【发布时间】：2020-10-15 06:45:52
【问题描述】：
我正在尝试创建一个线程池类，它接收多个函数并将它们放入队列中直到它们完成，然后我可以添加另一个函数来利用创建的线程，而不是在我想运行其他函数时创建它们.这就是为什么我包含一个条件变量来同步所有线程。
但是，代码无法正常工作，因为在调用函数时，对象会以某种方式进行复制。经过几次尝试，我无法弄清楚我错过了什么！
我期望的是hw 对象的成员函数greetings 与他的索引并行执行。但是当执行(o.*f)(std::forward<Args>(args)...); 行时，对象被复制，尽管复制构造函数被删除。因此，当它进入greetings 成员时，它会产生一个SEGMENTATION FAULT。
CMakeLists.txt
cmake_minimum_required(VERSION 3.5)
project(boost_asyo LANGUAGES CXX)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
add_executable(boost_asyo main.cpp)
target_link_libraries(${PROJECT_NAME} boost_thread boost_system)
main.cpp
#include <iostream>
#include <boost/asio.hpp>
#include <boost/thread.hpp>
#include <memory>
#include <mutex>
#include <condition_variable>
class Semaphore
{
std::mutex lock;
std::condition_variable cond;
int count;
public:
Semaphore()
{
count = 0;
}
void wait()
{
std::unique_lock<std::mutex> m(lock);
while(count > 0)
cond.wait(m, [this]{ return count == 0; });
}
void take()
{
std::unique_lock m(lock);
count++;
}
void give()
{
std::unique_lock m(lock);
count--;
if(count == 0)
{
cond.notify_one();
}
}
};
class ThreadPool
{
private:
boost::asio::io_service m_io_service;
std::unique_ptr<boost::asio::io_service::work> m_work;
boost::thread_group m_threads;
Semaphore m_sem;
public:
ThreadPool(size_t n)
{
this->m_work = std::make_unique<boost::asio::io_service::work>(m_io_service);
for (size_t ii = 0; ii < n; ii++)
{
m_threads.create_thread(boost::bind(&boost::asio::io_service::run, &this->m_io_service));
}
}
ThreadPool(const ThreadPool & v) = delete;
ThreadPool(ThreadPool && v) = delete;
~ThreadPool()
{
m_io_service.stop();
}
template<class type, class T, class T1, class... Args>
auto post(type T::*f, T1 &obj, Args... args)
{
this->m_sem.take();
this->m_io_service.post([&] ()
{
T o = static_cast<T&&>(obj);
(o.*f)(std::forward<Args>(args)...);
this->m_sem.give();
});
}
void wait()
{
this->m_sem.wait();
}
};
class HelloWorld
{
private:
public:
std::string m_str;
HelloWorld(std::string str) : m_str(str) {};
HelloWorld(const HelloWorld& v) = delete;
HelloWorld(HelloWorld&& v) = default;
~HelloWorld() = default;
void greetings(int ii)
{
for (int jj = 0; jj < 5; jj++)
{
std::cout << this->m_str << " " << ii << std::endl;
boost::this_thread::sleep_for(boost::chrono::seconds(1));
}
}
};
int main()
{
ThreadPool tp(8);
HelloWorld hw("Hola mundo");
for (int ii = 0; ii < 5; ii++)
{
tp.post(&HelloWorld::greetings, hw, ii);
}
tp.wait();
return 0;
}
此代码基于此代码，它可以正常工作，这与我想要对类和成员执行的操作类似。
#include <iostream>
#include <boost/asio.hpp>
#include <boost/thread.hpp>
#include <memory>
#include <mutex>
#include <condition_variable>
class Semaphore
{
std::mutex lock;
std::condition_variable cond;
int count;
public:
Semaphore()
{
count = 0;
}
void wait()
{
std::unique_lock<std::mutex> m(lock);
while(count > 0)
cond.wait(m, [this]{ return count == 0; });
}
void take()
{
std::unique_lock m(lock);
count++;
}
void give()
{
std::unique_lock m(lock);
count--;
if(count == 0)
{
cond.notify_one();
}
}
};
int main()
{
boost::asio::io_service io_service;
std::unique_ptr<boost::asio::io_service::work> work = std::make_unique<boost::asio::io_service::work>(io_service);
boost::thread_group threads;
for (size_t ii = 0; ii < 2; ii++)
{
std::cout << "id: " << ii << std::endl;
threads.create_thread(boost::bind(&boost::asio::io_service::run, &io_service));
}
Semaphore sem;
for (size_t ii = 0; ii < 3; ii++)
{
//Take
sem.take();
io_service.post([ii, &sem] ()
{
int id = 0;
while(id < 5)
{
id++;
printf("hello world %i\n", static_cast<int>(ii));
boost::this_thread::sleep_for(boost::chrono::seconds(1));
}
//Give
sem.give();
});
}
sem.wait();
for (size_t ii = 0; ii < 3; ii++)
{
sem.take();
io_service.post([ii, &sem] ()
{
int id = 0;
while(id < 5)
{
id++;
printf("bye world %i\n", static_cast<int>(ii));
boost::this_thread::sleep_for(boost::chrono::seconds(1));
}
sem.give();
});
}
sem.wait();
io_service.stop();
return 0;
}
【问题讨论】：
-
什么函数可以复制？什么是输出/预期输出？
-
是的，你是对的。我编辑了我的问题以提供更多详细信息。我期望的是成员函数与线程池并行运行
标签： c++ multithreading boost lambda threadpool