如何在函数中使用MPI_Bcast和MPI_Gather

Question

我是MPI的新手，并尝试学习如何在函数中使用MPI_Bcast和MPI_Gather。如果我按照以下方式不使用函数编写代码，它可以正常工作并给出正确的结果：
结束时打印结果：
localdata [0]：19，localdata [1]：19，localdata [2]：20，localdata [3]：20，localdata [4]：21，localdata [5]：21，localdata [6]：22，localdata [7]：22，

要使用4个处理器进行编译和运行，请使用以下命令：
:$ mpicc test.c -o test
:$ mpirun -np 4 test

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

int main(int argc, char** argv) {

    MPI_Init(&argc, &argv);
    int world_rank;
    MPI_Comm_rank(MPI_COMM_WORLD, &world_rank);
    int world_size;
    MPI_Comm_size(MPI_COMM_WORLD, &world_size);


    int i, total;
    int arr[20];
    int localdata[8];
    if (world_rank == 0) 
    {
        for(i=0;i<20;i++)
            arr[i]=i;       

        MPI_Bcast( &arr, 20, MPI_INT, 0, MPI_COMM_WORLD );

        printf("\n\n* At Process %d received\n", world_rank);   
        for(i=0;i<20;i++)
        {
            printf("ARR[%d]:%d, ",i, arr[i]);
            total=arr[i]+world_rank;
        }
        printf("\n");
        localdata[0]=total;
        localdata[1]=total;

        MPI_Gather(localdata, 2, MPI_INT, localdata, 2, MPI_INT,0, MPI_COMM_WORLD);

        printf("\n\nPrinting Result at the end:\n");
        for(i=0;i<8;i++)
        {
            printf("localdata[%d]:%d, ",i, localdata[i]);
        }
        printf("\n\n");
    } 
    else
    {   
        MPI_Bcast( &arr, 20, MPI_INT, 0, MPI_COMM_WORLD );

        printf("\n\n* At Process %d received\n", world_rank);   
        for(i=0;i<20;i++)
        {
            printf("ARR[%d]:%d, ",i, arr[i]);
            total=arr[i]+world_rank;
        }
        printf("\n");
        localdata[0]=total;
        localdata[1]=total;

        MPI_Gather(localdata, 2, MPI_INT, localdata, 2, MPI_INT,0, MPI_COMM_WORLD);
    }


    MPI_Finalize();
    return 0;
}

当我将这些代码放在一个名为function_cal的函数中时，它会给我以下错误：
*** Process received signal ***
Signal: Segmentation fault (11)
Signal code: Address not mapped (1)
Failing at address: 0x7fffdeb18040
以下是将MPI_Bcast和MPI_Gather放入函数后的代码。任何帮助将不胜感激。

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

void function_cal(int arr[20], int localdata[8], int world_rank)
{
    int i, total;

    MPI_Bcast( &arr, 20, MPI_INT, 0, MPI_COMM_WORLD );

    printf("\n\n* At Process %d received\n", world_rank);   
    for(i=0;i<20;i++)
    {
        printf("ARR[%d]:%d, ",i, arr[i]);
        total=arr[i]+world_rank;
    }
    printf("\n");
    localdata[0]=total;
    localdata[1]=total;

    MPI_Gather(localdata, 2, MPI_INT, localdata, 2, MPI_INT,0, MPI_COMM_WORLD);     
}

int main(int argc, char** argv) {

    MPI_Init(&argc, &argv);
    int world_rank;
    MPI_Comm_rank(MPI_COMM_WORLD, &world_rank);
    int world_size;
    MPI_Comm_size(MPI_COMM_WORLD, &world_size);


    int i;
    int arr[20];
    int localdata[8];
    if (world_rank == 0) 
    {
        for(i=0;i<20;i++)
            arr[i]=i;       

        function_cal(arr, localdata, world_rank);

        printf("\n\nPrinting Result at the end:\n");
        for(i=0;i<8;i++)
        {
            printf("localdata[%d]:%d, ",i, localdata[i]);
        }
        printf("\n\n");
    } 
    else
    {   
        function_cal(arr, localdata, world_rank);
    }


    MPI_Finalize();
    return 0;
}