MPI_Allgather分段故障无法发送到接收缓冲区

Question

我目前正在尝试编写一个非常简单的程序，但似乎无法阻止seg-faulting。这是我的计划：

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

int main ( int argc, char **argv )
{
   int my_id, num_procs;
   MPI_Init(&argc, &argv);

   MPI_Comm_rank(MPI_COMM_WORLD, &my_id);
   MPI_Comm_size(MPI_COMM_WORLD, &num_procs);

   int r1, r2;
   srand(time(NULL) * my_id);
   for(int i = 0; i < 2; i++)
   {
      if(i == 0)
      {
         r1 = rand() % 100;
      }
      else{
         r2 = rand() % 100;
      }
   }

   printf("\nProcess #%i has numbers %i and %i \n",my_id,r1,r2);
   printf("\n");

   int sendArray[2];
   //Put the nubers in sendArray
   sendArray[0] = r1;
   sendArray[1] = r2;

   int size = 2 * num_procs;
   int rbuf[size];
   for(int i = 0;i < size;i++)
   {
      rbuf[i] = 0;
   }

   //rbuf = (int *)malloc(gsize*100*sizeof(int));
   //Use MPI_Allgather
   MPI_Allgather( sendArray, 2, MPI_INT, rbuf, size,MPI_INT,MPI_COMM_WORLD ); //segfault HERE, must be using parameters incorrectly

   if(my_id == 0){
      printf("-------------------------------------\n");
   }

   //printf("\nProcess #%i has number %i in pos0\n",my_id,rbuf[0]);
   //printf("\nProcess #%i has number %i in pos1\n",my_id,rbuf[1]);
   //printf("\nProcess #%i has number %i in pos2\n",my_id,rbuf[2]);
   //printf("\nProcess #%i has number %i in pos3\n",my_id,rbuf[3]);

   MPI_Finalize();
}

这个想法非常基础。在每个进程中创建两个随机数，将它们存储在发送缓冲区中，在我的情况下 - 它是sendArray，然后调用MPI_Allgather将所有数字传播到每个进程，我试图将数字发送到接收缓冲区名为rbuf。我不确定我在这里做错了什么，但这段代码肯定是我称之为MPI_Allgather的段错误。