openmpi/src/mca/topo/base/topo_base_graph_create.c

/*
 * $HEADER$
 */

#include "mca/topo/base/base.h"

/*
 *
 * function - makes a new communicator to which topology information
 *            has been attached
 *
 * @param comm_old input communicator without topology (handle)
 * @param nnodes number of nodes in graph (integer)
 * @param index array of integers describing node degrees (see below)
 * @param edges array of integers describing graph edges (see below)
 * @param reorder ranking may be reordered (true) or not (false) (logical)
 * @param comm_graph communicator with graph topology added (handle)
 *
 * @retval MPI_SUCCESS
 * @retval MPI_ERR_OUT_OF_RESOURCE
 */

int topo_base_graph_create (lam_communicator_t *comm_old,
                            int nnodes,
                            int *index,
                            int *edges,
                            int reorder,
                            lam_communicator_t **comm_graph) {

    lam_group_t *newgroup;
    int  nedges;
    int  size;
    int  err;
    int  range[1][3];
    int  i;
    int  *topo;
    int  *p;

    /*
     * Create and error check the topology information.
     */
    nedges = index[nnodes - 1];
    topo = (int *) malloc((unsigned) (nnodes + nedges) * sizeof(int));
    if (topo == 0) {
        printf ("Out of resources\n");
        return MPI_ERR_OUT_OF_RESOURCE;
    }

    for (i = 0, p = topo; i < nnodes; ++i, ++p) {
        *p = *index++;
    }

    for (i = 0; i < nedges; ++i, ++p) {
         *p = *edges++;
         if (*p < 0 || *p >= nnodes) {
            free((char *) topo);
            return MPI_ERR_TOPOLOGY;
         }
    }
    /*
     * Create the group for the new communicator.
     */
    err = lam_comm_size (comm_old, &size);
    if (err != MPI_SUCCESS) {
        free((char *) topo);
        return err;
    }

    if (nnodes > size) {
        free((char *) topo);
        return MPI_ERR_ARG;
    }

    if (nnodes == size) {
        err = lam_comm_group (comm_old, &newgroup);
    } else {
        range[0][0] = 0;
        range[0][1] = nnodes - 1;
        range[0][2] = 1;
        err = lam_group_range_incl(comm_old->c_group, 1, range, &newgroup);
    }
    if (err != MPI_SUCCESS) {
        free((char *) topo);
        return err;
    }
    /*
     * Create the new communicator.
     */
    err = lam_comm_create (comm_old, newgroup, comm_graph);
    if (err != MPI_SUCCESS) {
         free((char *) topo);
         lam_group_free (&newgroup);
         return err;
    }
    /*
     * Set the communicator topology information.
     */
    if (*comm_graph != MPI_COMM_NULL) {
        (*comm_graph)->c_topo_type = MPI_GRAPH;
        (*comm_graph)->c_topo_nprocs = nnodes;
        (*comm_graph)->c_topo_nedges = nedges;
        (*comm_graph)->c_topo_index = topo;
        (*comm_graph)->c_topo_edges = topo + nnodes;
     }

    err = lam_group_free (&newgroup);
    if (err != MPI_SUCCESS) {
        return err;
    }

    return(MPI_SUCCESS);
}