c ++：MPI通信器作为全局变量 [英] c++: MPI communicator as global variable

问题描述

我需要在函数/类成员函数中访问MPI世界通信器。但是根据设计/约定，MPI环境和通信器总是在 int main（）开始时定义和初始化。

唯一的，简单的解决方案，我可以想到使用通信器的全局指针。

有人知道更好的方法吗？使用全局指针解决方案是危险的吗？

这个问题同样适用于裸骨骼MPI和Boost :: MPI（我在下面使用） p>

我提出的解决方案示例（未测试）：

  //全局变量。 h 
 extern boost :: mpi :: communicator * my_MPI_world_ptr; 
  

和

  // main.cpp 
 ... 
 int main（int argc，char * argv []）
 {
 boost :: mpi :: environment my_boost_mpi_env argc，argv）; 
 boost :: mpi :: communicator my_MPI_world; 
 my_MPI_world_ptr =& my_MPI_world; 
 
 my_MPI_rank = my_MPI_world_ptr-> rank（）; 
 size_MPI_WORLD = my_MPI_world_ptr-> size（）; 
 
 my_class an_Object; 
 an_Object.member_function_that_uses__MPI_world（）; 
 ... 
} 
  

解决方案

你是说实际的MPI MPI_COMM_WORLD 通信器（或者它的Boost封装器）？这已经是全球性的。如果使用不同的通信器将通信与正在编写的库分离，最好避免使用全局变量。在这种情况下，你可能想传递它（或指向它）的指针，并将其存储在需要它的类中。

I need the MPI world communicator to be accessible in functions/class member functions. But by design/convention, MPI environments and communicators are always defined and initialized at the beginning of int main().

The only, simple solution I can think of using a global pointer to the communicator.

Does anybody know of a better way? Is it dangerous to use the global pointer solution?

This problem applies equally well to bare-bones MPI, and to Boost::MPI (which I use below)

Example of my proposed solution (untested):

//globals.h
extern   boost::mpi::communicator  * my_MPI_world_ptr;

and

//main.cpp
...
int main(int argc, char* argv[])
{        
    boost::mpi::environment my_boost_mpi_env(argc, argv);
    boost::mpi::communicator my_MPI_world; 
    my_MPI_world_ptr = &my_MPI_world;       

    my_MPI_rank = my_MPI_world_ptr->rank();
    size_MPI_WORLD = my_MPI_world_ptr->size();    

    my_class an_Object;
    an_Object.member_function_that_uses__MPI_world();
   ...
}

解决方案

Do you mean the actual MPI MPI_COMM_WORLD communicator (or the Boost wrapper of it)? That is already global. If you are using a different communicator to separate communication from a library that you are writing, it would be better to avoid using a global variable for it at all. In that case, you might want to just pass it (or a pointer to it) around and store it in the classes that need it.

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