Add back debugging statements

Move conditional check inside while loop in
construct_filtered_io_info_list

1 files changed, 300 insertions, 4 deletions

diff --git a/src/H5Dmpio.c b/src/H5Dmpio.c
index c5a3fae..9239b21 100644
--- a/src/H5Dmpio.c
+++ b/src/H5Dmpio.c
@@ -86,6 +86,12 @@
 #define H5D_CHUNK_SELECT_IRREG        2
 #define H5D_CHUNK_SELECT_NONE         0
 
+#define PARALLEL_COMPRESS_DEBUG
+
+#ifdef PARALLEL_COMPRESS_DEBUG
+FILE *debug_file;
+#endif
+
 /******************/
 /* Local Typedefs */
 /******************/
@@ -403,6 +409,18 @@ H5D__mpio_array_gather(const H5D_io_info_t *io_info, void *local_array,
     *_gathered_array = gathered_array;
     *_gathered_array_num_entries = gathered_array_num_entries;
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+    HDfprintf(debug_file, " Contents of gathered array:\n");
+    HDfprintf(debug_file, "------------------------------\n");
+    for (size_t j = 0; j < (size_t) gathered_array_num_entries; j++) {
+        HDfprintf(debug_file, "| Chunk Entry %zd:\n", j);
+        HDfprintf(debug_file, "|  - Chunk Address: %a\n", ((H5D_filtered_collective_io_info_t *) gathered_array)[j].old_chunk.offset);
+        HDfprintf(debug_file, "|  - Chunk Length: %zd\n", ((H5D_filtered_collective_io_info_t *) gathered_array)[j].old_chunk.length);
+        HDfprintf(debug_file, "|  - Address of mspace: %x\n", ((H5D_filtered_collective_io_info_t *) gathered_array)[j].chunk_info.mspace);
+    }
+    HDfprintf(debug_file, "------------------------------\n\n");
+#endif
+
 done:
     if (receive_counts_array)
         H5MM_free(receive_counts_array);
@@ -895,6 +913,14 @@ H5D__chunk_collective_write(H5D_io_info_t *io_info, const H5D_type_info_t *type_
 
     FUNC_ENTER_PACKAGE
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+    char name[10];
+
+    snprintf(name, 10, "out - %d", H5F_mpi_get_rank(io_info->dset->oloc.file));
+
+    debug_file = fopen(name, "w");
+#endif
+
     /* Call generic selection operation */
     if(H5D__chunk_collective_io(io_info, type_info, fm) < 0)
         HGOTO_ERROR(H5E_DATASPACE, H5E_WRITEERROR, FAIL, "write error")
@@ -1327,6 +1353,16 @@ H5D__link_chunk_filtered_collective_io(H5D_io_info_t *io_info, const H5D_type_in
     if (H5D__construct_filtered_io_info_list(io_info, type_info, fm, &chunk_list, &chunk_list_num_entries) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTRECV, FAIL, "couldn't construct filtered I/O info list")
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+    HDfprintf(debug_file, "Incoming messages from other processes:\n");
+    HDfprintf(debug_file, "-----------------------------------------\n");
+    for (size_t j = 0; j < chunk_list_num_entries; j++) {
+        HDfprintf(debug_file, "| Owner of chunk at address %a is expecting messages from %d other processes.\n",
+                chunk_list[j].old_chunk.offset, chunk_list[j].num_writers - 1);
+    }
+    HDfprintf(debug_file, "-----------------------------------------\n\n");
+#endif
+
     if (io_info->op_type == H5D_IO_OP_WRITE) { /* Filtered collective write */
         H5D_chk_idx_info_t index_info;
         H5D_chunk_ud_t     udata;
@@ -1344,6 +1380,12 @@ H5D__link_chunk_filtered_collective_io(H5D_io_info_t *io_info, const H5D_type_in
         udata.common.storage = index_info.storage;
         udata.filter_mask = 0;
 
+
+#ifdef PARALLEL_COMPRESS_DEBUG
+        HDfprintf(debug_file, "Processing chunks:\n");
+        HDfprintf(debug_file, "---------------------------------------------------\n");
+#endif
+
         /* Iterate through all the chunks in the collective write operation,
          * updating each chunk with the data modifications from other processes,
          * then re-filtering the chunk.
@@ -1353,6 +1395,10 @@ H5D__link_chunk_filtered_collective_io(H5D_io_info_t *io_info, const H5D_type_in
             if (H5D__filtered_collective_chunk_entry_io(&chunk_list[i], io_info, type_info) < 0)
                 HGOTO_ERROR(H5E_DATASET, H5E_CANTRECV, FAIL, "couldn't process chunk entry")
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+        HDfprintf(debug_file, "---------------------------------------------------\n\n");
+#endif
+
         /* Gather the new chunk sizes to all processes for a collective reallocation
          * of the chunks in the file.
          */
@@ -1361,15 +1407,32 @@ H5D__link_chunk_filtered_collective_io(H5D_io_info_t *io_info, const H5D_type_in
                 (void **) &collective_chunk_list, &collective_chunk_list_num_entries, NULL) < 0)
             HGOTO_ERROR(H5E_DATASET, H5E_CANTRECV, FAIL, "couldn't gather new chunk sizes")
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+        HDfprintf(debug_file, "Reallocing chunks:\n");
+        HDfprintf(debug_file, "------------------------------\n");
+#endif
+
         /* Collectively re-allocate the modified chunks (from each process) in the file */
         for (i = 0; i < collective_chunk_list_num_entries; i++) {
             hbool_t insert;
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+            HDfprintf(debug_file, "| Reallocing chunk at address %a with new length of %zd.\n", collective_chunk_list[i].new_chunk.offset, collective_chunk_list[i].new_chunk.length);
+#endif
+
             if (H5D__chunk_file_alloc(&index_info, &collective_chunk_list[i].old_chunk, &collective_chunk_list[i].new_chunk,
                     &insert, collective_chunk_list[i].chunk_info.scaled) < 0)
                 HGOTO_ERROR(H5E_DATASET, H5E_CANTALLOC, FAIL, "unable to allocate chunk")
+
+#ifdef PARALLEL_COMPRESS_DEBUG
+            HDfprintf(debug_file, "| - Chunk now at address %a.\n|\n", collective_chunk_list[i].new_chunk);
+#endif
         } /* end for */
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+        HDfprintf(debug_file, "------------------------------\n\n");
+#endif
+
         if (NULL == (num_chunks_selected_array = (size_t *) H5MM_malloc((size_t) mpi_size * sizeof(*num_chunks_selected_array))))
             HGOTO_ERROR(H5E_DATASET, H5E_CANTALLOC, FAIL, "couldn't allocate num chunks selected array")
 
@@ -1377,6 +1440,15 @@ H5D__link_chunk_filtered_collective_io(H5D_io_info_t *io_info, const H5D_type_in
                 1, MPI_UNSIGNED_LONG_LONG, io_info->comm)))
             HMPI_GOTO_ERROR(FAIL, "MPI_Allgather failed", mpi_code)
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+        HDfprintf(debug_file, " Num Chunks Selected Array\n");
+        HDfprintf(debug_file, "------------------------------------\n");
+        for (size_t j = 0; j < (size_t) mpi_size; j++) {
+            HDfprintf(debug_file, "| Process %d has %zd chunks selected.\n", j, num_chunks_selected_array[j]);
+        }
+        HDfprintf(debug_file, "------------------------------------\n\n");
+#endif
+
         /* If this process has any chunks selected, create a MPI type for collectively
          * writing out the chunks to file. Otherwise, the process contributes to the
          * collective write with a none type.
@@ -1425,6 +1497,10 @@ H5D__link_chunk_filtered_collective_io(H5D_io_info_t *io_info, const H5D_type_in
         /* Participate in the collective re-insertion of all chunks modified
          * in this iteration into the chunk index
          */
+#ifdef PARALLEL_COMPRESS_DEBUG
+        HDfprintf(debug_file, "Reinserting chunks into chunk index.\n");
+        HDfprintf(debug_file, "---------------------------------------\n");
+#endif
 
         for (i = 0; i < collective_chunk_list_num_entries; i++) {
             udata.chunk_block = collective_chunk_list[i].new_chunk;
@@ -1432,7 +1508,15 @@ H5D__link_chunk_filtered_collective_io(H5D_io_info_t *io_info, const H5D_type_in
 
             if ((index_info.storage->ops->insert)(&index_info, &udata, io_info->dset) < 0)
                 HGOTO_ERROR(H5E_DATASET, H5E_CANTINSERT, FAIL, "unable to insert chunk address into index")
+
+#ifdef PARALLEL_COMPRESS_DEBUG
+            HDfprintf(debug_file, "| Successfully inserted chunk at address %a into the chunk index.\n", udata.chunk_block.offset);
+#endif
         } /* end for */
+
+#ifdef PARALLEL_COMPRESS_DEBUG
+        HDfprintf(debug_file, "---------------------------------------\n");
+#endif
     } /* end if */
 
 done:
@@ -1805,6 +1889,19 @@ H5D__multi_chunk_filtered_collective_io(H5D_io_info_t *io_info, const H5D_type_i
         udata.common.storage = index_info.storage;
         udata.filter_mask = 0;
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+        HDfprintf(debug_file, "Incoming messages from other processes:\n");
+        HDfprintf(debug_file, "-----------------------------------------\n");
+        for (size_t k = 0; k < chunk_list_num_entries; k++) {
+            HDfprintf(debug_file, "| Owner of chunk at address %a is expecting messages from %d other processes.\n",
+                    chunk_list[k].old_chunk.offset, chunk_list[k].num_writers - 1);
+        }
+        HDfprintf(debug_file, "-----------------------------------------\n\n");
+
+        HDfprintf(debug_file, "Processing chunks:\n");
+        HDfprintf(debug_file, "---------------------------------------------------\n");
+#endif
+
         /* Retrieve the maximum number of chunks being written among all processes */
         if (MPI_SUCCESS != (mpi_code = MPI_Allreduce(&chunk_list_num_entries, &max_num_chunks,
                 1, MPI_UNSIGNED_LONG_LONG, MPI_MAX, io_info->comm)))
@@ -1847,17 +1944,35 @@ H5D__multi_chunk_filtered_collective_io(H5D_io_info_t *io_info, const H5D_type_i
                     (void **) &collective_chunk_list, &collective_chunk_list_num_entries, NULL) < 0)
                 HGOTO_ERROR(H5E_DATASET, H5E_CANTRECV, FAIL, "couldn't gather new chunk sizes")
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+            HDfprintf(debug_file, "Reallocing chunks:\n");
+            HDfprintf(debug_file, "------------------------------\n");
+#endif
+
             /* Participate in the collective re-allocation of all chunks modified
              * in this iteration.
              */
             for (j = 0; j < collective_chunk_list_num_entries; j++) {
                 hbool_t insert = FALSE;
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+                HDfprintf(debug_file, "| Re-allocing chunk at address %a with new length of %llu bytes.\n",
+                        collective_chunk_list[j].new_chunk.offset, collective_chunk_list[j].new_chunk.length);
+#endif
+
                 if (H5D__chunk_file_alloc(&index_info, &collective_chunk_list[j].old_chunk, &collective_chunk_list[j].new_chunk,
                         &insert, chunk_list[j].chunk_info.scaled) < 0)
                     HGOTO_ERROR(H5E_DATASET, H5E_CANTALLOC, FAIL, "unable to allocate chunk")
+
+#ifdef PARALLEL_COMPRESS_DEBUG
+                HDfprintf(debug_file, "| Chunk now at address %a.\n|\n", collective_chunk_list[j].new_chunk);
+#endif
             } /* end for */
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+            HDfprintf(debug_file, "------------------------------\n\n");
+#endif
+
             /* If this process has a chunk to work on, create a MPI type for the
              * memory and file for writing out the chunk
              */
@@ -1869,6 +1984,11 @@ H5D__multi_chunk_filtered_collective_io(H5D_io_info_t *io_info, const H5D_type_i
                 /* XXX: offset could be wrong if a process runs out of chunks */
                 HDmemcpy(&chunk_list[i].new_chunk, &collective_chunk_list[mpi_rank].new_chunk, sizeof(chunk_list[i].new_chunk));
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+                HDfprintf(debug_file, "New chunk record after memcpy back to local:\n");
+                HDfprintf(debug_file, " - Chunk offset: %a, Chunk length: %lld\n", chunk_list[i].new_chunk.offset, chunk_list[i].new_chunk.length);
+#endif
+
                 H5_CHECKED_ASSIGN(mpi_type_count, int, chunk_list[i].new_chunk.length, hsize_t);
 
                 /* Create MPI memory type for writing to chunk */
@@ -1907,14 +2027,27 @@ H5D__multi_chunk_filtered_collective_io(H5D_io_info_t *io_info, const H5D_type_i
             /* Participate in the collective re-insertion of all chunks modified
              * in this iteration into the chunk index
              */
+#ifdef PARALLEL_COMPRESS_DEBUG
+            HDfprintf(debug_file, "Reinserting chunks into chunk index.\n");
+            HDfprintf(debug_file, "---------------------------------------\n");
+#endif
+
             for (j = 0; j < collective_chunk_list_num_entries; j++) {
                 udata.chunk_block = collective_chunk_list[j].new_chunk;
                 udata.common.scaled = collective_chunk_list[j].chunk_info.scaled;
 
                 if ((index_info.storage->ops->insert)(&index_info, &udata, io_info->dset) < 0)
                     HGOTO_ERROR(H5E_DATASET, H5E_CANTINSERT, FAIL, "unable to insert chunk address into index")
+
+#ifdef PARALLEL_COMPRESS_DEBUG
+                HDfprintf(debug_file, "| Successfully inserted chunk at address %a into the chunk index.\n", udata.chunk_block.offset);
+#endif
             } /* end for */
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+            HDfprintf(debug_file, "---------------------------------------\n");
+#endif
+
             if (collective_chunk_list)
                 collective_chunk_list = (H5D_filtered_collective_io_info_t *) H5MM_free(collective_chunk_list);
         } /* end for */
@@ -2599,6 +2732,39 @@ H5D__construct_filtered_io_info_list(const H5D_io_info_t *io_info, const H5D_typ
         chunk_node = H5SL_next(chunk_node);
     } /* end for */
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+    HDfprintf(debug_file, " Contents of local info array\n");
+    HDfprintf(debug_file, "------------------------------\n");
+    for (size_t j = 0; j < (size_t) num_chunks_selected; j++) {
+        HDfprintf(debug_file, "| Chunk Entry %zd:\n", j);
+        HDfprintf(debug_file, "|  - Chunk Address: %a\n", local_info_array[j].old_chunk.offset);
+        HDfprintf(debug_file, "|  - Chunk Length: %zd\n", local_info_array[j].old_chunk.length);
+        HDfprintf(debug_file, "|  - Address of mspace: %x\n", local_info_array[j].chunk_info.mspace);
+        HDfprintf(debug_file, "|  - Chunk Selection Type: %d\n", H5S_GET_SELECT_TYPE(local_info_array[j].chunk_info.mspace));
+        HDfprintf(debug_file, "|  - Chunk Num Elmts Sel.: %zd\n", H5S_GET_SELECT_NPOINTS(local_info_array[j].chunk_info.mspace));
+    }
+    HDfprintf(debug_file, "------------------------------\n\n");
+
+    HDfprintf(debug_file, "Testing mem/file space addresses:\n");
+    HDfprintf(debug_file, "-----------------------------------\n");
+
+    for (size_t j = 0; j < num_chunks_selected; j++) {
+        HDfprintf(debug_file, "| Testing chunk at address %a.\n", local_info_array[j].old_chunk.offset);
+        HDfprintf(debug_file, "| Mem Space:\n");
+        HDfprintf(debug_file, "|  - Extent Num elements: %zd\n", H5S_GET_EXTENT_NPOINTS(local_info_array[j].chunk_info.mspace));
+        HDfprintf(debug_file, "|  - Extent type: %d\n", H5S_GET_EXTENT_TYPE(local_info_array[j].chunk_info.mspace));
+        HDfprintf(debug_file, "|  - Selection Num elements: %zd\n", H5S_GET_SELECT_NPOINTS(local_info_array[j].chunk_info.mspace));
+        HDfprintf(debug_file, "|  - Selection type: %d\n", H5S_GET_SELECT_TYPE(local_info_array[j].chunk_info.mspace));
+        HDfprintf(debug_file, "| File Space:\n");
+        HDfprintf(debug_file, "|  - Extent Num elements: %zd\n", H5S_GET_EXTENT_NPOINTS(local_info_array[j].chunk_info.fspace));
+        HDfprintf(debug_file, "|  - Extent type: %d\n", H5S_GET_EXTENT_TYPE(local_info_array[j].chunk_info.fspace));
+        HDfprintf(debug_file, "|  - Selection Num elements: %zd\n", H5S_GET_SELECT_NPOINTS(local_info_array[j].chunk_info.fspace));
+        HDfprintf(debug_file, "|  - Selection type: %d\n|\n", H5S_GET_SELECT_TYPE(local_info_array[j].chunk_info.fspace));
+    }
+
+    HDfprintf(debug_file, "-----------------------------------\n\n");
+#endif
+
     /* Redistribute shared chunks to new owners as necessary */
     if (!no_overlap && (io_info->op_type == H5D_IO_OP_WRITE)) {
         size_t i;
@@ -2652,9 +2818,7 @@ H5D__construct_filtered_io_info_list(const H5D_io_info_t *io_info, const H5D_typ
                 }
 
                 num_writers++;
-
-                if (++i == overlap_info_array_num_entries) break;
-            } while (overlap_info_array[i].old_chunk.offset == chunk_addr);
+            } while (++i < overlap_info_array_num_entries && overlap_info_array[i].old_chunk.offset == chunk_addr);
 
             if (mpi_rank == new_owner) {
                 /* Make sure the new owner will know how many other processes will
@@ -2684,6 +2848,10 @@ H5D__construct_filtered_io_info_list(const H5D_io_info_t *io_info, const H5D_typ
 
                 mod_data_size += (size_t) iter_nelmts * type_info->src_type_size;
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+                HDfprintf(debug_file, "| Allocing %zd bytes for mod. data buffer.\n", (size_t) mod_data_size);
+#endif
+
                 if (NULL == (mod_data = (unsigned char *) H5MM_malloc(mod_data_size)))
                     HGOTO_ERROR(H5E_DATASET, H5E_CANTALLOC, FAIL, "couldn't allocate chunk modification send buffer")
 
@@ -2697,11 +2865,27 @@ H5D__construct_filtered_io_info_list(const H5D_io_info_t *io_info, const H5D_typ
                     HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to initialize memory selection information")
                 mem_iter_init = TRUE;
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+                HDfprintf(debug_file, "| Iterating over %lld elements.\n", iter_nelmts);
+#endif
+
                 /* Collect the modification data into the buffer */
                 if (!H5D__gather_mem(io_info->u.wbuf, chunk_entry.chunk_info.mspace, mem_iter,
                         (size_t) iter_nelmts, io_info->dxpl_cache, mod_data_p))
                     HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "couldn't gather from write buffer")
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+                HDfprintf(debug_file, "| - Mod. Data Buffer:\n");
+                HDfprintf(debug_file, "| - [");
+                for (size_t j = 0; j < (size_t) iter_nelmts; j++) {
+                    if (j > 0) HDfprintf(debug_file, ", ");
+                    HDfprintf(debug_file, "%lld", ((long *) mod_data_p)[j]);
+                }
+                HDfprintf(debug_file, "]\n|\n");
+
+                HDfprintf(debug_file, "| Sending modification data for chunk at address %a to process %d.\n", chunk_entry.old_chunk.offset, new_owner);
+#endif
+
                 /* Send modification data to new owner */
                 H5_CHECK_OVERFLOW(mod_data_size, size_t, int)
                 H5_CHECK_OVERFLOW(chunk_entry.chunk_info.index, hsize_t, int)
@@ -2709,12 +2893,19 @@ H5D__construct_filtered_io_info_list(const H5D_io_info_t *io_info, const H5D_typ
                         (int) chunk_entry.chunk_info.index, io_info->comm, &send_requests[num_send_requests++])))
                     HMPI_GOTO_ERROR(FAIL, "MPI_Isend failed", mpi_code)
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+                HDfprintf(debug_file, "| Mod. data sent.\n|\n");
+#endif
                 if (mod_data)
                     mod_data = (unsigned char *) H5MM_free(mod_data);
                 if (mem_iter_init && H5S_SELECT_ITER_RELEASE(mem_iter) < 0)
                     HGOTO_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "couldn't release selection iterator")
                 mem_iter_init = FALSE;
             } /* end else */
+
+#ifdef PARALLEL_COMPRESS_DEBUG
+            HDfprintf(debug_file, "| Chunk at address %a re-assigned to process %d.\n|\n", chunk_addr, new_owner);
+#endif
         } /* end for */
 
         /* Release old list */
@@ -2723,6 +2914,22 @@ H5D__construct_filtered_io_info_list(const H5D_io_info_t *io_info, const H5D_typ
 
         /* Local info list becomes modified (redistributed) chunk list */
         local_info_array = overlap_info_array;
+
+#ifdef PARALLEL_COMPRESS_DEBUG
+        HDfprintf(debug_file, "This process now has %d chunks selected after redistribution.\n\n", num_chunks_selected);
+
+        HDfprintf(debug_file, " Contents of local info array (after redistribution)\n");
+        HDfprintf(debug_file, "------------------------------\n");
+        for (size_t j = 0; j < (size_t) num_chunks_selected; j++) {
+            HDfprintf(debug_file, "| Chunk Entry %zd:\n", j);
+            HDfprintf(debug_file, "|  - Chunk Address: %a\n", local_info_array[j].old_chunk.offset);
+            HDfprintf(debug_file, "|  - Chunk Length: %zd\n", local_info_array[j].old_chunk.length);
+            HDfprintf(debug_file, "|  - Address of mspace: %x\n", local_info_array[j].chunk_info.fspace);
+            HDfprintf(debug_file, "|  - Chunk Selection Type: %d\n", H5S_GET_SELECT_TYPE(local_info_array[j].chunk_info.fspace));
+            HDfprintf(debug_file, "|  - Chunk Num Elmts Sel.: %zd\n", H5S_GET_SELECT_NPOINTS(local_info_array[j].chunk_info.fspace));
+        }
+        HDfprintf(debug_file, "------------------------------\n\n");
+#endif
     } /* end if */
 
     *chunk_list = local_info_array;
@@ -2805,6 +3012,11 @@ H5D__mpio_filtered_collective_write_type(H5D_filtered_collective_io_info_t *chun
         /* Ensure the list is sorted in ascending order of offset in the file */
         HDqsort(chunk_list, num_entries, sizeof(*chunk_list), H5D__cmp_filtered_collective_io_info_entry);
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+        HDfprintf(debug_file, "MPI Write type entries:\n");
+        HDfprintf(debug_file, "---------------------------------\n");
+#endif
+
         base_buf = chunk_list[0].buf;
         for (i = 0; i < num_entries; i++) {
             /* Set up the offset in the file, the length of the chunk data, and the relative
@@ -2813,8 +3025,22 @@ H5D__mpio_filtered_collective_write_type(H5D_filtered_collective_io_info_t *chun
             file_offset_array[i] = (MPI_Aint) chunk_list[i].new_chunk.offset;
             length_array[i] = (int) chunk_list[i].new_chunk.length;
             write_buf_array[i] = (MPI_Aint) chunk_list[i].buf - (MPI_Aint) base_buf;
+
+#ifdef PARALLEL_COMPRESS_DEBUG
+            HDfprintf(debug_file, "| Type Entry %zd:\n", i);
+            HDfprintf(debug_file, "|  - Offset: %a; Length: %zd\n", file_offset_array[i], length_array[i]);
+            HDfprintf(debug_file, "|  - Write buffer:\n|    [");
+            for (size_t j = 0; j < (size_t) length_array[i]; j++) {
+                HDfprintf(debug_file, "%c, ", ((char *) chunk_list[i].buf)[j]);
+            }
+            HDfprintf(debug_file, "]\n|\n");
+#endif
         } /* end for */
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+        HDfprintf(debug_file, "---------------------------------\n\n");
+#endif
+
         /* Create memory MPI type */
         if (MPI_SUCCESS != (mpi_code = MPI_Type_create_hindexed((int) num_entries, length_array, write_buf_array, MPI_BYTE, new_mem_type)))
             HMPI_GOTO_ERROR(FAIL, "MPI_Type_create_hindexed failed", mpi_code)
@@ -2877,8 +3103,13 @@ H5D__filtered_collective_chunk_entry_io(H5D_filtered_collective_io_info_t *chunk
     HDassert(io_info);
     HDassert(type_info);
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+    HDfprintf(debug_file, "| Chunk at address %a:\n", chunk_entry->old_chunk.offset);
+#endif
+
     /* XXX: Determine if a chunk is being fully overwritten by looking at the total selection
-     * in the dataspace
+     * in the dataspace. Possibly receive all data ahead of time so that the dataspaces can
+     * be ORed?
      */
 
     /* If this is a read operation or a write operation where the chunk is not being fully
@@ -2891,6 +3122,12 @@ H5D__filtered_collective_chunk_entry_io(H5D_filtered_collective_io_info_t *chunk
             : (hsize_t) H5S_GET_EXTENT_NPOINTS(chunk_entry->chunk_info.fspace) * type_info->src_type_size;
     chunk_entry->new_chunk.length = buf_size;
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+    HDfprintf(debug_file, "| - Allocing %zd bytes for chunk data buffer.\n", buf_size);
+    if (io_info->op_type == H5D_IO_OP_WRITE)
+        HDfprintf(debug_file, "| - Write type is: %s.\n", (full_overwrite) ? "overwrite" : "non-overwrite");
+#endif
+
     if (NULL == (chunk_entry->buf = H5MM_malloc(buf_size)))
         HGOTO_ERROR(H5E_DATASET, H5E_CANTALLOC, FAIL, "couldn't allocate chunk data buffer")
 
@@ -2906,6 +3143,17 @@ H5D__filtered_collective_chunk_entry_io(H5D_filtered_collective_io_info_t *chunk
                 io_info->dxpl_cache->err_detect, io_info->dxpl_cache->filter_cb,
                 (size_t *) &chunk_entry->new_chunk.length, &buf_size, &chunk_entry->buf) < 0)
             HGOTO_ERROR(H5E_PLINE, H5E_CANTFILTER, H5_ITER_ERROR, "couldn't unfilter chunk for modifying")
+
+#ifdef PARALLEL_COMPRESS_DEBUG
+        HDfprintf(debug_file, "| - After decompression: Nbytes=%zd; Buf_size=%zd.\n", chunk_entry->new_chunk.length, buf_size);
+
+        HDfprintf(debug_file, "| - Read buf:\n| - [");
+        for (size_t j = 0; j < chunk_entry->new_chunk.length / type_info->src_type_size; j++) {
+            if (j > 0) HDfprintf(debug_file, ", ");
+            HDfprintf(debug_file, "%lld", ((long *) chunk_entry->buf)[j]);
+        }
+        HDfprintf(debug_file, "]\n|\n");
+#endif
     } /* end if */
 
     /* Initialize iterator for memory selection */
@@ -2955,10 +3203,18 @@ H5D__filtered_collective_chunk_entry_io(H5D_filtered_collective_io_info_t *chunk
                         io_info->comm, &status)))
                     HMPI_GOTO_ERROR(FAIL, "MPI_Probe failed", mpi_code)
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+                HDfprintf(debug_file, "| - Found message from source %d with tag %d.\n", status.MPI_SOURCE, status.MPI_TAG);
+#endif
+
                 /* Retrieve the message size */
                 if (MPI_SUCCESS != (mpi_code = MPI_Get_count(&status, MPI_BYTE, &count)))
                     HMPI_GOTO_ERROR(FAIL, "MPI_Get_count failed", mpi_code)
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+                HDfprintf(debug_file, "| - Message size is %d bytes.\n", count);
+#endif
+
                 if (NULL == (mod_data = (unsigned char *) H5MM_malloc((size_t) count)))
                     HGOTO_ERROR(H5E_DATASET, H5E_CANTALLOC, FAIL, "couldn't allocate modification data receive buffer")
                 mod_data_p = mod_data;
@@ -2967,10 +3223,23 @@ H5D__filtered_collective_chunk_entry_io(H5D_filtered_collective_io_info_t *chunk
                         (int) chunk_entry->chunk_info.index, io_info->comm, &status)))
                     HMPI_GOTO_ERROR(FAIL, "MPI_Recv failed", mpi_code)
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+                HDfprintf(debug_file, "| - Received the message.\n");
+#endif
+
                 /* Decode the process' chunk file dataspace */
                 if (NULL == (dataspace = H5S_decode(&mod_data_p)))
                     HGOTO_ERROR(H5E_DATASET, H5E_CANTDECODE, FAIL, "unable to decode dataspace")
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+                HDfprintf(debug_file, "| Deserialized selection info:\n");
+                HDfprintf(debug_file, "| Mem Space:\n");
+                HDfprintf(debug_file, "|  - Extent Num elements: %zd\n", H5S_GET_EXTENT_NPOINTS(dataspace));
+                HDfprintf(debug_file, "|  - Extent type: %d\n", H5S_GET_EXTENT_TYPE(dataspace));
+                HDfprintf(debug_file, "|  - Selection Num elements: %zd\n", H5S_GET_SELECT_NPOINTS(dataspace));
+                HDfprintf(debug_file, "|  - Selection type: %d\n", H5S_GET_SELECT_TYPE(dataspace));
+#endif
+
                 if (H5S_select_iter_init(mem_iter, dataspace, type_info->dst_type_size) < 0)
                     HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to initialize memory selection information")
                 mem_iter_init = TRUE;
@@ -2978,6 +3247,20 @@ H5D__filtered_collective_chunk_entry_io(H5D_filtered_collective_io_info_t *chunk
                 if ((iter_nelmts = H5S_GET_SELECT_NPOINTS(dataspace)) < 0)
                     HGOTO_ERROR(H5E_DATASET, H5E_CANTCOUNT, FAIL, "dataspace is invalid")
 
+#ifdef PARALLEL_COMPRESS_DEBUG
+                HDfprintf(debug_file, "| Contents of message:\n| [");
+                for (size_t j = 0; j < iter_nelmts; j++) {
+                    if (j > 0) HDfprintf(debug_file, ", ");
+                    HDfprintf(debug_file, "%lld", ((long *) mod_data_p)[j]);
+                }
+                HDfprintf(debug_file, "]\n");
+#endif
+
+#ifdef PARALLEL_COMPRESS_DEBUG
+                HDfprintf(debug_file, "| Iter nelmts=%lld.\n", iter_nelmts);
+                HDfprintf(debug_file, "| Mem space selected points: %zd.\n| \n", H5S_GET_SELECT_NPOINTS(dataspace));
+#endif
+
                 /* Update the chunk data with the received modification data */
                 if (H5D__scatter_mem(mod_data_p, dataspace, mem_iter, (size_t) iter_nelmts,
                         io_info->dxpl_cache, chunk_entry->buf) < 0)
@@ -2997,6 +3280,19 @@ H5D__filtered_collective_chunk_entry_io(H5D_filtered_collective_io_info_t *chunk
                 mem_iter_init = FALSE;
             } /* end while */
 
+
+#ifdef PARALLEL_COMPRESS_DEBUG
+            HDfprintf(debug_file, "| - Chunk Data Buffer:\n");
+            HDfprintf(debug_file, "| - [");
+            for (size_t j = 0; j < chunk_entry->new_chunk.length / type_info->src_type_size; j++) {
+                if (j > 0) HDfprintf(debug_file, ", ");
+                HDfprintf(debug_file, "%lld", ((long *) chunk_entry->buf)[j]);
+            }
+            HDfprintf(debug_file, "]\n|\n");
+
+            HDfprintf(debug_file, "| - About to filter %zd bytes in buffer of size %zd.\n|\n", chunk_entry->new_chunk.length, buf_size);
+#endif
+
             /* Filter the chunk */
             if (H5Z_pipeline(&io_info->dset->shared->dcpl_cache.pline, 0, &filter_mask,
                     io_info->dxpl_cache->err_detect, io_info->dxpl_cache->filter_cb,