Merge Implementation of the mpio driver with selection I/O. (#3360)

4 files changed, 2139 insertions, 87 deletions

diff --git a/testpar/t_coll_chunk.c b/testpar/t_coll_chunk.c
index fd77988..1ff7a8e 100644
--- a/testpar/t_coll_chunk.c
+++ b/testpar/t_coll_chunk.c
@@ -782,7 +782,7 @@ coll_chunktest(const char *filename, int chunk_factor, int select_factor, int ap
     status = H5Pget_selection_io(xfer_plist, &selection_io_mode);
     VRFY((status >= 0), "testing property list get succeeded");
 
-    if (facc_type == FACC_MPIO && (selection_io_mode != H5D_SELECTION_IO_MODE_ON)) {
+    if (facc_type == FACC_MPIO && (selection_io_mode == H5D_SELECTION_IO_MODE_OFF)) {
         switch (api_option) {
             case API_LINK_HARD:
                 status = H5Pget(xfer_plist, H5D_XFER_COLL_CHUNK_LINK_HARD_NAME, &prop_value);
diff --git a/testpar/t_dset.c b/testpar/t_dset.c
index e401cd5..b75b6ae 100644
--- a/testpar/t_dset.c
+++ b/testpar/t_dset.c
@@ -3356,7 +3356,7 @@ actual_io_mode_tests(void)
     ret = H5Pclose(dxpl_id);
     VRFY((ret >= 0), "H5Pclose succeeded");
 
-    if (selection_io_mode != H5D_SELECTION_IO_MODE_ON) {
+    if (selection_io_mode == H5D_SELECTION_IO_MODE_OFF) {
         test_actual_io_mode(TEST_ACTUAL_IO_NO_COLLECTIVE);
 
         /*
diff --git a/testpar/t_select_io_dset.c b/testpar/t_select_io_dset.c
index eb64bfe..daeacf0 100644
--- a/testpar/t_select_io_dset.c
+++ b/testpar/t_select_io_dset.c
@@ -128,6 +128,11 @@ typedef enum {
 #define TEST_TCONV_BUF_TOO_SMALL               0x008
 #define TEST_IN_PLACE_TCONV                    0x010
 
+/* Definitions used by test_bug_optimized_bufs() and test_bug_api_library() */
+#define DIMS         10000
+#define BIG_X_FACTOR 1048576
+#define BIG_Y_FACTOR 32
+
 /*
  * Helper routine to set dxpl
  * --selection I/O mode
@@ -2960,6 +2965,8 @@ test_multi_dsets_all(int niter, hid_t fid, unsigned chunked, unsigned mwbuf)
     const void *wbufs[MULTI_NUM_DSETS];
     void       *rbufs[MULTI_NUM_DSETS];
 
+    curr_nerrors = nerrors;
+
     /* for n niter to ensure that all randomized dset_types with multi_dset_type_t will be covered */
     for (n = 0; n < niter; n++) {
 
@@ -3434,6 +3441,19 @@ test_no_selection_io_cause_mode(const char *filename, hid_t fapl, uint32_t test_
 
     /* Datatype conversion */
     if (test_mode & TEST_DATATYPE_CONVERSION) {
+
+        /* With one exception, all will land at H5FD__mpio_read/write_selection().
+         * As the xfer mode is H5FD_MPIO_INDEPENDENT, this will call
+         * H5FD__read/write_from_selection() triggering H5D_SEL_IO_NO_VECTOR_OR_SELECTION_IO_CB.
+         */
+        no_selection_io_cause_read_expected |= H5D_SEL_IO_NO_VECTOR_OR_SELECTION_IO_CB;
+
+        /* Exception case: This will turn off selection I/O landing at H5FD__mpio_write() */
+        if ((test_mode & TEST_TCONV_BUF_TOO_SMALL) && !(test_mode & TEST_IN_PLACE_TCONV))
+            no_selection_io_cause_write_expected |= H5D_SEL_IO_TCONV_BUF_TOO_SMALL;
+        else
+            no_selection_io_cause_write_expected |= H5D_SEL_IO_NO_VECTOR_OR_SELECTION_IO_CB;
+
         if (H5Pset_selection_io(dxpl, H5D_SELECTION_IO_MODE_ON) < 0)
             P_TEST_ERROR;
         tid = H5T_NATIVE_UINT;
@@ -3443,18 +3463,12 @@ test_no_selection_io_cause_mode(const char *filename, hid_t fapl, uint32_t test_
             if (H5Pset_buffer(dxpl, sizeof(int), NULL, NULL) < 0)
                 P_TEST_ERROR;
 
-            /* If we're using in-place type conversion sel io will succeed */
             if (test_mode & TEST_IN_PLACE_TCONV) {
                 if (H5Pset_modify_write_buf(dxpl, TRUE) < 0)
                     P_TEST_ERROR;
             }
-            else
-                no_selection_io_cause_write_expected |= H5D_SEL_IO_TCONV_BUF_TOO_SMALL;
-
             /* In-place type conversion for read doesn't require modify_write_buf */
         }
-
-        /* If the tconv buf is largge enough sel io will succeed */
     }
 
     /* Create 1d data space */
@@ -3521,6 +3535,31 @@ test_no_selection_io_cause_mode(const char *filename, hid_t fapl, uint32_t test_
 static void
 test_get_no_selection_io_cause(const char *filename, hid_t fapl)
 {
+    hid_t                   dxpl = H5I_INVALID_HID;
+    H5D_selection_io_mode_t selection_io_mode;
+
+    if (MAINPROCESS) {
+        printf("\n");
+        TESTING("for H5Pget_no_selection_io_cause()");
+    }
+
+    curr_nerrors = nerrors;
+
+    if ((dxpl = H5Pcreate(H5P_DATASET_XFER)) < 0)
+        P_TEST_ERROR;
+    if (H5Pget_selection_io(dxpl, &selection_io_mode) < 0)
+        P_TEST_ERROR;
+    if (H5Pclose(dxpl) < 0)
+        P_TEST_ERROR;
+
+    /* The following tests are based on H5D_SELECTION_IO_MODE_DEFAULT as the
+     * default setting in the library; skip the tests if that is not true */
+    if (selection_io_mode != H5D_SELECTION_IO_MODE_DEFAULT) {
+        if (MAINPROCESS)
+            SKIPPED();
+        return;
+    }
+
     test_no_selection_io_cause_mode(filename, fapl, TEST_DISABLE_BY_API);
     test_no_selection_io_cause_mode(filename, fapl, TEST_NOT_CONTIGUOUS_OR_CHUNKED_DATASET);
     test_no_selection_io_cause_mode(filename, fapl, TEST_DATATYPE_CONVERSION);
@@ -3533,6 +3572,366 @@ test_get_no_selection_io_cause(const char *filename, hid_t fapl)
     return;
 } /* test_get_no_selection_io_cause() */
 
+/*
+ * This bug is exposed when running testpar/t_coll_md.c via testphdf5.
+ *
+ * Optimized bufs (bufs[1] is NULL) is used when passing as a parameter to the mpio driver
+ * for selection I/O.  When computing mpi_bufs_base in that routine, it is not accounted
+ * for and therefore causing segmentation fault when running the test.
+ *
+ * Fix:
+ * Check for optimized bufs when computing mpi_bufs_base.
+ */
+static void
+test_bug_optimized_bufs(const char *filename, hid_t fapl)
+{
+    hid_t   dxpl      = H5I_INVALID_HID;
+    hid_t   dcpl      = H5I_INVALID_HID;
+    hid_t   fid       = H5I_INVALID_HID;
+    hid_t   did       = H5I_INVALID_HID;
+    hid_t   fspace_id = H5I_INVALID_HID;
+    hid_t   mspace_id = H5I_INVALID_HID;
+    hsize_t dims[1];
+    hsize_t cdims[1];
+    hsize_t start[1];
+    hsize_t stride[1];
+    hsize_t count[1];
+    hsize_t block[1];
+    int    *wbuf;
+
+    if ((fid = H5Fcreate(filename, H5F_ACC_TRUNC, H5P_DEFAULT, fapl)) < 0)
+        P_TEST_ERROR;
+
+    if ((dcpl = H5Pcreate(H5P_DATASET_CREATE)) < 0)
+        P_TEST_ERROR;
+
+    dims[0] = (hsize_t)mpi_size * (hsize_t)DIMS;
+
+    fspace_id = H5Screate_simple(1, dims, NULL);
+
+    cdims[0] = (hsize_t)mpi_size;
+
+    if (H5Pset_chunk(dcpl, 1, cdims) < 0)
+        P_TEST_ERROR;
+
+    if ((did = H5Dcreate2(fid, "bug_optimized_bufs", H5T_NATIVE_INT, fspace_id, H5P_DEFAULT, dcpl,
+                          H5P_DEFAULT)) < 0)
+        P_TEST_ERROR;
+
+    start[0]  = (hsize_t)mpi_rank;
+    stride[0] = (hsize_t)mpi_size;
+    count[0]  = DIMS;
+    block[0]  = 1;
+
+    if (H5Sselect_hyperslab(fspace_id, H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    if ((mspace_id = H5Screate_simple(1, count, NULL)) < 0)
+        P_TEST_ERROR;
+
+    if ((wbuf = calloc(1, count[0] * sizeof(int))) == NULL)
+        P_TEST_ERROR;
+
+    if ((dxpl = H5Pcreate(H5P_DATASET_XFER)) < 0)
+        P_TEST_ERROR;
+
+    /* Enable collection transfer mode */
+    if (H5Pset_dxpl_mpio(dxpl, H5FD_MPIO_COLLECTIVE) < 0)
+        P_TEST_ERROR;
+
+    /* Enable selection I/O */
+    if (H5Pset_selection_io(dxpl, H5D_SELECTION_IO_MODE_ON) < 0)
+        P_TEST_ERROR;
+
+    if (H5Dwrite(did, H5T_NATIVE_INT, mspace_id, fspace_id, dxpl, wbuf) < 0)
+        P_TEST_ERROR;
+
+    if (H5Dclose(did) < 0)
+        P_TEST_ERROR;
+
+    if (H5Pclose(dcpl) < 0)
+        P_TEST_ERROR;
+
+    if (H5Pclose(dxpl) < 0)
+        P_TEST_ERROR;
+
+    if (H5Sclose(fspace_id) < 0)
+        P_TEST_ERROR;
+
+    if (H5Sclose(mspace_id) < 0)
+        P_TEST_ERROR;
+
+    if (H5Fclose(fid) < 0)
+        P_TEST_ERROR;
+
+    return;
+
+} /* test_bug_optimized_bufs() */
+
+/*
+ * The bug is exposed when running testpar/t_pread.c.
+ *
+ * The file is created with userblock.  Before passing down to the mpio driver for
+ * selection I/O, the parameter offsets[] is added by base_addr (size of the uesrblock).
+ * For the independent case in the mpio driver for selection I/O,
+ * the intermediate routine for the API H5FDread/write_vector_from_selection() is called.
+ * The parameter offsets[] is passed as is to the intermediate routine which will
+ * be added again by base_addr causing incorrect data retrieval.
+ *
+ * Fix:
+ * The parameter offsets[] needs to be adjusted by the base_addr addition before calling
+ * the intermediate routine.
+ */
+static void
+test_bug_base_addr(const char *filename, hid_t fapl)
+{
+    hid_t   dxpl      = H5I_INVALID_HID;
+    hid_t   dxpl_read = H5I_INVALID_HID;
+    hid_t   fid       = H5I_INVALID_HID;
+    hid_t   did       = H5I_INVALID_HID;
+    hid_t   sid       = H5I_INVALID_HID;
+    hid_t   fcpl      = H5I_INVALID_HID;
+    hsize_t dims[1];
+    hid_t   tid = H5T_NATIVE_INT;
+    int     wbuf[DSET_SELECT_DIM];
+    int     rbuf[DSET_SELECT_DIM];
+    int     i;
+
+    /* Create user block */
+    if ((fcpl = H5Pcreate(H5P_FILE_CREATE)) < 0)
+        P_TEST_ERROR;
+
+    if (H5Pset_userblock(fcpl, 512) < 0)
+        P_TEST_ERROR;
+
+    if ((dxpl = H5Pcreate(H5P_DATASET_XFER)) < 0)
+        P_TEST_ERROR;
+
+    /* Create the file with userblock */
+    if ((fid = H5Fcreate(filename, H5F_ACC_TRUNC, fcpl, fapl)) < 0)
+        P_TEST_ERROR;
+
+    /* Create 1d data space */
+    dims[0] = DSET_SELECT_DIM;
+
+    if ((sid = H5Screate_simple(1, dims, NULL)) < 0)
+        P_TEST_ERROR;
+
+    if ((did = H5Dcreate2(fid, "bug_base_addr", H5T_NATIVE_INT, sid, H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT)) <
+        0)
+        P_TEST_ERROR;
+
+    /* Initialize data */
+    for (i = 0; i < DSET_SELECT_DIM; i++)
+        wbuf[i] = i;
+
+    if ((dxpl = H5Pcreate(H5P_DATASET_XFER)) < 0)
+        P_TEST_ERROR;
+
+    /* Enable selection I/O */
+    if (H5Pset_selection_io(dxpl, H5D_SELECTION_IO_MODE_ON) < 0)
+        P_TEST_ERROR;
+
+    /* Independent by default and with selection I/O ON for reading */
+    if ((dxpl_read = H5Pcopy(dxpl)) < 0)
+        P_TEST_ERROR;
+
+    /* Enable collective and with selection I/O ON for writing */
+    if (H5Pset_dxpl_mpio(dxpl, H5FD_MPIO_COLLECTIVE) < 0)
+        P_TEST_ERROR;
+
+    if (H5Dwrite(did, tid, H5S_ALL, H5S_ALL, dxpl, wbuf) < 0)
+        P_TEST_ERROR;
+
+    if (H5Dread(did, tid, H5S_ALL, H5S_ALL, dxpl_read, rbuf) < 0)
+        P_TEST_ERROR;
+
+    if (H5Dclose(did) < 0)
+        P_TEST_ERROR;
+
+    if (H5Pclose(dxpl) < 0)
+        P_TEST_ERROR;
+
+    if (H5Pclose(dxpl_read) < 0)
+        P_TEST_ERROR;
+
+    if (H5Sclose(sid) < 0)
+        P_TEST_ERROR;
+
+    if (H5Pclose(fcpl) < 0)
+        P_TEST_ERROR;
+
+    if (H5Fclose(fid) < 0)
+        P_TEST_ERROR;
+    return;
+
+} /* test_bug_base_addr() */
+
+/*
+ * This bug is exposed when running testpar/t_2Gio.c with at least 2 processes.
+ *
+ * The root problem is from calling an API function from within the library i.e.
+ * calling H5FDread/write_vector_from_selection() for independent access in the
+ * mpio driver for selection I/O.
+ *
+ * The test scenario is described below with the test writing to a dataset
+ * via H5Dwrite():
+ * --running with 2 processes
+ * --with selection I/O on
+ * --with COLLECTIVE xfer mode
+ *
+ * For process 1:
+ * The library internal calls H5D__write():
+ * --io_info.use_select_io is ON
+ * --io_info.use_select_io is OFF after calling H5D__typeinfo_init_phase2()
+ *   due to H5D_SEL_IO_TCONV_BUF_TOO_SMALL
+ * --H5D__mpio_opt_possible() returns 0 so xfer mode is set to
+ *   H5FD_MPIO_INDEPENDENT
+ * The library eventually calls H5FD__mpio_write() performing scalar calls for the writes
+ *
+ * For process 0:
+ * The library internal calls H5D__write():
+ * --io_info.use_select_io is ON
+ * --H5D__mpio_opt_possible() returns 0 so xfer mode is set to
+ *   H5FD_MPIO_INDEPENDENT
+ * The library eventually calls H5FD__mpio_write_selection():
+ * --since the xfer mode is INDEPENDENT it calls the API
+ *   H5FDwrite_vector_from_selection(), which eventually calls
+ *   H5FD__mpio_write_vector().  This routine obtains the
+ *   xfer mode via API context which returns COLLECTIVE.
+ *   Then the test hangs when trying to do MPI_File_set_view().
+ *
+ * Fix:
+ * Create wrapper functions for the API H5FDread/write_vector_from_selection() and
+ * they will be called by H5FD__mpio_read/write_selection() for independent access.
+ *
+ */
+static void
+test_bug_api_library(const char *filename, hid_t fapl)
+{
+    hid_t   dxpl      = H5I_INVALID_HID;
+    hid_t   fid       = H5I_INVALID_HID;
+    hid_t   did       = H5I_INVALID_HID;
+    hid_t   sid       = H5I_INVALID_HID;
+    hid_t   fspace_id = H5I_INVALID_HID;
+    hid_t   mspace_id = H5I_INVALID_HID;
+    hsize_t dims[2];
+    hsize_t start[2];
+    hsize_t stride[2];
+    hsize_t count[2];
+    hsize_t block[2];
+    int    *wbuf;
+    hsize_t i, j;
+
+    if ((fid = H5Fcreate(filename, H5F_ACC_TRUNC, H5P_DEFAULT, fapl)) < 0)
+        P_TEST_ERROR;
+
+    dims[0] = (hsize_t)BIG_X_FACTOR;
+    dims[1] = (hsize_t)BIG_Y_FACTOR;
+
+    if ((sid = H5Screate_simple(2, dims, NULL)) < 0)
+        P_TEST_ERROR;
+
+    if ((did = H5Dcreate2(fid, "bug_coll_to_ind", H5T_NATIVE_INT, sid, H5P_DEFAULT, H5P_DEFAULT,
+                          H5P_DEFAULT)) < 0)
+        P_TEST_ERROR;
+
+    if ((wbuf = malloc((size_t)dims[0] * (size_t)dims[1] * sizeof(int))) == NULL)
+        P_TEST_ERROR;
+
+    /* Each process takes a slabs of rows. */
+    block[0]  = (hsize_t)dims[0] / (hsize_t)mpi_size;
+    block[1]  = (hsize_t)dims[1];
+    stride[0] = block[0];
+    stride[1] = block[1];
+    count[0]  = 1;
+    count[1]  = 1;
+    start[0]  = (hsize_t)mpi_rank * block[0];
+    start[1]  = 0;
+
+    if ((fspace_id = H5Dget_space(did)) < 0)
+        P_TEST_ERROR;
+    if (MAINPROCESS) {
+        if (H5Sselect_none(fspace_id) < 0)
+            P_TEST_ERROR;
+    } /* end if */
+    else {
+        if (H5Sselect_hyperslab(fspace_id, H5S_SELECT_SET, start, stride, count, block) < 0)
+            P_TEST_ERROR;
+    } /* end else */
+
+    if ((mspace_id = H5Screate_simple(2, block, NULL)) < 0)
+        P_TEST_ERROR;
+    if (MAINPROCESS) {
+        if (H5Sselect_none(mspace_id) < 0)
+            P_TEST_ERROR;
+    } /* end if */
+
+    if ((dxpl = H5Pcreate(H5P_DATASET_XFER)) < 0)
+        P_TEST_ERROR;
+
+    /* Enable collective transfer */
+    if (H5Pset_dxpl_mpio(dxpl, H5FD_MPIO_COLLECTIVE) < 0)
+        P_TEST_ERROR;
+
+    /* Enable selection I/O */
+    if (H5Pset_selection_io(dxpl, H5D_SELECTION_IO_MODE_ON) < 0)
+        P_TEST_ERROR;
+
+    /* Put some trivial data in wbuf */
+    for (i = 0; i < block[0]; i++) {
+        for (j = 0; j < block[1]; j++) {
+            *wbuf = (int)((i + start[0]) * 100 + (j + start[1] + 1));
+            wbuf++;
+        }
+    }
+
+    /* With datatype conversion */
+    if (H5Dwrite(did, H5T_NATIVE_UCHAR, mspace_id, fspace_id, dxpl, wbuf) < 0)
+        P_TEST_ERROR;
+
+    if (H5Dclose(did) < 0)
+        P_TEST_ERROR;
+
+    if (H5Pclose(dxpl) < 0)
+        P_TEST_ERROR;
+
+    if (H5Sclose(fspace_id) < 0)
+        P_TEST_ERROR;
+
+    if (H5Sclose(mspace_id) < 0)
+        P_TEST_ERROR;
+
+    if (H5Fclose(fid) < 0)
+        P_TEST_ERROR;
+
+    return;
+
+} /* test_bug_api_library() */
+
+/*
+ * Verify bugs exposed when H5D_SELECTION_IO_MODE_ON is set as the
+ * default in the library.
+ */
+static void
+test_bugs_select_on(const char *filename, hid_t fapl)
+{
+    if (MAINPROCESS) {
+        printf("\n");
+        TESTING("to verify bugs exposed when H5D_SELECTION_IO_MODE_ON is set as library default");
+    }
+
+    curr_nerrors = nerrors;
+
+    test_bug_optimized_bufs(filename, fapl);
+    test_bug_base_addr(filename, fapl);
+    test_bug_api_library(filename, fapl);
+
+    CHECK_PASSED();
+    return;
+
+} /* test_bugs_select_on() */
+
 /*-------------------------------------------------------------------------
  * Function:    main
  *
@@ -3740,12 +4139,10 @@ main(int argc, char *argv[])
     if (H5Fclose(fid) < 0)
         P_TEST_ERROR;
 
-    if (MAINPROCESS) {
-        printf("\n");
-        TESTING("Testing for H5Pget_no_selection_io_cause()");
-    }
     test_get_no_selection_io_cause(FILENAME, fapl);
 
+    test_bugs_select_on(FILENAME, fapl);
+
     /* Barrier to make sure all ranks are done before deleting the file, and
      * also to clean up output (make sure PASSED is printed before any of the
      * following messages) */
diff --git a/testpar/t_vfd.c b/testpar/t_vfd.c
index 827faf4..5e9070d 100644
--- a/testpar/t_vfd.c
+++ b/testpar/t_vfd.c
@@ -100,6 +100,100 @@ static unsigned vector_write_test_6(int file_name_id, int mpi_rank, int mpi_size
                                     H5FD_mpio_collective_opt_t coll_opt_mode, const char *vfd_name);
 static unsigned vector_write_test_7(int file_name_id, int mpi_rank, int mpi_size, H5FD_mpio_xfer_t xfer_mode,
                                     H5FD_mpio_collective_opt_t coll_opt_mode, const char *vfd_name);
+/*
+ * Tests for selection I/O:
+ * They are derived from test_selection_io() in test/vfd.c and modified for parallel testing.
+ */
+
+/*
+ * Global declarations for selection I/O tests`
+ */
+
+/* Number of errors */
+int nerrors      = 0;
+int curr_nerrors = 0;
+
+/* Test file name */
+#define SELECT_FNAME "mpio_select_test_file"
+
+/* Dimemsion sizes */
+#define SEL_IO_DIM0 4
+#define SEL_IO_DIM1 8
+int sel_dim0 = SEL_IO_DIM0;
+int sel_dim1 = SEL_IO_DIM1;
+
+/* Write buffers */
+int *wbuf1    = NULL;
+int *wbuf2    = NULL;
+int *wbufs[2] = {NULL, NULL};
+
+/* File buffers */
+int *fbuf1    = NULL;
+int *fbuf2    = NULL;
+int *fbufs[2] = {NULL, NULL}; /* Array of file buffers     */
+
+/* Expected read buffers */
+int *erbuf1    = NULL;
+int *erbuf2    = NULL;
+int *erbufs[2] = {NULL, NULL}; /* Array of expected read buffers */
+
+/* iotypes for testing:
+    H5FD_MPIO_INDEPENDENT
+    H5FD_MPIO_COLLECTIVE
+    --H5FD_MPIO_COLLECTIVE_IO
+    --H5FD_MPIO_INDIVIDUAL_IO
+*/
+#define iotypes 3
+
+#define P_TEST_ERROR                                                                                         \
+    do {                                                                                                     \
+        nerrors++;                                                                                           \
+        H5_FAILED();                                                                                         \
+        AT();                                                                                                \
+    } while (0)
+
+#define CHECK_PASSED()                                                                                       \
+    do {                                                                                                     \
+        int err_result = (nerrors > curr_nerrors);                                                           \
+                                                                                                             \
+        MPI_Allreduce(MPI_IN_PLACE, &err_result, 1, MPI_INT, MPI_MAX, MPI_COMM_WORLD);                       \
+                                                                                                             \
+        if (MAINPROCESS) {                                                                                   \
+            if (err_result == 0)                                                                             \
+                PASSED();                                                                                    \
+            else                                                                                             \
+                HDputs("     ***TEST FAILED***");                                                            \
+        }                                                                                                    \
+    } while (0)
+
+/* Utility functions for selection I/O */
+static herr_t test_selection_io_read_verify(hid_t dxpl, int mpi_rank, hsize_t start[], hsize_t block[],
+                                            H5FD_t *lf, H5FD_mem_t type, uint32_t count, hid_t mem_spaces[],
+                                            hid_t file_spaces[], haddr_t offsets[], size_t element_sizes[],
+                                            uint32_t rbufcount, int *erb[], hbool_t shorten_rbufs);
+
+static herr_t test_selection_io_write(hid_t dxpl, H5FD_t *lf, H5FD_mem_t type, uint32_t count,
+                                      hid_t mem_spaces[], hid_t file_spaces[], haddr_t offsets[],
+                                      size_t element_sizes[], int *wb[]);
+
+/* Test functions for selection I/O */
+static void test_selection_io(int mpi_rank, int mpi_size);
+static void test_selection_io_real(int mpi_rank, int mpi_size, H5FD_t *lf, hid_t dxpl);
+static void test_selection_io_types_1d(int mpi_rank, int mpi_size, H5FD_t *lf, hid_t dxpl, H5FD_mem_t type,
+                                       haddr_t addrs[], size_t element_sizes[], hid_t mem_spaces[],
+                                       hid_t file_spaces[], hsize_t dims1[]);
+static void test_selection_io_types_2d(int mpi_rank, int mpi_size, H5FD_t *lf, hid_t dxpl, H5FD_mem_t type,
+                                       haddr_t addrs[], size_t element_sizes[], hid_t mem_spaces[],
+                                       hid_t file_spaces[], hsize_t dims2[]);
+static void test_selection_io_types_1d_2d(int mpi_rank, int mpi_size, H5FD_t *lf, hid_t dxpl, H5FD_mem_t type,
+                                          haddr_t addrs[], size_t element_sizes[], hid_t mem_spaces[],
+                                          hid_t file_spaces[], hsize_t dims1[], hsize_t dims2[]);
+static void test_selection_io_types_shorten(int mpi_rank, int mpi_size, H5FD_t *lf, hid_t dxpl,
+                                            H5FD_mem_t type, haddr_t addrs[], size_t element_sizes[],
+                                            hid_t mem_spaces[], hid_t file_spaces[], hsize_t dims1[],
+                                            hsize_t dims2[]);
+
+/****************************************************************************/
 
 /****************************************************************************/
 /***************************** Utility Functions ****************************/
@@ -4065,86 +4159,22 @@ vector_write_test_7(int file_name_id, int mpi_rank, int mpi_size, H5FD_mpio_xfer
 
 } /* vector_write_test_7() */
 
-/*-------------------------------------------------------------------------
- * Function:    main
- *
- * Purpose:     Run parallel VFD tests.
- *
- * Return:      Success: 0
- *
- *              Failure: 1
- *
- *-------------------------------------------------------------------------
- */
-
-int
-main(int argc, char **argv)
+static void
+test_vector_io(int mpi_rank, int mpi_size)
 {
     unsigned nerrs = 0;
-#ifdef H5_HAVE_SUBFILING_VFD
-    int required = MPI_THREAD_MULTIPLE;
-    int provided = 0;
-#endif
-    int mpi_size;
-    int mpi_rank = 0;
-
-#ifdef H5_HAVE_SUBFILING_VFD
-    if (MPI_SUCCESS != MPI_Init_thread(&argc, &argv, required, &provided)) {
-        printf("    MPI doesn't support MPI_Init_thread with MPI_THREAD_MULTIPLE. Exiting\n");
-        goto finish;
-    }
-
-    if (provided != required) {
-        printf("    MPI doesn't support MPI_Init_thread with MPI_THREAD_MULTIPLE. Exiting\n");
-        goto finish;
-    }
-#else
-    if (MPI_SUCCESS != MPI_Init(&argc, &argv)) {
-        printf("    MPI_Init failed. Exiting\n");
-        goto finish;
-    }
-#endif
-
-    MPI_Comm_size(comm, &mpi_size);
-    MPI_Comm_rank(comm, &mpi_rank);
 
-    /* Attempt to turn off atexit post processing so that in case errors
-     * occur during the test and the process is aborted, it will not hang
-     * in the atexit post processing.  If it does, it may try to make MPI
-     * calls which may not work.
-     */
-    if (H5dont_atexit() < 0)
-        printf("%d:Failed to turn off atexit processing. Continue.\n", mpi_rank);
-
-    H5open();
-
-    if (mpi_rank == 0) {
-        printf("=========================================\n");
-        printf("Parallel virtual file driver (VFD) tests\n");
-        printf("        mpi_size     = %d\n", mpi_size);
-        printf("=========================================\n");
-    }
-
-    if (mpi_size < 2) {
-        if (mpi_rank == 0)
-            printf("    Need at least 2 processes.  Exiting.\n");
-        goto finish;
-    }
-
-    alloc_and_init_file_images(mpi_size);
+    nerrs += alloc_and_init_file_images(mpi_size);
 
     if (!pass) {
 
         printf("\nAllocation and initialize of file image buffers failed.  Test aborted.\n");
+        nerrors += (int)nerrs;
+        return;
     }
 
     MPI_Barrier(comm);
 
-    if (mpi_rank == 0) {
-
-        printf("\n\n --- TESTING MPIO VFD --- \n\n");
-    }
-
     nerrs +=
         vector_read_test_1(0, mpi_rank, mpi_size, H5FD_MPIO_INDEPENDENT, H5FD_MPIO_INDIVIDUAL_IO, "mpio");
     nerrs += vector_read_test_1(0, mpi_rank, mpi_size, H5FD_MPIO_COLLECTIVE, H5FD_MPIO_INDIVIDUAL_IO, "mpio");
@@ -4312,18 +4342,1643 @@ main(int argc, char **argv)
                                  H5FD_SUBFILING_NAME);
 #endif
 
+    nerrors += (int)nerrs;
+
+    /* return(nerrs);*/
+
+} /* test_vector_io() */
+
+/*
+ * Utility routine to perform the actual selection I/O read
+ */
+static herr_t
+test_selection_io_read_verify(hid_t dxpl, int mpi_rank, hsize_t start[], hsize_t block[], H5FD_t *lf,
+                              H5FD_mem_t type, uint32_t count, hid_t mem_spaces[], hid_t file_spaces[],
+                              haddr_t offsets[], size_t element_sizes[], uint32_t rbufcount, int *erb[],
+                              hbool_t shorten_rbufs)
+{
+    int   *rbuf1    = NULL;
+    int   *rbuf2    = NULL;
+    int   *rbufs[2] = {NULL, NULL};
+    size_t bufsize;
+    int    i;
+    int    j;
+
+    bufsize = (hsize_t)(sel_dim0 * sel_dim1) * sizeof(int);
+    if ((rbuf1 = malloc(bufsize)) == NULL)
+        goto error;
+    if ((rbuf2 = malloc(bufsize)) == NULL)
+        goto error;
+    rbufs[0] = rbuf1;
+    rbufs[1] = rbuf2;
+
+    /* Initialize read buffer */
+    for (i = 0; i < (int)rbufcount; i++)
+        for (j = 0; j < sel_dim0 * sel_dim1; j++)
+            rbufs[i][j] = -1;
+
+    /* Handle elements in count that are not part of rbufcount */
+    for (i = (int)rbufcount; i < (int)count; i++)
+        if (shorten_rbufs)
+            rbufs[i] = NULL;
+        else
+            rbufs[i] = rbufs[rbufcount - 1];
+
+    /* Issue read call */
+    if (H5FDread_selection(lf, type, dxpl, count, mem_spaces, file_spaces, offsets, element_sizes,
+                           (void **)rbufs) < 0)
+        goto error;
+
+    /* Verify result */
+    for (i = 0; i < (int)rbufcount; i++) {
+        hsize_t endblock = MIN((start[i] + block[i]), (hsize_t)(sel_dim0 * sel_dim1));
+        for (j = (int)start[i]; j < (int)endblock; j++)
+            if (rbufs[i][j] != erb[i][j]) {
+                H5_FAILED();
+                AT();
+                printf(
+                    "data read from file does not match expected values at mapping array location %d: %d\n",
+                    i, mpi_rank);
+                printf("expected data: \n");
+                for (j = 0; j < sel_dim0 * sel_dim1; j++) {
+                    printf("%6d", erb[i][j]);
+                    if (!((j + 1) % sel_dim1))
+                        printf("\n");
+                }
+                printf("read data: \n");
+                for (j = 0; j < (sel_dim0 * sel_dim1); j++) {
+                    printf("%6d", rbufs[i][j]);
+                    if (!((j + 1) % sel_dim1))
+                        printf("\n");
+                }
+                goto error;
+            }
+    }
+
+    if (rbuf1)
+        free(rbuf1);
+    if (rbuf2)
+        free(rbuf2);
+    return 0;
+
+error:
+    if (rbuf1)
+        free(rbuf1);
+    if (rbuf2)
+        free(rbuf2);
+    return -1;
+
+} /* end test_selection_io_read_verify() */
+
+/*
+ * Utility routine to perform the actual selection I/O write
+ */
+static herr_t
+test_selection_io_write(hid_t dxpl, H5FD_t *lf, H5FD_mem_t type, uint32_t count, hid_t mem_spaces[],
+                        hid_t file_spaces[], haddr_t offsets[], size_t element_sizes[], int *wb[])
+{
+    const void **bufs = NULL; /* Avoids cast/const warnings */
+    int          i;
+    int          j;
+
+    if (NULL == (bufs = calloc(count, sizeof(void *))))
+        goto error;
+
+    /* Update write buffer */
+    for (i = 0; i < (int)count; i++) {
+        if (wb[i] && (i == 0 || wb[i] != wb[i - 1]))
+            for (j = 0; j < (sel_dim0 * sel_dim1); j++)
+                wb[i][j] += 2 * (sel_dim0 * sel_dim1);
+        bufs[i] = wb[i];
+    }
+
+    /* Issue write call */
+    if (H5FDwrite_selection(lf, type, dxpl, count, mem_spaces, file_spaces, offsets, element_sizes, bufs) < 0)
+        goto error;
+
+    if (bufs)
+        free(bufs);
+
+    return 0;
+
+error:
+    if (bufs)
+        free(bufs);
+    return -1;
+
+} /* end test_selection_io_write() */
+
+/*
+ * Perform the following tests that use shortened arrays for wbuf and element sizes
+ * --Test 1: Strided <> Strided 1D and 2D I/O for both file and memory spaces
+ * --Reset selections
+ * --Test 2: Strided <> Strided 2D I/O, 2 different selections in the same memory buffer
+ * --Reset selections
+ */
+static void
+test_selection_io_types_shorten(int mpi_rank, int mpi_size, H5FD_t *lf, hid_t dxpl, H5FD_mem_t type,
+                                haddr_t addrs[], size_t element_sizes[], hid_t mem_spaces[],
+                                hid_t file_spaces[], hsize_t dims1[], hsize_t dims2[])
+{
+    hsize_t start[2];                 /* start for hyperslab          */
+    hsize_t stride[2];                /* stride for hyperslab         */
+    hsize_t count[2];                 /* count for hyperslab          */
+    hsize_t block[2];                 /* block for hyperslab          */
+    hsize_t verify_start[2] = {0, 0}; /* Starting block for verified data */
+    hsize_t verify_block[2] = {0, 0}; /* Block size for verified data */
+    int     i;
+    int     j;
+    int     i2;
+    int     j2;
+
+    int shorten_element_sizes; /* Whether to shorten the element sizes array */
+
+    for (shorten_element_sizes = 0; shorten_element_sizes <= 1; shorten_element_sizes++) {
+        /*
+         * Test 1: Strided <> Strided 1D and 2D I/O
+         */
+        /* sel_dim1 must be even */
+        assert(sel_dim1 / 2 == (sel_dim1 + 1) / 2);
+
+        /* Strided selection in memory (1D) */
+        block[0]  = 1;
+        count[0]  = (hsize_t)(((sel_dim0 * sel_dim1) / 2) / mpi_size);
+        stride[0] = 2;
+        start[0]  = (hsize_t)mpi_rank * stride[0] * count[0];
+        if (H5Sselect_hyperslab(mem_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+            P_TEST_ERROR;
+
+        verify_start[0] = start[0];
+        verify_block[0] = (count[0] * stride[0]);
+
+        /* Strided selection in file (1D) */
+        start[0] = 1 + ((hsize_t)mpi_rank * stride[0] * count[0]);
+        if (H5Sselect_hyperslab(file_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+            P_TEST_ERROR;
+
+        /* Strided selection (across dim 1) in file (2D) */
+        block[0]  = 1;
+        block[1]  = 1;
+        count[0]  = (hsize_t)(sel_dim0 / mpi_size);
+        count[1]  = (hsize_t)sel_dim1 / 2;
+        stride[0] = 1;
+        stride[1] = 2;
+        start[0]  = (hsize_t)mpi_rank * count[0];
+        start[1]  = 1;
+        if (H5Sselect_hyperslab(file_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+            P_TEST_ERROR;
+
+        /* Strided selection (across dim 0) in memory (2D) */
+        block[0]  = 1;
+        block[1]  = 1;
+        count[0]  = (hsize_t)((sel_dim0 / 2) / mpi_size);
+        count[1]  = (hsize_t)sel_dim1;
+        stride[0] = 2;
+        stride[1] = 1;
+        start[0]  = 1 + ((hsize_t)mpi_rank * stride[0] * count[0]);
+        start[1]  = 0;
+        if (H5Sselect_hyperslab(mem_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+            P_TEST_ERROR;
+
+        verify_start[1] = start[0] * count[1];
+        verify_block[1] = (count[0] * count[1] * stride[0]);
+
+        /* Issue write call */
+        if (test_selection_io_write(dxpl, lf, type, 2, mem_spaces, file_spaces, addrs, element_sizes,
+                                    (int **)wbufs) < 0)
+            P_TEST_ERROR;
+
+        MPI_Barrier(comm);
+
+        /* Update file bufs */
+        for (i = 0; i < (sel_dim0 * sel_dim1) / 2; i++)
+            fbuf1[(2 * i) + 1] = wbuf1[2 * i];
+        for (i = 1, i2 = 0, j2 = 1; i < sel_dim0; i += 2)
+            for (j = 0; j < sel_dim1; j++) {
+                assert(i2 < sel_dim0);
+                fbuf2[i2 * sel_dim1 + j2] = wbuf2[i * sel_dim1 + j];
+                j2 += 2;
+                if (j2 >= sel_dim1) {
+                    i2++;
+                    j2 = 1;
+                }
+            }
+
+        /* Update expected read bufs */
+        for (i = 0; i < (sel_dim0 * sel_dim1); i++)
+            erbuf1[i] = -1;
+        for (i = 0; i < (sel_dim0 * sel_dim1) / 2; i++)
+            erbuf1[2 * i] = wbuf1[2 * i];
+        for (i = 0; i < sel_dim0; i++)
+            for (j = 0; j < sel_dim1; j++)
+                erbuf2[i * sel_dim1 + j] = -1;
+        for (i = 1; i < sel_dim0; i += 2)
+            for (j = 0; j < sel_dim1; j++)
+                erbuf2[i * sel_dim1 + j] = wbuf2[i * sel_dim1 + j];
+
+        /* Read and verify */
+        if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 2, mem_spaces,
+                                          file_spaces, addrs, element_sizes, 2, (int **)erbufs, FALSE) < 0)
+            P_TEST_ERROR;
+
+        MPI_Barrier(comm);
+
+        /*
+         * Reset selections
+         */
+        if (H5Sselect_all(mem_spaces[0]) < 0)
+            P_TEST_ERROR;
+        if (H5Sselect_all(file_spaces[0]) < 0)
+            P_TEST_ERROR;
+
+        /* Each process takes x number of elements */
+        block[0]  = dims1[0] / (hsize_t)mpi_size;
+        count[0]  = 1;
+        stride[0] = block[0];
+        start[0]  = (hsize_t)mpi_rank * block[0];
+
+        verify_start[0] = start[0];
+        verify_block[0] = block[0];
+
+        if (H5Sselect_hyperslab(mem_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+            P_TEST_ERROR;
+        if (H5Sselect_hyperslab(file_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+            P_TEST_ERROR;
+
+        if (H5Sselect_all(mem_spaces[1]) < 0)
+            P_TEST_ERROR;
+        if (H5Sselect_all(file_spaces[1]) < 0)
+            P_TEST_ERROR;
+
+        /* Each process takes x number of elements */
+        block[0]  = dims2[0] / (hsize_t)mpi_size;
+        block[1]  = dims2[1];
+        count[0]  = 1;
+        count[1]  = 1;
+        stride[0] = block[0];
+        stride[1] = block[1];
+        start[0]  = (hsize_t)mpi_rank * block[0];
+        start[1]  = 0;
+
+        verify_start[1] = start[0] * block[1];
+        verify_block[1] = (block[0] * block[1]);
+
+        if (H5Sselect_hyperslab(mem_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+            P_TEST_ERROR;
+        if (H5Sselect_hyperslab(file_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+            P_TEST_ERROR;
+
+        /* Read entire file buffer and verify */
+        if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 2, mem_spaces,
+                                          file_spaces, addrs, element_sizes, 2, (int **)fbufs, FALSE) < 0)
+            P_TEST_ERROR;
+
+        MPI_Barrier(comm);
+
+        /*
+         * Test 2: Strided <> Strided 2D I/O, 2 different selections in the same memory buffer
+         */
+        /* Switch mem and file spaces to both be 2D */
+        if (H5Sset_extent_simple(mem_spaces[0], 2, dims2, NULL) < 0)
+            P_TEST_ERROR;
+        if (H5Sset_extent_simple(file_spaces[0], 2, dims2, NULL) < 0)
+            P_TEST_ERROR;
+
+        /* Strided selection in memory (1st) */
+        block[0]  = 1;
+        block[1]  = 1;
+        count[0]  = (hsize_t)((sel_dim0 / 2) / mpi_size);
+        count[1]  = (hsize_t)sel_dim1;
+        stride[0] = 2;
+        stride[1] = 1;
+        start[0]  = (hsize_t)mpi_rank * count[0] * stride[0];
+        start[1]  = 0;
+
+        if (H5Sselect_hyperslab(mem_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+            P_TEST_ERROR;
+
+        verify_start[0] = start[0] * count[1];
+        verify_block[0] = (count[0] * count[1] * stride[0]);
+
+        /* Strided selection (across dim 0) in memory (2nd) */
+        start[0] = 1 + ((hsize_t)mpi_rank * count[0] * stride[0]);
+        if (H5Sselect_hyperslab(mem_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+            P_TEST_ERROR;
+
+        verify_start[1] = start[0] * count[1];
+        verify_block[1] = (count[0] * count[1] * stride[0]);
+
+        /* Strided selection in file (1st) */
+        block[0]  = 1;
+        block[1]  = 1;
+        count[0]  = (hsize_t)(sel_dim0 / mpi_size);
+        count[1]  = (hsize_t)sel_dim1 / 2;
+        stride[0] = 1;
+        stride[1] = 2;
+        start[0]  = (hsize_t)mpi_rank * count[0];
+        start[1]  = 0;
+        if (H5Sselect_hyperslab(file_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+            P_TEST_ERROR;
+
+        /* Strided selection (across dim 1) in file (2nd) */
+        block[0]  = 1;
+        block[1]  = 1;
+        count[0]  = (hsize_t)(sel_dim0 / mpi_size);
+        count[1]  = (hsize_t)sel_dim1 / 2;
+        stride[0] = 1;
+        stride[1] = 2;
+        start[0]  = (hsize_t)mpi_rank * count[0];
+        start[1]  = 1;
+        if (H5Sselect_hyperslab(file_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+            P_TEST_ERROR;
+
+        /* Use the same memory buffer for both selections */
+        wbufs[0] = wbuf2;
+
+        /* Shorten wbuf array */
+        if (shorten_element_sizes)
+            wbufs[1] = NULL;
+        else
+            wbufs[1] = wbufs[0];
+
+        /* Issue write call */
+        if (test_selection_io_write(dxpl, lf, type, 2, mem_spaces, file_spaces, addrs, element_sizes,
+                                    (int **)wbufs) < 0)
+            P_TEST_ERROR;
+
+        MPI_Barrier(comm);
+
+        /* Update file bufs - need to reuse 1D array so data stays consistent, so use math to
+         * find 1D index into 2D array */
+        for (i = 0, i2 = 0, j2 = 0; i < sel_dim0; i += 2)
+            for (j = 0; j < sel_dim1; j++) {
+                assert(i2 < sel_dim0);
+                fbuf1[(i2 * sel_dim1) + j2] = wbuf2[i * sel_dim1 + j];
+                j2 += 2;
+                if (j2 >= sel_dim1) {
+                    i2++;
+                    j2 = 0;
+                }
+            }
+        for (i = 1, i2 = 0, j2 = 1; i < sel_dim0; i += 2)
+            for (j = 0; j < sel_dim1; j++) {
+                assert(i2 < sel_dim0);
+                fbuf2[i2 * sel_dim1 + j2] = wbuf2[i * sel_dim1 + j];
+                j2 += 2;
+                if (j2 >= sel_dim1) {
+                    i2++;
+                    j2 = 1;
+                }
+            }
+
+        /* Update expected read buf */
+        for (i = 0; i < sel_dim0; i++)
+            for (j = 0; j < sel_dim1; j++)
+                erbuf2[i * sel_dim1 + j] = -1;
+        for (i = 0; i < sel_dim0; i += 2)
+            for (j = 0; j < sel_dim1; j++)
+                erbuf2[i * sel_dim1 + j] = wbuf2[i * sel_dim1 + j];
+        for (i = 1; i < sel_dim0; i += 2)
+            for (j = 0; j < sel_dim1; j++)
+                erbuf2[i * sel_dim1 + j] = wbuf2[i * sel_dim1 + j];
+
+        /* Read and verify */
+        if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 2, mem_spaces,
+                                          file_spaces, addrs, element_sizes, 1, (int **)&erbufs[1],
+                                          shorten_element_sizes ? TRUE : FALSE) < 0)
+            P_TEST_ERROR;
+
+        MPI_Barrier(comm);
+
+        /*
+         * Reset selections
+         */
+        if (H5Sselect_all(mem_spaces[0]) < 0)
+            P_TEST_ERROR;
+        if (H5Sselect_all(file_spaces[0]) < 0)
+            P_TEST_ERROR;
+
+        if (H5Sselect_all(mem_spaces[1]) < 0)
+            P_TEST_ERROR;
+        if (H5Sselect_all(file_spaces[1]) < 0)
+            P_TEST_ERROR;
+
+        /* Each process takes x number of elements */
+        block[0]  = dims2[0] / (hsize_t)mpi_size;
+        block[1]  = dims2[1];
+        count[0]  = 1;
+        count[1]  = 1;
+        stride[0] = block[0];
+        stride[1] = block[1];
+        start[0]  = (hsize_t)mpi_rank * block[0];
+        start[1]  = 0;
+
+        if (H5Sselect_hyperslab(mem_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+            P_TEST_ERROR;
+        if (H5Sselect_hyperslab(file_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+            P_TEST_ERROR;
+
+        if (H5Sselect_hyperslab(mem_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+            P_TEST_ERROR;
+        if (H5Sselect_hyperslab(file_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+            P_TEST_ERROR;
+
+        /* Read entire file buffer and verify */
+        verify_start[0] = start[0] * block[1];
+        verify_block[0] = (block[0] * block[1]);
+        verify_start[1] = start[0] * block[1];
+        verify_block[1] = (block[0] * block[1]);
+        if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 2, mem_spaces,
+                                          file_spaces, addrs, element_sizes, 2, (int **)fbufs, FALSE) < 0)
+            P_TEST_ERROR;
+
+        MPI_Barrier(comm);
+
+        /* Reset first spaces to 1D */
+        if (H5Sset_extent_simple(mem_spaces[0], 1, dims1, NULL) < 0)
+            P_TEST_ERROR;
+        if (H5Sset_extent_simple(file_spaces[0], 1, dims1, NULL) < 0)
+            P_TEST_ERROR;
+
+        /* Reset write buffer array */
+        wbufs[0] = wbuf1;
+        wbufs[1] = wbuf2;
+
+        /* Change to shortened element sizes array */
+        element_sizes[1] = 0;
+
+        MPI_Barrier(comm);
+    }
+
+    /* Reset element sizes array */
+    element_sizes[1] = element_sizes[0];
+
+    return;
+
+} /* test_selection_io_types_shorten() */
+
+/*
+ * Perform the following tests for 1 & 2 dimensional spaces:
+ * --Test 1: Strided 1D (memory) <> Strided 2D (file) I/O
+ * --Reset selections
+ * --Test 2: Strided 2D (memory) <> Strided 1D (file) I/O
+ * --Reset selections
+ */
+static void
+test_selection_io_types_1d_2d(int mpi_rank, int mpi_size, H5FD_t *lf, hid_t dxpl, H5FD_mem_t type,
+                              haddr_t addrs[], size_t element_sizes[], hid_t mem_spaces[],
+                              hid_t file_spaces[], hsize_t dims1[], hsize_t dims2[])
+{
+    hsize_t start[2];                 /* start for hyperslab          */
+    hsize_t stride[2];                /* stride for hyperslab         */
+    hsize_t count[2];                 /* count for hyperslab          */
+    hsize_t block[2];                 /* block for hyperslab          */
+    hsize_t verify_start[2] = {0, 0}; /* Starting block for verified data */
+    hsize_t verify_block[2] = {0, 0}; /* Block size for verified data */
+    int     i;
+    int     j;
+    int     i2;
+    int     j2;
+
+    /*
+     * Test 1: Strided 1D (memory) <> Strided 2D (file) I/O
+     */
+    /* Strided selection (across dim 1) in file */
+    block[0]  = 1;
+    block[1]  = 1;
+    count[0]  = (hsize_t)(sel_dim0 / mpi_size);
+    count[1]  = (hsize_t)sel_dim1 / 2;
+    stride[0] = 1;
+    stride[1] = 2;
+    start[0]  = (hsize_t)mpi_rank * count[0];
+    start[1]  = 1;
+    if (H5Sselect_hyperslab(file_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Strided selection in memory */
+    block[0]  = 1;
+    count[0]  = (hsize_t)(((sel_dim0 * sel_dim1) / 2) / mpi_size);
+    stride[0] = 2;
+    start[0]  = 1 + ((hsize_t)mpi_rank * stride[0] * count[0]);
+    if (H5Sselect_hyperslab(mem_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Issue write call */
+    if (test_selection_io_write(dxpl, lf, type, 1, &mem_spaces[0], &file_spaces[1], &addrs[1], element_sizes,
+                                (int **)&wbufs[0]) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /* Update file buf */
+    for (i = 1, i2 = 0, j2 = 1; i < (sel_dim0 * sel_dim1); i += 2) {
+        assert(i2 < sel_dim0);
+        fbuf2[(i2 * sel_dim1) + j2] = wbuf1[i];
+        j2 += 2;
+        if (j2 >= sel_dim1) {
+            i2++;
+            j2 = 1;
+        }
+    }
+
+    /* Update expected read buf */
+    for (i = 0; i < (sel_dim0 * sel_dim1); i++)
+        erbuf1[i] = -1;
+    for (i = 1; i < (sel_dim0 * sel_dim1); i += 2)
+        erbuf1[i] = wbuf1[i];
+
+    /* Read and verify */
+    verify_start[0] = start[0];
+    verify_block[0] = (count[0] * stride[0]);
+    if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 1, &mem_spaces[0],
+                                      &file_spaces[1], &addrs[1], element_sizes, 1, (int **)&erbufs[0],
+                                      FALSE) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /*
+     * Reset selections
+     */
+    if (H5Sselect_all(file_spaces[1]) < 0)
+        P_TEST_ERROR;
+
+    if (H5Sselect_all(mem_spaces[0]) < 0)
+        P_TEST_ERROR;
+
+    block[0]  = dims2[0] / (hsize_t)mpi_size;
+    block[1]  = dims2[1];
+    count[0]  = 1;
+    count[1]  = 1;
+    stride[0] = block[0];
+    stride[1] = block[1];
+    start[0]  = (hsize_t)mpi_rank * block[0];
+    start[1]  = 0;
+    if (H5Sselect_hyperslab(file_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    block[0]  = dims1[0] / (hsize_t)mpi_size;
+    count[0]  = 1;
+    stride[0] = block[0];
+    start[0]  = (hsize_t)mpi_rank * block[0];
+    if (H5Sselect_hyperslab(mem_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Read entire file buffer and verify */
+    verify_start[0] = start[0];
+    verify_block[0] = block[0];
+    if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 1, &mem_spaces[0],
+                                      &file_spaces[1], &addrs[1], element_sizes, 1, (int **)&fbufs[1],
+                                      FALSE) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /*
+     * Test 2: Strided 2D (memory) <> Strided 1D (file) I/O
+     */
+    /* Strided selection in file */
+    block[0]  = 1;
+    count[0]  = (hsize_t)(((sel_dim0 * sel_dim1) / 2) / mpi_size);
+    stride[0] = 2;
+    start[0]  = (hsize_t)mpi_rank * stride[0] * count[0];
+    if (H5Sselect_hyperslab(file_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Strided selection (across dim 0) in memory */
+    block[0]  = 1;
+    block[1]  = 1;
+    count[0]  = (hsize_t)((sel_dim0 / 2) / mpi_size);
+    count[1]  = (hsize_t)sel_dim1;
+    stride[0] = 2;
+    stride[1] = 1;
+    start[0]  = (hsize_t)mpi_rank * count[0] * stride[0];
+    start[1]  = 0;
+    if (H5Sselect_hyperslab(mem_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Issue write call */
+    if (test_selection_io_write(dxpl, lf, type, 1, &mem_spaces[1], &file_spaces[0], &addrs[0], element_sizes,
+                                (int **)&wbufs[1]) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /* Update file buf */
+    for (i = 0, i2 = 0; i < sel_dim0; i += 2)
+        for (j = 0; j < sel_dim1; j++) {
+            assert(i2 < (sel_dim0 * sel_dim1));
+            fbuf1[i2] = wbuf2[i * sel_dim1 + j];
+            i2 += 2;
+        }
+
+    /* Update expected read buf */
+    for (i = 0; i < sel_dim0; i++)
+        for (j = 0; j < sel_dim1; j++)
+            erbuf2[(i * sel_dim1) + j] = -1;
+    for (i = 0; i < sel_dim0; i += 2)
+        for (j = 0; j < sel_dim1; j++)
+            erbuf2[(i * sel_dim1) + j] = wbuf2[i * sel_dim1 + j];
+
+    /* Read and verify */
+    verify_start[0] = start[0] * count[1];
+    verify_block[0] = (count[0] * count[1] * stride[0]);
+    if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 1, &mem_spaces[1],
+                                      &file_spaces[0], &addrs[0], element_sizes, 1, (int **)&erbufs[1],
+                                      FALSE) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /*
+     * Reset selections
+     */
+    if (H5Sselect_all(file_spaces[0]) < 0)
+        P_TEST_ERROR;
+
+    if (H5Sselect_all(mem_spaces[1]) < 0)
+        P_TEST_ERROR;
+
+    /* Each process takes x number of elements */
+    block[0]  = dims1[0] / (hsize_t)mpi_size;
+    count[0]  = 1;
+    stride[0] = block[0];
+    start[0]  = (hsize_t)mpi_rank * block[0];
+    if (H5Sselect_hyperslab(file_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Each process takes x number of elements */
+    block[0]  = dims2[0] / (hsize_t)mpi_size;
+    block[1]  = dims2[1];
+    count[0]  = 1;
+    count[1]  = 1;
+    stride[0] = block[0];
+    stride[1] = block[1];
+    start[0]  = (hsize_t)mpi_rank * block[0];
+    start[1]  = 0;
+    if (H5Sselect_hyperslab(mem_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Read entire file buffer and verify */
+    verify_start[0] = start[0] * block[1];
+    verify_block[0] = (block[0] * block[1]);
+    if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 1, &mem_spaces[1],
+                                      &file_spaces[0], &addrs[0], element_sizes, 1, (int **)&fbufs[0],
+                                      FALSE) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    return;
+
+} /* test_selection_io_types_1d_2d() */
+
+/*
+ * Perform the following tests for 2 dimensional spaces:
+ * --Test 1: Simple 2D contiguous I/O for both file and memory spaces
+ * --Test 2: Strided (memory) <> Contiguous(file) 2D I/O
+ * --Reset selections
+ * --Test 3: Contiguous (memory) <> Strided (file) 2D I/O
+ * --Reset selections
+ * --Test 4: Strided (memory) <> Strided (file) 2D I/O
+ * --Reset selections
+ */
+static void
+test_selection_io_types_2d(int mpi_rank, int mpi_size, H5FD_t *lf, hid_t dxpl, H5FD_mem_t type,
+                           haddr_t addrs[], size_t element_sizes[], hid_t mem_spaces[], hid_t file_spaces[],
+                           hsize_t dims2[])
+{
+    hsize_t start[2];                 /* start for hyperslab          */
+    hsize_t stride[2];                /* stride for hyperslab         */
+    hsize_t count[2];                 /* count for hyperslab          */
+    hsize_t block[2];                 /* block for hyperslab          */
+    hsize_t verify_start[2] = {0, 0}; /* Starting block for verified data */
+    hsize_t verify_block[2] = {0, 0}; /* Block size for verified data */
+    int     i;
+    int     j;
+    int     i2;
+    int     j2;
+
+    /*
+     * Test 1: Simple 2D contiguous I/O
+     */
+
+    /* Contiguous selection in file and memory */
+    block[0]  = dims2[0] / (hsize_t)mpi_size;
+    block[1]  = dims2[1];
+    count[0]  = 1;
+    count[1]  = 1;
+    stride[0] = block[0];
+    stride[1] = block[1];
+    start[0]  = (hsize_t)mpi_rank * block[0];
+    start[1]  = 0;
+
+    if (H5Sselect_hyperslab(file_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+    if (H5Sselect_hyperslab(mem_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    if (test_selection_io_write(dxpl, lf, type, 1, &mem_spaces[1], &file_spaces[1], &addrs[1], element_sizes,
+                                (int **)&wbufs[1]) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /* Update file buf */
+    for (i = 0; i < sel_dim0; i++)
+        for (j = 0; j < sel_dim1; j++)
+            fbuf2[(i * sel_dim1) + j] = wbuf2[(i * sel_dim1) + j];
+
+    /* Read and verify */
+    verify_start[0] = start[0] * block[1];
+    verify_block[0] = (block[0] * block[1]);
+    if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 1, &mem_spaces[1],
+                                      &file_spaces[1], &addrs[1], element_sizes, 1, (int **)&fbufs[1],
+                                      FALSE) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /*
+     * Test 2: Strided (memory) <> Contiguous(file) 2D I/O
+     */
+    /* Contiguous selection in file */
+    count[0] = (hsize_t)((sel_dim0 / 2) / mpi_size);
+    count[1] = (hsize_t)sel_dim1;
+    start[0] = 1 + ((hsize_t)mpi_rank * count[0]);
+    start[1] = 0;
+    if (H5Sselect_hyperslab(file_spaces[1], H5S_SELECT_SET, start, NULL, count, NULL) < 0)
+        P_TEST_ERROR;
+
+    /* Strided selection in memory */
+    block[0]  = 1;
+    block[1]  = 1;
+    stride[0] = 2;
+    stride[1] = 1;
+    start[0]  = 1 + ((hsize_t)mpi_rank * stride[0] * count[0]);
+    start[1]  = 0;
+    if (H5Sselect_hyperslab(mem_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Issue write call */
+    if (test_selection_io_write(dxpl, lf, type, 1, &mem_spaces[1], &file_spaces[1], &addrs[1], element_sizes,
+                                (int **)&wbufs[1]) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /* Update file buf */
+    for (i = 0; i < sel_dim0 / 2; i++)
+        for (j = 0; j < sel_dim1; j++) {
+            fbuf2[((i + 1) * sel_dim1) + j] = wbuf2[(((2 * i) + 1) * sel_dim1) + j];
+        }
+
+    /* Update expected read buf */
+    for (i = 0; i < sel_dim0; i++)
+        for (j = 0; j < sel_dim1; j++)
+            erbuf2[(i * sel_dim1) + j] = -1;
+    for (i = 0; i < sel_dim0 / 2; i++)
+        for (j = 0; j < sel_dim1; j++)
+            erbuf2[(((2 * i) + 1) * sel_dim1) + j] = wbuf2[(((2 * i) + 1) * sel_dim1) + j];
+
+    /* Read and verify */
+    verify_start[0] = start[0] * count[1];
+    verify_block[0] = (count[0] * count[1] * stride[0]);
+    if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 1, &mem_spaces[1],
+                                      &file_spaces[1], &addrs[1], element_sizes, 1, (int **)&erbufs[1],
+                                      FALSE) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /*
+     * Reset selections
+     */
+    if (H5Sselect_all(mem_spaces[1]) < 0)
+        P_TEST_ERROR;
+    if (H5Sselect_all(file_spaces[1]) < 0)
+        P_TEST_ERROR;
+
+    block[0]  = dims2[0] / (hsize_t)mpi_size;
+    block[1]  = dims2[1];
+    count[0]  = 1;
+    count[1]  = 1;
+    stride[0] = block[0];
+    stride[1] = block[1];
+    start[0]  = (hsize_t)mpi_rank * block[0];
+    start[1]  = 0;
+
+    if (H5Sselect_hyperslab(mem_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+    if (H5Sselect_hyperslab(file_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Read entire file buffer and verify */
+    verify_start[0] = start[0] * block[1];
+    verify_block[0] = (block[0] * block[1]);
+    if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 1, &mem_spaces[1],
+                                      &file_spaces[1], &addrs[1], element_sizes, 1, (int **)&fbufs[1],
+                                      FALSE) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /*
+     * Test 3: Contiguous (memory) <> Strided (file) 2D I/O
+     */
+
+    /* Strided selection in file */
+    block[0]  = 1;
+    block[1]  = 1;
+    count[0]  = (hsize_t)(sel_dim0 / mpi_size);
+    count[1]  = (hsize_t)sel_dim1 / 2;
+    stride[0] = 1;
+    stride[1] = 2;
+    start[0]  = (hsize_t)mpi_rank * count[0];
+    start[1]  = 1;
+    if (H5Sselect_hyperslab(file_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Contiguous selection in memory */
+    if (H5Sselect_hyperslab(mem_spaces[1], H5S_SELECT_SET, start, NULL, count, NULL) < 0)
+        P_TEST_ERROR;
+
+    /* Issue write call */
+    if (test_selection_io_write(dxpl, lf, type, 1, &mem_spaces[1], &file_spaces[1], &addrs[1], element_sizes,
+                                (int **)&wbufs[1]) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /* Update file buf */
+    for (i = 0; i < sel_dim0; i++)
+        for (j = 0; j < sel_dim1 / 2; j++)
+            fbuf2[i * sel_dim1 + (2 * j) + 1] = wbuf2[i * sel_dim1 + (j + 1)];
+
+    /* Update expected read buf */
+    for (i = 0; i < sel_dim0; i++)
+        for (j = 0; j < sel_dim1; j++)
+            erbuf2[i * sel_dim1 + j] = -1;
+    for (i = 0; i < sel_dim0; i++)
+        for (j = 0; j < sel_dim1 / 2; j++)
+            erbuf2[i * sel_dim1 + (j + 1)] = wbuf2[i * sel_dim1 + (j + 1)];
+
+    /* Read and verify */
+    verify_start[0] = start[0] * count[1] * stride[1];
+    verify_block[0] = (count[0] * count[1] * stride[1]);
+    if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 1, &mem_spaces[1],
+                                      &file_spaces[1], &addrs[1], element_sizes, 1, (int **)&erbufs[1],
+                                      FALSE) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /*
+     * Reset selections
+     */
+    if (H5Sselect_all(mem_spaces[1]) < 0)
+        P_TEST_ERROR;
+    if (H5Sselect_all(file_spaces[1]) < 0)
+        P_TEST_ERROR;
+
+    block[0]  = dims2[0] / (hsize_t)mpi_size;
+    block[1]  = dims2[1];
+    count[0]  = 1;
+    count[1]  = 1;
+    stride[0] = block[0];
+    stride[1] = block[1];
+    start[0]  = (hsize_t)mpi_rank * block[0];
+    start[1]  = 0;
+
+    if (H5Sselect_hyperslab(mem_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+    if (H5Sselect_hyperslab(file_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Read entire file buffer and verify */
+    verify_start[0] = start[0] * block[1];
+    verify_block[0] = (block[0] * block[1]);
+    if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 1, &mem_spaces[1],
+                                      &file_spaces[1], &addrs[1], element_sizes, 1, (int **)&fbufs[1],
+                                      FALSE) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /*
+     * Test 4: Strided (memory) <> Strided (file) 2D I/O
+     */
+    /* sel_dim0 and sel_dim1 must be even */
+    assert(sel_dim0 / 2 == (sel_dim0 + 1) / 2);
+    assert(sel_dim1 / 2 == (sel_dim1 + 1) / 2);
+
+    /* Strided selection (across dim 0) in file */
+    block[0]  = 1;
+    block[1]  = 1;
+    count[0]  = (hsize_t)((sel_dim0 / 2) / mpi_size);
+    count[1]  = (hsize_t)sel_dim1;
+    stride[0] = 2;
+    stride[1] = 1;
+    start[0]  = 1 + ((hsize_t)mpi_rank * count[0] * stride[0]);
+    start[1]  = 0;
+    if (H5Sselect_hyperslab(file_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Strided selection (across dim 1) in memory */
+    block[0]  = 1;
+    block[1]  = 1;
+    count[0]  = (hsize_t)(sel_dim0 / mpi_size);
+    count[1]  = (hsize_t)sel_dim1 / 2;
+    stride[0] = 1;
+    stride[1] = 2;
+    start[0]  = (hsize_t)mpi_rank * count[0];
+    start[1]  = 1;
+    if (H5Sselect_hyperslab(mem_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Issue write call */
+    if (test_selection_io_write(dxpl, lf, type, 1, &mem_spaces[1], &file_spaces[1], &addrs[1], element_sizes,
+                                (int **)&wbufs[1]) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /* Update file buf */
+    for (i = 0, i2 = 1, j2 = 0; i < sel_dim0; i++)
+        for (j = 1; j < sel_dim1; j += 2) {
+            assert(i2 < sel_dim0);
+            fbuf2[i2 * sel_dim1 + j2] = wbuf2[i * sel_dim1 + j];
+            if (++j2 == sel_dim1) {
+                i2 += 2;
+                j2 = 0;
+            }
+        }
+
+    /* Update expected read buf */
+    for (i = 0; i < sel_dim0; i++)
+        for (j = 0; j < sel_dim1; j++)
+            erbuf2[i * sel_dim1 + j] = -1;
+    for (i = 0; i < sel_dim0; i++)
+        for (j = 1; j < sel_dim1; j += 2)
+            erbuf2[i * sel_dim1 + j] = wbuf2[i * sel_dim1 + j];
+    /* Read and verify */
+    verify_start[0] = start[0] * count[1] * stride[1];
+    verify_block[0] = (count[0] * count[1] * stride[1]);
+    if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 1, &mem_spaces[1],
+                                      &file_spaces[1], &addrs[1], element_sizes, 1, (int **)&erbufs[1],
+                                      FALSE) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /*
+     * Reset selections
+     */
+    if (H5Sselect_all(file_spaces[1]) < 0)
+        P_TEST_ERROR;
+    if (H5Sselect_all(mem_spaces[1]) < 0)
+        P_TEST_ERROR;
+
+    block[0]  = dims2[0] / (hsize_t)mpi_size;
+    block[1]  = dims2[1];
+    count[0]  = 1;
+    count[1]  = 1;
+    stride[0] = block[0];
+    stride[1] = block[1];
+    start[0]  = (hsize_t)mpi_rank * block[0];
+    start[1]  = 0;
+
+    if (H5Sselect_hyperslab(file_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+    if (H5Sselect_hyperslab(mem_spaces[1], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Read entire file buffer and verify */
+    verify_start[0] = start[0] * block[1];
+    verify_block[0] = (block[0] * block[1]);
+    if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 1, &mem_spaces[1],
+                                      &file_spaces[1], &addrs[1], element_sizes, 1, (int **)&fbufs[1],
+                                      FALSE) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    return;
+
+} /* test_selection_io_types_2d() */
+
+/*
+ * Perform the following tests for 1 dimensional spaces:
+ * --Test 1: Simple 1D contiguous I/O in both file and memory spaces
+ * --Test 2: Strided (memory) <> Contiguous (file) 1D I/O
+ * --Reset selections
+ * --Test 3: Contiguous (memory) <> Strided (file) 1D I/O
+ * --Reset selections
+ * --Test 4: Strided (memory) <> Strided 1D (file) I/O
+ * --Reset selections
+ */
+static void
+test_selection_io_types_1d(int mpi_rank, int mpi_size, H5FD_t *lf, hid_t dxpl, H5FD_mem_t type,
+                           haddr_t addrs[], size_t element_sizes[], hid_t mem_spaces[], hid_t file_spaces[],
+                           hsize_t dims1[])
+{
+    hsize_t start[2];                 /* start for hyperslab          */
+    hsize_t stride[2];                /* stride for hyperslab         */
+    hsize_t count[2];                 /* count for hyperslab          */
+    hsize_t block[2];                 /* block for hyperslab          */
+    hsize_t verify_start[2] = {0, 0}; /* Starting block for verified data */
+    hsize_t verify_block[2] = {0, 0}; /* Block size for verified data */
+    int     i;
+
+    /*
+     * Test 1: Simple 1D contiguous I/O
+     */
+
+    /* Contiguous selection in file and memory */
+    block[0]  = dims1[0] / (hsize_t)mpi_size;
+    count[0]  = 1;
+    stride[0] = block[0];
+    start[0]  = (hsize_t)mpi_rank * block[0];
+
+    if (H5Sselect_hyperslab(mem_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+    if (H5Sselect_hyperslab(file_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Issue write call */
+    if (test_selection_io_write(dxpl, lf, type, 1, &mem_spaces[0], &file_spaces[0], &addrs[0], element_sizes,
+                                (int **)&wbufs[0]) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /* Update file buf */
+    for (i = 0; i < sel_dim0 * sel_dim1; i++)
+        fbuf1[i] = wbuf1[i];
+
+    /* Read and verify */
+    verify_start[0] = start[0];
+    verify_block[0] = block[0];
+
+    if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 1, &mem_spaces[0],
+                                      &file_spaces[0], &addrs[0], element_sizes, 1, (int **)&fbufs[0],
+                                      FALSE) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /*
+     * Test 2: Strided (memory) <> Contiguous (file) 1D I/O
+     */
+    /* sel_dim1 must be even */
+    assert(sel_dim1 / 2 == (sel_dim1 + 1) / 2);
+
+    /* Contiguous selection in file */
+    count[0] = (hsize_t)(((sel_dim0 * sel_dim1) / 2) / mpi_size);
+    start[0] = 1 + ((hsize_t)mpi_rank * count[0]);
+    if (H5Sselect_hyperslab(file_spaces[0], H5S_SELECT_SET, start, NULL, count, NULL) < 0)
+        P_TEST_ERROR;
+
+    /* Strided selection in memory */
+    block[0]  = 1;
+    stride[0] = 2;
+    start[0]  = 1 + ((hsize_t)mpi_rank * stride[0] * count[0]);
+    if (H5Sselect_hyperslab(mem_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Issue write call */
+    if (test_selection_io_write(dxpl, lf, type, 1, &mem_spaces[0], &file_spaces[0], &addrs[0], element_sizes,
+                                (int **)&wbufs[0]) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /* Update file buf */
+    for (i = 0; i < (sel_dim0 * sel_dim1) / 2; i++)
+        fbuf1[i + 1] = wbuf1[(2 * i) + 1];
+
+    /* Update expected read buf */
+    for (i = 0; i < (sel_dim0 * sel_dim1); i++)
+        erbuf1[i] = -1;
+    for (i = 0; i < (sel_dim0 * sel_dim1) / 2; i++)
+        erbuf1[(2 * i) + 1] = wbuf1[(2 * i) + 1];
+
+    /* Read and verify */
+    verify_start[0] = start[0];
+    verify_block[0] = (count[0] * stride[0]);
+    if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 1, &mem_spaces[0],
+                                      &file_spaces[0], &addrs[0], element_sizes, 1, (int **)&erbufs[0],
+                                      FALSE) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /*
+     * Reset selections
+     */
+    if (H5Sselect_all(mem_spaces[0]) < 0)
+        P_TEST_ERROR;
+    if (H5Sselect_all(file_spaces[0]) < 0)
+        P_TEST_ERROR;
+
+    block[0]  = dims1[0] / (hsize_t)mpi_size;
+    count[0]  = 1;
+    stride[0] = block[0];
+    start[0]  = (hsize_t)mpi_rank * block[0];
+
+    if (H5Sselect_hyperslab(mem_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+    if (H5Sselect_hyperslab(file_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Read entire file buffer and verify */
+    verify_start[0] = start[0];
+    verify_block[0] = block[0];
+    if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 1, &mem_spaces[0],
+                                      &file_spaces[0], &addrs[0], element_sizes, 1, (int **)&fbufs[0],
+                                      FALSE) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /*
+     * Test 3: Contiguous (memory) <> Strided (file) 1D I/O
+     */
+    /* sel_dim1 must be even */
+    assert(sel_dim1 / 2 == (sel_dim1 + 1) / 2);
+
+    /* Strided selection in file */
+    block[0]  = 1;
+    count[0]  = (hsize_t)(((sel_dim0 * sel_dim1) / 2) / mpi_size); /* count is this value from twice above */
+    stride[0] = 2;                                                 /* stride is this value from twice above */
+    start[0]  = 1 + ((hsize_t)mpi_rank * stride[0] * count[0]);
+    if (H5Sselect_hyperslab(file_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Contiguous selection in memory */
+    start[0] = 1 + ((hsize_t)mpi_rank * count[0]);
+    if (H5Sselect_hyperslab(mem_spaces[0], H5S_SELECT_SET, start, NULL, count, NULL) < 0)
+        P_TEST_ERROR;
+
+    /* Issue write call */
+    if (test_selection_io_write(dxpl, lf, type, 1, &mem_spaces[0], &file_spaces[0], &addrs[0], element_sizes,
+                                (int **)&wbufs[0]) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /* Update file buf */
+    for (i = 0; i < (sel_dim0 * sel_dim1) / 2; i++)
+        fbuf1[(2 * i) + 1] = wbuf1[i + 1];
+
+    /* Update expected read buf */
+    for (i = 0; i < (sel_dim0 * sel_dim1); i++)
+        erbuf1[i] = -1;
+    for (i = 0; i < (sel_dim0 * sel_dim1) / 2; i++)
+        erbuf1[i + 1] = wbuf1[i + 1];
+
+    /* Read and verify */
+    verify_start[0] = start[0];
+    verify_block[0] = count[0];
+    if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 1, &mem_spaces[0],
+                                      &file_spaces[0], &addrs[0], element_sizes, 1, (int **)&erbufs[0],
+                                      FALSE) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /*
+     * Reset selections
+     */
+    if (H5Sselect_all(mem_spaces[0]) < 0)
+        P_TEST_ERROR;
+    if (H5Sselect_all(file_spaces[0]) < 0)
+        P_TEST_ERROR;
+
+    block[0]  = dims1[0] / (hsize_t)mpi_size;
+    count[0]  = 1;
+    stride[0] = block[0];
+    start[0]  = (hsize_t)mpi_rank * block[0];
+
+    if (H5Sselect_hyperslab(mem_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+    if (H5Sselect_hyperslab(file_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Read entire file buffer and verify */
+    verify_start[0] = start[0];
+    verify_block[0] = block[0];
+    if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 1, &mem_spaces[0],
+                                      &file_spaces[0], &addrs[0], element_sizes, 1, (int **)&fbufs[0],
+                                      FALSE) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /*
+     * Test 4: Strided (memory) <> Strided 1D (file) I/O
+     */
+    /* sel_dim1 must be even */
+    assert(sel_dim1 / 2 == (sel_dim1 + 1) / 2);
+
+    /* Strided selection in file */
+    block[0]  = 1;
+    count[0]  = (hsize_t)(((sel_dim0 * sel_dim1) / 2) / mpi_size);
+    stride[0] = 2;
+    start[0]  = 0 + ((hsize_t)mpi_rank * stride[0] * count[0]);
+    if (H5Sselect_hyperslab(file_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Strided selection in memory */
+    start[0] = 1 + ((hsize_t)mpi_rank * stride[0] * count[0]);
+    if (H5Sselect_hyperslab(mem_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Issue write call */
+    if (test_selection_io_write(dxpl, lf, type, 1, &mem_spaces[0], &file_spaces[0], &addrs[0], element_sizes,
+                                (int **)&wbufs[0]) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /* Update file buf */
+    for (i = 0; i < (sel_dim0 * sel_dim1) / 2; i++)
+        fbuf1[2 * i] = wbuf1[(2 * i) + 1];
+
+    /* Update expected read buf */
+    for (i = 0; i < (sel_dim0 * sel_dim1); i++)
+        erbuf1[i] = -1;
+    for (i = 0; i < (sel_dim0 * sel_dim1) / 2; i++)
+        erbuf1[(2 * i) + 1] = wbuf1[(2 * i) + 1];
+
+    /* Read and verify */
+    verify_start[0] = start[0];
+    verify_block[0] = (count[0] * stride[0]);
+    if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 1, &mem_spaces[0],
+                                      &file_spaces[0], &addrs[0], element_sizes, 1, (int **)&erbufs[0],
+                                      FALSE) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    /*
+     * Reset selections
+     */
+    if (H5Sselect_all(mem_spaces[0]) < 0)
+        P_TEST_ERROR;
+    if (H5Sselect_all(file_spaces[0]) < 0)
+        P_TEST_ERROR;
+
+    block[0]  = dims1[0] / (hsize_t)mpi_size;
+    count[0]  = 1;
+    stride[0] = block[0];
+    start[0]  = (hsize_t)mpi_rank * block[0];
+
+    if (H5Sselect_hyperslab(mem_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+    if (H5Sselect_hyperslab(file_spaces[0], H5S_SELECT_SET, start, stride, count, block) < 0)
+        P_TEST_ERROR;
+
+    /* Read entire file buffer and verify */
+    verify_start[0] = start[0];
+    verify_block[0] = block[0];
+    if (test_selection_io_read_verify(dxpl, mpi_rank, verify_start, verify_block, lf, type, 1, &mem_spaces[0],
+                                      &file_spaces[0], &addrs[0], element_sizes, 1, (int **)&fbufs[0],
+                                      FALSE) < 0)
+        P_TEST_ERROR;
+
+    MPI_Barrier(comm);
+
+    return;
+
+} /* test_selection_io_types_1d() */
+
+/*
+ *  Perform the following tests for selection I/O:
+ *
+ *  test_selection_io_types_1d():
+ *      ---Selection I/O tests for 1 dimensional spaces
+ *  test_selection_io_types_2d()
+ *      ---Selection I/O tests for 2 dimensional spaces
+ *  test_selection_io_types_1d_2d()
+ *      ---Selection I/O tests for 1 & 2 dimensional spaces
+ *  test_selection_io_types_shorten()
+ *      --Selection I/O tests that use shortened arrays for wbuf and element sizes
+ */
+static void
+test_selection_io_real(int mpi_rank, int mpi_size, H5FD_t *lf, hid_t dxpl)
+{
+    hid_t   mem_spaces[2]  = {H5I_INVALID_HID, H5I_INVALID_HID}; /* memory dataspaces vector */
+    hid_t   file_spaces[2] = {H5I_INVALID_HID, H5I_INVALID_HID}; /* file dataspaces vector */
+    hsize_t dims1[1];                                            /* 1d dimension sizes */
+    hsize_t dims2[2];                                            /* 2d dimension sizes */
+
+    H5FD_mem_t type;                                          /* File type */
+    haddr_t    addrs[2];                                      /* File allocation address */
+    size_t     element_sizes[2] = {sizeof(int), sizeof(int)}; /* Element size */
+    size_t     bufsize;                                       /* Buffer size */
+    int        i;
+    int        j;
+
+    curr_nerrors = nerrors;
+
+    /*
+     *  Default dimension sizes for mpi_size 1 or 2:
+     *  int sel_dim0 = SELECT_IO_DIM0;
+     *  int sel_dim1 = SELECT_IO_DIM1;
+     */
+    if (mpi_size >= 3) {
+        sel_dim0 = mpi_size * 2;
+        sel_dim1 = mpi_size * 4;
+    }
+
+    dims1[0] = (hsize_t)(sel_dim0 * sel_dim1);
+    dims2[0] = (hsize_t)sel_dim0, dims2[1] = (hsize_t)sel_dim1;
+
+    /* Create dataspaces - location 0 will be 1D and location 1 will be 2D */
+    if ((mem_spaces[0] = H5Screate_simple(1, dims1, NULL)) < 0)
+        P_TEST_ERROR;
+    if ((mem_spaces[1] = H5Screate_simple(2, dims2, NULL)) < 0)
+        P_TEST_ERROR;
+    if ((file_spaces[0] = H5Screate_simple(1, dims1, NULL)) < 0)
+        P_TEST_ERROR;
+    if ((file_spaces[1] = H5Screate_simple(2, dims2, NULL)) < 0)
+        P_TEST_ERROR;
+
+    /* Initialize global buffers:
+     * --wbuf1, wbuf2: write buffers
+     * --fbuf1, fbuf1: expected file buffers
+     * --erbuf1, erbuf2: expected read buffers
+     */
+    bufsize = (size_t)(sel_dim0 * sel_dim1) * sizeof(int);
+
+    if ((wbuf1 = malloc(bufsize)) == NULL)
+        P_TEST_ERROR;
+
+    if ((wbuf2 = malloc(bufsize)) == NULL)
+        P_TEST_ERROR;
+
+    wbufs[0] = wbuf1;
+    wbufs[1] = wbuf2;
+
+    if ((fbuf1 = malloc(bufsize)) == NULL)
+        P_TEST_ERROR;
+
+    if ((fbuf2 = malloc(bufsize)) == NULL)
+        P_TEST_ERROR;
+
+    fbufs[0] = fbuf1;
+    fbufs[1] = fbuf2;
+
+    if ((erbuf1 = malloc(bufsize)) == NULL)
+        P_TEST_ERROR;
+
+    if ((erbuf2 = malloc(bufsize)) == NULL)
+        P_TEST_ERROR;
+
+    erbufs[0] = erbuf1;
+    erbufs[1] = erbuf2;
+
+    /* Initialize data */
+    for (i = 0; i < sel_dim0; i++)
+        for (j = 0; j < sel_dim1; j++) {
+            wbuf1[(i * sel_dim1) + j] = (i * sel_dim1) + j;
+            wbuf2[(i * sel_dim1) + j] = (i * sel_dim1) + j + (sel_dim0 * sel_dim1);
+        }
+
+    /* Loop over memory types */
+    for (type = 1; type < H5FD_MEM_NTYPES; type++) {
+
+        addrs[0] = H5FDalloc(lf, type, H5P_DEFAULT, (sizeof(int) * (hsize_t)sel_dim0 * (hsize_t)sel_dim1));
+        addrs[1] = H5FDalloc(lf, type, H5P_DEFAULT, (sizeof(int) * (hsize_t)sel_dim0 * (hsize_t)sel_dim1));
+
+        test_selection_io_types_1d(mpi_rank, mpi_size, lf, dxpl, type, addrs, element_sizes, mem_spaces,
+                                   file_spaces, dims1);
+        test_selection_io_types_2d(mpi_rank, mpi_size, lf, dxpl, type, addrs, element_sizes, mem_spaces,
+                                   file_spaces, dims2);
+        test_selection_io_types_1d_2d(mpi_rank, mpi_size, lf, dxpl, type, addrs, element_sizes, mem_spaces,
+                                      file_spaces, dims1, dims2);
+        test_selection_io_types_shorten(mpi_rank, mpi_size, lf, dxpl, type, addrs, element_sizes, mem_spaces,
+                                        file_spaces, dims1, dims2);
+
+    } /* end for */
+
+    /* Close dataspaces */
+    for (i = 0; i < 2; i++) {
+        if (H5Sclose(mem_spaces[i]) < 0)
+            P_TEST_ERROR;
+        if (H5Sclose(file_spaces[i]) < 0)
+            P_TEST_ERROR;
+    }
+
+    /* Free the buffers */
+    if (wbuf1)
+        free(wbuf1);
+    if (wbuf2)
+        free(wbuf2);
+    if (fbuf1)
+        free(fbuf1);
+    if (fbuf2)
+        free(fbuf2);
+    if (erbuf1)
+        free(erbuf1);
+    if (erbuf2)
+        free(erbuf2);
+
+    CHECK_PASSED();
+
+    return;
+
+} /* test_selection_io_real() */
+
+/*
+ * These tests for selection I/O are derived from test_selection_io() in
+ * test/vfd.c and modified for parallel testing.
+ */
+static void
+test_selection_io(int mpi_rank, int mpi_size)
+{
+    H5FD_t  *lf   = NULL;            /* VFD struct ptr */
+    hid_t    fapl = H5I_INVALID_HID; /* File access property list */
+    char     filename[1024];         /* Test file name */
+    unsigned flags = 0;              /* File access flags */
+
+    unsigned collective;                      /* Types of I/O for testing */
+    hid_t    dxpl          = H5I_INVALID_HID; /* Dataset transfer property list */
+    hid_t    def_dxpl      = H5I_INVALID_HID; /* dxpl: independent access */
+    hid_t    col_xfer_dxpl = H5I_INVALID_HID; /* dxpl: collective access with collective I/O */
+    hid_t    ind_io_dxpl   = H5I_INVALID_HID; /* dxpl: collective access with individual I/O */
+
+    /* If I use fapl in this call, I got an environment printout */
+    h5_fixname(SELECT_FNAME, H5P_DEFAULT, filename, sizeof(filename));
+
+    if ((fapl = H5Pcreate(H5P_FILE_ACCESS)) < 0)
+        P_TEST_ERROR;
+
+    if (H5Pset_fapl_mpio(fapl, comm, info) < 0)
+        P_TEST_ERROR;
+
+    /* Create file */
+    flags = H5F_ACC_RDWR | H5F_ACC_CREAT | H5F_ACC_TRUNC;
+
+    if (NULL == (lf = H5FDopen(filename, flags, fapl, HADDR_UNDEF)))
+        P_TEST_ERROR;
+
+    /* Default dxpl which will be H5FD_MPIO_INDEPENDENT by default */
+    def_dxpl = H5Pcreate(H5P_DATASET_XFER);
+
+    /* Set dxpl for collective access which will have H5FD_MPIO_COLLECTIVE_IO as default */
+    if ((col_xfer_dxpl = H5Pcopy(def_dxpl)) < 0)
+        P_TEST_ERROR;
+    if (H5Pset_dxpl_mpio(col_xfer_dxpl, H5FD_MPIO_COLLECTIVE) < 0)
+        P_TEST_ERROR;
+
+    /* Set dxpl for H5FD_MPIO_INDIVIDUAL_IO */
+    if ((ind_io_dxpl = H5Pcopy(col_xfer_dxpl)) < 0)
+        P_TEST_ERROR;
+    if (H5Pset_dxpl_mpio_collective_opt(ind_io_dxpl, H5FD_MPIO_INDIVIDUAL_IO) < 0)
+        P_TEST_ERROR;
+
+    for (collective = 0; collective < iotypes; collective++) {
+        // for (collective = 0; collective < 1; collective++) {
+        if (collective)
+            dxpl = collective == 1 ? col_xfer_dxpl : ind_io_dxpl;
+        else
+            dxpl = def_dxpl;
+
+        if (MAINPROCESS) {
+            if (collective) {
+                if (collective == 1)
+                    printf("     Testing with Collective access: collective I/O         ");
+                else
+                    printf("     Testing with Collective_access: Individual I/O         ");
+            }
+            else
+                printf("     Testing with Independent access                        ");
+        }
+
+        /* Perform the actual tests */
+        test_selection_io_real(mpi_rank, mpi_size, lf, dxpl);
+    }
+
+    /* Close file */
+    if (H5FDclose(lf) < 0)
+        P_TEST_ERROR;
+
+    /* Close the fapl */
+    if (H5Pclose(fapl) < 0)
+        P_TEST_ERROR;
+
+    if (H5Pclose(def_dxpl) < 0)
+        P_TEST_ERROR;
+    if (H5Pclose(col_xfer_dxpl) < 0)
+        P_TEST_ERROR;
+    if (H5Pclose(ind_io_dxpl) < 0)
+        P_TEST_ERROR;
+
+    // if (MAINPROCESS && HDremove(filename) < 0)
+    //    P_TEST_ERROR;
+
+} /* test_selection_io() */
+
+/*-------------------------------------------------------------------------
+ * Function:    main
+ *
+ * Purpose:     Run parallel VFD tests.
+ *
+ * Return:      Success: 0
+ *
+ *              Failure: 1
+ *
+ *-------------------------------------------------------------------------
+ */
+
+int
+main(int argc, char **argv)
+{
+
+#ifdef H5_HAVE_SUBFILING_VFD
+    int required = MPI_THREAD_MULTIPLE;
+    int provided = 0;
+#endif
+    int mpi_size;
+    int mpi_rank;
+    int ret;
+
+#ifdef H5_HAVE_SUBFILING_VFD
+    if (MPI_SUCCESS != MPI_Init_thread(&argc, &argv, required, &provided)) {
+        printf("    MPI doesn't support MPI_Init_thread with MPI_THREAD_MULTIPLE. Exiting\n");
+        goto finish;
+    }
+
+    if (provided != required) {
+        printf("    MPI doesn't support MPI_Init_thread with MPI_THREAD_MULTIPLE. Exiting\n");
+        goto finish;
+    }
+#else
+    if (MPI_SUCCESS != MPI_Init(&argc, &argv)) {
+        printf("    MPI_Init failed. Exiting\n");
+        goto finish;
+    }
+#endif
+
+    MPI_Comm_size(comm, &mpi_size);
+    MPI_Comm_rank(comm, &mpi_rank);
+
+    /* Attempt to turn off atexit post processing so that in case errors
+     * occur during the test and the process is aborted, it will not hang
+     * in the atexit post processing.  If it does, it may try to make MPI
+     * calls which may not work.
+     */
+    if (H5dont_atexit() < 0)
+        printf("%d:Failed to turn off atexit processing. Continue.\n", mpi_rank);
+
+    H5open();
+
+    if (mpi_rank == 0) {
+        printf("=========================================\n");
+        printf("Parallel virtual file driver (VFD) tests\n");
+        printf("        mpi_size     = %d\n", mpi_size);
+        printf("=========================================\n");
+    }
+
+    MPI_Barrier(comm);
+
+    if (mpi_rank == 0)
+        printf("\n --- TESTING MPIO VFD: selection I/O --- \n");
+
+    test_selection_io(mpi_rank, mpi_size);
+
+    if (mpi_rank == 0)
+        printf("\n --- TESTING MPIO VFD: vector I/O --- \n");
+
+    if (mpi_size < 2) {
+        if (mpi_rank == 0) {
+            printf("     Need at least 2 processes to run tests for vector I/O.");
+            SKIPPED();
+        }
+        printf("\n");
+        goto finish;
+    }
+
+    test_vector_io(mpi_rank, mpi_size);
+
 finish:
     /* make sure all processes are finished before final report, cleanup
      * and exit.
      */
     MPI_Barrier(comm);
 
-    if (mpi_rank == 0) { /* only process 0 reports */
-        printf("===================================\n");
-        if (nerrs > 0)
-            printf("***vfd tests detected %d failures***\n", nerrs);
+    /* Gather errors from all processes */
+    MPI_Allreduce(&nerrors, &ret, 1, MPI_INT, MPI_MAX, MPI_COMM_WORLD);
+    nerrors = ret;
+
+    if (MAINPROCESS) {
+        printf("\n===================================\n");
+        if (nerrors)
+            printf("***Parallel vfd tests detected %d errors***\n", nerrors);
         else
-            printf("vfd tests finished with no failures\n");
+            printf("Parallel vfd tests finished with no errors\n");
         printf("===================================\n");
     }
 
@@ -4337,6 +5992,6 @@ finish:
     MPI_Finalize();
 
     /* cannot just return (nerrs) because exit code is limited to 1byte */
-    return (nerrs > 0);
+    return (nerrors != 0);
 
 } /* main() */