OpenMP 并行提速

<strong><span style="font-size:24px;">//测试VS2010下开启OpenPM并行提速</span></strong>

<span style="white-space:pre">	</span>LARGE_INTEGER tmp,time1,time2;long freq,costTime;QueryPerformanceFrequency(&tmp);freq = tmp.QuadPart;int k = 0;CString str;int kk[100];QueryPerformanceCounter(&time1);for (int i = 0;i<100;++i){kk[k] = i;k++;Sleep(10);}QueryPerformanceCounter(&time2);costTime = (long)((time2.QuadPart - time1.QuadPart) * 1000 / freq);

如上代码运行时间costTime = 999。开启OpenMP并行提速：1、项目---属性---配置属性---C/C++---语言---OpenMP支持---是（如下图）2、循环前添加

<span style="color:#ff0000;">#pragma omp parallel for</span>

如下图

	LARGE_INTEGER tmp,time1,time2;long freq,costTime;QueryPerformanceFrequency(&tmp);freq = tmp.QuadPart;int k = 0;CString str;int kk[100];QueryPerformanceCounter(&time1);

<pre name="code" class="cpp"><span style="white-space:pre">	</span><span style="color:#ff0000;">#pragma omp parallel for</span>

for (int i = 0;i<100;++i){kk[k] = i;k++;Sleep(10);}QueryPerformanceCounter(&time2);costTime = (long)((time2.QuadPart - time1.QuadPart) * 1000 / freq);

如上代码运行时间costTime = 135左右。我的机器是8核的，costTime 约等于 ceil（100/8）×10 = 130测试可显著提速，可看下运行完后kk数组中数据，可看出二者间的区别。不开启OpenMP 是按顺序0-99；开启后数据混乱，且每次运行都不一样。