c - MPI - 更改启动的进程数

Question

我从 MPI 开始。我想尝试一个经典的“Hello, world”程序，它也会打印每个进程的编号和一些其他信息。我的程序可以运行，但我对 mpiexec 的实际运行方式不太了解。问题是，当我指定进程数时，有时它们不会启动。例如，我使用这个命令:

mpiexec -np 4 ./hello

但只有 2 或 3 个进程启动，而不是 4 个。启动进程的数量发生变化，所以我真的很困惑。问题出在我的电脑上(我只有双核)还是这是正常现象？

---

你好.c:

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

int main(){
    MPI_Init(NULL, NULL);

    // Number of processes
    int world_size;
    MPI_Comm_size( MPI_COMM_WORLD, &world_size );

    // Number of current process
    int process_id;
    MPI_Comm_rank( MPI_COMM_WORLD, &process_id );

    // Processor name
    char processor_name[ MPI_MAX_PROCESSOR_NAME ];
    int name_len;
    MPI_Get_processor_name( processor_name, &name_len );

    printf("Hello! - sent from process %d running on processor %s.\n\
        Number of processes is %d.\n\
        Length of proc name is %d.\n\
        ***********************\n",
        process_id, processor_name, world_size, name_len);

    return 0;
}

Answer 1

我的错误很愚蠢。我只是在return 之前缺少MPI_Finalize() 函数。

---

正确代码:

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

int main(){
    MPI_Init(NULL, NULL);

    // Number of processes
    int world_size;
    MPI_Comm_size( MPI_COMM_WORLD, &world_size );

    // Number of current process
    int process_id;
    MPI_Comm_rank( MPI_COMM_WORLD, &process_id );

    // Processor name
    char processor_name[ MPI_MAX_PROCESSOR_NAME ];
    int name_len;
    MPI_Get_processor_name( processor_name, &name_len );

    printf("Hello! - sent from process %d running on processor %s.\n\
        Number of processes is %d.\n\
        Length of proc name is %d.\n\
        ***********************\n",
        process_id, processor_name, world_size, name_len);

    MPI_Finalize();
    return 0;
}