Howdy ho! My name is Simon Wybranski, I am a developer on the C++ AMP team!

In this blog post I am going to present a high-resolution timer for measuring the performance of C++ AMP algorithms. There is nothing specific in it to C++ AMP, so it can be used to measure elapsed time of your PPL algorithms or any other C++ code.

Listing of timer.h:

 1: #pragma once
 2: #include <windows.h>
 3:  
 4: struct Timer
 5: {
 6:     void Start() 
 7:     {
 8:         QueryPerformanceCounter(&m_start);
 9:     }
 10:  
 11:     void Stop() 
 12:     {
 13:         QueryPerformanceCounter(&m_stop);
 14:     }
 15:     
 16:     // Returns elapsed time in milliseconds (ms)
 17:     double Elapsed()
 18:     {
 19:         return (m_stop.QuadPart - m_start.QuadPart - m_overhead) \
 20:                                           * 1000.0 / m_freq.QuadPart;
 21:     }
 22:  
 23: private:
 24:  
 25:     // Returns the overhead of the timer in ticks
 26:     static LONGLONG GetOverhead()
 27:     {
 28:         Timer t;
 29:         t.Start();
 30:         t.Stop();
 31:         return t.m_stop.QuadPart - t.m_start.QuadPart;
 32:     }
 33:  
 34:     LARGE_INTEGER m_start;
 35:     LARGE_INTEGER m_stop;
 36:     static LARGE_INTEGER m_freq;
 37:     static LONGLONG m_overhead;
 38: };

 

Listing of timer.cpp:

 1: #include "timer.h"
 2:  
 3: // Initialize the resolution of the timer
 4: LARGE_INTEGER Timer::m_freq = \
 5:           (QueryPerformanceFrequency(&Timer::m_freq), Timer::m_freq);
 6:  
 7: // Calculate the overhead of the timer
 8: LONGLONG Timer::m_overhead = Timer::GetOverhead();

 

Snippet showing the usage:

 1: Timer t; 
 2: t.Start(); 
 3: // Your algorithm goes here 
 4: t.Stop(); 
 5:  
 6: std::cout << t.Elapsed() << " ms" << std::endl;

 

Enjoy!!