MPI 忽略 cin

Question

我写了下面的代码。它打算从控制台读取数字（到 data 变量）并将其发送到所有其他进程。但是 cin >> data 就被忽略了。

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

using namespace std;

int main(int argc, char* argv[]) {
  int rank, n;
  int i;
  MPI_Status status;
  MPI_Init(&argc, &argv);
  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
  MPI_Comm_size(MPI_COMM_WORLD, &n);
  int data = 322; // magic number 322 just for initialisation
  if (rank == 0)
  {
    cout << "From which process do you want to transfer data?" << endl;
    cin >> i;
    MPI_Send(&i, 1, MPI_INT, rank+1, 0, MPI_COMM_WORLD);
  }
  else
  {
    MPI_Recv(&i, 1, MPI_INT, rank-1, 0, MPI_COMM_WORLD, &status);

    if (rank < n - 1)
      MPI_Send(&i, 1, MPI_INT, rank+1, 0, MPI_COMM_WORLD);

    if(rank == i) {
      cout << "Process #"<< rank <<" waiting data to send. Please enter." << endl;
      cin >> data; //doesn't work

      for(int j = 0; j < n; j++)
        if(j != i)
          MPI_Send(&data, 1, MPI_INT, j, 7, MPI_COMM_WORLD);
    }
    else {
        int pata;
        MPI_Recv(&pata, 1, MPI_INT, i, 7, MPI_COMM_WORLD, &status);
        cout << "Process "<< rank <<" received data (" << pata << ") from process #" << i << endl;
    }
  }
  MPI_Finalize( );
}

控制台看起来像：

From which process do you want to transfer data?
2
Process #2 waiting data to send. Please enter.
Process 1 received data (322) from process #2
Process 3 received data (322) from process #2

我已经尝试过 cin.clear() 和 cin.ignore()。

Answer 1

stdin 通常从 mpirun/mpiexec 重定向到排名 0.

可能有选项（取决于您使用的是哪种实现运行）重定向到您选择的等级，and/or 重定向到所有等级。

最重要的是，我不认为你正在尝试的是可以实现的。

MPI 忽略 cin

MPI ignores cin

c++

mpi

cin