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#define _GNU_SOURCE
#include "orte_config.h"
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <mpi.h>
#define NUM_CHILDREN 5
int main(int argc, char* argv[])
{
int msg;
MPI_Comm parent, children[NUM_CHILDREN];
int rank, size, i;
char hostname[OPAL_MAXHOSTNAMELEN];
pid_t pid;
char *child_argv[2] = { "", NULL };
MPI_Init(NULL, NULL);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
MPI_Comm_size(MPI_COMM_WORLD, &size);
MPI_Comm_get_parent(&parent);
/* If we get COMM_NULL back, then we're the parent */
if (MPI_COMM_NULL == parent) {
pid = getpid();
/* First, spawn all the children. Give them an argv
identifying which child they are */
for (i = 0; i < NUM_CHILDREN; ++i) {
printf("Parent [pid %ld] about to spawn child #%d\n",
(long)pid, i);
asprintf(&(child_argv[0]), "%d", i);
MPI_Comm_spawn(argv[0], child_argv, 1, MPI_INFO_NULL,
0, MPI_COMM_WORLD, &children[i],
MPI_ERRCODES_IGNORE);
printf("Parent done with spawn of child %d\n", i);
}
/* Now send each of the children a message */
if (0 == rank) {
for (i = 0; i < NUM_CHILDREN; ++i) {
printf("Parent sending message to child %d\n", i);
MPI_Send(&i, 1, MPI_INT, 0, 1, children[i]);
}
}
/* Now disconnect from each of the children */
for (i = 0; i < NUM_CHILDREN; ++i) {
printf("Parent disconnecting from child %d\n", i);
MPI_Comm_disconnect(&children[i]);
printf("Parent disconnected from child %d\n", i);
}
}
/* Otherwise, we're the child */
else {
gethostname(hostname, sizeof(hostname));
if (argc == 1) {
printf("ERROR: child did not receive exepcted argv!\n");
i = -1;
} else {
i = atoi(argv[1]);
}
pid = getpid();
printf("Hello from the child %d on host %s pid %ld\n", i, hostname, (long)pid);
if (0 == rank) {
MPI_Recv(&msg, 1, MPI_INT, 0, 1, parent, MPI_STATUS_IGNORE);
printf("Child %d received msg: %d\n", i, msg);
if (i != msg) {
printf("ERROR: Child %d got wrong message (got %d, expected %d)\n",
i, msg, i);
}
}
MPI_Comm_disconnect(&parent);
printf("Child %d disconnected\n", i);
}
MPI_Finalize();
return 0;
}
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