Don't allocate space for the requests if the

underlying topology has no neighbors.

This commit fixes issue #2402.

Signed-off-by: George Bosilca <bosilca@icl.utk.edu>

ompi/mca/coll/basic/coll_basic_neighbor_allgather.c

@@ -48,6 +48,8 @@ mca_coll_basic_neighbor_allgather_cart(const void *sbuf, int scount,
     ptrdiff_t lb, extent;
     int rc = MPI_SUCCESS, dim, nreqs;
 
+    if( 0 == cart->ndims ) return OMPI_SUCCESS;
+
     ompi_datatype_get_extent(rdtype, &lb, &extent);
 
     reqs = preqs = coll_base_comm_get_reqs( module->base_data, 4 * cart->ndims );
@@ -129,6 +131,7 @@ mca_coll_basic_neighbor_allgather_graph(const void *sbuf, int scount,
     int rc = MPI_SUCCESS, neighbor;
 
     mca_topo_base_graph_neighbors_count (comm, rank, &degree);
+    if( 0 == degree) return OMPI_SUCCESS;
 
     edges = graph->edges;
     if (rank > 0) {
@@ -181,6 +184,7 @@ mca_coll_basic_neighbor_allgather_dist_graph(const void *sbuf, int scount,
 
     indegree = dist_graph->indegree;
     outdegree = dist_graph->outdegree;
+    if( 0 == (indegree + outdegree) ) return OMPI_SUCCESS;
 
     inedges = dist_graph->in;
     outedges = dist_graph->out;

ompi/mca/coll/basic/coll_basic_neighbor_allgatherv.c

@@ -47,6 +47,8 @@ mca_coll_basic_neighbor_allgatherv_cart(const void *sbuf, int scount, struct omp
     ptrdiff_t lb, extent;
     int rc = MPI_SUCCESS, dim, i, nreqs;
 
+    if( 0 == cart->ndims ) return OMPI_SUCCESS;
+
     ompi_datatype_get_extent(rdtype, &lb, &extent);
 
     reqs = preqs = coll_base_comm_get_reqs( module->base_data, 4 * cart->ndims);
@@ -116,6 +118,7 @@ mca_coll_basic_neighbor_allgatherv_graph(const void *sbuf, int scount, struct om
     ptrdiff_t lb, extent;
 
     mca_topo_base_graph_neighbors_count (comm, rank, &degree);
+    if( 0 == degree ) return OMPI_SUCCESS;
 
     edges = graph->edges;
     if (rank > 0) {
@@ -166,6 +169,7 @@ mca_coll_basic_neighbor_allgatherv_dist_graph(const void *sbuf, int scount, stru
 
     indegree = dist_graph->indegree;
     outdegree = dist_graph->outdegree;
+    if( 0 == (indegree + outdegree) ) return OMPI_SUCCESS;
 
     inedges = dist_graph->in;
     outedges = dist_graph->out;

ompi/mca/coll/basic/coll_basic_neighbor_alltoall.c

@@ -46,6 +46,8 @@ mca_coll_basic_neighbor_alltoall_cart(const void *sbuf, int scount, struct ompi_
     ptrdiff_t lb, rdextent, sdextent;
     int rc = MPI_SUCCESS, dim, nreqs;
 
+    if( 0 == cart->ndims ) return OMPI_SUCCESS;
+
     ompi_datatype_get_extent(rdtype, &lb, &rdextent);
     ompi_datatype_get_extent(sdtype, &lb, &sdextent);
     reqs = preqs = coll_base_comm_get_reqs( module->base_data, 4 * cart->ndims);
@@ -146,6 +148,7 @@ mca_coll_basic_neighbor_alltoall_graph(const void *sbuf, int scount, struct ompi
     const int *edges;
 
     mca_topo_base_graph_neighbors_count (comm, rank, &degree);
+    if( 0 == degree ) return OMPI_SUCCESS;
 
     edges = graph->edges;
     if (rank > 0) {
@@ -205,6 +208,7 @@ mca_coll_basic_neighbor_alltoall_dist_graph(const void *sbuf, int scount,struct
 
     indegree = dist_graph->indegree;
     outdegree = dist_graph->outdegree;
+    if( 0 == (indegree + outdegree) ) return OMPI_SUCCESS;
 
     inedges = dist_graph->in;
     outedges = dist_graph->out;

ompi/mca/coll/basic/coll_basic_neighbor_alltoallv.c

@@ -47,6 +47,8 @@ mca_coll_basic_neighbor_alltoallv_cart(const void *sbuf, const int scounts[], co
     ptrdiff_t lb, rdextent, sdextent;
     ompi_request_t **reqs, **preqs;
 
+    if( 0 == cart->ndims ) return OMPI_SUCCESS;
+
     ompi_datatype_get_extent(rdtype, &lb, &rdextent);
     ompi_datatype_get_extent(sdtype, &lb, &sdextent);
     reqs = preqs = coll_base_comm_get_reqs( module->base_data, 4 * cart->ndims );
@@ -133,6 +135,7 @@ mca_coll_basic_neighbor_alltoallv_graph(const void *sbuf, const int scounts[], c
     const int *edges;
 
     mca_topo_base_graph_neighbors_count (comm, rank, &degree);
+    if( 0 == degree ) return OMPI_SUCCESS;
 
     edges = graph->edges;
     if (rank > 0) {
@@ -191,6 +194,7 @@ mca_coll_basic_neighbor_alltoallv_dist_graph(const void *sbuf, const int scounts
 
     indegree = dist_graph->indegree;
     outdegree = dist_graph->outdegree;
+    if( 0 == (indegree + outdegree) ) return OMPI_SUCCESS;
 
     inedges = dist_graph->in;
     outedges = dist_graph->out;