A High Resolution Performance Timer

Trifon — Mon, 02 May 2005 11:06:44 GMT

We publish here some code for a high resolution performance
timer that can be used to measure the performance of your code
to nanosecond accuracy.

The code is beased on this article [url]http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnpag/html/scalenethowto09.asp[/url]
but it has been modified so that the timer can be started and
stopped many times and its Duration property will return the
cumulative elapsed time that the timer has been running.

Normally you will use the PerformanceTimer class as follows:

Create a new instance of the PerformanceTimer class.
Call the StartTimer method.
Execute any code you need to measure its duration in time.
Call the StopTimer method.
Read the Duration property to get the cumulative elapsed time the timer has been running.
You may also read this property while the timer is running.
Call the Reset method to set the Duration property to 0.

[code]using System;
using System.Runtime.InteropServices;

namespace Bluebit.Utility
{
/// <summary>The %PerformanceTimer% class can be used to measure intervals of time.</summary>
/// <remarks>
/// <para>Normally you will use the PerformanceTimer class is as
/// follows:</para>
/// <list type="bullet">
/// <item>Create a new instance of the %PerformanceTimer% class.</item>
/// <item>Call the
/// <a href="Bluebit.Learning~Bluebit.Utility.PerformanceTimer~StartTimer.html">StartTimer</a>
/// method.</item>
/// <item>Execute any code you need to measure its duration in time.</item>
/// <item>Call the
/// <a href="Bluebit.Learning~Bluebit.Utility.PerformanceTimer~StopTimer.html">StopTimer</a>
/// method.</item>
/// <item>Read the
/// <a href="Bluebit.Learning~Bluebit.Utility.PerformanceTimer~Duration.html">Duration</a>
/// property to get the cumulative elapsed time the timer has been running. You may
/// also read this property while the timer is running.</item>
/// <item>Call the
/// <a href="Bluebit.Learning~Bluebit.Utility.PerformanceTimer~Reset.html">Reset</a>
/// method to set the
/// <a href="Bluebit.Learning~Bluebit.Utility.PerformanceTimer~Duration.html">Duration</a>
/// property to 0.</item>
/// </list>
/// </remarks>
public class PerformanceTimer
{
/////////////////////
#region PRIVATE FIELDS
private long _freq; // internal performance-counter frequency, in counts per second
private long _bias; // the time it takes to execute a StartTimer and a StopTimer command.
private long _start; // last time the timer was started
private long _stop; // last time the timer was stopped
private long _duration; // cumulative elapsed time.
private bool _running; // current state of the timer.
#endregion
/////////////////////
#region EXTERNAL DECLARATIONS
[DllImport("kernel32.dll")]
extern static short QueryPerformanceCounter(ref long x);
[DllImport("kernel32.dll")]
extern static short QueryPerformanceFrequency(ref long x);
#endregion
/////////////////////
#region CONSTRUCTOR
/// <summary>Creates a new instance of the %PerformanceTimer% class</summary>
public PerformanceTimer()
{
QueryPerformanceFrequency(ref _freq);
if (_freq == 0)
throw new ApplicationException("The installed hardware does not support a high-resolution performance counter.");

// calculate the _bias; the first result maybe inaccurate
StartTimer();
StopTimer();
StartTimer();
StopTimer();
_bias = _stop - _start;
_duration = 0;
}
#endregion
/////////////////////
#region PUBLIC METHODS
/// <summary>Starts the timer.</summary>
public void StartTimer()
{
if (!_running)
{
_running = true;
QueryPerformanceCounter(ref _start);
}
}

/// <summary>
/// Stops the timer.
/// </summary>
public void StopTimer()
{
if (_running)
{
QueryPerformanceCounter(ref _stop);
long d = _stop - _start - _bias;
d = (d > 0) ? d : 0;
_duration += d;
_running = false;
}
}
/// <summary>
/// Resets the timer.
/// </summary>
/// <remarks>
/// The %Reset% method sets the %Duration% of the timer to zero. If the timer is
/// running it is stopped.
/// </remarks>
public void Reset()
{
if (_running) StopTimer();
_duration = 0;
}

#endregion
/////////////////////
#region PUBLIC PROPERTIES
/// <summary>Gets the cumulative elapsed time the timer has been running.</summary>
/// <value>
/// A %System.Double% representing the number of seconds the timer has been
/// running.
/// </value>
public double Duration
{
get
{
if (_running)
{
QueryPerformanceCounter(ref _stop);
long d = _stop - _start - _bias;
d = (d > 0) ? d : 0;
return (double)(_duration + d) / (double)_freq;
}

return (double)_duration / (double)_freq;
}
}
/// <summary>
/// Gets the current performance-counter frequency, in counts per second.
/// </summary>
public long Frequency
{
get { return _freq; }
}

/// <summary>
/// Gets the current state of the timer.
/// </summary>
/// <value>
/// true if timer is running, false if timer is
/// stopped.
/// </value>
/// <remarks>
/// The %StartTimer% method sets this property to true whereas the
/// %StopTimer% method sets it to false
/// </remarks>
public bool IsRunning
{
get { return _running; }
}
#endregion
/////////////////////
}
}[/code]

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A High Resolution Performance Timer