waveformgraph uses all CPU and crash

[Norbert-emka]

Hi,

I have two problems with the WaveFormGraph in a visual studio 2005 application:

I have a data acquisition system which reads data from transmitters and then plot data in several WaveFormGraph (one for each transmitter). Each graph has a thread and is in a separated window.

The problem is that each WaveFormGraph uses around 15-20% of my CPU.

I plot, with the PlotY, method around 50 points every 50ms.

If my application is in background or reduced in the task bar, it uses only 2-3% of the CPU but when the graph need to be refreshed, it use all the CPU.

This is my first problem.

The second one is a crash that occurred in the WaveFormGraph. I have an exception that I can not catch. I get this stack:

************** Texte de l'exception **************

System.InvalidOperationException: La collection a été modifiée ; l'opération d'énumération peut ne pas s'exécuter.

   à System.Collections.Hashtable.HashtableEnumerator.MoveNext()

   à NationalInstruments.UI.Internal.by.e(ComponentDrawArgsInternal A_0)

   à NationalInstruments.UI.Internal.by.b(ComponentDrawArgsInternal A_0)

   à NationalInstruments.Restricted.ControlElement.a(ComponentDrawArgsInternal A_0, Rectangle A_1, Boolean A_2)

   à NationalInstruments.Restricted.ControlElement.DrawChildren(ComponentDrawArgsInternal args, Rectangle clipRectangle)

   à NationalInstruments.Restricted.ControlElement.a(ComponentDrawArgsInternal A_0, Rectangle A_1, Boolean A_2)

   à NationalInstruments.Restricted.ControlElement.DrawChildren(ComponentDrawArgsInternal args, Rectangle clipRectangle)

   à NationalInstruments.Restricted.ControlElement.a(ComponentDrawArgsInternal A_0, Rectangle A_1, Boolean A_2)

   à NationalInstruments.Restricted.ControlElement.a(ComponentDrawArgsInternal A_0, Rectangle A_1)

   à NationalInstruments.Restricted.ControlElement.Paint(PaintEventArgs e)

   à NationalInstruments.UI.WindowsForms.ControlBase.OnPaint(PaintEventArgs e)

   à System.Windows.Forms.Control.PaintWithErrorHandling(PaintEventArgs e, Int16 layer, Boolean disposeEventArgs)

   à System.Windows.Forms.Control.WmPaint(Message& m)

   à System.Windows.Forms.Control.WndProc(Message& m)

   à System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)

   à System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)

   à System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

My application still runs but the graph only displays a red cross.

Thanks,

Norbert

[elite_code_monkey]

I would say that the CPU usage is justified (considering the plotting frequency - 20Hz).

Have you tried decimating, or cutting in half, the plotting frequency (after all, the human eye can only detect changes at around 10Hz - I think)

You can do a few things to improve performace (see the online help)

Anyhow, regarding the crash - I've had this happen to me.  I discovered that my data contained NaN values (these values caused my graphs to crash - red "X")

Good Luck

[drohacek]

Set the ProcessSpecialValues property on the plot object to true to make the plot properly handle NaN. Please be aware that this negatively impacts performance.

David Rohacek

National Instruments