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#include "mpi.h"
#include "stdio.h"
#include "stdlib.h"
#define LOOP_COUNT 10
void linear(MPI_Comm intracomm, int injectionPoint) {
int lineRank, lineSize, message;
MPI_Status status; // eventually we have to start checking this...
MPI_Comm intercomm;
MPI_Comm_rank(intracomm, &lineRank);
MPI_Comm_size(intracomm, &lineSize);
MPI_Intercomm_create(intracomm, 0, MPI_COMM_WORLD, injectionPoint, 99, &intercomm);
if (lineRank == lineSize-1) {
// Injection point.
MPI_Recv(&message, 1, MPI_INT, lineRank-1, 1, intracomm, &status);
MPI_Send(&lineRank, 1, MPI_INT, 0, 2, intercomm);
} else if (lineRank == 0) {
// Line entrance.
MPI_Send(&lineRank, 1, MPI_INT, lineRank+1, 1, intracomm);
} else {
// Rest of the line.
MPI_Recv(&message, 1, MPI_INT, lineRank-1, 1, intracomm, &status);
MPI_Send(&lineRank, 1, MPI_INT, lineRank+1, 1, intracomm);
}
MPI_Comm_free(&intercomm);
}
void loop(MPI_Comm intracomm, int injectionPoint) {
int i;
int ringRank, ringSize;
int origin, dest, message;
MPI_Status status; // eventually we have to start checking this...
MPI_Comm intercomm;
int buf[10000] = { 10 };
MPI_Comm_rank(intracomm, &ringRank);
MPI_Comm_size(intracomm, &ringSize);
MPI_Intercomm_create(intracomm, 0, MPI_COMM_WORLD, 0, 99, &intercomm);
if (ringRank == 0) {
origin = injectionPoint-1;
MPI_Recv(buf, 10, MPI_INT, origin, 2, intercomm, &status);
message = ringRank;
MPI_Send(buf, 10, MPI_INT, (ringRank + 1) % ringSize, 2, intracomm);
}
dest = (ringRank + 1) % ringSize;
origin = (ringRank + ringSize - 1) % ringSize;
for (i = 0; i < LOOP_COUNT; ++i) {
MPI_Recv(buf, 10, MPI_INT, origin, 2, intracomm, &status);
message = ringRank;
MPI_Send(buf, 10, MPI_INT, dest, 2, intracomm);
}
MPI_Comm_free(&intercomm);
}
int main(int argc, char *argv[])
{
int i, color;
int rank, nprocs, injectionPoint;
MPI_Comm intracomm;
MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
MPI_Comm_size(MPI_COMM_WORLD, &nprocs);
// Divide ranks into injection line & ring.
injectionPoint = atoi(argv[1]);
color = (rank < injectionPoint) ? 0 : 1;
MPI_Comm_split(MPI_COMM_WORLD, color, rank, &intracomm);
// First send message down the linear path, then inject it into the ring.
if (rank < injectionPoint) {
linear(intracomm, injectionPoint);
} else {
loop(intracomm, injectionPoint);
}
MPI_Comm_free(&intracomm);
MPI_Finalize();
return 0;
}
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