使用 pybind11 共享 MPI 通信器

Sharing an MPI communicator using pybind11

假设我已经围绕 MPI 通信器创建了一个包装器:

class Communicator {
   public:
      Communicator() : comm(MPI_COMM_WORLD) {}

      Communicator(int const color, int const key) {
        MPI_Comm_split(MPI_COMM_WORLD, color, key, &comm);
      }

      Communicator(MPI_Comm comm) : comm(comm) {}

      MPI_Comm GetComm() const { return comm; }
    private:
      MPI_Comm comm;
}; 

我想使用 pybind11 围绕这个对象创建一个 python 包装器,看起来像这样:

void CommunicatorWrapper(pybind11::module &m) {
   py::class_<Communicator, std::shared_ptr<Communicator> > commWrap(m, "Communicator");

   commWrap.def(py::init( []() { return new Communicator(); } ));
   commWrap.def(py::init( [](int const color, int const key) { return new Communicator(color, key); } ));
   commWrap.def(py::init( [](MPI_Comm comm) { return new Communicator(comm); } ));
   commWrap.def("GetComm", &Communicator::GetComm);
}

但是,我想要 python 看到的 MPI_Comm 类型 mpi4py.MPI.Comm。这可能吗?如果是,怎么做?

以上(天真的)实现导致以下行为:

comm = Communicator(MPI.COMM_WORLD)

错误:

TypeError: __init__(): incompatible constructor arguments. The following argument types are supported:
1. Communicator()
2. Communicator(arg0: int, arg1: int)
3. Communicator(arg0: int)

comm = Communicator()
print(comm.GetComm())

打印 -2080374784。鉴于 MPI_Comm 是什么,这种行为是有道理的,但显然不是我需要的功能。

我通过将包装器更改为

解决了这个问题
#include <mpi4py/mpi4py.h>

pybind11::handle CallGetComm(Communicator *comm) {
    const int rc = import_mpi4py();
    return pybind11::handle(PyMPIComm_New(comm->GetComm()));;
}

void CommunicatorWrapper(pybind11::module &m) {
   py::class_<Communicator, std::shared_ptr<Communicator> > commWrap(m, "Communicator");

   commWrap.def(py::init( []() { return new Communicator(); } ));
   commWrap.def(py::init( [](int const color, int const key) { return new Communicator(color, key); } ));
   commWrap.def(py::init( [](pybind11::handle const& comm) {
     const int rc = import_mpi4py();
     assert(rc==0);
     return new Communicator(*PyMPIComm_Get(comm.ptr()));
    } ));
   commWrap.def("GetComm", &CallGetComm);
}