Solution 2

Solution 2

C

#include <stdlib.h>
#include <stdio.h>
#include <mpi.h>

#define NDATA 10000

int main(int argc, char* argv[]){

    int me, nprocs, i = 0;
    MPI_Status status;

    float a[NDATA];
    float b[NDATA];

    MPI_Init(&argc, &argv);
    MPI_Comm_size(MPI_COMM_WORLD, &nprocs);
    MPI_Comm_rank(MPI_COMM_WORLD, &me);

    /* Initialize data */
    for(i=0;i<NDATA;++i){
    a[i] = me;
    }
    /* Protect against the use with a number of processes != 2 */
    if(nprocs!=2 && me==0){
    printf("\n\tThis program must run on 2 processors");
    return 0;
    }
    /* Send and Receive data */
    if(me==0){
      MPI_Send(a, NDATA, MPI_REAL, 1, 0, MPI_COMM_WORLD);
      MPI_Recv(b, NDATA, MPI_REAL, 1, 0, MPI_COMM_WORLD, &status);
    }
    else{
      MPI_Recv(b, NDATA, MPI_REAL, 0, 0, MPI_COMM_WORLD, &status);
      MPI_Send(a, NDATA, MPI_REAL, 0, 0, MPI_COMM_WORLD);
    }

    printf("\tI am task %d and I have received b(0) = %1.2f \n", me, b[0]);

    MPI_Finalize();
    return 0;
}

FORTRAN

program hello

  use mpi

  implicit none

  integer ierr, me, nprocs, errcode
  integer status(MPI_STATUS_SIZE)

  integer,parameter :: ndata = 10000
  real              :: a(ndata)
  real              :: b(ndata)

  call MPI_INIT(ierr)
  call MPI_COMM_SIZE(MPI_COMM_WORLD, nprocs, ierr)
  call MPI_COMM_RANK(MPI_COMM_WORLD, me, ierr)

  !$ Initialize data 
  a = me
  !$ Protect against the use with a number of processes != 2
  if (nprocs .ne. 2) then
     print *,"This program must run on 2 processors"
     call MPI_ABORT(MPI_COMM_WORLD, errcode, ierr)
     stop
  endif
  !$ Send and Receive data    
  if (me==0) then
     call MPI_SEND(a,ndata,MPI_REAL,1,0,MPI_COMM_WORLD,ierr)
     call MPI_RECV(b,ndata,MPI_REAL,1,0,MPI_COMM_WORLD,status,ierr)
  else
     call MPI_RECV(b,ndata,MPI_REAL,0,0,MPI_COMM_WORLD,status,ierr)
     call MPI_SEND(a,ndata,MPI_REAL,0,0,MPI_COMM_WORLD,ierr)
  endif

  print *,'I am proc ',me,' and I have received b(1) = ',b(1)
  call MPI_FINALIZE(ierr)

end program hello