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/*
* Copyright (C) by Argonne National Laboratory
* See COPYRIGHT in top-level directory
*/
/** PGROUP Creation (Intercommunicator Method)
* James Dinan <dinan@mcs.anl.gov>
* May, 2011
*
* In this test, processes create an intracommunicator and creation is
* collective only on the members of the new communicator, not on the parent
* communicator. This is accomplished by building up and merging
* intercommunicators starting with MPI_COMM_SELF for each process involved.
*/
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <mpi.h>
#include "mpitest.h"
#define INTERCOMM_TAG 0
const int verbose = 0;
void pgroup_create(int grp_size, int *pid_list, MPI_Comm * group_out);
void pgroup_free(MPI_Comm * group);
/** Free the group
*/
void pgroup_free(MPI_Comm * group)
{
/* Note: It's ok to compare predefined handles */
if (*group == MPI_COMM_NULL || *group == MPI_COMM_SELF)
return;
MPI_Comm_free((MPI_Comm *) group);
}
/* Create a processor group containing the processes in pid_list.
*
* NOTE: pid_list list must be identical and sorted on all processes
*/
void pgroup_create(int grp_size, int *pid_list, MPI_Comm * group_out)
{
int i, grp_me, me, nproc, merge_size;
MPI_Comm pgroup, inter_pgroup;
MPI_Comm_rank(MPI_COMM_WORLD, &me);
MPI_Comm_size(MPI_COMM_WORLD, &nproc);
/* CASE: Group size 0 */
if (grp_size == 0) {
*group_out = MPI_COMM_NULL;
return;
}
/* CASE: Group size 1 */
else if (grp_size == 1 && pid_list[0] == me) {
*group_out = MPI_COMM_SELF;
return;
}
/* CHECK: If I'm not a member, return COMM_NULL */
grp_me = -1;
for (i = 0; i < grp_size; i++) {
if (pid_list[i] == me) {
grp_me = i;
break;
}
}
if (grp_me < 0) {
*group_out = MPI_COMM_NULL;
return;
}
pgroup = MPI_COMM_SELF;
for (merge_size = 1; merge_size < grp_size; merge_size *= 2) {
int gid = grp_me / merge_size;
MPI_Comm pgroup_old = pgroup;
if (gid % 2 == 0) {
/* Check if right partner doesn't exist */
if ((gid + 1) * merge_size >= grp_size)
continue;
MPI_Intercomm_create(pgroup, 0, MPI_COMM_WORLD, pid_list[(gid + 1) * merge_size],
INTERCOMM_TAG, &inter_pgroup);
MPI_Intercomm_merge(inter_pgroup, 0 /* LOW */ , &pgroup);
} else {
MPI_Intercomm_create(pgroup, 0, MPI_COMM_WORLD, pid_list[(gid - 1) * merge_size],
INTERCOMM_TAG, &inter_pgroup);
MPI_Intercomm_merge(inter_pgroup, 1 /* HIGH */ , &pgroup);
}
MPI_Comm_free(&inter_pgroup);
if (pgroup_old != MPI_COMM_SELF)
MPI_Comm_free(&pgroup_old);
}
*group_out = pgroup;
}
int main(int argc, char **argv)
{
int me, nproc, i;
int gsize, *glist;
MPI_Comm group;
MTest_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD, &me);
MPI_Comm_size(MPI_COMM_WORLD, &nproc);
gsize = nproc / 2 + (nproc % 2);
glist = malloc(gsize * sizeof(int));
for (i = 0; i < nproc; i += 2)
glist[i / 2] = i;
MPI_Barrier(MPI_COMM_WORLD);
if (me % 2 == 0) {
int gme, gnproc;
double t1, t2;
t1 = MPI_Wtime();
pgroup_create(gsize, glist, &group);
t2 = MPI_Wtime();
MPI_Barrier(group);
MPI_Comm_rank(group, &gme);
MPI_Comm_size(group, &gnproc);
if (verbose)
printf("[%d] Group rank = %d, size = %d time = %f sec\n", me, gme, gnproc, t2 - t1);
pgroup_free(&group);
}
free(glist);
MTest_Finalize(0);
return MTestReturnValue(0);
}
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