#include <stddef.h>
#include <mpi.h>

// Switch 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 val;
	int val0;
	if(rank==0) {val = 74;}
	if(rank==1) {val = 32;}

	// check
	printf("Process %d I have the value %d at 2\n",rank,val);

	// First switch
	if(rank==0) {
		MPI_Sendrecv ( &val , 1 , MPI_INTEGER , 1 , tag , &val0 , 1 , MPI_INTEGER , 1 , tag , MPI_COMM_WORLD , MPI_STATUS_IGNORE  );
		val = val0;
	}
	if(rank==1) {
		MPI_Sendrecv ( &val , 1 , MPI_INTEGER , 0 , tag , &val0 , 1 , MPI_INTEGER , 0 , tag , MPI_COMM_WORLD , MPI_STATUS_IGNORE  );
		val = val0;
	}

	// check
	printf("Process %d I have the value %d at 1\n",rank,val);

	// Second switch
	if(rank==0) {
		MPI_Sendrecv ( &val , 1 , MPI_INTEGER , 1 , tag , &val0 , 1 , MPI_INTEGER , 1 , tag , MPI_COMM_WORLD , MPI_STATUS_IGNORE  );
		val = val0;
	}
	if(rank==1) {
		MPI_Sendrecv ( &val , 1 , MPI_INTEGER , 0 , tag , &val0 , 1 , MPI_INTEGER , 0 , tag , MPI_COMM_WORLD , MPI_STATUS_IGNORE  );
		val = val0;
	}

	// check
	printf("Process %d I have the value %d at 2\n",rank,val);

	MPI_Finalize(); // Close MPI

	return 0;
}