Win32简单多线程等待“耗时”

/*
 *    @brief BusyWait等待方式耗时测试
 * @file busy_loop.cpp
 */

#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <windows.h>
#include <time.h>

DWORD WINAPI ThreadProc(LPVOID lpParameter);

int main(int argc, char* argv[])
{
    HANDLE handle;
    DWORD numThreadId = 0;
    DWORD exitCode = 0;
    DWORD begin = 0;
    DWORD elapsed = 0;

    ///< 普通调用方式
    puts("time normal funciton call...");
    begin = GetTickCount();
    ThreadProc((LPVOID)1);
    elapsed = GetTickCount() - begin;
    printf("function call took %d.%.03d seconds \n",
        elapsed/1000, elapsed%1000);

    ////< 线程调用方式
    puts("Thread function begin..");
    begin = GetTickCount();
    handle = CreateThread(NULL, 0, ThreadProc, (LPVOID)1, 0, &numThreadId);
    if (NULL == handle)
    {
        return 0;
    }

    ///< 主线程等待子线程结束方式1 循环等待
    /*
    for (;;)    ///<
    {
        GetExitCodeThread(handle, &exitCode);    ///< 这个函数是获得线程的退出码
        if (exitCode != STILL_ACTIVE)
            break;
    }
    */

    ///< 主线程等待子线程结束方式2 消息等待
    ///< 这种方式下耗时和线程调用方式相比 差不多
    WaitForSingleObject(handle, INFINITE);    ///< INFINITE - 无限等待

    elapsed = GetTickCount() - begin;
    printf("thread call took %d.%.03d seconds \n",
        elapsed/1000, elapsed%1000);
    CloseHandle(handle);

    return 0;
}

DWORD WINAPI ThreadProc(LPVOID lpParameter)
{
    int i = 0;
    int inside = 0;
    double val = 0.0;

    srand((unsigned int)time(NULL));

    for (i = 0; i < 1000000; ++i)
    {
        double x = (double)(rand())/RAND_MAX;    ///< 产生0~1的数
        double y = (double)(rand())/RAND_MAX;
        if ((x*x + y*y) <= 1.0)                    ///< 落在半径为1的圆内
            inside++;
    }
    val = (double)inside/i;
    printf("PI = %.8g\n", val * 4);                ///< 科学计数法输出

    return 0;
}