服务器多线程学习

#include<iostream>
#include<thread>//线程头文件
#include<future>//简单说std::future提供了一种访问异步操作结果的机制
#include<cmath>//数学操作头文件
#include<vector>
#include<chrono>//获取本机器参考线程数的头文件
#include<cstdlib>//C语言中的stdlib.h在C++被重命名为cstdlib
#include<ctime>////C语言中的time.h在C++被重命名为ctime

using namespace std;

//沉重的计算事实上就算这样计算也很快
double caculate(double v)
{
	if (v<=0)
	{
		return v;
	}
	this_thread::sleep_for(chrono::milliseconds(10));//线程延时操作，为了模拟数据很多处理慢
	return sqrt((v*v + sqrt(v - 5)*(v + 2.5) / 2.0) / v);
}
//for_each
template<typename Iter,typename Fun>
double visitRange( thread::id id,Iter iterBegin, Iter iterEnd, Fun func)
{
	auto curId = this_thread::get_id();//获取主线程ID
	if (id == curId)
	{
		cout << curId << "hello main thread\n" << endl;
	}
	else
	{
		cout << curId << "hello work thread\n";
	}
	double v = 0;
	for (auto iter = iterBegin; iter < iterEnd; ++iter)
	{
		v += func(*iter);
	}
	return v;
}

//多线程 处理一组数据 将一组数据分为两半
int main()
{
	auto mainThreadId = this_thread::get_id();
	vector<double> v;
	for (int i = 0; i < 1000; ++i)
	{
		v.push_back(rand());
	}
	cout << v.size() << endl;
	double value = 0.0;
	auto nowc = clock();//记录时间
	//单线程总数据操作
	for (auto& info :v)
	{
		value += caculate(info);
	}
	auto finc = clock();//记录时间
	cout << "time value =" << finc- nowc << endl;
	cout << "value =" <<value << endl;

	auto midIter = v.begin() + (v.size() / 2);//分割vector
	//第二部分
	nowc = clock();//记录子线程时间
	double anotherv = 0.0;
	auto iterEnd = v.end();
	//传入线程
	thread s([&anotherv, mainThreadId, midIter, iterEnd]()
	{
		anotherv = visitRange(mainThreadId,midIter, iterEnd, caculate);
	});
	auto id = s.get_id();  //获取s线程id
	auto halfv = visitRange(mainThreadId,v.begin(), midIter, caculate);
	s.join();

	finc = clock();//记录子线程时间
	cout << "duo timevalue =" << finc - nowc << endl;

	cout << "anotherv =" << (anotherv) << endl;
	cout << "halfv =" << (halfv) << endl;
	cout << "Allvalue =" << (halfv + anotherv) << endl;
}