mpi第五站 - 自定义mpi中的广播

#include 
#include 
#include 
#include 
#include 
using namespace std;

void my_bcast(void* data, int count, MPI_Datatype datatype, int root,
              MPI_Comm communicator) {
    int world_rank;
    MPI_Comm_rank(communicator, &world_rank);
    int world_size;
    MPI_Comm_size(communicator, &world_size);

    if (world_rank == root) {
        // If we are the root process, send our data to everyone
        int i;
        for (i = 0; i < world_size; i++) {
            if (i != world_rank) {
                MPI_Send(data, count, datatype, i, 0, communicator);
            }
        }
        cout << "Process " << world_rank << " broadcasting data " << data << endl;
    } else {
        // If we are a receiver process, receive the data from the root
        MPI_Recv(data, count, datatype, root, 0, communicator,
                 MPI_STATUS_IGNORE);
        cout << "Process " << world_rank << " received data " << data << " from root process "  << endl;
    }
}

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

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

    int data = 100;
    my_bcast(&data, 1, MPI_INT, 0, MPI_COMM_WORLD);

    MPI_Finalize();
    return 0;
}

这个程序很容易理解

mpicxx main.cpp -o main.out

mpirun -np 5 ./main.out 

输出为：

Process 0 broadcasting data 0x7fff5225c7c4
Process 1 received data 0x7ffe888c6804 from root process 
Process 2 received data 0x7ffddffaa6b4 from root process 
Process 3 received data 0x7ffc4ab036d4 from root process 
Process 4 received data 0x7ffd4bf7fa34 from root process