/* lab01Starter.c 
 *
 * Send an integer process 0 to all other processes
*/
#include <stdio.h>
#include <string.h>
#include <mpi.h>

int main(int argc, char* argv[]) {
    int         my_rank;       /* rank of process      */
    int         size;           /* number of processes  */
    int         source;        /* rank of sender       */
    int         dest;          /* rank of receiver     */
    int         tag = 0;       /* tag for messages     */
    double      pi = 3.14159;
    int         len;
    char        name[100];     // Processor name
    char        message[100];  
    int         i;
    double      start_time, 
                end_time;    
    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, &size);
    
    MPI_Get_processor_name(name, &len);

    if (my_rank == 0) {
         start_time = MPI_Wtime();
	 
	 for(i=1; i < size; i++)
	 {
	     printf("Process 0 sending %f to process %d\n", pi, i);
   	     MPI_Send(&pi, 1, MPI_DOUBLE, i, tag, MPI_COMM_WORLD);
         }
   	 end_time = MPI_Wtime();
	 
	 for(i = 1; i < size; i++)
	 {
	     MPI_Recv(message, 100, MPI_CHAR, i, tag, MPI_COMM_WORLD, &status);
	     printf("%s\n", message);
	 }
  	 printf("Total time for sending/recieving data: %f\n",
	                end_time - start_time);

    } 
    else { //Process other than root
	 MPI_Recv(&pi, 1, MPI_DOUBLE, 0, tag, MPI_COMM_WORLD, &status);
         sprintf(message, 
	     "Process %d: received %f on machine %s", my_rank, pi, name);
         MPI_Send(message, strlen(message)+1, MPI_CHAR, 0, tag,
                	    MPI_COMM_WORLD);

    }
 
    /* Shut down MPI */
    MPI_Finalize();
    
    return 0;
} /* main */

/*

cc lab01Starter.c

mpirun -np 4 a.out
Process 0 sending 3.141590 to process 1
Process 0 sending 3.141590 to process 2
Process 0 sending 3.141590 to process 3
Process 1: received 3.141590 on machine sn3313
Process 2: received 3.141590 on machine sn3313
Process 3: received 3.141590 on machine sn3313
Total time for sending/recieving data: 0.008137


*/