linux下多线程C++运行时间统计

CMakeLists.txt

下面所有的代码的CMakeLists.txt如下

cmake_minimum_required(VERSION 2.8)

list(APPEND CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake/Modules)

# else can not fin nullptr and so on.
set (CMAKE_CXX_STANDARD 11)

#project name
project(thread_test)

#debug
set(CMAKE_BUILD_TYPE debug )
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC -march=native -fopenmp -g2 -ggdb -lpthread")

# thread_create
set( EXE_NAME thread_create_test )
set(APP_SRC thread_create.cpp)
add_executable(${EXE_NAME} ${APP_SRC} )
target_link_libraries(${EXE_NAME})

clock

clock函数在ctime中，用于统计cpu时钟时间，在程序是单线程时，相对准确，但是如果开启多线程，则会出现很大误差。如下面的程序

#include <iostream>
#include <pthread.h>
#include <unistd.h>

#include <ctime>
#include <unistd.h>
#include <vector>

using namespace std;

void* thread_1(void*)
{
    // clock_t t;
    // t = clock();
    for (int i = 0; i < 20000; ++i)
    {
        for (int j = 0; j < 20000; ++j)
        {
            int m = 2*3*4*5*6;
        }
    }
    // t = clock() - t;
    // cout << (unsigned int)pthread_self() << ", time : " << ((double)t)/CLOCKS_PER_SEC << "s" << endl;
}


// the two thread will run arandom order(simutaneously).
int main()
{
    cout << "pthread create test" << endl;

    int ret = 0;
    pthread_t th_id_1, th_id_2;

    clock_t t;
    t = clock();
    std::vector<pthread_t> vec_thread(10);
    for (int i = 0; i < vec_thread.size(); ++i)
    {
        ret = pthread_create( &vec_thread[i], NULL, thread_1, NULL );
        if( ret )
        {
            cout << "create thread 1 failed..." << endl;
            return -1;
        }
    }

    for (int i = 0; i < vec_thread.size(); ++i)
    {
        pthread_join( vec_thread[i], NULL );
    }

    t = clock() - t;
    cout << "all time : " << ((double)t)/CLOCKS_PER_SEC << "s" << endl;

    return 0;
}

运行需要1s左右，但是会记录10s左右的时间，因为每个线程中，cpu的clock都在计数，因此这个时间是不准确的。

time

time也在ctime中，它是记录系统时间，以s为最小单位，如下面的程序

#include <iostream>
#include <pthread.h>
#include <unistd.h>

#include <ctime>
#include <unistd.h>
#include <vector>

using namespace std;

void* thread_1(void*)
{
    // clock_t t;
    // t = clock();
    for (int i = 0; i < 20000; ++i)
    {
        for (int j = 0; j < 20000; ++j)
        {
            int m = 2*3*4*5*6;
        }
    }
    // t = clock() - t;
    // cout << (unsigned int)pthread_self() << ", time : " << ((double)t)/CLOCKS_PER_SEC << "s" << endl;
}


// the two thread will run arandom order(simutaneously).
int main()
{
    cout << "pthread create test" << endl;

    int ret = 0;
    pthread_t th_id_1, th_id_2;

    time_t t;
    t = time(NULL);
    std::vector<pthread_t> vec_thread(10);
    for (int i = 0; i < vec_thread.size(); ++i)
    {
        ret = pthread_create( &vec_thread[i], NULL, thread_1, NULL );
        if( ret )
        {
            cout << "create thread 1 failed..." << endl;
            return -1;
        }
    }

    for (int i = 0; i < vec_thread.size(); ++i)
    {
        pthread_join( vec_thread[i], NULL );
    }

    double cost_t = time(NULL) - t;
    cout << "all time : " << cost_t  << "s" << endl;

    return 0;
}

timeval

timeval在sys/time.h头文件中，是一个结构体，其中包含经过的秒和微秒，可以通过运算求出比较精确的时间，具体如下面的代码

#include <iostream>
#include <pthread.h>
#include <unistd.h>

#include <ctime>
#include <sys/time.h>
#include <unistd.h>
#include <vector>

using namespace std;

void* thread_1(void*)
{
    // clock_t t;
    // t = clock();
    for (int i = 0; i < 20000; ++i)
    {
        for (int j = 0; j < 20000; ++j)
        {
            int m = 2*3*4*5*6;
        }
    }
    // t = clock() - t;
    // cout << (unsigned int)pthread_self() << ", time : " << ((double)t)/CLOCKS_PER_SEC << "s" << endl;
}


// the two thread will run arandom order(simutaneously).
int main()
{
    timeval t_start, t_end;
    cout << "pthread create test" << endl;

    int ret = 0;
    pthread_t th_id_1, th_id_2;

    gettimeofday( &t_start, NULL);
    std::vector<pthread_t> vec_thread(10);
    for (int i = 0; i < vec_thread.size(); ++i)
    {
        ret = pthread_create( &vec_thread[i], NULL, thread_1, NULL );
        if( ret )
        {
            cout << "create thread 1 failed..." << endl;
            return -1;
        }
    }

    for (int i = 0; i < vec_thread.size(); ++i)
    {
        pthread_join( vec_thread[i], NULL );
    }

    gettimeofday( &t_end, NULL);
    double delta_t = (t_end.tv_sec-t_start.tv_sec) + 
                    (t_end.tv_usec-t_start.tv_usec)/1000000.0;
    cout << "all time : " << delta_t  << "s" << endl;

    return 0;
}

linux下多线程C++运行时间统计

linux下多线程C++运行时间统计

CMakeLists.txt

clock

time

timeval

参考链接

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