/* pingpong.c -- pingpong 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 <stdio.h>
#include <string.h>
#include "mpi.h"

int main(int argc, char* argv[]) {
    int         my_rank;       /* rank of process      */
    int         numprocesses;  /* number of processes  */
    int         tag = 0;       /* tag for messages     */
    int 	x = 0, count=0;
    int		startTime = 0;
    int		endTime = 0;
    int         numTimes;
    char        message[100];  /* storage for message  */

    MPI_Status  status;        /* return status for    */
                               /* receive              */
	
	    /* Start up MPI */
    MPI_Init(&argc, &argv);

    if (argc < 2)
	numTimes = 100;
    else
	numTimes = atoi(argv[1]);
		
     printf("Numtimes=%d\n",numTimes);
     
     strcpy(message, "Hello World");
	
    /* Find out process rank  */
    MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);

    /* Find out number of processes */
    MPI_Comm_size(MPI_COMM_WORLD, &numprocesses);
	
	
	
    if (my_rank == 0)
    {
	startTime = MPI_Wtime();
	printf("Start time=%d\n", startTime);
	
	for(x=0; x < numTimes; x++)
	{
	    count++;
//	    printf("%d Sending %d...", my_rank, count);
	    MPI_Send(&count, 1, MPI_INT, 1, tag, MPI_COMM_WORLD);
	    MPI_Send(message, strlen(message)+1, MPI_CHAR, 1, tag, 
	                MPI_COMM_WORLD);
	    MPI_Recv(&count, 1, MPI_INT, 1, tag, MPI_COMM_WORLD, &status); 
	    MPI_Recv(message, strlen(message)+1, MPI_CHAR, 1, tag, 
	                MPI_COMM_WORLD, &status); 
//	    printf("%d Receiving %d\n", my_rank, count);
	}
	
	endTime = MPI_Wtime();
	printf("Endtime=%d, totaltime=%d\n", endTime, endTime-startTime);
		
      } else if (my_rank == 1)
	{
  	    for(x=0; x < numTimes; x++)
	    {
       	        MPI_Recv(&count, 1, MPI_INT, 0, tag, MPI_COMM_WORLD, &status); 
	        MPI_Recv(message, strlen(message)+1, MPI_CHAR, 0, 
		          tag, MPI_COMM_WORLD, &status);
//	        printf("%d receiving %s, %d\n", my_rank, message, count);
		count++;
  	        MPI_Send(&count, 1, MPI_INT, 0, tag, MPI_COMM_WORLD);
	        MPI_Send(message, strlen(message)+1, MPI_CHAR, 0, 
		          tag, MPI_COMM_WORLD);
//	        printf("%d sending %s, %d\n", my_rank, message, count);
	    }
	}
	
 
        MPI_Finalize();
        return 0;
}