c++ - MPI:Waitany 对 ibcast 调用没有反应

Question

以下代码是主/工作模式的实现。

Ibcast 用于终止所有工作人员，因为我们不知道程序开始时问题的大小。

MPI_Waitany() 用于等待 Irecv 获取新数据和 Ibcast 终止程序。

问题是在收到来自主站的所有 MPI_Send() 后，MPI_Waitany 会阻塞。所以 MPI_Ibcast() 不会返回阻塞

if (myid == 0) { //Master
    bool test = false;
    MPI_Request mpi_request;
    for (int i = 0; i < 10; ++i) {
       //Sending I 1..10 to Worker
       MPI_Send(&i, 1, MPI_INT, 1, 10, MPI_COMM_WORLD);
       cout << "Sending: " << i <<  endl;
   }
   cout << "Bcast Worker finished" << endl;
   //Only to show even if the Bcast ist fired after worker is finished.
   sleep(10);
   //Using Ibcast for because Bcast can not Send to Ibcast in worker.
   MPI_Ibcast(&test, 1, MPI_C_BOOL, 0, MPI_COMM_WORLD, &mpi_request);

   MPI_Wait(&mpi_request, MPI_STATUS_IGNORE);
   cout << "Root Fin" << endl;

} else { //Worker
   while (true) {
       bool test = true;
       int i = 20;
       MPI_Request mpi_request[2];
       MPI_Ibcast(&test, 1, MPI_C_BOOL, 0, MPI_COMM_WORLD, &mpi_request[0]);
       MPI_Irecv(&i, 1, MPI_INT, 0, 10, MPI_COMM_WORLD, &mpi_request[1]);

       int RequestID = 0;

       //Wait passes 10 Times for Send
       //Wait can not pass after work is done.
       MPI_Waitany(2, mpi_request, &RequestID, MPI_STATUS_IGNORE);
       cout << "The \'I\' i got is: " << i <<" The Boolean is:" << test << endl;
       if (!test)
           break;
   }
}
//OUTPUT
//Sending: 0
//Sending: 1
//Sending: 2
//Sending: 3
//Sending: 4
//Sending: 5
//Sending: 6
//Sending: 7
//Sending: 8
//The 'I' i got is: 0 The Boolean is:1
//The 'I' i got is: 1 The Boolean is:1
//Sending: 9
//Bcast Worker finished
//The 'I' i got is: 2 The Boolean is:1
//Root Fin
//The 'I' i got is: 3 The Boolean is:1
//The 'I' i got is: 4 The Boolean is:1
//The 'I' i got is: 5 The Boolean is:1
//The 'I' i got is: 6 The Boolean is:1
//The 'I' i got is: 7 The Boolean is:1
//The 'I' i got is: 8 The Boolean is:1
//The 'I' i got is: 9 The Boolean is:1
//No more output Programm is not Terminating and stuck in MPI_Waitany(); 

以下是解锁有效的更简单示例。

if (myid == 0) {
   bool test = false;
   MPI_Request mpi_request;


   MPI_Ibcast(&test, 1, MPI_C_BOOL, 0, MPI_COMM_WORLD, &mpi_request);
   MPI_Wait(&mpi_request, MPI_STATUS_IGNORE);
   cout << "Root Fin" << endl;

} else {
   bool test = true;
   cout << "Value is:" << test << endl;
   int i = 20;
   MPI_Request mpi_request[2];
   sleep(2);
   MPI_Ibcast(&test, 1, MPI_C_BOOL, 0, MPI_COMM_WORLD, &mpi_request[0]);
   MPI_Irecv(&i, 1, MPI_INT, 0, 10, MPI_COMM_WORLD, &mpi_request[1]);

   int RequestID = 0;
   sleep(2);
   MPI_Waitany(2, mpi_request, &RequestID, MPI_STATUS_IGNORE);
   //Should Print 0 in Begining is 1
   cout << "Value is:" << test << endl;
}

//OUTPUT
//Value is:1
//Root Fin
//Value is:0

Answer 1

您的程序卡在等待第 11 个发送或第 11 个 ibcast 上。如果您最终等待第 11 次发送或第 1 次 ibcast，它将完成。

这是我的(未经测试的)答案。

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


using namespace std;


int myid, numprocs;
char processor_name[MPI_MAX_PROCESSOR_NAME];

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


    int namelen;

    MPI_Comm_size(MPI_COMM_WORLD, &numprocs);
    MPI_Comm_rank(MPI_COMM_WORLD, &myid);
    MPI_Get_processor_name(processor_name, &namelen);

    MPI_Barrier(MPI_COMM_WORLD);
    if (myid == 0) { //Master
        bool test = false;
        MPI_Request mpi_request;
        for (int i = 0; i < 10; ++i) {
            //Sending I 1..10 to Worker
            MPI_Send(&i, 1, MPI_INT, 1, 10, MPI_COMM_WORLD);
            cout << "Sending: " << i <<  endl;
        }
        cout << "Bcast Worker finished" << endl;
        //Only to show even if the Bcast ist fired after worker is finished.
        sleep(10);
        //Using Ibcast for because Bcast can not Send to Ibcast in worker.
        MPI_Ibcast(&test, 1, MPI_C_BOOL, 0, MPI_COMM_WORLD, &mpi_request);
        MPI_Wait(&mpi_request, MPI_STATUS_IGNORE);
        cout << "Root Fin" << endl;

    } else { //Worker
        bool test = true;
        MPI_Request mpi_request[2];
        MPI_Ibcast(&test, 1, MPI_C_BOOL, 0, MPI_COMM_WORLD, &mpi_request[0]);

        while (true) {
            int i = 20;
            MPI_Irecv(&i, 1, MPI_INT, 0, 10, MPI_COMM_WORLD, &mpi_request[1]);

            int RequestID = 0;

            //Wait passes 10 Times for Send
            //Wait can not pass after work is done.

            MPI_Waitany(2, mpi_request, &RequestID, MPI_STATUS_IGNORE);

            cout << "The \'I\' i got is: " << i <<" The Boolean is:" << test << endl;
            if (!test)
                break;
        }
    }
    MPI_Finalize();
    return 0;
}