checks for sendcount and recvcount(s) being zero have slightly different

consequences depending on whether the communicator is an intra or an inter
communicator. 

fixes trac:2415

This commit was SVN r23187.

The following Trac tickets were found above:
  Ticket 2415 --> https://svn.open-mpi.org/trac/ompi/ticket/2415

ompi/mpi/c/allgather.c

@@ -10,6 +10,7 @@
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
  * Copyright (c) 2007      Cisco Systems, Inc.  All rights reserved.
+ * Copyright (c) 2010      University of Houston.  All rights reserved.
  * $COPYRIGHT$
  * 
  * Additional copyrights may follow
@@ -89,12 +90,24 @@ int MPI_Allgather(void *sendbuf, int sendcount, MPI_Datatype sendtype,
 
     /* Do we need to do anything?  Everyone had to give the same send
        signature, which means that everyone must have given a
-       sendcount > 0 if there's anything to send.  If we're doing
-       IN_PLACE, however, check recvcount, not sendcount. */
-
-    if ((MPI_IN_PLACE != sendbuf && 0 == sendcount) ||
-        (0 == recvcount)) {
-        return MPI_SUCCESS;
+       sendcount > 0 if there's anything to send for the intra-communicator
+       case.  If we're doing IN_PLACE, however, check recvcount, 
+       not sendcount. */
+    if ( OMPI_COMM_IS_INTRA(comm) ) {
+       if ((MPI_IN_PLACE != sendbuf && 0 == sendcount) ||
+            (0 == recvcount)) {
+            return MPI_SUCCESS;
+	}
+    }
+    else if ( OMPI_COMM_IS_INTER(comm) ){
+        /* for inter comunicators, the communication pattern
+           need not be symmetric. Specifically, one group is
+	   allows to have sendcount=0, while the other has
+           a valid sendcount. Thus, the only way not to do
+           anything is if both sendcount and recvcount are zero. */
+	if ( 0 == sendcount && 0 == recvcount ) {
+	    return MPI_SUCCESS;
+	}
     }
 
     OPAL_CR_ENTER_LIBRARY();

ompi/mpi/c/allgatherv.c

@@ -9,6 +9,7 @@
  *                         University of Stuttgart.  All rights reserved.
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
+ * Copyright (c) 2010      University of Houston.  All rights reserved.
  * $COPYRIGHT$
  * 
  * Additional copyrights may follow
@@ -108,14 +109,22 @@ int MPI_Allgatherv(void *sendbuf, int sendcount, MPI_Datatype sendtype,
        signature, which means that everyone must have given a
        sum(recvounts) > 0 if there's anything to do. */
 
-    for (i = 0; i < ompi_comm_size(comm); ++i) {
-        if (0 != recvcounts[i]) {
-            break;
-        }
-    }
-    if (i >= ompi_comm_size(comm)) {
-        return MPI_SUCCESS;
+    if ( OMPI_COMM_IS_INTRA( comm) ) {
+	for (i = 0; i < ompi_comm_size(comm); ++i) {
+	    if (0 != recvcounts[i]) {
+		break;
+	    }
+	}
+	if (i >= ompi_comm_size(comm)) {
+	    return MPI_SUCCESS;
+	}
     }
+    /* There is no rule that can be applied for inter-communicators, since
+       recvcount(s)=0 only indicates that the processes in the other group 
+       do not send anything, sendcount=0 only indicates that I do not send
+       anything. However, other processes in my group might very well send 
+       something */
+
 
     OPAL_CR_ENTER_LIBRARY();