#include <mpi.h>

#include <stdio.h>

#define DEBUG

#include <mpi_samples.h>

static void comms(int _) {

int rank, world;

MPI_Comm local_comm, inter_comm, intra_comm;

MPI_Init(NULL, NULL);

MPI_Comm_rank(MPI_COMM_WORLD, &rank);

MPI_Comm_size(MPI_COMM_WORLD, &world);

int color = rank % 2;

// (MPI_Comm comm, int color, int key, MPI_Comm * newcomm)

MPI_Comm_split(MPI_COMM_WORLD, color, rank, &local_comm);

int local_rank, local;

MPI_Comm_rank(local_comm, &local_rank);

MPI_Comm_size(local_comm, &local);

LOG_WITH_RANK("local: %d \n", local_rank);

if (!color) {

MPI_Intercomm_create(local_comm, 0, MPI_COMM_WORLD, 1, 0, &inter_comm);

int x = 3;

MPI_Send(&x, 1, MPI_INT, local_rank, 0, inter_comm);

LOG_WITH_RANK("local: %d sent message \n", local_rank);

} else {

MPI_Intercomm_create(local_comm, 0, MPI_COMM_WORLD, 0, 0, &inter_comm);

int y = 0;

LOG_WITH_RANK("local: %d will wait for message \n", local_rank);

MPI_Recv(&y, 1, MPI_INT, local_rank, 0, inter_comm, MPI_STATUS_IGNORE);

LOG_WITH_RANK("local: %d got message \n", local_rank);

}

MPI_Intercomm_merge(inter_comm, color, &intra_comm);

int intra_rank, intra_size;

MPI_Comm_rank(intra_comm, &intra_rank);

MPI_Comm_size(intra_comm, &intra_size);

LOG_WITH_RANK("local: %d intra: %d\n", local_rank, intra_rank);

MPI_Comm_free(&local_comm);

MPI_Comm_free(&inter_comm);

MPI_Comm_free(&intra_comm);

MPI_Finalize();

}

SAMPLE(comms, 0)