How to: Use the High-Resolution Timer

Some devices support a high-resolution timer. This timer, when present, provides more precise measurements than you can obtain by using the TickCount property, which has a 1-millisecond resolution. In applications where precise time measurements are important, the high-resolution timer provides the best results. For example, some Direct3D applications display more smoothly when the animation is based on the high-resolution timer. You can also use this timer in an application to determine how much time a method or a section of code requires to execute.

Example

This code example provides a class that makes it easier to use the high-resolution timer in managed code on Windows CE. The example has the following features:

  • Platform invoke declarations for the native methods in Windows CE.

  • A property that is used to get the frequency of the high-resolution counter.

  • A property that is used to get the value of the high-resolution counter.

  • An implementation that supports the TickCount property as a fallback if the QueryPerformanceCounter function is not supported or is emulated.

  • An example of how the high-resolution counter can be used to time an operation.

Public Class HiResTimer
    Private isPerfCounterSupported As Boolean = False 
    Private timerFrequency As Int64 = 0

    ' Windows CE native library with QueryPerformanceCounter(). 
    Private Const [lib] As String = "coredll.dll" 

    Public Declare Function QueryPerformanceCounter Lib "Coredll.dll" _
    (ByRef count As Int64) As Integer 

    Public Declare Function QueryPerformanceFrequency Lib "Coredll.dll" _
    (ByRef timerFrequency As Int64) As Integer     

    Public Sub New() 
        ' Query the high-resolution timer only if it is supported. 
        ' A returned frequency of 1000 typically indicates that it is not 
        ' supported and is emulated by the OS using the same value that is 
        ' returned by Environment.TickCount. 
        ' A return value of 0 indicates that the performance counter is 
        ' not supported. 
        Dim returnVal As Integer = QueryPerformanceFrequency(timerFrequency)

        If returnVal <> 0 AndAlso timerFrequency <> 1000 Then 
            ' The performance counter is supported.
            isPerfCounterSupported = True 
        Else 
            ' The performance counter is not supported. Use 
            ' Environment.TickCount instead.
            timerFrequency = 1000
        End If 

    End Sub 


    Public ReadOnly Property Frequency() As Int64 
        Get 
            Return timerFrequency
        End Get 
    End Property 


    Public ReadOnly Property Value() As Int64 
        Get 
            Dim tickCount As Int64 = 0

            If isPerfCounterSupported Then 
                ' Get the value here if the counter is supported.
                QueryPerformanceCounter(tickCount)
                Return tickCount
            Else 
                ' Otherwise, use Environment.TickCount 
                Return CType(Environment.TickCount, Int64)
            End If 
        End Get 
    End Property 


    Shared Sub Main() 
        Dim timer As New HiResTimer()

        ' This example shows how to use the high-resolution counter to  
        ' time an operation.  
        ' Get counter value before the operation starts. 
        Dim counterAtStart As Int64 = timer.Value

        ' Perform an operation that takes a measureable amount of time. 
        Dim count As Integer 
        For count = 0 To 9999
            count += 1
            count -= 1
        Next count

        ' Get counter value after the operation ends. 
        Dim counterAtEnd As Int64 = timer.Value

        ' Get time elapsed in tenths of milliseconds 
        Dim timeElapsedInTicks As Int64 = counterAtEnd - counterAtStart
        Dim timeElapseInTenthsOfMilliseconds As Int64 = timeElapsedInTicks * 10000 / timer.Frequency


        MessageBox.Show("Time Spent in operation (tenths of ms) " + timeElapseInTenthsOfMilliseconds.ToString + vbLf + "Counter Value At Start: " + counterAtStart.ToString + vbLf + "Counter Value At End : " + counterAtEnd.ToString + vbLf + "Counter Frequency : " + timer.Frequency.ToString)

    End Sub 
End Class
public class HiResTimer
{
    private bool isPerfCounterSupported = false;
    private Int64 frequency = 0;

    // Windows CE native library with QueryPerformanceCounter(). 
    private const string lib = "coredll.dll";
    [DllImport(lib)]
    private static extern int QueryPerformanceCounter(ref Int64 count);
    [DllImport(lib)]
    private static extern int QueryPerformanceFrequency(ref Int64 frequency);

    public HiResTimer()
    {
        // Query the high-resolution timer only if it is supported. 
        // A returned frequency of 1000 typically indicates that it is not 
        // supported and is emulated by the OS using the same value that is 
        // returned by Environment.TickCount. 
        // A return value of 0 indicates that the performance counter is 
        // not supported. 
        int returnVal = QueryPerformanceFrequency(ref frequency);

        if (returnVal != 0 && frequency != 1000)
        {
            // The performance counter is supported.
            isPerfCounterSupported = true;
        }
        else
        {
            // The performance counter is not supported. Use 
            // Environment.TickCount instead.
            frequency = 1000;
        }
    }

    public Int64 Frequency
    {
        get
        {
            return frequency;
        }
    }

    public Int64 Value
    {
        get
        {
            Int64 tickCount = 0;

            if (isPerfCounterSupported)
            {
                // Get the value here if the counter is supported.
                QueryPerformanceCounter(ref tickCount);
                return tickCount;
            }
            else
            {
                // Otherwise, use Environment.TickCount. 
                return (Int64)Environment.TickCount;
            }
        }
    }

    static void Main()
    {
        HiResTimer timer = new HiResTimer();

        // This example shows how to use the high-resolution counter to  
        // time an operation.  

        // Get counter value before the operation starts.
        Int64 counterAtStart = timer.Value;

        // Perform an operation that takes a measureable amount of time. 
        for (int count = 0; count < 10000; count++)
        {
            count++;
            count--;
        }

        // Get counter value when the operation ends.
        Int64 counterAtEnd = timer.Value;

        // Get time elapsed in tenths of a millisecond.
        Int64 timeElapsedInTicks = counterAtEnd - counterAtStart;
        Int64 timeElapseInTenthsOfMilliseconds =
            (timeElapsedInTicks * 10000) / timer.Frequency;

        MessageBox.Show("Time Spent in operation (tenths of ms) "
                       + timeElapseInTenthsOfMilliseconds +
                       "\nCounter Value At Start: " + counterAtStart +
                       "\nCounter Value At End : " + counterAtEnd +
                       "\nCounter Frequency : " + timer.Frequency);
    }
}

Compiling the Code

This example requires references to the following namespaces:

See Also

Other Resources

Building Applications and Core Tasks in the .NET Compact Framework

Interoperability in the .NET Compact Framework