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ring.c
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ring.c
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#include <mpi.h>
#include <stdio.h>
#include <stdlib.h>
#define SIZE 20
#define POS 10
#define INITIAL_VALUE 10
int main(int argc, char *argv[])
{
int i, rank, size, next, prev, tag = 201;
int array_size = SIZE;
int pos = POS;
int *send_array;
int *recv_array;
MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
MPI_Comm_size(MPI_COMM_WORLD, &size);
fprintf(stderr, "Rank %d has cleared MPI_Init\n", rank);
next = (rank + 1) % size;
prev = (rank + size - 1) % size;
send_array = malloc(sizeof(int) * SIZE);
recv_array = malloc(sizeof(int) * SIZE);
for (i = 0; i < array_size; ++i) {
send_array[i] = 17;
recv_array[i] = -1;
}
if (0 == rank) {
send_array[pos] = INITIAL_VALUE;
MPI_Send(send_array, array_size, MPI_INT, next, tag, MPI_COMM_WORLD);
}
while (1) {
recv_array[pos] = -1;
MPI_Recv(recv_array, array_size, MPI_INT, prev, tag, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
send_array[pos] = recv_array[pos];
if (rank == 0) {
--send_array[pos];
}
MPI_Send(send_array, array_size, MPI_INT, next, tag, MPI_COMM_WORLD);
if (0 == send_array[pos]) {
break;
}
}
if (rank == 0) {
MPI_Recv(recv_array, array_size, MPI_INT, prev, tag, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
}
fprintf(stderr, "Rank %d has completed ring\n", rank);
MPI_Barrier(MPI_COMM_WORLD);
fprintf(stderr, "Rank %d has completed MPI_Barrier\n", rank);
MPI_Finalize();
return 0;
}