/* tags.c SJ

   An example of using tags to restrict messages
*/
   
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <mpi.h>

#define MAXP 32

#define MESSAGES 4

/* a variable needeed for call, result not used */
static MPI_Status tmpstat;

int main(int argc, char **argv)
{
  int PID,	/* process-ID */
	  P;	/* number of processes */ 

  /* own variables */

  int v1, i, m;

  /* keep these 3 calls */
  MPI_Init(&argc, &argv);
  MPI_Comm_rank(MPI_COMM_WORLD, &PID);
  MPI_Comm_size(MPI_COMM_WORLD, &P);

  /* actual code */

  if (PID == 0) {

	  /* process 0 is the master */

	  int p;

	  MPI_Status stat;

	  printf("0: receive from any process messages with tag %d\n",
			 MESSAGES);

	  for (p = 1; p < P; p++) {
		  MPI_Recv(&v1, 1, MPI_INT, MPI_ANY_SOURCE, MESSAGES,
				   MPI_COMM_WORLD, &stat);
		  printf("0: process %d returned %d with tag %d\n",
				 stat.MPI_SOURCE, v1, stat.MPI_TAG);
	  }

	  printf("0: receive from process 1 messages with any tag\n");
	  for (m = 0; m < MESSAGES-1; m++) {
		  MPI_Recv(&v1, 1, MPI_INT, 1, MPI_ANY_TAG, MPI_COMM_WORLD, &stat);
		  printf("0: process %d returned %d with tag %d\n",
				 stat.MPI_SOURCE, v1, stat.MPI_TAG);
	  }

	  printf("0: receive rest\n");

	  for (m = 0; m < (MESSAGES-1)*(P-2); m++) {
		  MPI_Recv(&v1, 1, MPI_INT, MPI_ANY_SOURCE, MPI_ANY_TAG,
				   MPI_COMM_WORLD, &stat);
		  printf("0: process %d returned %d with tag %d\n",
				 stat.MPI_SOURCE, v1, stat.MPI_TAG);
	  }

  } else {
	  /* all other processes */


	  /* an array to control progress of send requests */
	  MPI_Request req[MESSAGES+1];

	  /* an array of statuses */
	  MPI_Status stats[MESSAGES+1];

	  /* array of messages to send */
	  int rnd[MESSAGES+1];

	  srand(PID);

	  /* send MESSAGES msgs to 0 */

	  for (m = 1; m <= MESSAGES; m++) {
		  sleep(rand()%3);
		  rnd[m] = rand() % 10;
		  MPI_Isend(rnd+m, 1, MPI_INT, 0, m, MPI_COMM_WORLD, req+m);
	  }

	  /* wait until all sent */
	  MPI_Waitall(MESSAGES, req+1, stats+1);

	  sleep(2);

	  printf("%d: sent:", PID);
	  for (m = 1; m <= MESSAGES; m++) {
		  printf(" %d", rnd[m]);
	  }
	  printf("\n");
  }

  /* keep this call */
  MPI_Finalize();

  exit(0);

}