anel.c

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

int main(int argc, char* argv[]) {
	MPI_Init(NULL, NULL);
	int rank;
	MPI_Comm_rank(MPI_COMM_WORLD, &rank);
	int size;
	MPI_Comm_size(MPI_COMM_WORLD, &size);
	int token;
	if (rank != 0) {
		MPI_Recv(&token, 1, MPI_INT, rank - 1, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
		printf("P%d recebeu token %d de P%d\n", rank, token, rank - 1);
	} else {
		token = -1;
	}
	MPI_Send(&token, 1, MPI_INT, (rank + 1) % size, 0, MPI_COMM_WORLD);
	if (rank == 0) {
		MPI_Recv(&token, 1, MPI_INT, size - 1, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
		printf("P%d recebeu token %d de P%d\n", rank, token, size - 1);
	}
	MPI_Finalize();
}

// mpicc -o anel anel.c
// mpirun -n 2 ./anel