问如何知道MPI请求的接收方和发送方

EN

#include <boost/mpi.hpp>
#include <iostream>
#include <string>
#include <boost/serialization/string.hpp>
namespace mpi = boost::mpi;

int main()
{
    mpi::environment env;
    mpi::communicator world;

    if (world.rank() == 0) {
        std::string msg, out_msg = "Hello from rank 0.";
        world.send(1, 17, out_msg);
    } else {
        mpi::request req[1];
        mpi::status stat[1];
        std::string rmsg;

        req[0] = world.irecv(mpi::any_source, mpi::any_tag, rmsg);
        mpi::wait_all(req, req + 1, stat);

        std::cout << "Got " << rmsg << std::endl;
        std::cout << "From   " << stat[0].source() << std::endl;
        std::cout << "Tagged " << stat[0].tag() << std::endl;
    }

    return 0;
}