mpi/neighbor_allgatherv: fix copy&paste error and add helpers

This commit adds a helper function to get the inbound and outbound
neighbor count and updates the neighbor_allgatherv bindings to use the
correct count when checking the input parameters.

Fixes open-mpi#2324

Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>
(cherry picked from commit 3c0e94a)
Signed-off-by: Nathan Hjelm <hjelmn@me.com>

ompi/mca/topo/base/base.h

@@ -194,6 +194,9 @@ OMPI_DECLSPEC int
 mca_topo_base_dist_graph_neighbors_count(ompi_communicator_t *comm,
                                          int *inneighbors, int *outneighbors, int *weighted);
 
+
+int mca_topo_base_neighbor_count (ompi_communicator_t *comm, int *indegree, int *outdegree);
+
 END_C_DECLS
 
 #endif /* MCA_BASE_TOPO_H */

ompi/mca/topo/base/topo_base_frame.c

@@ -71,6 +71,31 @@ static int mca_topo_base_open(mca_base_open_flag_t flags)
     return mca_base_framework_components_open(&ompi_topo_base_framework, flags);
 }
 
+int mca_topo_base_neighbor_count (ompi_communicator_t *comm, int *indegree, int *outdegree) {
+  if (OMPI_COMM_IS_CART(comm)) {
+    /* cartesian */
+    /* outdegree is always 2*ndims because we need to iterate over
+       empty buffers for MPI_PROC_NULL */
+    *outdegree = *indegree = 2 * comm->c_topo->mtc.cart->ndims;
+  } else if (OMPI_COMM_IS_GRAPH(comm)) {
+    /* graph */
+    int rank, nneighbors;
+
+    rank = ompi_comm_rank (comm);
+    mca_topo_base_graph_neighbors_count (comm, rank, &nneighbors);
+
+    *outdegree = *indegree = nneighbors;
+  } else if (OMPI_COMM_IS_DIST_GRAPH(comm)) {
+    /* graph */
+    *indegree = comm->c_topo->mtc.dist_graph->indegree;
+    *outdegree = comm->c_topo->mtc.dist_graph->outdegree;
+  } else {
+    return OMPI_ERR_BAD_PARAM;
+  }
+
+  return OMPI_SUCCESS;
+}
+
 MCA_BASE_FRAMEWORK_DECLARE(ompi, topo, "OMPI Topo", NULL,
                            mca_topo_base_open, mca_topo_base_close,
                            mca_topo_base_static_components, 0);

ompi/mpi/c/neighbor_allgatherv.c

@@ -12,7 +12,7 @@
  *                         All rights reserved.
  * Copyright (c) 2010      University of Houston.  All rights reserved.
  * Copyright (c) 2012 Cisco Systems, Inc.  All rights reserved.
- * Copyright (c) 2012-2013 Los Alamos National Security, LLC.  All rights
+ * Copyright (c) 2012-2016 Los Alamos National Security, LLC.  All rights
  *                         reserved.
  * Copyright (c) 2015      Research Organization for Information Science
  *                         and Technology (RIST). All rights reserved.
@@ -32,6 +32,7 @@
 #include "ompi/communicator/communicator.h"
 #include "ompi/errhandler/errhandler.h"
 #include "ompi/datatype/ompi_datatype.h"
+#include "ompi/mca/topo/base/base.h"
 #include "ompi/memchecker.h"
 #include "ompi/mca/topo/topo.h"
 #include "ompi/mca/topo/base/base.h"
@@ -50,20 +51,20 @@ int MPI_Neighbor_allgatherv(const void *sendbuf, int sendcount, MPI_Datatype sen
                             void *recvbuf, const int recvcounts[], const int displs[],
                             MPI_Datatype recvtype, MPI_Comm comm)
 {
-    int i, size, err;
+    int in_size, out_size, err;
 
     MEMCHECKER(
         int rank;
         ptrdiff_t ext;
 
         rank = ompi_comm_rank(comm);
-        size = ompi_comm_size(comm);
+        mca_topo_base_neighbor_count (comm, &in_size, &out_size);
         ompi_datatype_type_extent(recvtype, &ext);
 
         memchecker_datatype(recvtype);
         memchecker_comm (comm);
         /* check whether the receive buffer is addressable. */
-        for (i = 0; i < size; i++) {
+        for (int i = 0; i < in_size; ++i) {
             memchecker_call(&opal_memchecker_base_isaddressable,
                             (char *)(recvbuf)+displs[i]*ext,
                             recvcounts[i], recvtype);
@@ -107,8 +108,8 @@ int MPI_Neighbor_allgatherv(const void *sendbuf, int sendcount, MPI_Datatype sen
          get the size of the remote group here for both intra- and
          intercommunicators */
 
-        size = ompi_comm_remote_size(comm);
-        for (i = 0; i < size; ++i) {
+        mca_topo_base_neighbor_count (comm, &in_size, &out_size);
+        for (int i = 0; i < in_size; ++i) {
           if (recvcounts[i] < 0) {
             return OMPI_ERRHANDLER_INVOKE(comm, MPI_ERR_COUNT, FUNC_NAME);
           }
@@ -141,31 +142,9 @@ int MPI_Neighbor_allgatherv(const void *sendbuf, int sendcount, MPI_Datatype sen
         }
     }
 
-    /* Do we need to do anything?  Everyone had to give the same
-       signature, which means that everyone must have given a
-       sum(recvounts) > 0 if there's anything to do. */
-
-    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 */
-
-
     /* Invoke the coll component to perform the back-end operation */
     err = comm->c_coll.coll_neighbor_allgatherv(sendbuf, sendcount, sendtype,
                                                 recvbuf, recvcounts, displs,
                                                 recvtype, comm, comm->c_coll.coll_neighbor_allgatherv_module);
     OMPI_ERRHANDLER_RETURN(err, comm, err, FUNC_NAME);
 }
-