1 /* A simple example pingpong pogram to test MPI_Send and MPI_Recv */
8 main(int argc, char *argv[])
10 const int tag1 = 42, tag2= 43; /* Message tag */
18 err = MPI_Init(&argc, &argv); /* Initialize MPI */
19 if (err != MPI_SUCCESS) {
20 printf("MPI initialization failed!\n");
23 err = MPI_Comm_size(MPI_COMM_WORLD, &size); /* Get nr of tasks */
24 err = MPI_Comm_rank(MPI_COMM_WORLD, &rank); /* Get id of this process */
26 printf("run this program with exactly 2 processes (-np 2)\n");
31 printf("\n *** Ping-pong test (MPI_Send/MPI_Recv) ***\n\n");
34 /* start pingpong tests between several pairs */
35 for (pivot=0; pivot<size-1; pivot++) {
38 printf("\n== pivot=%d : pingpong [%d] <--> [%d]\n",pivot,pivot,pivot+1);
41 printf("[%d] About to send 1st message '%d' to process [%d] \n", rank,msg, dst);
42 err = MPI_Send(&msg, 1, MPI_INT, dst, tag1, MPI_COMM_WORLD);
44 err = MPI_Recv(&msg, 1, MPI_INT, dst, tag2, MPI_COMM_WORLD, &status); /* Receive a message */
45 printf("[%d] Received relpy message '%d' from process [%d] \n", rank,msg, dst);
48 if ((pivot+1) == rank) {
50 err = MPI_Recv(&msg, 1, MPI_INT, src, tag1, MPI_COMM_WORLD, &status); /* Receive a message */
51 printf("[%d] Received 1st message '%d' from process [%d] \n", rank,msg, src);
53 printf("[%d] increment message's value to '%d'\n", rank,msg);
54 printf("[%d] About to send back message '%d' to process [%d] \n", rank,msg, src);
55 err = MPI_Send(&msg, 1, MPI_INT, src, tag2, MPI_COMM_WORLD);
58 err = MPI_Finalize(); /* Terminate MPI */