MPI Hello World 範例程式

MPI 平行程式設計入門

使用 MPI 傳遞訊息實作分散式 Hello World。

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

#define MAX_STRING 100

int main(int argc, char **argv) {
    char greeting[MAX_STRING];
    int comm_sz, my_rank;
    
    MPI_Init(&argc, &argv);
    MPI_Comm_size(MPI_COMM_WORLD, &comm_sz);
    MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
    
    if (my_rank != 0) {
        sprintf(greeting, "Greetings from process %d of %d!", my_rank, comm_sz);
        MPI_Send(greeting, strlen(greeting)+1, MPI_CHAR, 0, 0, MPI_COMM_WORLD);
    } else {
        printf("Greetings from process %d of %d!\n", my_rank, comm_sz);
        for (int q = 1; q < comm_sz; ++q) {
            MPI_Recv(greeting, MAX_STRING, MPI_CHAR, q, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
            printf("%s\n", greeting);
        }
    }
    MPI_Finalize();
    return 0;
}

編譯與執行

mpicc -o hello hello.c
mpirun -np 4 ./hello

輸出範例

Greetings from process 0 of 4!
Greetings from process 1 of 4!
Greetings from process 2 of 4!
Greetings from process 3 of 4!