Implement selection vector I/O with collective chunk filling (#3826)

* Changes for ECP-344: Implement selection vector I/O with collective chunk filling.
Also fix a bug in H5FD__mpio_write_vector() to account for fixed size optimization
when computing max address.

* Fixes based on PR review comments:
For H5Dchunk.c: fix H5MM_xfree()
For H5FDmpio.c:
1) Revert the fix to H5FD__mpio_write_vector()
2) Apply the patch from Neil on the proper length of s_sizes reported by H5FD__mpio_vector_build_types()

* Put back the logic of dividing up the work among all the mpi ranks similar to the
original H5D__chunk_collective_fill() routine.

* Add a test to verify the fix for the illegal reference problem in H5FD__mpio_write_vector().

4 files changed, 434 insertions, 189 deletions

diff --git a/src/H5Dchunk.c b/src/H5Dchunk.c
index 41d774d..c8bad76 100644
--- a/src/H5Dchunk.c
+++ b/src/H5Dchunk.c
@@ -5536,11 +5536,9 @@ done:
 /*-------------------------------------------------------------------------
  * Function:    H5D__chunk_collective_fill
  *
- * Purpose:     Use MPIO collective write to fill the chunks (if number of
- *              chunks to fill is greater than the number of MPI procs;
- *              otherwise use independent I/O).
+ * Purpose:     Use MPIO selection vector I/O for writing fill chunks
  *
- * Return:    Non-negative on success/Negative on failure
+ * Return:      Non-negative on success/Negative on failure
  *
  *-------------------------------------------------------------------------
  */
@@ -5554,19 +5552,24 @@ H5D__chunk_collective_fill(const H5D_t *dset, H5D_chunk_coll_fill_info_t *chunk_
     int              mpi_code;                 /* MPI return code */
     size_t           num_blocks;               /* Number of blocks between processes. */
     size_t           leftover_blocks;          /* Number of leftover blocks to handle */
-    int              blocks, leftover;         /* converted to int for MPI */
-    MPI_Aint        *chunk_disp_array = NULL;
-    MPI_Aint        *block_disps      = NULL;
-    int             *block_lens       = NULL;
-    MPI_Datatype     mem_type = MPI_BYTE, file_type = MPI_BYTE;
-    H5FD_mpio_xfer_t prev_xfer_mode;         /* Previous data xfer mode */
-    bool             have_xfer_mode = false; /* Whether the previous xffer mode has been retrieved */
-    bool             need_sort      = false;
-    size_t           i;                   /* Local index variable */
+    int              blocks;                   /* converted to int for MPI */
+    int              leftover;                 /* converted to int for MPI */
+    H5FD_mpio_xfer_t prev_xfer_mode;           /* Previous data xfer mode */
+    bool             have_xfer_mode = false;   /* Whether the previous xffer mode has been retrieved */
+    size_t           i;                        /* Local index variable */
+    haddr_t         *io_addrs = NULL;
+    size_t          *io_sizes = NULL;
+    const void     **io_wbufs = NULL;
+    H5FD_mem_t       io_types[2];
+    bool             all_same_block_len = true;
+    bool             need_sort          = false;
+    size_t           io_2sizes[2];
     herr_t           ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_PACKAGE
 
+    assert(chunk_fill_info->num_chunks != 0);
+
     /*
      * If a separate fill buffer is provided for partial chunks, ensure
      * that the "don't filter partial edge chunks" flag is set.
@@ -5589,6 +5592,7 @@ H5D__chunk_collective_fill(const H5D_t *dset, H5D_chunk_coll_fill_info_t *chunk_
     /* Distribute evenly the number of blocks between processes. */
     if (mpi_size == 0)
         HGOTO_ERROR(H5E_DATASET, H5E_BADVALUE, FAIL, "Resulted in division by zero");
+
     num_blocks =
         (size_t)(chunk_fill_info->num_chunks / (size_t)mpi_size); /* value should be the same on all procs */
 
@@ -5602,157 +5606,97 @@ H5D__chunk_collective_fill(const H5D_t *dset, H5D_chunk_coll_fill_info_t *chunk_
     H5_CHECKED_ASSIGN(leftover, int, leftover_blocks, size_t);
 
     /* Check if we have any chunks to write on this rank */
-    if (num_blocks > 0 || (leftover && leftover > mpi_rank)) {
-        MPI_Aint partial_fill_buf_disp = 0;
-        bool     all_same_block_len    = true;
-
-        /* Allocate buffers */
-        if (NULL == (chunk_disp_array = (MPI_Aint *)H5MM_malloc((size_t)(blocks + 1) * sizeof(MPI_Aint))))
-            HGOTO_ERROR(H5E_DATASET, H5E_CANTALLOC, FAIL, "couldn't allocate chunk file displacement buffer");
-
-        if (partial_chunk_fill_buf) {
-            MPI_Aint fill_buf_addr;
-            MPI_Aint partial_fill_buf_addr;
-
-            /* Calculate the displacement between the fill buffer and partial chunk fill buffer */
-            if (MPI_SUCCESS != (mpi_code = MPI_Get_address(fill_buf, &fill_buf_addr)))
-                HMPI_GOTO_ERROR(FAIL, "MPI_Get_address failed", mpi_code)
-            if (MPI_SUCCESS != (mpi_code = MPI_Get_address(partial_chunk_fill_buf, &partial_fill_buf_addr)))
-                HMPI_GOTO_ERROR(FAIL, "MPI_Get_address failed", mpi_code)
-
-#if H5_CHECK_MPI_VERSION(3, 1)
-            partial_fill_buf_disp = MPI_Aint_diff(partial_fill_buf_addr, fill_buf_addr);
-#else
-            partial_fill_buf_disp = partial_fill_buf_addr - fill_buf_addr;
-#endif
+    if (num_blocks > 0 || leftover > mpi_rank) {
 
-            /*
-             * Allocate all-zero block displacements array. If a block's displacement
-             * is left as zero, that block will be written to from the regular fill
-             * buffer. If a block represents an unfiltered partial edge chunk, its
-             * displacement will be set so that the block is written to from the
-             * unfiltered fill buffer.
-             */
-            if (NULL == (block_disps = (MPI_Aint *)H5MM_calloc((size_t)(blocks + 1) * sizeof(MPI_Aint))))
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTALLOC, FAIL, "couldn't allocate block displacements buffer");
-        }
+        if (NULL == (io_addrs = H5MM_malloc((size_t)(blocks + 1) * sizeof(*io_addrs))))
+            HGOTO_ERROR(H5E_RESOURCE, H5E_CANTALLOC, FAIL,
+                        "couldn't allocate space for I/O addresses vector");
 
-        /*
-         * Perform initial scan of chunk info list to:
-         *  - make sure that chunk addresses are monotonically non-decreasing
-         *  - check if all blocks have the same length
-         */
-        for (i = 1; i < chunk_fill_info->num_chunks; i++) {
-            if (chunk_fill_info->chunk_info[i].addr < chunk_fill_info->chunk_info[i - 1].addr)
-                need_sort = true;
-
-            if (chunk_fill_info->chunk_info[i].chunk_size != chunk_fill_info->chunk_info[i - 1].chunk_size)
-                all_same_block_len = false;
-        }
+        if (NULL == (io_wbufs = H5MM_malloc((size_t)(blocks + 1) * sizeof(*io_wbufs))))
+            HGOTO_ERROR(H5E_RESOURCE, H5E_CANTALLOC, FAIL, "couldn't allocate space for I/O buffers vector");
+    }
 
-        if (need_sort)
-            qsort(chunk_fill_info->chunk_info, chunk_fill_info->num_chunks,
-                  sizeof(struct chunk_coll_fill_info), H5D__chunk_cmp_coll_fill_info);
+    /*
+     * Perform initial scan of chunk info list to:
+     *  - make sure that chunk addresses are monotonically non-decreasing
+     *  - check if all blocks have the same length
+     */
+    for (i = 1; i < chunk_fill_info->num_chunks; i++) {
+        if (chunk_fill_info->chunk_info[i].addr < chunk_fill_info->chunk_info[i - 1].addr)
+            need_sort = true;
 
-        /* Allocate buffer for block lengths if necessary */
-        if (!all_same_block_len)
-            if (NULL == (block_lens = (int *)H5MM_malloc((size_t)(blocks + 1) * sizeof(int))))
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTALLOC, FAIL, "couldn't allocate chunk lengths buffer");
+        if (chunk_fill_info->chunk_info[i].chunk_size != chunk_fill_info->chunk_info[i - 1].chunk_size)
+            all_same_block_len = false;
+    }
 
-        for (i = 0; i < (size_t)blocks; i++) {
-            size_t idx = i + (size_t)(mpi_rank * blocks);
+    /*
+     * Note that we sort all of the chunks here, and not just a subset
+     * corresponding to this rank. We do this since we have found MPI I/O to work
+     * better when each rank writes blocks that are contiguous in the file,
+     * and by sorting the full list we maximize the chance of that happening.
+     */
+    if (need_sort)
+        qsort(chunk_fill_info->chunk_info, chunk_fill_info->num_chunks, sizeof(struct chunk_coll_fill_info),
+              H5D__chunk_cmp_coll_fill_info);
 
-            /* store the chunk address as an MPI_Aint */
-            chunk_disp_array[i] = (MPI_Aint)(chunk_fill_info->chunk_info[idx].addr);
+    /*
+     * If all the chunks have the same length, use the compressed feature
+     * to store the size.
+     * Otherwise, allocate the array of sizes for storing chunk sizes.
+     */
+    if (all_same_block_len) {
+        io_2sizes[0] = chunk_fill_info->chunk_info[0].chunk_size;
+        io_2sizes[1] = 0;
+    }
+    else {
+        if (NULL == (io_sizes = H5MM_malloc((size_t)(blocks + 1) * sizeof(*io_sizes))))
+            HGOTO_ERROR(H5E_RESOURCE, H5E_CANTALLOC, FAIL, "couldn't allocate space for I/O sizes vector");
+    }
 
-            if (!all_same_block_len)
-                H5_CHECKED_ASSIGN(block_lens[i], int, chunk_fill_info->chunk_info[idx].chunk_size, size_t);
+    /*
+     * Since the type of all chunks is raw data, use the compressed feature
+     * to store the chunk type.
+     */
+    io_types[0] = H5FD_MEM_DRAW;
+    io_types[1] = H5FD_MEM_NOLIST;
 
-            if (chunk_fill_info->chunk_info[idx].unfiltered_partial_chunk) {
-                assert(partial_chunk_fill_buf);
-                block_disps[i] = partial_fill_buf_disp;
-            }
-        } /* end for */
+    /*
+     * For the chunks corresponding to this rank, fill in the
+     * address, size and buf pointer for each chunk.
+     */
+    for (i = 0; i < (size_t)blocks; i++) {
+        size_t idx = i + (size_t)(mpi_rank * blocks);
 
-        /* Calculate if there are any leftover blocks after evenly
-         * distributing. If there are, then round-robin the distribution
-         * to processes 0 -> leftover.
-         */
-        if (leftover && leftover > mpi_rank) {
-            chunk_disp_array[blocks] =
-                (MPI_Aint)chunk_fill_info->chunk_info[(blocks * mpi_size) + mpi_rank].addr;
-
-            if (!all_same_block_len)
-                H5_CHECKED_ASSIGN(block_lens[blocks], int,
-                                  chunk_fill_info->chunk_info[(blocks * mpi_size) + mpi_rank].chunk_size,
-                                  size_t);
-
-            if (chunk_fill_info->chunk_info[(blocks * mpi_size) + mpi_rank].unfiltered_partial_chunk) {
-                assert(partial_chunk_fill_buf);
-                block_disps[blocks] = partial_fill_buf_disp;
-            }
+        io_addrs[i] = chunk_fill_info->chunk_info[idx].addr;
 
-            blocks++;
-        }
+        if (!all_same_block_len)
+            io_sizes[i] = chunk_fill_info->chunk_info[idx].chunk_size;
 
-        /* Create file and memory types for the write operation */
-        if (all_same_block_len) {
-            int block_len;
+        if (chunk_fill_info->chunk_info[idx].unfiltered_partial_chunk)
+            io_wbufs[i] = partial_chunk_fill_buf;
+        else
+            io_wbufs[i] = fill_buf;
+    }
 
-            H5_CHECKED_ASSIGN(block_len, int, chunk_fill_info->chunk_info[0].chunk_size, size_t);
+    /*
+     * For the leftover chunk corresponding to this rank, fill in the
+     * address, size and buf pointer for the chunk.
+     */
+    if (leftover > mpi_rank) {
+        io_addrs[blocks] = chunk_fill_info->chunk_info[(blocks * mpi_size) + mpi_rank].addr;
 
-            mpi_code =
-                MPI_Type_create_hindexed_block(blocks, block_len, chunk_disp_array, MPI_BYTE, &file_type);
-            if (mpi_code != MPI_SUCCESS)
-                HMPI_GOTO_ERROR(FAIL, "MPI_Type_create_hindexed_block failed", mpi_code)
+        if (!all_same_block_len)
+            io_sizes[blocks] = chunk_fill_info->chunk_info[(blocks * mpi_size) + mpi_rank].chunk_size;
 
-            if (partial_chunk_fill_buf) {
-                /*
-                 * If filters are disabled for partial edge chunks, those chunks could
-                 * potentially have the same block length as the other chunks, but still
-                 * need to be written to using the unfiltered fill buffer. Use an hindexed
-                 * block type rather than an hvector.
-                 */
-                mpi_code =
-                    MPI_Type_create_hindexed_block(blocks, block_len, block_disps, MPI_BYTE, &mem_type);
-                if (mpi_code != MPI_SUCCESS)
-                    HMPI_GOTO_ERROR(FAIL, "MPI_Type_create_hindexed_block failed", mpi_code)
-            }
-            else {
-                mpi_code = MPI_Type_create_hvector(blocks, block_len, 0, MPI_BYTE, &mem_type);
-                if (mpi_code != MPI_SUCCESS)
-                    HMPI_GOTO_ERROR(FAIL, "MPI_Type_create_hvector failed", mpi_code)
-            }
-        }
-        else {
-            /*
-             * Currently, different block lengths implies that there are partial
-             * edge chunks and the "don't filter partial edge chunks" flag is set.
-             */
+        if (chunk_fill_info->chunk_info[(blocks * mpi_size) + mpi_rank].unfiltered_partial_chunk) {
             assert(partial_chunk_fill_buf);
-            assert(block_lens);
-            assert(block_disps);
-
-            mpi_code = MPI_Type_create_hindexed(blocks, block_lens, chunk_disp_array, MPI_BYTE, &file_type);
-            if (mpi_code != MPI_SUCCESS)
-                HMPI_GOTO_ERROR(FAIL, "MPI_Type_create_hindexed failed", mpi_code)
-
-            mpi_code = MPI_Type_create_hindexed(blocks, block_lens, block_disps, MPI_BYTE, &mem_type);
-            if (mpi_code != MPI_SUCCESS)
-                HMPI_GOTO_ERROR(FAIL, "MPI_Type_create_hindexed failed", mpi_code)
+            io_wbufs[blocks] = partial_chunk_fill_buf;
         }
+        else
+            io_wbufs[blocks] = fill_buf;
 
-        if (MPI_SUCCESS != (mpi_code = MPI_Type_commit(&file_type)))
-            HMPI_GOTO_ERROR(FAIL, "MPI_Type_commit failed", mpi_code)
-        if (MPI_SUCCESS != (mpi_code = MPI_Type_commit(&mem_type)))
-            HMPI_GOTO_ERROR(FAIL, "MPI_Type_commit failed", mpi_code)
-    } /* end if */
-
-    /* Set MPI-IO VFD properties */
-
-    /* Set MPI datatypes for operation */
-    if (H5CX_set_mpi_coll_datatypes(mem_type, file_type) < 0)
-        HGOTO_ERROR(H5E_DATASET, H5E_CANTSET, FAIL, "can't set MPI-I/O properties");
+        blocks++;
+    }
 
     /* Get current transfer mode */
     if (H5CX_get_io_xfer_mode(&prev_xfer_mode) < 0)
@@ -5763,31 +5707,24 @@ H5D__chunk_collective_fill(const H5D_t *dset, H5D_chunk_coll_fill_info_t *chunk_
     if (H5CX_set_io_xfer_mode(H5FD_MPIO_COLLECTIVE) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTSET, FAIL, "can't set transfer mode");
 
-    /* Low-level write (collective) */
-    if (H5F_shared_block_write(H5F_SHARED(dset->oloc.file), H5FD_MEM_DRAW, (haddr_t)0,
-                               (blocks) ? (size_t)1 : (size_t)0, fill_buf) < 0)
-        HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "unable to write raw data to file");
-
     /* Barrier so processes don't race ahead */
     if (MPI_SUCCESS != (mpi_code = MPI_Barrier(mpi_comm)))
         HMPI_GOTO_ERROR(FAIL, "MPI_Barrier failed", mpi_code)
 
+    /* Perform the selection vector I/O for the chunks */
+    if (H5F_shared_vector_write(H5F_SHARED(dset->oloc.file), (uint32_t)blocks, io_types, io_addrs,
+                                all_same_block_len ? io_2sizes : io_sizes, io_wbufs) < 0)
+        HGOTO_ERROR(H5E_DATASET, H5E_WRITEERROR, FAIL, "vector write call failed");
+
 done:
     if (have_xfer_mode)
-        /* Set transfer mode */
+        /* Restore transfer mode */
         if (H5CX_set_io_xfer_mode(prev_xfer_mode) < 0)
             HDONE_ERROR(H5E_DATASET, H5E_CANTSET, FAIL, "can't set transfer mode");
 
-    /* free things */
-    if (MPI_BYTE != file_type)
-        if (MPI_SUCCESS != (mpi_code = MPI_Type_free(&file_type)))
-            HMPI_DONE_ERROR(FAIL, "MPI_Type_free failed", mpi_code)
-    if (MPI_BYTE != mem_type)
-        if (MPI_SUCCESS != (mpi_code = MPI_Type_free(&mem_type)))
-            HMPI_DONE_ERROR(FAIL, "MPI_Type_free failed", mpi_code)
-    H5MM_xfree(chunk_disp_array);
-    H5MM_xfree(block_disps);
-    H5MM_xfree(block_lens);
+    H5MM_xfree(io_addrs);
+    H5MM_xfree(io_wbufs);
+    H5MM_xfree(io_sizes);
 
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5D__chunk_collective_fill() */
@@ -5805,6 +5742,7 @@ H5D__chunk_cmp_coll_fill_info(const void *_entry1, const void *_entry2)
 
     FUNC_LEAVE_NOAPI(H5_addr_cmp(entry1->addr, entry2->addr))
 } /* end H5D__chunk_cmp_coll_fill_info() */
+
 #endif /* H5_HAVE_PARALLEL */
 
 /*-------------------------------------------------------------------------
diff --git a/src/H5FDmpio.c b/src/H5FDmpio.c
index d5dd126..8aae79e 100644
--- a/src/H5FDmpio.c
+++ b/src/H5FDmpio.c
@@ -106,7 +106,7 @@ static herr_t H5FD__mpio_ctl(H5FD_t *_file, uint64_t op_code, uint64_t flags, co
 /* Other functions */
 static herr_t H5FD__mpio_vector_build_types(uint32_t count, H5FD_mem_t types[], haddr_t addrs[],
                                             size_t sizes[], H5_flexible_const_ptr_t bufs[],
-                                            haddr_t *s_addrs[], size_t *s_sizes[],
+                                            haddr_t *s_addrs[], size_t *s_sizes[], uint32_t *s_sizes_len,
                                             H5_flexible_const_ptr_t *s_bufs[], bool *vector_was_sorted,
                                             MPI_Offset *mpi_off, H5_flexible_const_ptr_t *mpi_bufs_base,
                                             int *size_i, MPI_Datatype *buf_type, bool *buf_type_created,
@@ -1675,7 +1675,8 @@ done:
 static herr_t
 H5FD__mpio_vector_build_types(uint32_t count, H5FD_mem_t types[], haddr_t addrs[], size_t sizes[],
                               H5_flexible_const_ptr_t bufs[], haddr_t *s_addrs[], size_t *s_sizes[],
-                              H5_flexible_const_ptr_t *s_bufs[], bool *vector_was_sorted, MPI_Offset *mpi_off,
+                              uint32_t *s_sizes_len, H5_flexible_const_ptr_t *s_bufs[],
+                              bool *vector_was_sorted, MPI_Offset *mpi_off,
                               H5_flexible_const_ptr_t *mpi_bufs_base, int *size_i, MPI_Datatype *buf_type,
                               bool *buf_type_created, MPI_Datatype *file_type, bool *file_type_created,
                               char *unused)
@@ -1716,6 +1717,10 @@ H5FD__mpio_vector_build_types(uint32_t count, H5FD_mem_t types[], haddr_t addrs[
     /* Get bio I/O transition point (may be lower than 2G for testing) */
     bigio_count = H5_mpi_get_bigio_count();
 
+    /* Start with s_sizes_len at count */
+    if (s_sizes_len)
+        *s_sizes_len = count;
+
     if (count == 1) {
         /* Single block.  Just use a series of MPI_BYTEs for the file view.
          */
@@ -1808,8 +1813,13 @@ H5FD__mpio_vector_build_types(uint32_t count, H5FD_mem_t types[], haddr_t addrs[
             if (!fixed_size) {
                 if ((*s_sizes)[i] == 0) {
                     assert(vector_was_sorted);
+                    assert(i > 0);
                     fixed_size = true;
                     size       = sizes[i - 1];
+
+                    /* Return the used length of the s_sizes buffer */
+                    if (s_sizes_len)
+                        *s_sizes_len = (uint32_t)i;
                 }
                 else {
                     size = (*s_sizes)[i];
@@ -2098,7 +2108,7 @@ H5FD__mpio_read_vector(H5FD_t *_file, hid_t H5_ATTR_UNUSED dxpl_id, uint32_t cou
     if (xfer_mode == H5FD_MPIO_COLLECTIVE) {
         /* Build MPI types, etc. */
         if (H5FD__mpio_vector_build_types(count, types, addrs, sizes, (H5_flexible_const_ptr_t *)bufs,
-                                          &s_addrs, &s_sizes, (H5_flexible_const_ptr_t **)&s_bufs,
+                                          &s_addrs, &s_sizes, NULL, (H5_flexible_const_ptr_t **)&s_bufs,
                                           &vector_was_sorted, &mpi_off,
                                           (H5_flexible_const_ptr_t *)&mpi_bufs_base, &size_i, &buf_type,
                                           &buf_type_created, &file_type, &file_type_created, &unused) < 0)
@@ -2464,17 +2474,21 @@ H5FD__mpio_write_vector(H5FD_t *_file, hid_t H5_ATTR_UNUSED dxpl_id, uint32_t co
         HGOTO_ERROR(H5E_VFL, H5E_CANTGET, FAIL, "can't get MPI-I/O transfer mode");
 
     if (xfer_mode == H5FD_MPIO_COLLECTIVE) {
+        uint32_t s_sizes_len;
+
         /* Build MPI types, etc. */
         if (H5FD__mpio_vector_build_types(count, types, addrs, sizes, (H5_flexible_const_ptr_t *)bufs,
-                                          &s_addrs, &s_sizes, (H5_flexible_const_ptr_t **)&s_bufs,
-                                          &vector_was_sorted, &mpi_off,
+                                          &s_addrs, &s_sizes, &s_sizes_len,
+                                          (H5_flexible_const_ptr_t **)&s_bufs, &vector_was_sorted, &mpi_off,
                                           (H5_flexible_const_ptr_t *)&mpi_bufs_base, &size_i, &buf_type,
                                           &buf_type_created, &file_type, &file_type_created, &unused) < 0)
             HGOTO_ERROR(H5E_VFL, H5E_CANTGET, FAIL, "can't build MPI datatypes for I/O");
 
-        /* Compute max address written to */
+        /* Compute max address written to.  Note s_sizes is indexed according to the length of that array as
+         * reported by H5FD__mpio_vector_build_types(), which may be shorter if using the compressed arrays
+         * feature. */
         if (count > 0)
-            max_addr = s_addrs[count - 1] + (haddr_t)(s_sizes[count - 1]);
+            max_addr = s_addrs[count - 1] + (haddr_t)(s_sizes[s_sizes_len - 1]);
 
         /* free sorted vectors if they exist */
         if (!vector_was_sorted) {
diff --git a/testpar/t_filters_parallel.c b/testpar/t_filters_parallel.c
index 6c05408..f60431b 100644
--- a/testpar/t_filters_parallel.c
+++ b/testpar/t_filters_parallel.c
@@ -547,8 +547,9 @@ verify_chunk_opt_status(size_t num_dsets, test_mode_t test_mode, bool any_io, bo
 
         /* Verify selection I/O mode on rank 0 */
         if (mpi_rank == 0) {
-            /* No actual I/O performed, only reported I/O will be from allocation, even if "no" datasets were
-             * involved (num_dsets == 0 implies the call was expected to fail, but it fails after allocation).
+            /* No actual I/O performed, the only reported I/O will be from allocation which is vector I/O,
+             * even if "no" datasets were involved (num_dsets == 0 implies the call was expected to fail,
+             * but it fails after allocation).
              * Also if the test mode is mixed filtered and unfiltered and the call did not fail, then there
              * will always be an I/O callback made with raw data. This is because unfiltered datasets fall
              * back to scalar I/O when mixed with filtered, and scalar I/O reports an I/O call was made even
@@ -557,9 +558,18 @@ verify_chunk_opt_status(size_t num_dsets, test_mode_t test_mode, bool any_io, bo
              * filtered dataset with no selection. Vector I/O does report an I/O call was made if passed a raw
              * data element of size 0, so this is consistent. */
             if (!any_io) {
-                if (did_alloc || (num_dsets > 0 && test_mode == USE_MULTIPLE_DATASETS_MIXED_FILTERED))
+                if (did_alloc && (num_dsets > 0 && test_mode == USE_MULTIPLE_DATASETS_MIXED_FILTERED)) {
+                    VRFY((H5D_VECTOR_IO | H5D_SCALAR_IO) == actual_sel_io_mode_reduced,
+                         "verified actual selection I/O mode was vector and scalar I/O");
+                }
+                else if (did_alloc) {
+                    VRFY(H5D_VECTOR_IO == actual_sel_io_mode_reduced,
+                         "verified actual selection I/O mode was vector I/O");
+                }
+                else if (num_dsets > 0 && test_mode == USE_MULTIPLE_DATASETS_MIXED_FILTERED) {
                     VRFY(H5D_SCALAR_IO == actual_sel_io_mode_reduced,
                          "verified actual selection I/O mode was scalar I/O");
+                }
                 else
                     VRFY(0 == actual_sel_io_mode_reduced,
                          "verified actual selection I/O mode was 0 (no I/O)");
@@ -588,19 +598,18 @@ verify_chunk_opt_status(size_t num_dsets, test_mode_t test_mode, bool any_io, bo
                 switch (test_mode) {
                     case USE_SINGLE_DATASET:
                     case USE_MULTIPLE_DATASETS:
-                        /* Collective case with only filtered datasets. If we performed allocation then there
-                         * should be scalar I/O for allocation in addition to vector I/O for the actual data.
-                         * If we're reading from an unallocated dataset then there should be no actual I/O.
-                         * Otherwise there should only be vector I/O. */
-                        if (did_alloc)
-                            VRFY((H5D_SCALAR_IO | H5D_VECTOR_IO) == actual_sel_io_mode_reduced,
-                                 "verified actual selection I/O mode was scalar and vector I/O");
-                        else if (unalloc_read)
+                        /* Collective case with only filtered datasets.
+                         * If we're reading from an unallocated dataset then there
+                         * should be no actual I/O.
+                         * Otherwise, only vector I/O is reported whether or not
+                         * allocation happened. */
+                        if (unalloc_read)
                             VRFY(0 == actual_sel_io_mode_reduced,
                                  "verified actual selection I/O mode was 0 (no I/O)");
-                        else
+                        else { /* did_alloc || !unalloc_read */
                             VRFY(H5D_VECTOR_IO == actual_sel_io_mode_reduced,
                                  "verified actual selection I/O mode was vector I/O");
+                        }
                         break;
 
                     case USE_MULTIPLE_DATASETS_MIXED_FILTERED:
diff --git a/testpar/t_vfd.c b/testpar/t_vfd.c
index ac524ac..79b7e01 100644
--- a/testpar/t_vfd.c
+++ b/testpar/t_vfd.c
@@ -40,13 +40,14 @@ const char *FILENAMES[] = {"mpio_vfd_test_file_0",      /*0*/
                            "mpio_vfd_test_file_4",      /*4*/
                            "mpio_vfd_test_file_5",      /*5*/
                            "mpio_vfd_test_file_6",      /*6*/
-                           "subfiling_vfd_test_file_0", /*7*/
-                           "subfiling_vfd_test_file_1", /*8*/
-                           "subfiling_vfd_test_file_2", /*9*/
-                           "subfiling_vfd_test_file_3", /*10*/
-                           "subfiling_vfd_test_file_4", /*11*/
-                           "subfiling_vfd_test_file_5", /*12*/
-                           "subfiling_vfd_test_file_6", /*13*/
+                           "mpio_vfd_test_file_7",      /*7*/
+                           "subfiling_vfd_test_file_0", /*8*/
+                           "subfiling_vfd_test_file_1", /*9*/
+                           "subfiling_vfd_test_file_2", /*10*/
+                           "subfiling_vfd_test_file_3", /*11*/
+                           "subfiling_vfd_test_file_4", /*12*/
+                           "subfiling_vfd_test_file_5", /*13*/
+                           "subfiling_vfd_test_file_6", /*14*/
                            NULL};
 
 /* File Test Images
@@ -100,6 +101,8 @@ 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);
+static unsigned vector_write_test_8(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.
@@ -4159,6 +4162,280 @@ vector_write_test_7(int file_name_id, int mpi_rank, int mpi_size, H5FD_mpio_xfer
 
 } /* vector_write_test_7() */
 
+/*-------------------------------------------------------------------------
+ * Function:    vector_write_test_8()
+ *
+ * Purpose:     This test is to verify the fix for the following problem
+ *              in H5FD__mpio_write_vector when calculating max_addr:
+ *              --illegal reference occurs when referencing the s_sizes array
+ *                with <count - 1> due to <count> exceeding the length of the
+ *                size array which uses the compressed feature.
+ *
+ *              1) Open the test file with the specified VFD, and set
+ *                 the eoa.
+ *
+ *              2) Set the test file in a known state by writing zeros
+ *                 to all bytes in the test file.  Since we have already
+ *                 tested this, do this via a vector write of zero_fi_buf.
+ *
+ *              3) Barrier
+ *
+ *              4) For each rank, define base_index equal to:
+ *
+ *                     mpi_rank * INTS_PER_RANK
+ *
+ *                 and define base_addr equal to
+ *
+ *                     base_index * sizeof(int32_t).
+ *
+ *                 Setup a vector of length INTS_PER_RANK - 1.
+ *                 Set up the size array with the compressed feature:
+ *                  --The first element has size (2 * sizeof(int32_t))
+ *                  --The second and third elements are of size sizeof(int32_t)
+ *                  --The fourth element is zero.
+ *                  Set up addrs and bufs accordingly.
+ *
+ *                 Write the vector.
+ *
+ *              5) Barrier
+ *
+ *              6) On each rank, read the entire file into the read_fi_buf,
+ *                 and compare against increasing_fi_buf.
+ *                 Report failure if any differences are detected.
+ *
+ *              7) Close the test file.  On rank 0, delete the test file.
+ *
+ * Return:      false on success, true if any errors are detected.
+ *
+ *-------------------------------------------------------------------------
+ */
+static unsigned
+vector_write_test_8(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)
+{
+    const char *fcn_name = "vector_write_test_8()";
+    char        test_title[120];
+    char        filename[512];
+    haddr_t     eoa;
+    haddr_t     base_addr;
+    bool        show_progress = false;
+    hid_t       fapl_id       = H5I_INVALID_HID; /* file access property list ID */
+    hid_t       dxpl_id       = H5I_INVALID_HID; /* data access property list ID */
+    H5FD_t     *lf            = NULL;            /* VFD struct ptr               */
+    int         cp            = 0;
+    int         i;
+    int         base_index;
+    uint32_t    count = 0;
+    size_t      sizes[4];
+    H5FD_mem_t  types[2];
+
+    haddr_t     *tt_addrs = NULL; /* For storing addrs */
+    const void **tt_bufs  = NULL; /* For storing buf pointers */
+
+    pass = true;
+
+    if (mpi_rank == 0) {
+
+        if (xfer_mode == H5FD_MPIO_INDEPENDENT) {
+
+            snprintf(test_title, sizeof(test_title), "parallel vector write test 8 -- %s / independent",
+                     vfd_name);
+        }
+        else if (coll_opt_mode == H5FD_MPIO_INDIVIDUAL_IO) {
+
+            snprintf(test_title, sizeof(test_title), "parallel vector write test 8 -- %s / col op / ind I/O",
+                     vfd_name);
+        }
+        else {
+
+            assert(coll_opt_mode == H5FD_MPIO_COLLECTIVE_IO);
+
+            snprintf(test_title, sizeof(test_title), "parallel vector write test 8 -- %s / col op / col I/O",
+                     vfd_name);
+        }
+
+        TESTING(test_title);
+    }
+
+    show_progress = ((show_progress) && (mpi_rank == 0));
+
+    if (show_progress)
+        fprintf(stdout, "\n%s: cp = %d, pass = %d.\n", fcn_name, cp++, pass);
+
+    /* 1) Allocate local buffers for addrs and bufs,
+          open the test file with the specified VFD, set the eoa, and setup the dxpl */
+    if (pass) {
+
+        tt_addrs = (haddr_t *)malloc((INTS_PER_RANK) * sizeof(haddr_t *));
+        tt_bufs  = (const void **)malloc((INTS_PER_RANK) * sizeof(void *));
+
+        if (tt_addrs == NULL || tt_bufs == NULL) {
+            pass         = false;
+            failure_mssg = "Can't allocate local addrs and bufs buffers.";
+        }
+
+        if (pass) {
+            eoa = (haddr_t)mpi_size * (haddr_t)INTS_PER_RANK * (haddr_t)(sizeof(int32_t));
+
+            setup_vfd_test_file(file_name_id, filename, mpi_size, xfer_mode, coll_opt_mode, vfd_name, eoa,
+                                &lf, &fapl_id, &dxpl_id);
+        }
+    }
+
+    if (show_progress)
+        fprintf(stdout, "%s: cp = %d, pass = %d.\n", fcn_name, cp++, pass);
+
+    /* 2) Using rank zero, write the entire negative_fi_buf to
+     *    the file.
+     */
+    if (pass) {
+
+        size_t image_size = (size_t)mpi_size * (size_t)INTS_PER_RANK * sizeof(int32_t);
+
+        if (mpi_rank == 0) {
+
+            if (H5FDwrite(lf, H5FD_MEM_DRAW, H5P_DEFAULT, (haddr_t)0, image_size, (void *)zero_fi_buf) < 0) {
+
+                pass         = false;
+                failure_mssg = "H5FDwrite() on rank 0 failed.\n";
+            }
+        }
+    }
+
+    /* 3) Barrier */
+    MPI_Barrier(comm);
+
+    if (show_progress)
+        fprintf(stdout, "%s: cp = %d, pass = %d.\n", fcn_name, cp++, pass);
+
+    /* 4) For each rank, define base_index equal to:
+     *
+     *        mpi_rank * INTS_PER_RANK
+     *
+     *    and define base_addr equal to
+     *
+     *        base_index * sizeof(int32_t).
+     *
+     *    Set up the array of sizes and types with the compressed feature
+     *    as described in the routine header description.
+     */
+    if (pass) {
+
+        base_index = (mpi_rank * INTS_PER_RANK);
+        base_addr  = (haddr_t)base_index * (haddr_t)sizeof(int32_t);
+
+        count = INTS_PER_RANK - 1;
+
+        types[0] = H5FD_MEM_DRAW;
+        types[1] = H5FD_MEM_NOLIST;
+
+        sizes[0] = 2 * sizeof(int32_t);
+        sizes[1] = sizeof(int32_t);
+        sizes[2] = sizeof(int32_t);
+        sizes[3] = 0;
+
+        tt_addrs[0] = base_addr;
+        tt_bufs[0]  = (const void *)(&(increasing_fi_buf[base_index]));
+
+        tt_addrs[0] = base_addr;
+        base_index += 2;
+        base_addr = (haddr_t)base_index * (haddr_t)sizeof(int32_t);
+
+        for (i = 1; i < (INTS_PER_RANK - 1); i++) {
+
+            tt_addrs[i] = base_addr + ((haddr_t)(i - 1) * (haddr_t)sizeof(int32_t));
+            tt_bufs[i]  = (const void *)(&(increasing_fi_buf[base_index + (i - 1)]));
+        }
+
+        if (H5FDwrite_vector(lf, dxpl_id, count, types, tt_addrs, sizes, tt_bufs) < 0) {
+
+            pass         = false;
+            failure_mssg = "H5FDwrite_vector() failed (1).\n";
+        }
+    }
+
+    if (show_progress)
+        fprintf(stdout, "%s: cp = %d, pass = %d.\n", fcn_name, cp++, pass);
+
+    /* 5) Barrier */
+    MPI_Barrier(comm);
+
+    if (show_progress)
+        fprintf(stdout, "%s: cp = %d, pass = %d.\n", fcn_name, cp++, pass);
+
+    /* 6) On each rank, read the entire file into the read_fi_buf,
+     *    and compare against increasing_fi_buf
+     *    Report failure if any differences are detected.
+     */
+    if (pass) {
+
+        size_t image_size = (size_t)mpi_size * (size_t)INTS_PER_RANK * sizeof(int32_t);
+
+        if (H5FDread(lf, H5FD_MEM_DRAW, H5P_DEFAULT, (haddr_t)0, image_size, (void *)read_fi_buf) < 0) {
+
+            pass         = false;
+            failure_mssg = "H5FDread() failed.\n";
+        }
+
+        for (i = 0; ((pass) && (i < mpi_size * INTS_PER_RANK)); i++) {
+
+            if (read_fi_buf[i] != increasing_fi_buf[i]) {
+
+                pass         = false;
+                failure_mssg = "unexpected data read from file (1)";
+            }
+        }
+    } /* end if */
+
+    if (show_progress)
+        fprintf(stdout, "%s: cp = %d, pass = %d.\n", fcn_name, cp++, pass);
+
+    /* 7) Barrier */
+    MPI_Barrier(comm);
+
+    if (show_progress)
+        fprintf(stdout, "%s: cp = %d, pass = %d.\n", fcn_name, cp++, pass);
+
+    /* 8) Close the test file and delete it (on rank 0 only).
+     *    Close FAPL and DXPL.
+     */
+    takedown_vfd_test_file(mpi_rank, filename, &lf, &fapl_id, &dxpl_id);
+
+    /* Free the local buffers */
+    if (tt_addrs) {
+        free(tt_addrs);
+        tt_addrs = NULL;
+    }
+
+    if (tt_bufs) {
+        free(tt_bufs);
+        tt_bufs = NULL;
+    }
+
+    if (show_progress)
+        fprintf(stdout, "%s: cp = %d, pass = %d.\n", fcn_name, cp++, pass);
+
+    /* report results */
+    if (mpi_rank == 0) {
+
+        if (pass) {
+
+            PASSED();
+        }
+        else {
+
+            H5_FAILED();
+
+            if ((disp_failure_mssgs) || (show_progress)) {
+                fprintf(stdout, "%s: failure_mssg = \"%s\"\n", fcn_name, failure_mssg);
+            }
+        }
+    }
+
+    return (!pass);
+
+} /* vector_write_test_8() */
+
 static void
 test_vector_io(int mpi_rank, int mpi_size)
 {
@@ -4249,6 +4526,13 @@ test_vector_io(int mpi_rank, int mpi_size)
     nerrs +=
         vector_write_test_7(6, mpi_rank, mpi_size, H5FD_MPIO_COLLECTIVE, H5FD_MPIO_COLLECTIVE_IO, "mpio");
 
+    nerrs +=
+        vector_write_test_8(7, mpi_rank, mpi_size, H5FD_MPIO_INDEPENDENT, H5FD_MPIO_INDIVIDUAL_IO, "mpio");
+    nerrs +=
+        vector_write_test_8(7, mpi_rank, mpi_size, H5FD_MPIO_COLLECTIVE, H5FD_MPIO_INDIVIDUAL_IO, "mpio");
+    nerrs +=
+        vector_write_test_8(7, mpi_rank, mpi_size, H5FD_MPIO_COLLECTIVE, H5FD_MPIO_COLLECTIVE_IO, "mpio");
+
     MPI_Barrier(comm);
 
 #ifdef H5_HAVE_SUBFILING_VFD