two-process ping-pong -- send from 0 to 1 and send back * from 1 to 0

/* ping_pong.c -- two-process ping-pong -- send from 0 to 1 and send back
* from 1 to 0
*
* Input: none
* Output: time elapsed for each ping-pong
*
* Notes:
* 1. Size of message is MAX_ORDER floats.
* 2. Number of ping-pongs is MAX.
*
* See Chap 12, pp. 267 & ff. in PPMPI.
*/

#include
#include "mpi.h"

#define MAX_ORDER 100
#define MAX 2

main(int argc, char* argv[]) {
int p;
int my_rank;
int test;
int min_size = 0;
int max_size = 16;
int incr = 8;
float x[MAX_ORDER];
int size;
int pass;
MPI_Status status;
int i;
double wtime_overhead;
double start, finish;
double raw_time;
MPI_Comm comm;

MPI_Init(&argc, &argv);
MPI_Comm_size(MPI_COMM_WORLD, &p);
MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
MPI_Comm_dup(MPI_COMM_WORLD, &comm);

wtime_overhead = 0.0;
for (i = 0; i < 100; i++) {
start = MPI_Wtime();
finish = MPI_Wtime();
wtime_overhead = wtime_overhead + (start - finish);
}
wtime_overhead = wtime_overhead/100.0;

if (my_rank == 0) {
for (test = 0, size = min_size;
size <= max_size; size = size + incr, test++) {
for (pass = 0; pass < MAX; pass++) {
MPI_Barrier(comm);
start = MPI_Wtime();
MPI_Send(x, size, MPI_FLOAT, 1, 0, comm);
MPI_Recv(x, size, MPI_FLOAT, 1, 0, comm,
&status);
finish = MPI_Wtime();
raw_time = finish - start - wtime_overhead;
printf("%d %f\n", size, raw_time);
}
}
} else { /* my_rank == 1 */
for (test = 0, size = min_size; size <= max_size;
size = size + incr, test++) {
for (pass = 0; pass < MAX; pass++) {
MPI_Barrier(comm);
MPI_Recv(x, size, MPI_FLOAT, 0, 0, comm,
&status);
MPI_Send(x, size, MPI_FLOAT, 0, 0, comm);
}
}
}


MPI_Finalize();
} /* main */