Forgot to include the check for 0 in the Allreduce case (already got

Reduce and Reduce_scatter)

This commit was SVN r6929.

ompi/mpi/c/allreduce.c

@@ -62,6 +62,14 @@ int MPI_Allreduce(void *sendbuf, void *recvbuf, int count,
         OMPI_ERRHANDLER_CHECK(err, comm, err, FUNC_NAME);
     }
 
+    /* MPI-1, p114, says that each process must supply at least
+       one element.  But at least the Pallas benchmarks call
+       MPI_REDUCE with a count of 0.  So be sure to handle it. */
+    
+    if (0 == count) {
+        return MPI_SUCCESS;
+    }
+
     /* Invoke the coll component to perform the back-end operation */
 
     err = comm->c_coll.coll_allreduce(sendbuf, recvbuf, count,