多线程在进行复杂运算时能够大量节约时间
提醒自己能够在多线程运算的时候一定要充分利用

能够省下2/3的时间

测试代码

#include<vector>
#include <iostream>
#include <thread>
using namespace cv;
using namespace std;
int result1 = 0 ;
bool thread_flag1 = false;
bool thread_flag2 = false;
bool thread_flag3 = false;
bool thread_flag4 = false;


void add_fn (int time)
{
    int result = 0;
    for (int i = 0 ;i < 10000000 ;i++)
    {
        result +=  i ;
    }  
    // cout << "the " << time  <<"time " << result <<endl;
    if (time == 1 ) thread_flag1 = true;
    else if (time == 2 ) thread_flag2 = true;
    else if (time == 3 ) thread_flag3 = true;
    else thread_flag4 = true;

    // return result ;
}
void check_thread()
{
    auto beforeTime = std::chrono::steady_clock::now();
    while(1)
    {
        if(thread_flag1&&thread_flag2&&thread_flag3&&thread_flag4)
        {
            auto afterTime = std::chrono::steady_clock::now();
            double duration_microsecond = std::chrono::duration<double, std::micro>(afterTime - beforeTime).count();
            cout << "threads take times"<< duration_microsecond <<"microsecond" <<endl;
            break;
        }
    
    }
    
}

int main()
{
    thread check(check_thread);
    check.detach();
    for (int i = 0;i < 4 ; i++)
    {
        std::thread t(add_fn , i);
        t.detach();
    }
    auto beforeTime = std::chrono::steady_clock::now();
    for (int i = 0;i < 4 ; i++)
    {
        add_fn(i);
    }
    auto afterTime = std::chrono::steady_clock::now();
    double duration_microsecond = std::chrono::duration<double, std::micro>(afterTime - beforeTime).count();
    cout << "all take times"<< duration_microsecond <<"microsecond" <<endl;
    
    while(1)
    {
        
    }
}