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#include "mpi.h"
#include <unistd.h>
#define INLOOP 0
#define FINISH 1
int main(int argc, char **argv) {
MPI_Init(&argc, &argv);
int rank, size;
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
MPI_Comm_size(MPI_COMM_WORLD, &size);
int counter = 0;
int COUNT = 1;
int SOURCE = (rank + size - 1) % size;
int TARGET = (rank + 1) % size;
int TAG = 0;
if (rank == 0) { // initialize loop
MPI_Send(&counter, COUNT, MPI_INT, TARGET, TAG, MPI_COMM_WORLD);
}
while (true) {
MPI_Status status;
MPI_Recv(&counter, COUNT, MPI_INT, SOURCE, TAG, MPI_COMM_WORLD, &status);
if (status.MPI_TAG == INLOOP) {
printf("rank %d: counter: %d\n", rank, counter++);
usleep(500000);
}
if (TAG == INLOOP) {
MPI_Send(&counter, COUNT, MPI_INT, TARGET, TAG, MPI_COMM_WORLD);
}
}
MPI_Finalize();
return 0;
}