
+                s->total_gc_time += temp_time;
+            }
+
+            /* Just check the first group information. */
+            if (grp_counter == 0) {
+                if (H5Gget_info(grp_id, &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");
+                }
+            }
+
+            /* Then carry out the attribute operation. */
+            if (s->asteps != 0 && grp_counter % s->asteps == 0)
+                result = add_default_group_attr(s, grp_id, grp_counter);
+
+            if (result == false) {
+                printf("Cannot create group attributes. \n");
+                TEST_ERROR;
+            }
+            grp_counter++;
+
+            /* Generate groups in the next level */
+            result = gen_tree_struct(s, level - 1, ne_per_level, grp_id);
+            if (result == false) {
+                printf("Cannot create nested groups. \n");
+                TEST_ERROR;
+            }
+
+            /*  close the group ID. No problem. */
+            if (H5Gclose(grp_id) < 0) {
+                printf("H5Gclose failed. \n");
+                TEST_ERROR;
+            }
+        }
+    }
+
+    return true;
+
+error:
+
+    H5E_BEGIN_TRY
+    {
+        H5Gclose(grp_id);
+    }
+    H5E_END_TRY;
+
+    return false;
+}
+
+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;
+    bool                  wg_ret = false;
+    struct timespec       start_time, end_time;
+    unsigned int          num_elems_per_level;
+
+    if (!state_init(&s, argc, argv)) {
+        printf("state_init failed\n");
+        TEST_ERROR;
+    }
+
+    personality = HDstrstr(s.progname, "vfd_swmr_log_");
+
+    if (personality != NULL && HDstrcmp(personality, "vfd_swmr_log_writer") == 0)
+        writer = true;
+    else if (personality != NULL && HDstrcmp(personality, "vfd_swmr_log_reader") == 0)
+        writer = false;
+    else {
+        printf("unknown personality, expected vfd_swmr_log_{reader,writer}\n");
+        TEST_ERROR;
+    }
+
+    if (writer == false) {
+        printf("Reader is skipped for the performance tests.\n");
+        return EXIT_SUCCESS;
+    }
+
+    /* config, tick_len, max_lag, writer, flush_raw_data, md_pages_reserved, md_file_path */
+    init_vfd_swmr_config(&config, s.tick_len, s.max_lag, writer, FALSE, 128, "./group-shadow");
+    /* Create the log file log-test under the current directory. */
+    init_vfd_swmr_log(&config, "./log-test");
+
+    /* 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, page buffer size, config to vfd_swmr_create_fapl().*/
+    if ((fapl = vfd_swmr_create_fapl(!s.old_style_grp, s.use_vfd_swmr, true, s.pbs, &config)) < 0) {
+        printf("vfd_swmr_create_fapl failed\n");
+        TEST_ERROR;
+    }
+
+    /* Set fs_strategy (file space strategy) and fs_page_size (file space page size) */
+    if ((fcpl = vfd_swmr_create_fcpl(H5F_FSPACE_STRATEGY_PAGE, s.ps)) < 0) {
+        HDprintf("vfd_swmr_create_fcpl() failed");
+        TEST_ERROR;
+    }
+
+    if (s.nglevels > 0) {
+        if (s.grp_op_pattern != ' ' || s.at_pattern != ' ') {
+            printf("For nested group creation test, only the default option is supported.\n");
+            printf("Please re-run the tests with the appopriate option.\n");
+            TEST_ERROR;
+        }
+    }
+
+    if (s.gperf) {
+
+        if (HDclock_gettime(CLOCK_MONOTONIC, &start_time) == -1) {
+            fprintf(stderr, "HDclock_gettime failed");
+            TEST_ERROR;
+        }
+    }
+
+    s.file = H5Fcreate(s.filename, H5F_ACC_TRUNC, fcpl, fapl);
+
+    if (s.gperf) {
+
+        if (HDclock_gettime(CLOCK_MONOTONIC, &end_time) == -1) {
+            fprintf(stderr, "HDclock_gettime failed");
+            TEST_ERROR;
+        }
+
+        s.fo_total_time = TIME_PASSED(start_time, end_time);
+    }
+
+    if (s.file < 0) {
+        printf("H5Fcreate failed\n");
+        TEST_ERROR;
+    }
+
+    /* If generating nested groups, calculate the maximum number of
+          elements per level.  */
+    if (s.nglevels > 0)
+        num_elems_per_level = obtain_tree_level_elems(s.nsteps, s.nglevels);
+
+    if (s.gperf) {
+
+        if (HDclock_gettime(CLOCK_MONOTONIC, &start_time) == -1) {
+            fprintf(stderr, "HDclock_gettime failed");
+            TEST_ERROR;
+        }
+    }
+
+    /* If generating nested groups */
+    if (s.nglevels > 0) {
+
+        /* for the recursive call, the groups under the root is treated as one level */
+        wg_ret = gen_tree_struct(&s, s.nglevels + 1, num_elems_per_level, s.file);
+        if (wg_ret == false) {
+            printf("write nested group failed at group counter  %u\n", grp_counter);
+            TEST_ERROR;
+        }
+    }
+    else {
+        for (step = 0; step < s.nsteps; step++) {
+
+            dbgf(2, "writer: step %d\n", step);
+            wg_ret = group_operations(&s, step);
+            if (wg_ret == false) {
+                printf("write_group failed at step %d\n", step);
+                TEST_ERROR;
+            }
+        }
+    }
+
+    if (s.gperf) {
+
+        if (HDclock_gettime(CLOCK_MONOTONIC, &end_time) == -1) {
+
+            fprintf(stderr, "HDclock_gettime failed");
+            TEST_ERROR;
+        }
+
+        s.total_time   = TIME_PASSED(start_time, end_time);
+        s.mean_time    = s.total_time / s.nsteps;
+        s.mean_gc_time = s.total_gc_time / s.nsteps;
+    }
+
+    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 (s.gperf) {
+
+        if (HDclock_gettime(CLOCK_MONOTONIC, &start_time) == -1) {
+
+            fprintf(stderr, "HDclock_gettime failed");
+
+            TEST_ERROR;
+        }
+    }
+
+    if (H5Fclose(s.file) < 0) {
+        printf("H5Fclose failed\n");
+        TEST_ERROR;
+    }
+
+    if (s.gperf) {
+
+        if (HDclock_gettime(CLOCK_MONOTONIC, &end_time) == -1) {
+
+            fprintf(stderr, "HDclock_gettime failed");
+
+            TEST_ERROR;
+        }
+
+        s.fc_total_time = TIME_PASSED(start_time, end_time);
+    }
+
+    /* Performance statistics summary */
+    if (s.gperf) {
+
+        if (verbosity != 0) {
+
+            fprintf(stdout, "\nPerformance Test Configuration: ");
+            if (s.use_vfd_swmr)
+                fprintf(stdout, " Using VFD SWMR \n");
+            else
+                fprintf(stdout, " Not using VFD SWMR \n");
+
+            if (s.old_style_grp)
+                fprintf(stdout, " Groups: Created via the earlist file format(old-style) \n");
+            else
+                fprintf(stdout, " Groups: Created via the latest file format(new-style) \n");
+
+            fprintf(stdout, "\n");
+
+            fprintf(stdout, "The length of a tick              = %u\n", s.tick_len);
+            fprintf(stdout, "The maximum expected lag(in ticks)= %u\n", s.max_lag);
+            fprintf(stdout, "The page size(in bytes)           = %u\n", s.ps);
+            fprintf(stdout, "The page buffer size(in bytes)    = %u\n", s.pbs);
+            fprintf(stdout, "\n");
+            fprintf(stdout, "Number of groups                  = %u\n", s.nsteps);
+            fprintf(stdout, "Group Nested levels               = %u\n", s.nglevels);
+            fprintf(stdout, "Number of attributes              = %u\n", s.num_attrs);
+            fprintf(stdout, "Number of element per attribute   = 1\n");
+            if (s.vlstr_test)
+                fprintf(stdout, "Attribute datatype is variable length string. \n");
+            else if (s.filetype == H5T_STD_U32BE)
+                fprintf(stdout, "Attribute datatype is big-endian unsigned 32-bit integer.\n");
+            else
+                fprintf(stdout, "Attribute datatype is native unsigned 32-bit integer.\n");
+
+            fprintf(stdout, "\n");
+            fprintf(stdout,
+                    "(If the nested level is 0, all the groups are created directly under the root.)\n\n");
+            fprintf(stdout, "group creation maximum time                       =%lf\n", s.max_gc_time);
+            fprintf(stdout, "group creation minimum time                       =%lf\n", s.min_gc_time);
+        }
+
+        fprintf(stdout, "group creation total time                           = %lf\n", s.total_gc_time);
+        fprintf(stdout, "group creation mean time(per group)                 = %lf\n", s.mean_gc_time);
+        fprintf(stdout, "group creation and attributes generation total time = %lf\n", s.total_time);
+        fprintf(stdout, "group creation and attributes generation mean time(per group) = %lf\n", s.mean_time);
+        fprintf(stdout, "H5Fcreate time = %lf\n", s.fo_total_time);
+        fprintf(stdout, "H5Fclose time  = %lf\n", s.fc_total_time);
+    }
+
+    return EXIT_SUCCESS;
+
+error:
+    H5E_BEGIN_TRY
+    {
+        H5Pclose(fapl);
+        H5Pclose(fcpl);
+        H5Sclose(s.one_by_one_sid);
+        H5Fclose(s.file);
+    }
+    H5E_END_TRY;
+
+    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 */