使用MPI和C ++发送静态内存2D阵列

Question

I am having some trouble sending arrays using MPI. I currently have an array called positions of static memory. I gradually fill the array in a recursive manner. Eventually, I send the array to slave processors to complete the filling.

const int SIZE = 8;
const int DEPTH = 3 ;

void recursion(int column, int positions[SIZE], int rank, int numtasks) {
  //other code
  positions[DEPTH] = row;
  MPI_Send(&positions, SIZE, MPI_INT, r, 1, MPI::COMM_WORLD) ;
  //other code }

int main() {
  int positions[SIZE];
  MPI::Init();
  rank = MPI::COMM_WORLD.Get_rank();
  numtasks = MPI::COMM_WORLD.Get_size();
  char name[MPI::MAX_PROCESSOR_NAME];
  memset(name,0,MPI::MAX_PROCESSOR_NAME);
  MPI::Get_processor_name(name,len);
  memset(name+len,0,MPI::MAX_PROCESSOR_NAME-len);
  if(rank == MASTER) {
    recursion(0, positions, rank, numtasks); }
  if(rank != MASTER) {
  MPI_Recv(&positions, SIZE, MPI_INT, 0, MPI::ANY_TAG, MPI::COMM_WORLD, &stat);

Using the cout function, I managed to discover that the positions array before sending is :

0 2 4 0 1055625616 32621 4252832 0 

The numbers after the second 0 are array spots that I have not filled yet. But the positions array after recv is:

-196000928 32767 -196001336 3 -1769860728 54 1047301632 32621 

Even when I change the numbers on the array on the Master processor, the slave always receives the same array.

Can anyone tell me where I am going wrong, and how to fix these arrays?

Answer 1

The error is in the line MPI_Send(&positions, SIZE, MPI_INT, r, 1, MPI::COMM_WORLD); . You should not use &positions but positions instead. positions type is int * and so &positions type is int ** and you really are just sending garbage in this case instead of real array.