[C++知识库]基于C++11的多线程_2

// StudyThread_2.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <thread>
#include <iostream>
#include <future>

//简单函数
int addFunc(int i, int j)
{
	std::cout << "sub thread:" << std::this_thread::get_id() << std::endl;
	std::this_thread::sleep_for(std::chrono::seconds(1));
	return i + j;
}

//复杂函数: 求阶乘
long long factorial(int x)
{
	std::cout << "sub thread:" << std::this_thread::get_id() << std::endl;
	long long f;
	if (x == 0 || x == 1)
		f = 1;
	else
		f = factorial(x - 1)*x;
	std::cout << "factorial finish..." << std::endl;
	return f;
}

void printSomething()
{}

int main()
{
	std::cout << "Main thread:" << std::this_thread::get_id() << std::endl;

	//直接使用std::thread启动线程，我们无法获取到线程的返回值
// 	std::thread t(addFunc, 1, 2);
// 	if (t.joinable())
// 	{
// 		t.join();
// 	}

	//---------------------------------------------------------------------------------------------------------
	//这个时候我们引入另一种启动线程的方式std::async
	//注意std::async的返回值是std::future
// 	int a = 1;
// 	int b = 2;
// 	std::future<int> iResFut = std::async(std::launch::async, addFunc, a, b);
// 	std::cout << "iResFut.vaild() = " << iResFut.valid() << std::endl;			//true：由std::asyc返回的std::future，其vaild是true
// 	iResFut.wait();
// 	std::cout << "iResFut.vaild() = " << iResFut.valid() << std::endl;			//true：wait()返回之后，vaild为true
// 	int c = iResFut.get();				//使用get()获取future中的值
// 	std::cout << "iResFut.vaild() = " << iResFut.valid() << std::endl;			//false：在对std::future调用get()之后，vaild为false
// 	//int d = iResFut.get();
// 	std::cout << a << "+" << b << "=" << c << std::endl;

	//---------------------------------------------------------------------------------------------------------
	//std::future<int> fut;
	//std::cout << fut.valid() << std::endl;					//false：直接构造一个future对象，它没有关联任何共享状态，vaild是false
	//std::cout << fut.get() << std::endl;					//此时会抛出异常
//---------------------------------------------------------------------------------------------------------
	//注意std::shared_future的使用
// 	int a = 5, b = 6;
// 	std::future<int> iResFut = std::async(std::launch::async, addFunc, a, b);
// 	iResFut.wait();
// 	int c = iResFut.get();
// 	std::cout << a << "+" << b << "=" << c << std::endl;
// 	std::shared_future<long long> iFacFut = std::async(std::launch::async, factorial, c);
// 	iFacFut.wait();
// 	std::cout << "iFacFut.vaild() = " << iFacFut.valid() << std::endl;
// 	long long d = iFacFut.get();
// 	std::cout << c << " 的阶乘= " << d << std::endl;
// 	std::cout << "iFacFut.vaild() = " << iFacFut.valid() << std::endl;
// 	long long e = iFacFut.get();
// 	std::cout << c << " 的阶乘= " << e << std::endl;
// 	long long f = iFacFut.get();
// 	std::cout << c << " 的阶乘= " << f << std::endl;

//---------------------------------------------------------------------------------------------------------
	//std::lauch::deferred

// 	int a = 10;
// 	std::future<long long> iResFut = std::async(std::launch::deferred, factorial, a);
// 	iResFut.wait();
// 	std::cout << a << " 的阶乘= " << iResFut.get() << std::endl;

	//-------------------------------------------------------------------------------

	std::cout << "I Love China" << std::endl;
	system("pause");
	return 0;
}