使用pybind11将Python解释器嵌入到多线程C ++程序中

巴瓦扎

我试图使用pybind11来使第三方C ++库调用Python方法。该库是多线程的，每个线程创建一个Python对象，然后对该对象的方法进行大量调用。

我的问题是py::gil_scoped_acquire acquire;死锁的调用。下面给出了重现该问题的最少代码。我究竟做错了什么？

// main.cpp
class Wrapper
{
public:
  Wrapper()
  {
    py::gil_scoped_acquire acquire;
    auto obj = py::module::import("main").attr("PythonClass")();
    _get_x = obj.attr("get_x");
    _set_x = obj.attr("set_x");
  }
  
  int get_x() 
  {
    py::gil_scoped_acquire acquire;
    return _get_x().cast<int>();
  }

  void set_x(int x)
  {
    py::gil_scoped_acquire acquire;
    _set_x(x);
  }

private:
  py::object _get_x;
  py::object _set_x;
};


void thread_func()
{
  Wrapper w;

  for (int i = 0; i < 10; i++)
  {
    w.set_x(i);
    std::cout << "thread: " << std::this_thread::get_id() << " w.get_x(): " << w.get_x() << std::endl;
    std::this_thread::sleep_for(100ms);    
  }
}

int main() {
  py::scoped_interpreter python;
  
  std::vector<std::thread> threads;

  for (int i = 0; i < 5; ++i)
    threads.push_back(std::thread(thread_func));

  for (auto& t : threads)
    t.join();

  return 0;
}

和Python代码：

// main.py
class PythonClass:
    def __init__(self):
        self._x = 0

    def get_x(self):
        return self._x

    def set_x(self, x):
        self._x = x

相关问题可以在此处和此处找到，但并不能帮助我解决问题。

巴瓦扎

在启动辅助线程（已添加py::gil_scoped_release release;）之前，我设法通过在主线程中释放GIL来解决了该问题。对于任何有兴趣的人，现在可以使用以下方法（还添加了清理Python对象的功能）：

#include <pybind11/embed.h>  
#include <iostream>
#include <thread>
#include <chrono>
#include <sstream>

namespace py = pybind11;
using namespace std::chrono_literals;

class Wrapper
{
public:
  Wrapper()
  {
    py::gil_scoped_acquire acquire;
    _obj = py::module::import("main").attr("PythonClass")();
    _get_x = _obj.attr("get_x");
    _set_x = _obj.attr("set_x");

  }
  
  ~Wrapper()
  {
    _get_x.release();
    _set_x.release();
  }

  int get_x() 
  {
    py::gil_scoped_acquire acquire;
    return _get_x().cast<int>();
  }

  void set_x(int x)
  {
    py::gil_scoped_acquire acquire;
    _set_x(x);
  }

private:
  py::object _obj;
  py::object _get_x;
  py::object _set_x;
};


void thread_func(int iteration)
{
  Wrapper w;

  for (int i = 0; i < 10; i++)
  {
    w.set_x(i);
    std::stringstream msg;
    msg << "iteration: " << iteration << " thread: " << std::this_thread::get_id() << " w.get_x(): " << w.get_x() << std::endl;
    std::cout << msg.str();
    std::this_thread::sleep_for(100ms);    
  }
}

int main() {
  py::scoped_interpreter python;
  py::gil_scoped_release release; // add this to release the GIL

  std::vector<std::thread> threads;
  
  for (int i = 0; i < 5; ++i)
    threads.push_back(std::thread(thread_func, 1));

  for (auto& t : threads)
    t.join();

  return 0;
}

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