Implementation of the mpio driver with selection I/O. (#3222)

* This changes the default selection I/O to on for MPIO.

1 files changed, 16 insertions, 14 deletions

diff --git a/src/H5Dio.c b/src/H5Dio.c
index 89afde5..b978139 100644
--- a/src/H5Dio.c
+++ b/src/H5Dio.c
@@ -415,8 +415,14 @@ H5D__read(size_t count, H5D_dset_io_info_t *dset_info)
                 HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't get MPI-I/O transfer mode");
 
             /* Only report the collective I/O mode if we're actually performing collective I/O */
-            if (xfer_mode == H5FD_MPIO_COLLECTIVE)
+            if (xfer_mode == H5FD_MPIO_COLLECTIVE) {
                 H5CX_set_mpio_actual_io_mode(io_info.actual_io_mode);
+
+                /* If we did selection I/O, report that we used "link chunk" mode, since that's the most
+                 * analogous to what selection I/O does */
+                if (io_info.use_select_io == H5D_SELECTION_IO_MODE_ON)
+                    H5CX_set_mpio_actual_chunk_opt(H5D_MPIO_LINK_CHUNK);
+            }
         }
 #endif /* H5_HAVE_PARALLEL */
     }
@@ -1131,20 +1137,16 @@ H5D__typeinfo_init_phase2(H5D_io_info_t *io_info)
     assert(io_info);
 
     /* If selection I/O mode is default (auto), enable it here if the VFD supports it (it will be turned off
-     * later if something else conflicts), otherwise disable it.  If we're using the MPIO VFD, the automatic
-     * selection will happen in H5D__mpio_opt_possible() inside H5D__ioinfo_adjust(). */
-#ifdef H5_HAVE_PARALLEL
-    if (!io_info->using_mpi_vfd)
-#endif /* H5_HAVE_PARALLEL */
-        if (io_info->use_select_io == H5D_SELECTION_IO_MODE_DEFAULT) {
-            if (H5F_has_vector_select_io(io_info->dsets_info[0].dset->oloc.file,
-                                         io_info->op_type == H5D_IO_OP_WRITE))
-                io_info->use_select_io = H5D_SELECTION_IO_MODE_ON;
-            else {
-                io_info->use_select_io = H5D_SELECTION_IO_MODE_OFF;
-                io_info->no_selection_io_cause |= H5D_SEL_IO_DEFAULT_OFF;
-            }
+     * later if something else conflicts), otherwise disable it */
+    if (io_info->use_select_io == H5D_SELECTION_IO_MODE_DEFAULT) {
+        if (H5F_has_vector_select_io(io_info->dsets_info[0].dset->oloc.file,
+                                     io_info->op_type == H5D_IO_OP_WRITE))
+            io_info->use_select_io = H5D_SELECTION_IO_MODE_ON;
+        else {
+            io_info->use_select_io = H5D_SELECTION_IO_MODE_OFF;
+            io_info->no_selection_io_cause |= H5D_SEL_IO_DEFAULT_OFF;
         }
+    }
 
     /* If we're doing type conversion and we might be doing selection I/O, check if the buffers are large
      * enough to handle the whole I/O */