[mpich-commits] [mpich] MPICH primary repository branch, master, updated. v3.1.2-72-g1290951

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http://git.mpich.org/mpich.git/commitdiff/12909511b352b3b6d069b8d1f933b383f8447704

commit 12909511b352b3b6d069b8d1f933b383f8447704
Author: Xin Zhao <xinzhao3 at illinois.edu>
Date:   Tue Aug 5 15:32:08 2014 -0500

    Bug-fix: correct the calculation of SHM base addrs.
    
    The calculation of SHM base addrs is not correct when there are
    processes allocating zero byte SHM window.
    
    Suppose rank 0 and rank 2 has non-zero bytes SHM window whereas
    rank 1 has zero byte SHM window.
    The original and wrong calculation is:
    win_base(rank 2) = win_base(rank 0) + win_size(rank 1).
    The correct calculation should be:
    win_base(rank 2) = win_base(rank 0) + win_size(rank 0).
    
    Signed-off-by: Pavan Balaji <balaji at anl.gov>

diff --git a/src/mpid/ch3/channels/nemesis/src/ch3_win_fns.c b/src/mpid/ch3/channels/nemesis/src/ch3_win_fns.c
index 82c5aec..8049289 100644
--- a/src/mpid/ch3/channels/nemesis/src/ch3_win_fns.c
+++ b/src/mpid/ch3/channels/nemesis/src/ch3_win_fns.c
@@ -303,17 +303,24 @@ static int MPIDI_CH3I_Win_allocate_shm(MPI_Aint size, int disp_unit, MPID_Info *
         }
 
         char *cur_base = (*win_ptr)->shm_base_addr;
+        int cur_rank = 0;
         node_shm_base_addrs[0] = (*win_ptr)->shm_base_addr;
         for (i = 1; i < node_size; ++i) {
             if (node_sizes[i]) {
+                /* For the base addresses, we track the previous
+                 * process that has allocated non-zero bytes of shared
+                 * memory.  We can not simply use "i-1" for the
+                 * previous process because rank "i-1" might not have
+                 * allocated any memory. */
                 if (noncontig) {
-                    node_shm_base_addrs[i] = cur_base + MPIDI_CH3_ROUND_UP_PAGESIZE(node_sizes[i-1]);
+                    node_shm_base_addrs[i] = cur_base + MPIDI_CH3_ROUND_UP_PAGESIZE(node_sizes[cur_rank]);
                 } else {
-                    node_shm_base_addrs[i] = cur_base + node_sizes[i-1];
+                    node_shm_base_addrs[i] = cur_base + node_sizes[cur_rank];
                 }
                 cur_base = node_shm_base_addrs[i];
+                cur_rank = i;
             } else {
-                node_shm_base_addrs[i] = NULL; /* FIXME: Is this right? */
+                node_shm_base_addrs[i] = NULL;
             }
         }
 

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

Summary of changes:
 src/mpid/ch3/channels/nemesis/src/ch3_win_fns.c |   13 ++++++++++---
 1 files changed, 10 insertions(+), 3 deletions(-)


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