The sum of the local and remote recvcounts is identical (per MPI standard

requirement) so the recvcounts array is bounded by the number of
participants in the local group.

This commit was SVN r26496.

ompi/mpi/c/reduce_scatter.c

@@ -46,11 +46,11 @@ int MPI_Reduce_scatter(void *sendbuf, void *recvbuf, int *recvcounts,
     MEMCHECKER(
         int rank;
         
-        size = ompi_comm_remote_size(comm);
+        size = ompi_comm_size(comm);
         rank = ompi_comm_rank(comm);
         for (count = i = 0; i < size; ++i) {
             if (0 == recvcounts[i]) {
-                ++count;
+                count += recvcounts[i];
             }
         }
 
@@ -95,12 +95,10 @@ int MPI_Reduce_scatter(void *sendbuf, void *recvbuf, int *recvcounts,
         }
         OMPI_ERRHANDLER_CHECK(err, comm, err, FUNC_NAME);
 
-        /* We always define the remote group to be the same as the
-           local group in the case of an intracommunicator, so it's
-           safe to get the size of the remote group here for both
-           intra- and intercommunicators */
-
-        size = ompi_comm_remote_size(comm);
+        /* Based on the standard each group has to provide the same total
+           number of elements, so the size of the recvcounts array depends
+           on the number of participants in the local group.  */
+        size = ompi_comm_size(comm);
         for (i = 0; i < size; ++i) {
           OMPI_CHECK_DATATYPE_FOR_SEND(err, datatype, recvcounts[i]);
           OMPI_ERRHANDLER_CHECK(err, comm, err, FUNC_NAME);
@@ -111,7 +109,7 @@ int MPI_Reduce_scatter(void *sendbuf, void *recvbuf, int *recvcounts,
        element.  But at least the Pallas benchmarks call MPI_REDUCE
        with a count of 0.  So be sure to handle it.  Grrr... */
 
-    size = ompi_comm_remote_size(comm);
+    size = ompi_comm_size(comm);
     for (count = i = 0; i < size; ++i) {
         if (0 == recvcounts[i]) {
             ++count;