Merge branch 'develop' into feature/coding_standardsfeature/coding_standards

1 files changed, 151 insertions, 132 deletions

diff --git a/testpar/t_coll_md_read.c b/testpar/t_coll_md_read.c
index 912388c..cabdea0 100644
--- a/testpar/t_coll_md_read.c
+++ b/testpar/t_coll_md_read.c
@@ -5,7 +5,7 @@
  * 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://support.hdfgroup.org/ftp/HDF5/releases.  *
+ * 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.                                                        *
  * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
@@ -27,18 +27,16 @@
  * an if (mpi_rank == 0) check.
  */
 #define PARTIAL_NO_SELECTION_NO_SEL_PROCESS (mpi_rank == mpi_size - 1)
-#define PARTIAL_NO_SELECTION_DATASET_NAME "partial_no_selection_dset"
-#define PARTIAL_NO_SELECTION_DATASET_NDIMS 2
-#define PARTIAL_NO_SELECTION_Y_DIM_SCALE 5
-#define PARTIAL_NO_SELECTION_X_DIM_SCALE 5
+#define PARTIAL_NO_SELECTION_DATASET_NAME   "partial_no_selection_dset"
+#define PARTIAL_NO_SELECTION_DATASET_NDIMS  2
+#define PARTIAL_NO_SELECTION_Y_DIM_SCALE    5
+#define PARTIAL_NO_SELECTION_X_DIM_SCALE    5
 
 #define MULTI_CHUNK_IO_ADDRMAP_ISSUE_DIMS 2
 
-#define LINK_CHUNK_IO_SORT_CHUNK_ISSUE_NO_SEL_PROCESS (mpi_rank == mpi_size - 1)
-#define LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DATASET_NAME   "linked_chunk_io_sort_chunk_issue"
-#define LINK_CHUNK_IO_SORT_CHUNK_ISSUE_Y_DIM_SCALE    20000
-#define LINK_CHUNK_IO_SORT_CHUNK_ISSUE_CHUNK_SIZE     1
-#define LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS           1
+#define LINK_CHUNK_IO_SORT_CHUNK_ISSUE_COLL_THRESH_NUM 10000
+#define LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DATASET_NAME    "linked_chunk_io_sort_chunk_issue"
+#define LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS            1
 
 /*
  * A test for issue HDFFV-10501. A parallel hang was reported which occurred
@@ -49,32 +47,34 @@
  * in strictly non-decreasing order of chunk address. For version 1 and 2 B-trees,
  * this caused the non-participating ranks to issue a collective MPI_Bcast() call
  * which the other ranks did not issue, thus causing a hang.
- * 
+ *
  * However, since these ranks are not actually reading/writing anything, this call
  * can simply be removed and the address used for the read/write can be set to an
  * arbitrary number (0 was chosen).
  */
-void test_partial_no_selection_coll_md_read(void)
+void
+test_partial_no_selection_coll_md_read(void)
 {
     const char *filename;
-    hsize_t    *dataset_dims = NULL;
+    hsize_t *   dataset_dims = NULL;
     hsize_t     max_dataset_dims[PARTIAL_NO_SELECTION_DATASET_NDIMS];
     hsize_t     sel_dims[1];
-    hsize_t     chunk_dims[PARTIAL_NO_SELECTION_DATASET_NDIMS] = { PARTIAL_NO_SELECTION_Y_DIM_SCALE, PARTIAL_NO_SELECTION_X_DIM_SCALE };
+    hsize_t     chunk_dims[PARTIAL_NO_SELECTION_DATASET_NDIMS] = {PARTIAL_NO_SELECTION_Y_DIM_SCALE,
+                                                              PARTIAL_NO_SELECTION_X_DIM_SCALE};
     hsize_t     start[PARTIAL_NO_SELECTION_DATASET_NDIMS];
     hsize_t     stride[PARTIAL_NO_SELECTION_DATASET_NDIMS];
     hsize_t     count[PARTIAL_NO_SELECTION_DATASET_NDIMS];
     hsize_t     block[PARTIAL_NO_SELECTION_DATASET_NDIMS];
-    hid_t       file_id = H5I_INVALID_HID;
-    hid_t       fapl_id = H5I_INVALID_HID;
-    hid_t       dset_id = H5I_INVALID_HID;
-    hid_t       dcpl_id = H5I_INVALID_HID;
-    hid_t       dxpl_id = H5I_INVALID_HID;
+    hid_t       file_id   = H5I_INVALID_HID;
+    hid_t       fapl_id   = H5I_INVALID_HID;
+    hid_t       dset_id   = H5I_INVALID_HID;
+    hid_t       dcpl_id   = H5I_INVALID_HID;
+    hid_t       dxpl_id   = H5I_INVALID_HID;
     hid_t       fspace_id = H5I_INVALID_HID;
     hid_t       mspace_id = H5I_INVALID_HID;
     int         mpi_rank, mpi_size;
-    void       *data = NULL;
-    void       *read_buf = NULL;
+    void *      data     = NULL;
+    void *      read_buf = NULL;
 
     MPI_Comm_rank(MPI_COMM_WORLD, &mpi_rank);
     MPI_Comm_size(MPI_COMM_WORLD, &mpi_size);
@@ -97,8 +97,8 @@ void test_partial_no_selection_coll_md_read(void)
     dataset_dims = HDmalloc(PARTIAL_NO_SELECTION_DATASET_NDIMS * sizeof(*dataset_dims));
     VRFY((dataset_dims != NULL), "malloc succeeded");
 
-    dataset_dims[0] = PARTIAL_NO_SELECTION_Y_DIM_SCALE * mpi_size;
-    dataset_dims[1] = PARTIAL_NO_SELECTION_X_DIM_SCALE * mpi_size;
+    dataset_dims[0]     = (hsize_t)PARTIAL_NO_SELECTION_Y_DIM_SCALE * (hsize_t)mpi_size;
+    dataset_dims[1]     = (hsize_t)PARTIAL_NO_SELECTION_X_DIM_SCALE * (hsize_t)mpi_size;
     max_dataset_dims[0] = H5S_UNLIMITED;
     max_dataset_dims[1] = H5S_UNLIMITED;
 
@@ -111,9 +111,11 @@ void test_partial_no_selection_coll_md_read(void)
     dcpl_id = H5Pcreate(H5P_DATASET_CREATE);
     VRFY((dcpl_id >= 0), "H5Pcreate succeeded");
 
-    VRFY((H5Pset_chunk(dcpl_id, PARTIAL_NO_SELECTION_DATASET_NDIMS, chunk_dims) >= 0), "H5Pset_chunk succeeded");
+    VRFY((H5Pset_chunk(dcpl_id, PARTIAL_NO_SELECTION_DATASET_NDIMS, chunk_dims) >= 0),
+         "H5Pset_chunk succeeded");
 
-    dset_id = H5Dcreate2(file_id, PARTIAL_NO_SELECTION_DATASET_NAME, H5T_NATIVE_INT, fspace_id, H5P_DEFAULT, dcpl_id, H5P_DEFAULT);
+    dset_id = H5Dcreate2(file_id, PARTIAL_NO_SELECTION_DATASET_NAME, H5T_NATIVE_INT, fspace_id, H5P_DEFAULT,
+                         dcpl_id, H5P_DEFAULT);
     VRFY((dset_id >= 0), "H5Dcreate2 succeeded");
 
     /*
@@ -121,23 +123,25 @@ void test_partial_no_selection_coll_md_read(void)
      *
      * The ranks will write rows across the dataset.
      */
-    start[0] = PARTIAL_NO_SELECTION_Y_DIM_SCALE * mpi_rank;
-    start[1] = 0;
+    start[0]  = (hsize_t)PARTIAL_NO_SELECTION_Y_DIM_SCALE * (hsize_t)mpi_rank;
+    start[1]  = 0;
     stride[0] = PARTIAL_NO_SELECTION_Y_DIM_SCALE;
     stride[1] = PARTIAL_NO_SELECTION_X_DIM_SCALE;
-    count[0] = 1;
-    count[1] = mpi_size;
-    block[0] = PARTIAL_NO_SELECTION_Y_DIM_SCALE;
-    block[1] = PARTIAL_NO_SELECTION_X_DIM_SCALE;
+    count[0]  = 1;
+    count[1]  = (hsize_t)mpi_size;
+    block[0]  = PARTIAL_NO_SELECTION_Y_DIM_SCALE;
+    block[1]  = PARTIAL_NO_SELECTION_X_DIM_SCALE;
 
-    VRFY((H5Sselect_hyperslab(fspace_id, H5S_SELECT_SET, start, stride, count, block) >= 0), "H5Sselect_hyperslab succeeded");
+    VRFY((H5Sselect_hyperslab(fspace_id, H5S_SELECT_SET, start, stride, count, block) >= 0),
+         "H5Sselect_hyperslab succeeded");
 
     sel_dims[0] = count[1] * (PARTIAL_NO_SELECTION_Y_DIM_SCALE * PARTIAL_NO_SELECTION_X_DIM_SCALE);
 
     mspace_id = H5Screate_simple(1, sel_dims, NULL);
     VRFY((mspace_id >= 0), "H5Screate_simple succeeded");
 
-    data = HDcalloc(1, count[1] * (PARTIAL_NO_SELECTION_Y_DIM_SCALE * PARTIAL_NO_SELECTION_X_DIM_SCALE) * sizeof(int));
+    data = HDcalloc(1, count[1] * (PARTIAL_NO_SELECTION_Y_DIM_SCALE * PARTIAL_NO_SELECTION_X_DIM_SCALE) *
+                           sizeof(int));
     VRFY((data != NULL), "calloc succeeded");
 
     dxpl_id = H5Pcreate(H5P_DATASET_XFER);
@@ -157,9 +161,11 @@ void test_partial_no_selection_coll_md_read(void)
      * the particular code path where the issue lies and we don't
      * want the library doing multi-chunk I/O behind our backs.
      */
-    VRFY((H5Pset_dxpl_mpio_chunk_opt(dxpl_id, H5FD_MPIO_CHUNK_ONE_IO) >= 0), "H5Pset_dxpl_mpio_chunk_opt succeeded");
+    VRFY((H5Pset_dxpl_mpio_chunk_opt(dxpl_id, H5FD_MPIO_CHUNK_ONE_IO) >= 0),
+         "H5Pset_dxpl_mpio_chunk_opt succeeded");
 
-    read_buf = HDmalloc(count[1] * (PARTIAL_NO_SELECTION_Y_DIM_SCALE * PARTIAL_NO_SELECTION_X_DIM_SCALE) * sizeof(int));
+    read_buf = HDmalloc(count[1] * (PARTIAL_NO_SELECTION_Y_DIM_SCALE * PARTIAL_NO_SELECTION_X_DIM_SCALE) *
+                        sizeof(int));
     VRFY((read_buf != NULL), "malloc succeeded");
 
     /*
@@ -173,13 +179,17 @@ void test_partial_no_selection_coll_md_read(void)
     /*
      * Finally have each rank read their section of data back from the dataset.
      */
-    VRFY((H5Dread(dset_id, H5T_NATIVE_INT, mspace_id, fspace_id, dxpl_id, read_buf) >= 0), "H5Dread succeeded");
+    VRFY((H5Dread(dset_id, H5T_NATIVE_INT, mspace_id, fspace_id, dxpl_id, read_buf) >= 0),
+         "H5Dread succeeded");
 
     /*
      * Check data integrity just to be sure.
      */
     if (!PARTIAL_NO_SELECTION_NO_SEL_PROCESS) {
-        VRFY((!HDmemcmp(data, read_buf, count[1] * (PARTIAL_NO_SELECTION_Y_DIM_SCALE * PARTIAL_NO_SELECTION_X_DIM_SCALE) * sizeof(int))), "memcmp succeeded");
+        VRFY((!HDmemcmp(data, read_buf,
+                        count[1] * (PARTIAL_NO_SELECTION_Y_DIM_SCALE * PARTIAL_NO_SELECTION_X_DIM_SCALE) *
+                            sizeof(int))),
+             "memcmp succeeded");
     }
 
     if (dataset_dims) {
@@ -219,40 +229,35 @@ void test_partial_no_selection_coll_md_read(void)
  *  major: Internal error (too specific to document in detail)
  *  minor: Some MPI function failed
  *  #009: H5Dmpio.c line 2546 in H5D__obtain_mpio_mode(): Message truncated, error stack:
- *PMPI_Bcast(1600)..................: MPI_Bcast(buf=0x1df98e0, count=18, MPI_BYTE, root=0, comm=0x84000006) failed
- *MPIR_Bcast_impl(1452).............:
- *MPIR_Bcast(1476)..................:
+ *PMPI_Bcast(1600)..................: MPI_Bcast(buf=0x1df98e0, count=18, MPI_BYTE, root=0, comm=0x84000006)
+ *failed MPIR_Bcast_impl(1452).............: MPIR_Bcast(1476)..................:
  *MPIR_Bcast_intra(1249)............:
  *MPIR_SMP_Bcast(1088)..............:
  *MPIR_Bcast_binomial(239)..........:
- *MPIDI_CH3U_Receive_data_found(131): Message from rank 0 and tag 2 truncated; 2616 bytes received but buffer size is 18
- *  major: Internal error (too specific to document in detail)
- *  minor: MPI Error String
+ *MPIDI_CH3U_Receive_data_found(131): Message from rank 0 and tag 2 truncated; 2616 bytes received but buffer
+ *size is 18 major: Internal error (too specific to document in detail) minor: MPI Error String
  *
  */
-void test_multi_chunk_io_addrmap_issue(void)
+void
+test_multi_chunk_io_addrmap_issue(void)
 {
     const char *filename;
-    hsize_t start[MULTI_CHUNK_IO_ADDRMAP_ISSUE_DIMS];
-    hsize_t stride[MULTI_CHUNK_IO_ADDRMAP_ISSUE_DIMS];
-    hsize_t count[MULTI_CHUNK_IO_ADDRMAP_ISSUE_DIMS];
-    hsize_t block[MULTI_CHUNK_IO_ADDRMAP_ISSUE_DIMS];
-    hsize_t dims[MULTI_CHUNK_IO_ADDRMAP_ISSUE_DIMS] = {10, 5};
-    hsize_t chunk_dims[MULTI_CHUNK_IO_ADDRMAP_ISSUE_DIMS] = {5, 5};
-    hsize_t max_dims[MULTI_CHUNK_IO_ADDRMAP_ISSUE_DIMS] = {H5S_UNLIMITED, H5S_UNLIMITED};
-    hid_t file_id = H5I_INVALID_HID;
-    hid_t fapl_id = H5I_INVALID_HID;
-    hid_t dset_id = H5I_INVALID_HID;
-    hid_t dcpl_id = H5I_INVALID_HID;
-    hid_t dxpl_id = H5I_INVALID_HID;
-    hid_t space_id = H5I_INVALID_HID;
-    void *read_buf = NULL;
-    int mpi_rank;
-    int data[5][5] = { {0, 1, 2, 3, 4},
-                       {0, 1, 2, 3, 4},
-                       {0, 1, 2, 3, 4},
-                       {0, 1, 2, 3, 4},
-                       {0, 1, 2, 3, 4} };
+    hsize_t     start[MULTI_CHUNK_IO_ADDRMAP_ISSUE_DIMS];
+    hsize_t     stride[MULTI_CHUNK_IO_ADDRMAP_ISSUE_DIMS];
+    hsize_t     count[MULTI_CHUNK_IO_ADDRMAP_ISSUE_DIMS];
+    hsize_t     block[MULTI_CHUNK_IO_ADDRMAP_ISSUE_DIMS];
+    hsize_t     dims[MULTI_CHUNK_IO_ADDRMAP_ISSUE_DIMS]       = {10, 5};
+    hsize_t     chunk_dims[MULTI_CHUNK_IO_ADDRMAP_ISSUE_DIMS] = {5, 5};
+    hsize_t     max_dims[MULTI_CHUNK_IO_ADDRMAP_ISSUE_DIMS]   = {H5S_UNLIMITED, H5S_UNLIMITED};
+    hid_t       file_id                                       = H5I_INVALID_HID;
+    hid_t       fapl_id                                       = H5I_INVALID_HID;
+    hid_t       dset_id                                       = H5I_INVALID_HID;
+    hid_t       dcpl_id                                       = H5I_INVALID_HID;
+    hid_t       dxpl_id                                       = H5I_INVALID_HID;
+    hid_t       space_id                                      = H5I_INVALID_HID;
+    void *      read_buf                                      = NULL;
+    int         mpi_rank;
+    int data[5][5] = {{0, 1, 2, 3, 4}, {0, 1, 2, 3, 4}, {0, 1, 2, 3, 4}, {0, 1, 2, 3, 4}, {0, 1, 2, 3, 4}};
 
     MPI_Comm_rank(MPI_COMM_WORLD, &mpi_rank);
 
@@ -277,7 +282,8 @@ void test_multi_chunk_io_addrmap_issue(void)
     dcpl_id = H5Pcreate(H5P_DATASET_CREATE);
     VRFY((dcpl_id >= 0), "H5Pcreate succeeded");
 
-    VRFY((H5Pset_chunk(dcpl_id, MULTI_CHUNK_IO_ADDRMAP_ISSUE_DIMS, chunk_dims) >= 0), "H5Pset_chunk succeeded");
+    VRFY((H5Pset_chunk(dcpl_id, MULTI_CHUNK_IO_ADDRMAP_ISSUE_DIMS, chunk_dims) >= 0),
+         "H5Pset_chunk succeeded");
 
     dset_id = H5Dcreate2(file_id, "dset", H5T_NATIVE_INT, space_id, H5P_DEFAULT, dcpl_id, H5P_DEFAULT);
     VRFY((dset_id >= 0), "H5Dcreate2 succeeded");
@@ -286,9 +292,10 @@ void test_multi_chunk_io_addrmap_issue(void)
     VRFY((dxpl_id >= 0), "H5Pcreate succeeded");
 
     VRFY((H5Pset_dxpl_mpio(dxpl_id, H5FD_MPIO_COLLECTIVE) >= 0), "H5Pset_dxpl_mpio succeeded");
-    VRFY((H5Pset_dxpl_mpio_chunk_opt(dxpl_id, H5FD_MPIO_CHUNK_MULTI_IO) >= 0), "H5Pset_dxpl_mpio_chunk_opt succeeded");
+    VRFY((H5Pset_dxpl_mpio_chunk_opt(dxpl_id, H5FD_MPIO_CHUNK_MULTI_IO) >= 0),
+         "H5Pset_dxpl_mpio_chunk_opt succeeded");
 
-    start[1] = 0;
+    start[1]  = 0;
     stride[0] = stride[1] = 1;
     count[0] = count[1] = 5;
     block[0] = block[1] = 1;
@@ -298,7 +305,8 @@ void test_multi_chunk_io_addrmap_issue(void)
     else
         start[0] = 5;
 
-    VRFY((H5Sselect_hyperslab(space_id, H5S_SELECT_SET, start, stride, count, block) >= 0), "H5Sselect_hyperslab succeeded");
+    VRFY((H5Sselect_hyperslab(space_id, H5S_SELECT_SET, start, stride, count, block) >= 0),
+         "H5Sselect_hyperslab succeeded");
     if (mpi_rank != 0)
         VRFY((H5Sselect_none(space_id) >= 0), "H5Sselect_none succeeded");
 
@@ -330,21 +338,34 @@ void test_multi_chunk_io_addrmap_issue(void)
  * collective metadata reads being made only by process 0 in H5D__sort_chunk().
  *
  * NOTE: Due to the way that the threshold value which pertains to this test
- * is currently calculated within HDF5, there are several conditions that this
- * test must maintain. Refer to the function H5D__sort_chunk in H5Dmpio.c for
- * a better idea of why.
+ * is currently calculated within HDF5, the following two conditions must be
+ * true to trigger the issue:
+ *
+ * Condition 1: A certain threshold ratio must be met in order to have HDF5
+ * obtain all chunk addresses collectively inside H5D__sort_chunk(). This is
+ * given by the following:
  *
- * Condition 1: We need to make sure that the test always selects every single
- * chunk in the dataset. It is fine if the selection is split up among multiple
- * ranks, but their combined selection must cover the whole dataset.
+ *     (sum_chunk * 100) / (dataset_nchunks * mpi_size) >= 30%
  *
- * Condition 2: The number of chunks in the dataset divided by the number of MPI
- * ranks must exceed or equal 10000. In other words, each MPI rank must be
- * responsible for 10000 or more unique chunks.
+ * where:
+ *     * `sum_chunk` is the combined sum of the number of chunks selected in
+ *       the dataset by all ranks (chunks selected by more than one rank count
+ *       individually toward the sum for each rank selecting that chunk)
+ *     * `dataset_nchunks` is the number of chunks in the dataset (selected
+ *       or not)
+ *     * `mpi_size` is the size of the MPI Communicator
  *
- * Condition 3: This test will currently only be reliably reproducable for 2 or 3
- * MPI ranks. The threshold value calculated reduces to a constant 100 / mpi_size,
- * and is compared against a default value of 30%.
+ * Condition 2: `sum_chunk` divided by `mpi_size` must exceed or equal a certain
+ * threshold (as of this writing, 10000).
+ *
+ * To satisfy both these conditions, we #define a macro,
+ * LINK_CHUNK_IO_SORT_CHUNK_ISSUE_COLL_THRESH_NUM, which corresponds to the
+ * value of the H5D_ALL_CHUNK_ADDR_THRES_COL_NUM macro in H5Dmpio.c (the
+ * 10000 threshold from condition 2). We then create a dataset of that many
+ * chunks and have each MPI rank write to and read from a piece of every single
+ * chunk in the dataset. This ensures chunk utilization is the max possible
+ * and exceeds our 30% target ratio, while always exactly matching the numeric
+ * chunk threshold value of condition 2.
  *
  * Failure in this test may either cause a hang, or, due to how the MPI calls
  * pertaining to this issue might mistakenly match up, may cause an MPI error
@@ -359,31 +380,30 @@ void test_multi_chunk_io_addrmap_issue(void)
  *MPIR_Bcast(1476)........:
  *MPIR_Bcast_intra(1249)..:
  *MPIR_SMP_Bcast(1088)....:
- *MPIR_Bcast_binomial(250): message sizes do not match across processes in the collective routine: Received 2096 but expected 320000
- *  major: Internal error (too specific to document in detail)
- *  minor: MPI Error String
+ *MPIR_Bcast_binomial(250): message sizes do not match across processes in the collective routine: Received
+ *2096 but expected 320000 major: Internal error (too specific to document in detail) minor: MPI Error String
  */
-void test_link_chunk_io_sort_chunk_issue(void)
+void
+test_link_chunk_io_sort_chunk_issue(void)
 {
     const char *filename;
-    hsize_t *dataset_dims = NULL;
-    hsize_t  max_dataset_dims[LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS];
-    hsize_t  sel_dims[1];
-    hsize_t  chunk_dims[LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS] = { LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS };
-    hsize_t  start[LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS];
-    hsize_t  stride[LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS];
-    hsize_t  count[LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS];
-    hsize_t  block[LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS];
-    hid_t    file_id = H5I_INVALID_HID;
-    hid_t    fapl_id = H5I_INVALID_HID;
-    hid_t    dset_id = H5I_INVALID_HID;
-    hid_t    dcpl_id = H5I_INVALID_HID;
-    hid_t    dxpl_id = H5I_INVALID_HID;
-    hid_t    fspace_id = H5I_INVALID_HID;
-    hid_t    mspace_id = H5I_INVALID_HID;
-    int      mpi_rank, mpi_size;
-    void    *data = NULL;
-    void    *read_buf = NULL;
+    hsize_t     dataset_dims[LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS];
+    hsize_t     sel_dims[LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS];
+    hsize_t     chunk_dims[LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS];
+    hsize_t     start[LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS];
+    hsize_t     stride[LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS];
+    hsize_t     count[LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS];
+    hsize_t     block[LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS];
+    hid_t       file_id   = H5I_INVALID_HID;
+    hid_t       fapl_id   = H5I_INVALID_HID;
+    hid_t       dset_id   = H5I_INVALID_HID;
+    hid_t       dcpl_id   = H5I_INVALID_HID;
+    hid_t       dxpl_id   = H5I_INVALID_HID;
+    hid_t       fspace_id = H5I_INVALID_HID;
+    hid_t       mspace_id = H5I_INVALID_HID;
+    int         mpi_rank, mpi_size;
+    void *      data     = NULL;
+    void *      read_buf = NULL;
 
     MPI_Comm_rank(MPI_COMM_WORLD, &mpi_rank);
     MPI_Comm_size(MPI_COMM_WORLD, &mpi_size);
@@ -403,13 +423,13 @@ void test_link_chunk_io_sort_chunk_issue(void)
     file_id = H5Fcreate(filename, H5F_ACC_TRUNC, H5P_DEFAULT, fapl_id);
     VRFY((file_id >= 0), "H5Fcreate succeeded");
 
-    dataset_dims = HDmalloc(LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS * sizeof(*dataset_dims));
-    VRFY((dataset_dims != NULL), "malloc succeeded");
-
-    dataset_dims[0] = LINK_CHUNK_IO_SORT_CHUNK_ISSUE_CHUNK_SIZE * mpi_size * LINK_CHUNK_IO_SORT_CHUNK_ISSUE_Y_DIM_SCALE;
-    max_dataset_dims[0] = H5S_UNLIMITED;
+    /*
+     * Create a one-dimensional dataset of exactly LINK_CHUNK_IO_SORT_CHUNK_ISSUE_COLL_THRESH_NUM
+     * chunks, where every rank writes to a piece of every single chunk to keep utilization high.
+     */
+    dataset_dims[0] = (hsize_t)mpi_size * (hsize_t)LINK_CHUNK_IO_SORT_CHUNK_ISSUE_COLL_THRESH_NUM;
 
-    fspace_id = H5Screate_simple(LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS, dataset_dims, max_dataset_dims);
+    fspace_id = H5Screate_simple(LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS, dataset_dims, NULL);
     VRFY((fspace_id >= 0), "H5Screate_simple succeeded");
 
     /*
@@ -418,29 +438,33 @@ void test_link_chunk_io_sort_chunk_issue(void)
     dcpl_id = H5Pcreate(H5P_DATASET_CREATE);
     VRFY((dcpl_id >= 0), "H5Pcreate succeeded");
 
-    VRFY((H5Pset_chunk(dcpl_id, LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS, chunk_dims) >= 0), "H5Pset_chunk succeeded");
+    /* Chunk size is equal to MPI size since each rank writes to a piece of every chunk */
+    chunk_dims[0] = (hsize_t)mpi_size;
+
+    VRFY((H5Pset_chunk(dcpl_id, LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DIMS, chunk_dims) >= 0),
+         "H5Pset_chunk succeeded");
 
-    dset_id = H5Dcreate2(file_id, LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DATASET_NAME, H5T_NATIVE_INT, fspace_id, H5P_DEFAULT, dcpl_id, H5P_DEFAULT);
+    dset_id = H5Dcreate2(file_id, LINK_CHUNK_IO_SORT_CHUNK_ISSUE_DATASET_NAME, H5T_NATIVE_INT, fspace_id,
+                         H5P_DEFAULT, dcpl_id, H5P_DEFAULT);
     VRFY((dset_id >= 0), "H5Dcreate2 succeeded");
 
     /*
      * Setup hyperslab selection to split the dataset among the ranks.
-     *
-     * The ranks will write rows across the dataset.
      */
-    stride[0] = LINK_CHUNK_IO_SORT_CHUNK_ISSUE_CHUNK_SIZE;
-    count[0] = (dataset_dims[0] / LINK_CHUNK_IO_SORT_CHUNK_ISSUE_CHUNK_SIZE) / mpi_size;
-    start[0] = count[0] * mpi_rank;
-    block[0] = LINK_CHUNK_IO_SORT_CHUNK_ISSUE_CHUNK_SIZE;
+    start[0]  = (hsize_t)mpi_rank;
+    stride[0] = (hsize_t)mpi_size;
+    count[0]  = LINK_CHUNK_IO_SORT_CHUNK_ISSUE_COLL_THRESH_NUM;
+    block[0]  = 1;
 
-    VRFY((H5Sselect_hyperslab(fspace_id, H5S_SELECT_SET, start, stride, count, block) >= 0), "H5Sselect_hyperslab succeeded");
+    VRFY((H5Sselect_hyperslab(fspace_id, H5S_SELECT_SET, start, stride, count, block) >= 0),
+         "H5Sselect_hyperslab succeeded");
 
-    sel_dims[0] = count[0] * (LINK_CHUNK_IO_SORT_CHUNK_ISSUE_CHUNK_SIZE);
+    sel_dims[0] = count[0];
 
     mspace_id = H5Screate_simple(1, sel_dims, NULL);
     VRFY((mspace_id >= 0), "H5Screate_simple succeeded");
 
-    data = HDcalloc(1, count[0] * (LINK_CHUNK_IO_SORT_CHUNK_ISSUE_CHUNK_SIZE) * sizeof(int));
+    data = HDcalloc(1, count[0] * sizeof(int));
     VRFY((data != NULL), "calloc succeeded");
 
     dxpl_id = H5Pcreate(H5P_DATASET_XFER);
@@ -460,32 +484,27 @@ void test_link_chunk_io_sort_chunk_issue(void)
      * the particular code path where the issue lies and we don't
      * want the library doing multi-chunk I/O behind our backs.
      */
-    VRFY((H5Pset_dxpl_mpio_chunk_opt(dxpl_id, H5FD_MPIO_CHUNK_ONE_IO) >= 0), "H5Pset_dxpl_mpio_chunk_opt succeeded");
+    VRFY((H5Pset_dxpl_mpio_chunk_opt(dxpl_id, H5FD_MPIO_CHUNK_ONE_IO) >= 0),
+         "H5Pset_dxpl_mpio_chunk_opt succeeded");
 
-    read_buf = HDmalloc(count[0] * (LINK_CHUNK_IO_SORT_CHUNK_ISSUE_CHUNK_SIZE) * sizeof(int));
+    read_buf = HDmalloc(count[0] * sizeof(int));
     VRFY((read_buf != NULL), "malloc succeeded");
 
-    VRFY((H5Sselect_hyperslab(fspace_id, H5S_SELECT_SET, start, stride, count, block) >= 0), "H5Sselect_hyperslab succeeded");
+    VRFY((H5Sselect_hyperslab(fspace_id, H5S_SELECT_SET, start, stride, count, block) >= 0),
+         "H5Sselect_hyperslab succeeded");
 
-    sel_dims[0] = count[0] * (LINK_CHUNK_IO_SORT_CHUNK_ISSUE_CHUNK_SIZE);
+    sel_dims[0] = count[0];
 
     VRFY((H5Sclose(mspace_id) >= 0), "H5Sclose succeeded");
 
     mspace_id = H5Screate_simple(1, sel_dims, NULL);
     VRFY((mspace_id >= 0), "H5Screate_simple succeeded");
 
-    read_buf = HDrealloc(read_buf, count[0] * (LINK_CHUNK_IO_SORT_CHUNK_ISSUE_CHUNK_SIZE) * sizeof(int));
-    VRFY((read_buf != NULL), "realloc succeeded");
-
     /*
      * Finally have each rank read their section of data back from the dataset.
      */
-    VRFY((H5Dread(dset_id, H5T_NATIVE_INT, mspace_id, fspace_id, dxpl_id, read_buf) >= 0), "H5Dread succeeded");
-
-    if (dataset_dims) {
-        HDfree(dataset_dims);
-        dataset_dims = NULL;
-    }
+    VRFY((H5Dread(dset_id, H5T_NATIVE_INT, mspace_id, fspace_id, dxpl_id, read_buf) >= 0),
+         "H5Dread succeeded");
 
     if (data) {
         HDfree(data);