The initial coding for the superblock read optization

2 files changed, 49 insertions, 2 deletions

diff --git a/src/H5FDmpio.h b/src/H5FDmpio.h
index 6ee0a1a..9bcc182 100644
--- a/src/H5FDmpio.h
+++ b/src/H5FDmpio.h
@@ -29,6 +29,27 @@
 #endif /* H5_HAVE_PARALLEL */
 
 #ifdef H5_HAVE_PARALLEL
+#define H5FD_GET_MPI_RANK_AND_SIZE(rank,size, f) { \
+  (rank) = 0; (size) = 1;                          \
+  if (H5F_HAS_FEATURE((f), H5FD_FEAT_HAS_MPI)) {   \
+      (rank) = H5F_mpi_get_rank((f));              \
+      (size) = H5F_mpi_get_size((f));              \
+  } else {                                         \
+      int mpi_initialized = 0, mpi_finalized = 0;  \
+      MPI_Initialized(&mpi_initialized);           \
+      MPI_Finalized(&mpi_finalized);               \
+      if (mpi_initialized && !mpi_finalized) {     \
+          MPI_Comm_rank(MPI_COMM_WORLD, &(rank));  \
+          MPI_Comm_size(MPI_COMM_WORLD, &(size));  \
+      }                                            \
+  }}
+  
+#define H5FD_GET_MPI_COMM(comm, f) {               \
+  if (H5F_HAS_FEATURE((f), H5FD_FEAT_HAS_MPI))     \
+      (comm) = H5F_mpi_get_comm((f));              \
+  else (comm) = MPI_COMM_WORLD;                    \
+  }
+
 /*Turn on H5FDmpio_debug if H5F_DEBUG is on */
 #ifdef H5F_DEBUG
 #ifndef H5FDmpio_DEBUG
diff --git a/src/H5Fsuper.c b/src/H5Fsuper.c
index 7c70a64..32051f3 100644
--- a/src/H5Fsuper.c
+++ b/src/H5Fsuper.c
@@ -333,6 +333,7 @@ H5F__super_read(H5F_t *f, hid_t meta_dxpl_id, hid_t raw_dxpl_id, hbool_t initial
     unsigned      	rw_flags;           /* Read/write permissions for file */
     hbool_t 		skip_eof_check = FALSE; /* Whether to skip checking the EOF value */
     herr_t              ret_value = SUCCEED; /* Return value */
+    int                 mpi_rank = 0, mpi_size = 1;
 
     FUNC_ENTER_PACKAGE_TAG(meta_dxpl_id, H5AC__SUPERBLOCK_TAG, FAIL)
 
@@ -354,8 +355,33 @@ H5F__super_read(H5F_t *f, hid_t meta_dxpl_id, hid_t raw_dxpl_id, hbool_t initial
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "can't get property list")
 
     /* Find the superblock */
-    if(H5FD_locate_signature(&fdio_info, &super_addr) < 0)
-        HGOTO_ERROR(H5E_FILE, H5E_NOTHDF5, FAIL, "unable to locate file signature")
+#ifdef H5_HAVE_PARALLEL
+    H5FD_GET_MPI_RANK_AND_SIZE(mpi_rank, mpi_size, f);
+    /* If we are an MPI application with at least two processes, the
+     * following superblock signature location optimization is applicable.
+     */
+    if ( mpi_size > 1 ) {
+         MPI_Comm this_comm = MPI_COMM_NULL;
+
+	 if ( mpi_rank == 0 ) {
+	      if(H5FD_locate_signature(&fdio_info, &super_addr) < 0)
+		  HGOTO_ERROR(H5E_FILE, H5E_NOTHDF5, FAIL, "unable to locate file signature")
+	 }
+	 H5FD_GET_MPI_COMM(this_comm, f);
+	 if (( this_comm == MPI_COMM_NULL ) ||
+	     ( MPI_Bcast(&super_addr,sizeof(super_addr), MPI_BYTE, 0, this_comm) != MPI_SUCCESS))
+               HGOTO_ERROR(H5E_FILE, H5E_NOTHDF5, FAIL, "unable to locate file signature")
+    }
+    else {
+    /* Locate the signature as per per the serial library */
+#endif	/* H5_HAVE_PARALLEL */
+
+         if(H5FD_locate_signature(&fdio_info, &super_addr) < 0)
+	     HGOTO_ERROR(H5E_FILE, H5E_NOTHDF5, FAIL, "unable to locate file signature")
+
+#ifdef H5_HAVE_PARALLEL
+    }
+#endif
     if(HADDR_UNDEF == super_addr)
         HGOTO_ERROR(H5E_FILE, H5E_NOTHDF5, FAIL, "file signature not found")