program ping_pong
	use mpi
	implicit none
	integer :: rank, nb_mpi_processes, ierror, tag, statu(MPI_STATUS_SIZE), n, ball
	integer :: niter = 6
 
	! Ping Pong program
 
	tag = 7777
 
	call MPI_INIT( ierror )
	call MPI_COMM_SIZE( MPI_COMM_WORLD , nb_mpi_processes , ierror )
	call MPI_COMM_RANK( MPI_COMM_WORLD , rank , ierror )
 
	if(nb_mpi_processes /= 2) stop 'This program is design to be run with 2 processes only'
 
	ball = 0
	do n=1,niter
 
		if(rank==0) then
			call MPI_SEND ( ball , 1 , MPI_INTEGER , 1 , tag , MPI_COMM_WORLD , MPI_STATUS_IGNORE , ierror ) ! 0 send ball to 1, and wait for transfer to be finished
			call MPI_RECV ( ball , 1 , MPI_INTEGER , 1 , tag , MPI_COMM_WORLD , MPI_STATUS_IGNORE , ierror ) ! 0 receive ball from 1, and wait for transfer to be finished
			ball = ball + 2
		end if
 
		if(rank==1) then
			call MPI_RECV ( ball , 1 , MPI_INTEGER , 0 , tag , MPI_COMM_WORLD , MPI_STATUS_IGNORE , ierror )
			ball = ball + 1
			call MPI_SEND ( ball , 1 , MPI_INTEGER , 0 , tag , MPI_COMM_WORLD , MPI_STATUS_IGNORE , ierror )
		end if
 
		print*, 'Process',rank,'iter',n,'ball value is :',ball
 
		call MPI_BARRIER(MPI_COMM_WORLD,ierror) ! A barrier. processes stop here, and can pass it only if ALL processes are here. Useful for debug, can impact performances
 
	end do
 
	call MPI_FINALIZE ( ierror ) ! Close MPI
 
end program ping_pong

#include <stddef.h>
#include <mpi.h>
 
// Ping Pong program
 
int main(int argc, char** argv) 
{
	MPI_Init(NULL, NULL);
	int nb_mpi_processes;
	MPI_Comm_size(MPI_COMM_WORLD, &nb_mpi_processes);
	int rank;
	MPI_Comm_rank(MPI_COMM_WORLD, &rank);
 
	if(nb_mpi_processes != 2) { printf("This program is design to be run with 2 processes only"); return 0;}
 
	int tag = 7777;
	int ball = 0;
	int n;
	int niter = 6;
	for (n=1;n<=niter;n++) 
	{
		if(rank==0) {
			MPI_Send ( &ball , 1 , MPI_INTEGER , 1 , tag , MPI_COMM_WORLD ); // 0 send ball to 1, and wait for transfer to be finished
			MPI_Recv ( &ball , 1 , MPI_INTEGER , 1 , tag , MPI_COMM_WORLD, MPI_STATUS_IGNORE); // 0 receive ball from 1, and wait for transfer to be finished
			ball = ball + 2;
    	}
 
		if(rank==1) {
			MPI_Recv ( &ball , 1 , MPI_INTEGER , 0 , tag , MPI_COMM_WORLD, MPI_STATUS_IGNORE );
			ball = ball + 1;
			MPI_Send ( &ball , 1 , MPI_INTEGER , 0 , tag , MPI_COMM_WORLD );
		}
 
		printf("Process %d iter %d ball value is : %d\n",rank,n,ball);
 
		MPI_Barrier(MPI_COMM_WORLD); // A barrier. processes stop here, and can pass it only if ALL processes are here. Useful for debug, can impact performances
	}
 
	MPI_Finalize(); // Close MPI
 
	return 0;
}