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High Resolution Elapsed Timer

, 12 Dec 2001
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A simple high resolution timer class to help time code blocks.

Introduction

The motivation for this came when I needed to time sections of code while analyzing performance issues. The existing timers did not provide the necessary granularity to accurately measure execution times in microseconds. So I ended up creating this simple class to do the timing.

Here's the class declaration:

// HighResElapsedTimer.h: interface for the HighResElapsedTimer class.
//
//////////////////////////////////////////////////////////////////////

#if !defined(HIGHRESELAPSEDTIMER_H_INCLUDED_)
#define HIGHRESELAPSEDTIMER_H_INCLUDED_

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

// File:  HighResElapsedTimer.h
// Author:  Chen Venkataraman (venkatar@sig.com)
// Date:  Wed Dec 6, 2001
//
// Purpose: 
//  For determing elapsed time details during execution of code blocks 
//  (initially for debug builds only)
//
//  Sample usage:
//
//  {
//    #ifdef _DEBUG
//     HighResElapsedTimer  elapsedTime("block id");
//    #endif
//
//    ... rest of the code block
//  }
//
//    At the end of the above block, trace msg of the form
//    "block id : Elapsed time - xxxx.xxx microseconds" is spit out

#ifdef _DEBUG

class HighResElapsedTimer  
{
public:
  HighResElapsedTimer(const CString& strName) : m_strName(strName)
  {
    if (m_llFrequency == 0)      // frequency value not yet set
    {
      LARGE_INTEGER  liFrequency;

      QueryPerformanceFrequency(&liFrequency);
      m_llFrequency = liFrequency.QuadPart;
    }

    QueryPerformanceCounter(&m_llCounter);
  }

  virtual ~HighResElapsedTimer()
  {
    LARGE_INTEGER    liNow;
    QueryPerformanceCounter(&liNow);
    double duration = (double)
      (liNow.QuadPart - m_llCounter.QuadPart)/m_llFrequency;

    TRACE(_T("%s : Elapsed time = %.3lf microseconds\n"), 
                                      m_strName, duration);
  }

private:
  CString      m_strName;
  LARGE_INTEGER  m_llCounter;

private:
  static LONGLONG  m_llFrequency; 
  // Frequency setting is based hardware clock which doesn't
  // does change - so we want to set this only once

private:
  HighResElapsedTimer(const HighResElapsedTimer&);
  HighResElapsedTimer& operator=(const HighResElapsedTimer&);
};

#endif  // _DEBUG

#endif  // !defined(HIGHRESELAPSEDTIMER_H_INCLUDED_)

... and here is the implementation.

// HighResElapsedTime.cpp: implementation of the HighResElapsedTime class.
//
//////////////////////////////////////////////////////////////////////

#include "stdafx.h"
#include "HighResElapsedTimer.h"

#ifdef _DEBUG

/* static */
LONGLONG HighResElapsedTimer::m_llFrequency = 0;

#endif    // _DEBUG

Since I was timing the code execution only during debug builds, I've guarded the code using #ifdef _DEBUG's & used TRACE for output. If you want to time release builds or output differently, it should be fairly trivial to do so.

I've tested this only on NT4 SP6a & hopefully it will work on Win95 m/cs also.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

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About the Author

Chen Venkataraman
Software Developer (Senior)
United States United States
No Biography provided

Comments and Discussions

 
Generalseconds, not microseconds PinmemberAnonymous5-Jun-02 6:58 
GeneralOther timers PinmemberDean Wyant18-Dec-01 4:37 
GeneralRe: Other timers PinmemberRick York18-Dec-01 10:06 
GeneralRe: Other timers PinmemberDean Wyant18-Dec-01 15:24 
GeneralRe: Other timers PinmemberRick York18-Dec-01 17:23 
GeneralRe: Other timers PinmemberDean Wyant19-Dec-01 5:04 
GeneralRe: Other timers PinmemberCrispy20-Dec-01 14:17 
QuestionWhat does QueryPerformanceCounter do? Pinmembermoliate14-Dec-01 0:02 
AnswerRe: What does QueryPerformanceCounter do? PinmemberDaniel Lohmann14-Dec-01 0:49 

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