使用MPI_Sendrecv实现MPI_Allgather

 1 int main(int argc, char *argv[])
 2 {
 3     int rank, size;
 4     MPI_Status status;
 5     int S[20], R[20];
 6     int i;
 7 
 8     MPI_Init(&argc, &argv);
 9     MPI_Comm_rank(MPI_COMM_WORLD, &rank);
10     MPI_Comm_size(MPI_COMM_WORLD, &size);
11 
12     for (i = 0; i<20; i++)
13     {
14         S[i] = (rank + 1)*(i + 1);
15         R[i] = 0;
16     }
17     for (i = 0; i<size; i++){
18             MPI_Sendrecv(S, 4, MPI_INT, i, 123, &R[i*4], 4, MPI_INT, i, 123, MPI_COMM_WORLD, &status);
19     }
20 
21     MPI_Barrier(MPI_COMM_WORLD);
22     cout << "the data on proc " << rank << " is " ;
23     for (int i = 0; i < 20; i++) {
24         cout << R[i] << " ";
25     }
26     MPI_Barrier(MPI_COMM_WORLD);
27     MPI_Finalize();
28     return 1;
29 }