Greetings program in MPI

/* greetings.c -- greetings program
*
* Send a message from all processes with rank != 0 to process 0.
* Process 0 prints the messages received.
*
* Input: none.
* Output: contents of messages received by process 0.
*
* See Chapter 3, pp. 41 & ff in PPMPI.
*/
#include
#include
#include "mpi.h"

main(int argc, char* argv[]) {
int my_rank; /* rank of process */
int p; /* number of processes */
int source; /* rank of sender */
int dest; /* rank of receiver */
int tag = 0; /* tag for messages */
char message[100]; /* storage for message */
MPI_Status status; /* return status for */
/* receive */

/* Start up MPI */
MPI_Init(&argc, &argv);

/* Find out process rank */
MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);

/* Find out number of processes */
MPI_Comm_size(MPI_COMM_WORLD, &p);

if (my_rank != 0) {
/* Create message */
sprintf(message, "Greetings from process %d!",
my_rank);
dest = 0;
/* Use strlen+1 so that '\0' gets transmitted */
MPI_Send(message, strlen(message)+1, MPI_CHAR,
dest, tag, MPI_COMM_WORLD);
} else { /* my_rank == 0 */
for (source = 1; source < p; source++) {
MPI_Recv(message, 100, MPI_CHAR, source, tag,
MPI_COMM_WORLD, &status);
printf("%s\n", message);
}
}

/* Shut down MPI */
MPI_Finalize();
} /* main */