[mpich-commits] [mpich] MPICH primary repository branch, master, updated. v3.1b1-85-g4a13e98

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       via  f8901ffe8923a9a1a9e155593e79a2dc7a6ec209 (commit)
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- Log -----------------------------------------------------------------
http://git.mpich.org/mpich.git/commitdiff/4a13e98629fd3bd8d2004ab5f5ea7c6e851bce57

commit 4a13e98629fd3bd8d2004ab5f5ea7c6e851bce57
Author: Rob Latham <robl at mcs.anl.gov>
Date:   Fri Oct 4 16:18:38 2013 -0500

    compile error

diff --git a/src/mpi/romio/adio/ad_bg/ad_bg_hints.c b/src/mpi/romio/adio/ad_bg/ad_bg_hints.c
index 47a0e77..1866df5 100644
--- a/src/mpi/romio/adio/ad_bg/ad_bg_hints.c
+++ b/src/mpi/romio/adio/ad_bg/ad_bg_hints.c
@@ -258,7 +258,6 @@ void ADIOI_BG_SetInfo(ADIO_File fd, MPI_Info users_info, int *error_code)
      process hints for it. */
 	ADIOI_Info_check_and_install_int(fd, users_info, "striping_unit", 
 		&(fd->hints->striping_unit), myname, error_code);
-	}
 
 	memset( value, 0, MPI_MAX_INFO_VAL+1 );
         ADIOI_Info_get(users_info, ADIOI_BG_NAGG_IN_PSET_HINT_NAME, MPI_MAX_INFO_VAL,

http://git.mpich.org/mpich.git/commitdiff/f8901ffe8923a9a1a9e155593e79a2dc7a6ec209

commit f8901ffe8923a9a1a9e155593e79a2dc7a6ec209
Author: Rob Latham <robl at mcs.anl.gov>
Date:   Wed Oct 2 16:39:40 2013 -0500

    improve comments, formatting on some tricky code
    
    I end up looking at this code only about once every six months.  Add
    more comments so the next time I'm here, I don't have to re-learn the
    teeny-tiny details.

diff --git a/src/mpi/romio/adio/ad_bg/ad_bg_aggrs.c b/src/mpi/romio/adio/ad_bg/ad_bg_aggrs.c
index 0d6ab5b..d8b42ef 100644
--- a/src/mpi/romio/adio/ad_bg/ad_bg_aggrs.c
+++ b/src/mpi/romio/adio/ad_bg/ad_bg_aggrs.c
@@ -520,14 +520,43 @@ void ADIOI_BG_GPFS_Calc_file_domains(ADIO_Offset *st_offsets,
     fd_start             = *fd_start_ptr;
     fd_end               = *fd_end_ptr;
 
+    /* each process will have a file domain of some number of gpfs blocks, but
+     * the division of blocks is not likely to be even.  Some file domains will
+     * be "large" and others "small"
+     *
+     * Example: consider  17 blocks distributed over 3 aggregators.
+     * nb_cn_small = 17/3 = 5
+     * naggs_large = 17 - 3*(17/3) = 17 - 15  = 2
+     * naggs_small = 3 - 2 = 1
+     *
+     * and you end up with file domains of {5-blocks, 6-blocks, 6-blocks}
+     *
+     * what about (relatively) small files?  say, a file of 1000 blocks
+     * distributed over 2064 aggregators:
+     * nb_cn_small = 1000/2064 = 0
+     * naggs_large = 1000 - 2064*(1000/2064) = 1000
+     * naggs_small = 2064 - 1000 = 1064
+     * and you end up with domains of {0, 0, 0, ... 1, 1, 1 ...}
+     *
+     * it might be a good idea instead of having all the zeros up front, to
+     * "mix" those zeros into the fd_size array.  that way, no pset/bridge-set
+     * is left with zero work.  In fact, even if the small file domains aren't
+     * zero, it's probably still a good idea to mix the "small" file domains
+     * across the fd_size array to keep the io nodes in balance */
+
+
     ADIO_Offset n_gpfs_blk    = fd_gpfs_range / blksize;
     ADIO_Offset nb_cn_small   = n_gpfs_blk/naggs;
     ADIO_Offset naggs_large   = n_gpfs_blk - naggs * (n_gpfs_blk/naggs);
     ADIO_Offset naggs_small   = naggs - naggs_large;
 
-    for (i=0; i<naggs; i++)
-        if (i < naggs_small) fd_size[i] = nb_cn_small     * blksize;
-                        else fd_size[i] = (nb_cn_small+1) * blksize;
+    for (i=0; i<naggs; i++) {
+	if (i < naggs_small) {
+	    fd_size[i] = nb_cn_small     * blksize;
+	} else {
+	    fd_size[i] = (nb_cn_small+1) * blksize;
+	}
+    }
 
 #   if AGG_DEBUG
      DBG_FPRINTF(stderr,"%s(%d): "

-----------------------------------------------------------------------

Summary of changes:
 src/mpi/romio/adio/ad_bg/ad_bg_aggrs.c |   35 +++++++++++++++++++++++++++++--
 src/mpi/romio/adio/ad_bg/ad_bg_hints.c |    1 -
 2 files changed, 32 insertions(+), 4 deletions(-)


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