Creating a Hi-Res Timer

  • Thread starter Thread starter Scott McNair
  • Start date Start date
S

Scott McNair

Hi,

I'm trying to create a hi-resolution timer for an application that I'm
working on which needs to be sensitive to at least 10ms. I'd like to
have it mimic the built-in MS timer as much as possible, mainly for ease
of code re-use.

I've found several examples of how to use QueryPerformanceCounter and
QueryPerformanceFrequency to get high-precision time, and I've written
something that works fine for single iterations, but when the timer
starts to repeat itself, the app gets bogged down. I realize it's
bogging down due to recursion, but that's sort of the nature of the beast
with a timer.

Does anybody have a suggestion for how I can recurse elegantly, or
barring that, some good example code for how to implement a hi-res timer
that's MS-like?

My current code is attached:

Class HiResTimer
Declare Function QueryPerformanceCounter Lib "Kernel32" (ByRef X As
Long) As Short
Declare Function QueryPerformanceFrequency Lib "Kernel32" (ByRef X As
Long) As Short

Private iEnabled As Boolean = False
Private StartCount As Long = 0
Private CurrentCount As Long = 0
Private Frequency As Long = 0
Private iInterval As Long = 0
Private Overhead As Long = 0

Public Interval As Long = 1000

Public Property Enabled() As Boolean
Get
Return iEnabled
End Get
Set(ByVal value As Boolean)
iEnabled = value
RaiseEvent EnabledEvent()
End Set
End Property

Public Event Tick()
Private Event EnabledEvent()

Public Sub New()
If (QueryPerformanceCounter(StartCount) = 0) Then
Throw New HiResTimerException()
End If
If (QueryPerformanceCounter(CurrentCount) = 0) Then
Throw New HiResTimerException()
End If
' calculate the time just to call start and end
Overhead = (CurrentCount - StartCount)
End Sub

Private Sub EnabledSub() Handles Me.EnabledEvent
If iEnabled = True Then
'Get the interval in terms of microseconds
iInterval = Interval / 1000
If (QueryPerformanceCounter(StartCount) = 0) Then
Throw New HiResTimerException()
End If
If (QueryPerformanceCounter(CurrentCount) = 0) Then
Throw New HiResTimerException()
End If
QueryPerformanceFrequency(Frequency)
While ((CurrentCount - StartCount - Overhead) / Frequency) <
iInterval
QueryPerformanceCounter(CurrentCount)
End While
RaiseEvent Tick()
RaiseEvent EnabledEvent()
End If
End Sub
End Class

Public Class HiResTimerException
Inherits System.ApplicationException

Overrides ReadOnly Property Message() As String
Get
Return "HiResTimer: QueryPerformanceCounter[Kernel32]
returned 0"
End Get
End Property
End Class
 
Can't you use System.Timer.Timer? Ticks are generated out of process
and it's supposedly very accurate.
Click to expand...

Actually I performed a test that had some scary results, which prompted
this search:

* I captured the current time in a variable (StartTime).

* I created a timer with a tick of 10ms, then enabled the timer. In the
timer's ontick event, I had it increment a variable by 1.

* When the number reached 1000 (i.e. after what should have been 10
seconds, at 10ms*1000 ticks) I captured the EndTime. I then displayed
datediff between StartTime and EndTime. The process which should have
taken 10 seconds actually took more like 15.

I took it a step further and found a third-party hi-res timer component,
and had the two components "race" each other to 1000 ticks @ 10ms per
tick. The third-party component hit 1000 ticks at exactly 10 seconds, at
which point the MS timer had only reached 651 ticks, for a deficiency of
34.9%.

Then for fun I raised the count to 10,000 ticks, and lowered the per-tick
rate to 1ms (still 10sec, but at the highest granularity). In the time
it took the third-party to run 10,000 iterations (in exactly 10 seconds,
mind you) the MS timer ran a measly 671 times, for a deficiency of
93.29%.

I then altered the tick count upward, to see when it would normalize...
when I got to 100 count at 100ms, the MS timer reported about 92 ticks
out of 100 (8% deficiency). I then bumped it to 80 count at 125ms (or
1/8 of a second) and at that point it seemed to normalize.

In probably 99.9% of my coding, the MS timer would work fine.
Unfortunately, right now I'm writing an application that requires a 10ms
granularity (it's calling on hardware that requires finely tuned and
calibrated steps), and having a disparity of about 35% is unacceptable
for this application.

I suppose I could just use the third-party component, but its
implementation is kind of clunky, and I'd prefer something that mimics
the MS timer code style.

Thanks for listening to my rant. :)

-Scott
 
Actually I performed a test that had some scary results, which prompted
this search:
Click to expand...

Which timer did you use? .NET has 3 timers, System.Windows.Forms.Timer
isn't accurate.
 
Scott McNair said:
Can't you use System.Timer.Timer? Ticks are generated out of process
and it's supposedly very accurate.
Click to expand...

Actually I performed a test that had some scary results, which prompted
this search:

* I captured the current time in a variable (StartTime).

* I created a timer with a tick of 10ms, then enabled the timer. In the
timer's ontick event, I had it increment a variable by 1.
[Timer is not very accurate]
Click to expand...

Well, as 'System.Windows.Forms.Timer' is the only timer which has an
'OnTick' method, you have definitely used the wrong timer:

| The Windows Forms Timer component is single-threaded, and is
| limited to an accuracy of 55 milliseconds.

Take a look at 'System.Timers.Timer' (with 'AutoReset' set to 'True') or
maybe 'System.Threading.Timer'.
 
Which timer did you use? .NET has 3 timers, System.Windows.Forms.Timer
isn't accurate.
Click to expand...

Ah, that's the one I used.

After I sent the last email I looked into System.Timers.Timer, but I keep
running into problems with cross-thread issues. I've used the items in
http://msdn2.microsoft.com/en-us/library/ms171728(VS.80).aspx to try to get
around this, but with not much success. My guess is that I'm calling the
thread so much (100 times a second!) that I'm stepping on my own toes by
executing the background worker before it has a chance to complete its
prior cycle.
 
Herfried K. Wagner said:
Scott McNair said:
Can't you use System.Timer.Timer? Ticks are generated out of process
and it's supposedly very accurate.
Click to expand...

Actually I performed a test that had some scary results, which prompted
this search:

* I captured the current time in a variable (StartTime).

* I created a timer with a tick of 10ms, then enabled the timer. In the
timer's ontick event, I had it increment a variable by 1.
[Timer is not very accurate]
Click to expand...

Well, as 'System.Windows.Forms.Timer' is the only timer which has an
'OnTick' method, you have definitely used the wrong timer:

| The Windows Forms Timer component is single-threaded, and is
| limited to an accuracy of 55 milliseconds.

Take a look at 'System.Timers.Timer' (with 'AutoReset' set to 'True') or
maybe 'System.Threading.Timer'.
Click to expand...
Have you tried vbAccelerator to see if he has one similiar to "vbAccelerator
VB6 Safe High Resolution (Multi-Media) Timer "

Galen
 
Have you tried vbAccelerator to see if he has one similiar to
"vbAccelerator VB6 Safe High Resolution (Multi-Media) Timer "
Click to expand...

If there is one, it's extremely well-hidden on that site.

I can however import the VB6 DLL into my project and it works without a
hitch.
 
Hi,

I'm trying to create a hi-resolution timer for an application that I'm
working on which needs to be sensitive to at least 10ms. I'd like to
have it mimic the built-in MS timer as much as possible, mainly for ease
of code re-use.

I've found several examples of how to use QueryPerformanceCounter and
QueryPerformanceFrequency to get high-precision time, and I've written
something that works fine for single iterations, but when the timer
starts to repeat itself, the app gets bogged down. I realize it's
bogging down due to recursion, but that's sort of the nature of the beast
with a timer.

Does anybody have a suggestion for how I can recurse elegantly, or
barring that, some good example code for how to implement a hi-res timer
that's MS-like?

My current code is attached:

Class HiResTimer
Declare Function QueryPerformanceCounter Lib "Kernel32" (ByRef X As
Long) As Short
Declare Function QueryPerformanceFrequency Lib "Kernel32" (ByRef X As
Long) As Short

Private iEnabled As Boolean = False
Private StartCount As Long = 0
Private CurrentCount As Long = 0
Private Frequency As Long = 0
Private iInterval As Long = 0
Private Overhead As Long = 0

Public Interval As Long = 1000

Public Property Enabled() As Boolean
Get
Return iEnabled
End Get
Set(ByVal value As Boolean)
iEnabled = value
RaiseEvent EnabledEvent()
End Set
End Property

Public Event Tick()
Private Event EnabledEvent()

Public Sub New()
If (QueryPerformanceCounter(StartCount) = 0) Then
Throw New HiResTimerException()
End If
If (QueryPerformanceCounter(CurrentCount) = 0) Then
Throw New HiResTimerException()
End If
' calculate the time just to call start and end
Overhead = (CurrentCount - StartCount)
End Sub

Private Sub EnabledSub() Handles Me.EnabledEvent
If iEnabled = True Then
'Get the interval in terms of microseconds
iInterval = Interval / 1000
If (QueryPerformanceCounter(StartCount) = 0) Then
Throw New HiResTimerException()
End If
If (QueryPerformanceCounter(CurrentCount) = 0) Then
Throw New HiResTimerException()
End If
QueryPerformanceFrequency(Frequency)
While ((CurrentCount - StartCount - Overhead) / Frequency) <
iInterval
QueryPerformanceCounter(CurrentCount)
End While
RaiseEvent Tick()
RaiseEvent EnabledEvent()
End If
End Sub
End Class

Public Class HiResTimerException
Inherits System.ApplicationException

Overrides ReadOnly Property Message() As String
Get
Return "HiResTimer: QueryPerformanceCounter[Kernel32]
returned 0"
End Get
End Property
End Class
Click to expand...

I'll look and see, but I wrote a timer based on the multi-media timers a
long time ago. It was based on Karl Peterson's multi-media timer
objects. The resolution is close to 1ms on most hardware. Of cousre,
it's written in C#, not vb.net...
 
After I sent the last email I looked into System.Timers.Timer, but I
keep running into problems with cross-thread issues. I've used the
items in http://msdn2.microsoft.com/en-us/library/ms171728(VS.80).aspx
to try to get around this, but with not much success. My guess is
that I'm calling the thread so much (100 times a second!) that I'm
stepping on my own toes by executing the background worker before it
has a chance to complete its prior cycle.
Click to expand...

System.Timers.Timers is a high resolution timer, it should be able to
handle the accuracies you need easily. Cross threading issues can be solved
with a bit of code rearranging... shouldn't really be much of an issue?

You can also look at System.Threading.Timers too.
 
Ah, that's the one I used.

After I sent the last email I looked into System.Timers.Timer, but I
keep running into problems with cross-thread issues. I've used the
items in http://msdn2.microsoft.com/en-us/library/ms171728(VS.80).aspx
to try to get around this, but with not much success. My guess is
that I'm calling the thread so much (100 times a second!) that I'm
stepping on my own toes by executing the background worker before it
has a chance to complete its prior cycle.
Click to expand...

Not sure if you saw this yet:

http://msdn.microsoft.com/msdnmag/issues/04/02/TimersinNET/
 
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