--- /dev/null
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "mpi.h"
+#include "mpitest.h"
+
+#define RING_NUM_NEIGHBORS 2
+
+static int validate_dgraph(MPI_Comm dgraph_comm)
+{
+ int comm_topo;
+ int src_sz, dest_sz;
+ int wgt_flag, ierr;
+ int srcs[RING_NUM_NEIGHBORS], dests[RING_NUM_NEIGHBORS];
+ int *src_wgts, *dest_wgts;
+
+ int world_rank, world_size;
+ int idx, nbr_sep;
+
+ comm_topo = MPI_UNDEFINED;
+ MPI_Topo_test(dgraph_comm, &comm_topo);
+ switch (comm_topo) {
+ case MPI_DIST_GRAPH :
+ break;
+ default:
+ fprintf(stderr, "dgraph_comm is NOT of type MPI_DIST_GRAPH\n");
+ return 0;
+ }
+
+ ierr = MPI_Dist_graph_neighbors_count(dgraph_comm,
+ &src_sz, &dest_sz, &wgt_flag);
+ if (ierr != MPI_SUCCESS) {
+ fprintf(stderr, "MPI_Dist_graph_neighbors_count() fails!\n");
+ return 0;
+ }
+/*
+ else
+ fprintf(stderr, "MPI_Dist_graph_neighbors_count() succeeds!\n");
+*/
+
+ if (wgt_flag) {
+ fprintf(stderr, "dgraph_comm is NOT created with MPI_UNWEIGHTED\n");
+ return 0;
+ }
+/*
+ else
+ fprintf(stderr, "dgraph_comm is created with MPI_UNWEIGHTED\n");
+*/
+ if (src_sz != RING_NUM_NEIGHBORS || dest_sz != RING_NUM_NEIGHBORS) {
+ fprintf(stderr, "source or destination edge array is not of size %d.\n",
+ RING_NUM_NEIGHBORS);
+ fprintf(stderr, "src_sz = %d, dest_sz = %d\n", src_sz, dest_sz);
+ return 0;
+ }
+
+ /*
+ src_wgts and dest_wgts could be anything, e.g. NULL, since
+ MPI_Dist_graph_neighbors_count() returns MPI_UNWEIGHTED.
+ Since this program has a Fortran77 version, and standard Fortran77
+ has no pointer and NULL, so use MPI_UNWEIGHTED for the weighted arrays.
+ */
+ src_wgts = MPI_UNWEIGHTED;
+ dest_wgts = MPI_UNWEIGHTED;
+ ierr = MPI_Dist_graph_neighbors(dgraph_comm,
+ src_sz, srcs, src_wgts,
+ dest_sz, dests, dest_wgts);
+ if (ierr != MPI_SUCCESS) {
+ fprintf(stderr, "MPI_Dist_graph_neighbors() fails!\n");
+ return 0;
+ }
+/*
+ else
+ fprintf(stderr, "MPI_Dist_graph_neighbors() succeeds!\n");
+*/
+
+ /*
+ Check if the neighbors returned from MPI are really
+ the nearest neighbors within a ring.
+ */
+ MPI_Comm_size(MPI_COMM_WORLD, &world_size);
+ MPI_Comm_rank(MPI_COMM_WORLD, &world_rank);
+
+ for (idx=0; idx < src_sz; idx++) {
+ nbr_sep = abs(srcs[idx] - world_rank);
+ if ( nbr_sep != 1 && nbr_sep != (world_size-1) ) {
+ fprintf(stderr, "srcs[%d]=%d is NOT a neighbor of my rank %d.\n",
+ idx, srcs[idx], world_rank);
+ return 0;
+ }
+ }
+ for (idx=0; idx < dest_sz; idx++) {
+ nbr_sep = abs(dests[idx] - world_rank);
+ if ( nbr_sep != 1 && nbr_sep != (world_size-1) ) {
+ fprintf(stderr, "dests[%d]=%d is NOT a neighbor of my rank %d.\n",
+ idx, dests[idx], world_rank);
+ return 0;
+ }
+ }
+
+ /*
+ fprintf(stderr, "dgraph_comm is of type MPI_DIST_GRAPH "
+ "of a bidirectional ring.\n");
+ */
+ return 1;
+}
+
+/*
+ Specify a distributed graph of a bidirectional ring of the MPI_COMM_WORLD,
+ i.e. everyone only talks to left and right neighbors.
+*/
+int main(int argc, char *argv[])
+{
+ MPI_Comm dgraph_comm;
+ int world_size, world_rank, ierr;
+ int errs = 0;
+
+ int src_sz, dest_sz;
+ int degs[1];
+ int srcs[RING_NUM_NEIGHBORS], dests[RING_NUM_NEIGHBORS];
+
+ MTest_Init(&argc, &argv);
+ MPI_Comm_size(MPI_COMM_WORLD, &world_size);
+ MPI_Comm_rank(MPI_COMM_WORLD, &world_rank);
+
+ degs[0] = 2;
+ srcs[0] = world_rank;
+ dests[0] = world_rank-1 < 0 ? world_size-1 : world_rank-1 ;
+ dests[1] = world_rank+1 >= world_size ? 0 : world_rank+1 ;
+ ierr = MPI_Dist_graph_create(MPI_COMM_WORLD, 1, srcs, degs, dests,
+ MPI_UNWEIGHTED, MPI_INFO_NULL, 1,
+ &dgraph_comm);
+ if ( ierr != MPI_SUCCESS ) {
+ fprintf(stderr, "MPI_Dist_graph_create() fails!\n");
+ MPI_Abort(MPI_COMM_WORLD, 1);
+ return 1;
+ }
+ if (!validate_dgraph(dgraph_comm)) {
+ fprintf(stderr, "MPI_Dist_graph_create() does NOT create "
+ "a bidirectional ring graph!\n");
+ MPI_Abort(MPI_COMM_WORLD, 1);
+ return 1;
+ }
+ MPI_Comm_free(&dgraph_comm);
+
+ src_sz = 2;
+ srcs[0] = world_rank-1 < 0 ? world_size-1 : world_rank-1 ;
+ srcs[1] = world_rank+1 >= world_size ? 0 : world_rank+1 ;
+ dest_sz = 2;
+ dests[0] = world_rank-1 < 0 ? world_size-1 : world_rank-1 ;
+ dests[1] = world_rank+1 >= world_size ? 0 : world_rank+1 ;
+ ierr = MPI_Dist_graph_create_adjacent(MPI_COMM_WORLD,
+ src_sz, srcs, MPI_UNWEIGHTED,
+ dest_sz, dests, MPI_UNWEIGHTED,
+ MPI_INFO_NULL, 1, &dgraph_comm);
+ if ( ierr != MPI_SUCCESS ) {
+ fprintf(stderr, "MPI_Dist_graph_create_adjacent() fails!\n");
+ MPI_Abort(MPI_COMM_WORLD, 1);
+ return 1;
+ }
+ if (!validate_dgraph(dgraph_comm)) {
+ fprintf(stderr, "MPI_Dist_graph_create_adjacent() does NOT create "
+ "a bidirectional ring graph!\n");
+ MPI_Abort(MPI_COMM_WORLD, 1);
+ return 1;
+ }
+ MPI_Comm_free(&dgraph_comm);
+
+ MTest_Finalize(errs);
+ MPI_Finalize();
+ return 0;
+}
