QueryPerformanceCounter（）测试Windows Embedded Compact 7

循环遍历QueryPerformanceCounter（）并保存值：

// Main loop for timer test for ( int i = 0; i < ITERATIONS; i++ ) // ITERATIONS = 1000 { QueryPerformanceCounter(&li); time[i] = double(li.QuadPart) / PCFreq; //1,193,182 per second } //calculate the difference between each call // and save in difference[] for ( int j = 0; j < (ITERATIONS - 1) ; j++ ) { difference[j] = time[j+1] - time[j]; } 

（除以PCFreq给出每次通话之间的时间。）

据说高分辨率计时器/计数器正在工作，因为它没有返回默认频率1000。

每个时间戳（一千个时间戳调用）之间的平均值为11.990884微秒。

这似乎非常缓慢。

这个测试有缺陷吗？

或者为什么在1.1Ghz Celeron上报告这么慢的值？

Answer 1

在第一个循环中消除浮点数学可能是值得的，以便不考虑Win 7 Desktop和Embedded Compact 7之间的（潜在）差异。 所以，像：

 LARGE_INTEGER counter[ITERATIONS]; // Main loop for timer test for ( int i = 0; i < ITERATIONS; i++ ) // ITERATIONS = 1000 { QueryPerformanceCounter(&counter[i]); } time[0] = double(counter[0].QuadPart) / PCFreq; //1,193,182 per second //calculate the difference between each call // and save in difference[] for ( int j = 0; j < (ITERATIONS - 1) ; j++ ) { time[j+1] = double(counter[j+1].QuadPart) / PCFreq; //1,193,182 per second difference[j] = time[j+1] - time[j]; }