Fortran和C++线程

Question

我有以下调用C++函数parallel_klu的Fortran代码。每次调用parallel_klu时，它都会创建八个线程(以执行另一个名为factor的函数)，并在返回Fortran后销毁这些线程。

program linkFwithCPP        
   use iso_c_binding
   implicit none 
   interface
   subroutine my_routine (Ax, Ai, Ap, b, n, nz) bind (C, name = "parallel_klu")
   import :: c_double
   import :: c_int
   integer (c_int), intent (out), dimension (*) :: Ap
   integer (c_int), intent (out), dimension (*) :: Ai
   real (c_double), intent (out), dimension (*) :: Ax
   real (c_double), intent (out), dimension (*) :: b
   integer(c_int), value :: n
   integer(c_int), value :: nz
   end subroutine
   end interface


   integer,parameter ::n=10
   integer,parameter ::nz=34

   ! declare the 4 arrays
   real (c_double), dimension (0:nz-1) :: Ax
   real (c_double), dimension (0:n-1) :: b
   integer (c_int), dimension (0:n) :: Ap
   integer (c_int), dimension (0:nz-1) :: Ai
   !Inputing array values
    open(unit = 1, file = 'Ax.txt')
    read(1,*) Ax         
    close(1)

    open(unit = 2, file = 'Ai.txt')
    read(2,*) Ai            
    close(2)

    open(unit = 3, file = 'Ap.txt')
    read(3,*) Ap            
    close(3)

    open(unit = 4, file = 'b.txt')
    read(4,*) b            
    close(4)


    ! Call C++ function
    call my_routine(Ax, Ai, Ap, b, n, nz)
    write (*, *) "Fortran: b:", b
    pause
 end program linkFwithCPP  

C++中的函数如下：

 void parallel_klu(double Ax[], int Ai[], int Ap[], double b[], const int n, const int nz)
{
  threadList.push_back(std::thread(factor, Ap, Ai, Ax, b, Q, P, Pinv, n, 0, 5000));
  threadList.push_back(std::thread(factor, Ap, Ai, Ax, b, Q, P, Pinv, n, 5000, 10000));
  threadList.push_back(std::thread(factor, Ap, Ai, Ax, b, Q, P, Pinv, n, 10000, 15000));
  threadList.push_back(std::thread(factor, Ap, Ai, Ax, b, Q, P, Pinv, n, 15000, 20000));
  threadList.push_back(std::thread(factor, Ap, Ai, Ax, b, Q, P, Pinv, n, 20000, 25000));
  threadList.push_back(std::thread(factor, Ap, Ai, Ax, b, Q, P, Pinv, n, 25000, 30000));
  threadList.push_back(std::thread(factor, Ap, Ai, Ax, b, Q, P, Pinv, n, 30000, 35000));
  threadList.push_back(std::thread(factor, Ap, Ai, Ax, b, Q, P, Pinv, n, 35000, 40000));

// wait for all threads to finish
for (auto& threadID : threadList){
    threadID.join();
}

}

有没有办法避免每次调用函数parallel_klu时都创建8个线程？类似于在第一次调用时创建它们，然后发送一个信号让线程再次执行。

Answer 1

首先，我强烈建议弄清楚线程创建是否会影响应用程序的性能。

如果是，您可以使用称为线程池的概念，线程池基本上是一组您可以向其发送任务的线程，它在无事可做时保持线程的构造/活动。这个概念也可以用来确定工作线程的数量。在this answer中提供了一些很好的建议。