Avoid creating MPI datatypes on ranks with 0 chunks to write'

1 files changed, 68 insertions, 53 deletions

diff --git a/src/H5Dchunk.c b/src/H5Dchunk.c
index 8962348..92cdfda 100644
--- a/src/H5Dchunk.c
+++ b/src/H5Dchunk.c
@@ -4958,6 +4958,7 @@ H5D__chunk_collective_fill(const H5D_t *dset, H5D_chunk_coll_info_t *chunk_info,
     H5FD_mpio_xfer_t prev_xfer_mode;    /* Previous data xfer mode */
     hbool_t     have_xfer_mode = FALSE; /* Whether the previous xffer mode has been retrieved */
     hbool_t     need_addr_sort = FALSE;
+    hbool_t     created_mpi_datatypes = FALSE;  /* Whether MPI datatypes were created */
     int         i;                  /* Local index variable */
     herr_t ret_value = SUCCEED;     /* Return value */
 
@@ -4980,9 +4981,9 @@ H5D__chunk_collective_fill(const H5D_t *dset, H5D_chunk_coll_info_t *chunk_info,
         HGOTO_ERROR(H5E_DATASET, H5E_BADVALUE, FAIL, "Resulted in division by zero")
     num_blocks = (size_t)(chunk_info->num_io / (size_t)mpi_size); /* value should be the same on all procs */
 
-    /* after evenly distributing the blocks between processes, are
-       there any leftover blocks for each individual process
-       (round-robin) */
+    /* After evenly distributing the blocks between processes, are there any
+     * leftover blocks for each individual process (round-robin)?
+     */
     leftover_blocks = (size_t)(chunk_info->num_io % (size_t)mpi_size);
 
     /* Cast values to types needed by MPI */
@@ -4990,58 +4991,70 @@ H5D__chunk_collective_fill(const H5D_t *dset, H5D_chunk_coll_info_t *chunk_info,
     H5_CHECKED_ASSIGN(leftover, int, leftover_blocks, size_t);
     H5_CHECKED_ASSIGN(block_len, int,  chunk_size, size_t);
 
-    /* Allocate buffers */
-    /* (MSC - should not need block_lens if MPI_type_create_hindexed_block is working) */
-    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(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")
+    /* Check if we have any chunks to write on this rank */
+    if(num_blocks > 0 || (leftover && leftover > mpi_rank)) {
+        /* Allocate buffers */
+        /* (MSC - should not need block_lens if MPI_type_create_hindexed_block is working) */
+        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(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")
 
-    for(i = 0 ; i < blocks ; i++) {
-        /* store the chunk address as an MPI_Aint */
-        chunk_disp_array[i] = (MPI_Aint)(chunk_info->addr[i + mpi_rank*blocks]);
+        for(i = 0 ; i < blocks ; i++) {
+            /* store the chunk address as an MPI_Aint */
+            chunk_disp_array[i] = (MPI_Aint)(chunk_info->addr[i + (mpi_rank * blocks)]);
 
-        /* MSC - should not need this if MPI_type_create_hindexed_block is working */
-        block_lens[i] = block_len;
+            /* MSC - should not need this if MPI_type_create_hindexed_block is working */
+            block_lens[i] = block_len;
 
-        /* make sure that the addresses in the datatype are
-           monotonically non decreasing */
-        if(i && (chunk_disp_array[i] < chunk_disp_array[i - 1]))
-            need_addr_sort = TRUE;
-    } /* end for */
+            /* Make sure that the addresses in the datatype are
+             * monotonically non-decreasing
+             */
+            if(i && (chunk_disp_array[i] < chunk_disp_array[i - 1]))
+                need_addr_sort = TRUE;
+        } /* end for */
 
-    /* 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_info->addr[blocks*mpi_size + mpi_rank];
-        if(blocks && (chunk_disp_array[blocks] < chunk_disp_array[blocks - 1]))
-            need_addr_sort = TRUE;
-        block_lens[blocks] = block_len;
-        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_info->addr[(blocks * mpi_size) + mpi_rank];
+            if(blocks && (chunk_disp_array[blocks] < chunk_disp_array[blocks - 1]))
+                need_addr_sort = TRUE;
+            block_lens[blocks] = block_len;
+            blocks++;
+        }
 
-    /*
-     * Ensure that the blocks are sorted in monotonically non-decreasing
-     * order of offset in the file.
-     */
-    if(need_addr_sort)
-        HDqsort(chunk_disp_array, blocks, sizeof(MPI_Aint), H5D__chunk_cmp_addr);
+        /* Ensure that the blocks are sorted in monotonically non-decreasing
+         * order of offset in the file.
+         */
+        if(need_addr_sort)
+            HDqsort(chunk_disp_array, blocks, sizeof(MPI_Aint), H5D__chunk_cmp_addr);
 
-    /* MSC - should use this if MPI_type_create_hindexed block is working:
-     * mpi_code = MPI_Type_create_hindexed_block(blocks, block_len, chunk_disp_array, MPI_BYTE, &file_type);
-     */
-    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)
-    if(MPI_SUCCESS != (mpi_code = MPI_Type_commit(&file_type)))
-        HMPI_GOTO_ERROR(FAIL, "MPI_Type_commit failed", mpi_code)
-
-    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)
-    if(MPI_SUCCESS != (mpi_code = MPI_Type_commit(&mem_type)))
-        HMPI_GOTO_ERROR(FAIL, "MPI_Type_commit failed", mpi_code)
+        /* MSC - should use this if MPI_type_create_hindexed block is working:
+         * mpi_code = MPI_Type_create_hindexed_block(blocks, block_len, chunk_disp_array, MPI_BYTE, &file_type);
+         */
+        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)
+        if(MPI_SUCCESS != (mpi_code = MPI_Type_commit(&file_type)))
+            HMPI_GOTO_ERROR(FAIL, "MPI_Type_commit failed", mpi_code)
+
+        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)
+        if(MPI_SUCCESS != (mpi_code = MPI_Type_commit(&mem_type)))
+            HMPI_GOTO_ERROR(FAIL, "MPI_Type_commit failed", mpi_code)
+
+        /* Indicate that the MPI types were created */
+        created_mpi_datatypes = TRUE;
+    } /* end if */
+    else {
+        /* Set up file & memory MPI types, to participate in collective write */
+        file_type = MPI_BYTE;
+        mem_type = MPI_BYTE;
+    } /* end else */
 
     /* Set MPI-IO VFD properties */
 
@@ -5073,10 +5086,12 @@ done:
             HDONE_ERROR(H5E_DATASET, H5E_CANTSET, FAIL, "can't set transfer mode")
 
     /* free things */
-    if(MPI_SUCCESS != (mpi_code = MPI_Type_free(&file_type)))
-        HMPI_DONE_ERROR(FAIL, "MPI_Type_free failed", mpi_code)
-    if(MPI_SUCCESS != (mpi_code = MPI_Type_free(&mem_type)))
-        HMPI_DONE_ERROR(FAIL, "MPI_Type_free failed", mpi_code)
+    if(created_mpi_datatypes) {
+        if(MPI_SUCCESS != (mpi_code = MPI_Type_free(&file_type)))
+            HMPI_DONE_ERROR(FAIL, "MPI_Type_free failed", mpi_code)
+        if(MPI_SUCCESS != (mpi_code = MPI_Type_free(&mem_type)))
+            HMPI_DONE_ERROR(FAIL, "MPI_Type_free failed", mpi_code)
+    } /* end if */
     H5MM_xfree(chunk_disp_array);
     H5MM_xfree(block_lens);