[svn-r5429] Purpose:

    Bug fix/Code improvement.

Description:
    Currently, the chunk data allocation routine invoked to allocate space for
    the entire dataset is inefficient.  It writes out each chunk in the dataset,
    whether it is already allocated or not.  Additionally, this happens not
    only when it is created, but also anytime it is opened for writing, or the
    dataset is extended.  Worse, there's too much parallel I/O syncronization,
    which slows things down even more.

Solution:
    Only attempt to write out chunks that don't already exist.  Additionally,
    share the I/O writing between all the nodes, instead of writing everything
    with process 0.  Then, only block with MPI_Barrier if chunks were actually
    created.

Platforms tested:
    IRIX64 6.5 (modi4)

1 files changed, 56 insertions, 0 deletions

diff --git a/src/H5FDmpio.c b/src/H5FDmpio.c
index f4ba335..3572390 100644
--- a/src/H5FDmpio.c
+++ b/src/H5FDmpio.c
@@ -449,6 +449,62 @@ H5FD_mpio_communicator(H5FD_t *_file)
 
 
 /*-------------------------------------------------------------------------
+ * Function:	H5FD_mpio_mpi_rank
+ *
+ * Purpose:	Returns the MPI rank for a process
+ *
+ * Return:	Success: non-negative
+ *		Failure: negative
+ *
+ * Programmer:	Quincey Koziol
+ *              Thursday, May 16, 2002
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+int
+H5FD_mpio_mpi_rank(H5FD_t *_file)
+{
+    H5FD_mpio_t	*file = (H5FD_mpio_t*)_file;
+
+    FUNC_ENTER(H5FD_mpio_mpi_rank, FAIL);
+    assert(file);
+    assert(H5FD_MPIO==file->pub.driver_id);
+
+    FUNC_LEAVE(file->mpi_rank);
+} /* end H5FD_mpio_mpi_rank() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5FD_mpio_mpi_size
+ *
+ * Purpose:	Returns the number of MPI processes
+ *
+ * Return:	Success: non-negative
+ *		Failure: negative
+ *
+ * Programmer:	Quincey Koziol
+ *              Thursday, May 16, 2002
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+int
+H5FD_mpio_mpi_size(H5FD_t *_file)
+{
+    H5FD_mpio_t	*file = (H5FD_mpio_t*)_file;
+
+    FUNC_ENTER(H5FD_mpio_mpi_rank, FAIL);
+    assert(file);
+    assert(H5FD_MPIO==file->pub.driver_id);
+
+    FUNC_LEAVE(file->mpi_size);
+} /* end H5FD_mpio_mpi_size() */
+
+
+/*-------------------------------------------------------------------------
  * Function:	H5FD_mpio_setup
  *
  * Purpose:	Set the buffer type BTYPE, file type FTYPE, and absolute base