I'm using a Threading.DispatcherTimer and every tick of the timer runs a subroutine.
Is it possible that if the subroutine takes longer then 1s for the processor to finish that it will mess up the time of the timer that is counting in seconds?
Try
timercount = Nothing
timercount = New DispatcherTimer()
timercount.Interval = TimeSpan.FromSeconds(1)
timercount.Start()
AddHandler timercount.Tick, AddressOf TickMe 'Every Second the 'TickMe' Method runs
Catch ex As Exception
' MessageBox.Show(ex.Message)
End Try
Private Sub TickMe()
CL(0).Actual = H.Actual
TextBoxSerialNumber.Focus()
IntSec = IntSec + 1
H.ActualBoxTime = H.ActualBoxTime.AddSeconds(1)
CL(0).ActualBoxTime = H.ActualBoxTime
If IntSec Mod 60 = 0 Then
H.Actual = H.Actual + 1
CL(0).Actual = H.Actual
End If
CL(0).TargetBox = H.TargetBox
PopulateCutGrid(CL)
End Sub
I've found after 50-60 minutes of counting it's off by almost 10 minutes!
From the MSDN article regarding DispatchTimer:
Timers are not guaranteed to execute exactly when the time interval occurs, but they are guaranteed to not execute before the time interval occurs. This is because DispatcherTimer operations are placed on the Dispatcher queue like other operations. When the DispatcherTimer operation executes is dependent on the other jobs in the queue and their priorities.
If you need something more precise, I would recommend System.Threading.Timer. Each time the method of this timer is invoked, a ThreadPool thread is used. From this article:
The callback method executed by the timer should be reentrant, because it is called on ThreadPool threads. The callback can be executed simultaneously on two thread pool threads if the timer interval is less than the time required to execute the callback, or if all thread pool threads are in use and the callback is queued multiple times.
Also forgot to mention that you'll need to use Invoke and InvokeRequired for WinForms or Dispatcher for WPF (I think, since I don't use WPF).
Edit 1:
Regarding your comment about needing total seconds, you can just store the original DateTime somewhere, and total seconds would be calculated using (DateTime.Now - StoredDateTime).TotalSeconds(). I would also recommend reading this article about threading in WPF to see if it applies in your case.
Edit2:
Actually, since I think the only thing you're after is a precise count of elapsed time, you could use a Stopwatch to keep track of time. Try using the regular DispatchTimer and just refer to the stopwatch each "tick" of that timer. That way, the Stopwatch is what keeps track of time, not the timer that could be used just for updating the UI.
Related
This is my first time using VBA in Outlook so please bear with me
I've created a basic Macro that does various things to folders. Since this takes a while I decided to make a status window that says what its currently doing. I simply keep setting one of the label's values with this
Function UpdateStatus(Message As String)
StatusForm.StatusUpdate.Caption = Message
StatusForm.Repaint
End Function
The issue is that after it runs for a bit (5-15 seconds) the window and the rest of outlook locks; the form no longer updates and has a "(Not Responding)" in its window title.
I feel like I'm somehow dead locking the UI thread but I'm at a loss on how to work around it. Commenting out Repaint not surprisingly doesn't let it update at all, but outside of that I don't know where to look
Any suggestions?
Try adding DoEvents in your computationally intensive loop. This yields the executing code to the UI thread so that other things can get done when you have computationally intensive stuff going on in the background. Office is single-threaded, so you can block the UI when you are running macros.
Sample:
Sub LockUI()
Dim x
x = Timer
Do While Timer - x < 5
'Blocks the UI for 5 seconds
Loop
End Sub
Sub LockUI2()
Dim x
x = Timer
Do While Timer - x < 5
'Doesn't block the UI
DoEvents
Loop
End Sub
In my VB.NET program is a time consuming function that gets data and updates the UI at a periodic interval. I moved this function to another thread, but it now takes much longer to execute. Using the stopwatch class, I calculated that when it is part of the main thread, it takes 130 ms, but in the separate thread it takes 542 ms, so that's more than 4 times slower.
My CPU is a Core I5 M520 (2 cores), so I don't now why is it taking so much longer.
I am using the System.Threading.Thread class. I also tried to set the new thread's priority higher, but this had no effect.
Why is the separate thread taking so much longer and is there a way I can speed it up?
Thanks
The code:
Public Sub update(ByVal temp As Visual)
SyncLock mUpdateQueue
If Not mUpdateQueue.Contains(temp) Then
mUpdateQueue.Enqueue(temp)
End If
End SyncLock
If Not mainThread.IsAlive Then ' moet hierdie beter doen
mainThread = New Thread(AddressOf DataFetchThread)
mainThread.Start()
End If
End Sub
Private Sub DataFetchThread()
Dim s As New Stopwatch()
s.Start()
Dim temp As Visual = Nothing
While mUpdateQueue.Count > 0
SyncLock mUpdateQueue
temp = mUpdateQueue.Peek()
End SyncLock
mDataCollector.updateV(temp)
SyncLock mUpdateQueue
mUpdateQueue.Dequeue()
End SyncLock
End While
s.Stop()
Debug.WriteLine("thread run time: " & s.ElapsedMilliseconds)
End Sub
mDataCollector.updateV(temp): This function get data from a database and plots the points on a picturebox to create a graph. It wouldn't make a lot of sense to add all of the code here.
To ask this question in another way: Is it normal that the second thread takes much longer to execute or is there something wrong with my code?
You are accessing the mUpdateQueue variable from multiple threads and using locks to gaurd access to it. This is fine, but using locks has an overhead (to aquire the lock, and during the time that the other threads wait to aquire the lock). This is probably why your new thread is taking longer: it is waiting on the locking.
You could try using the ReaderWriterLockSlim class which may provide faster access to your variables. Just remember that it implements IDisposable so you need to call Dispose on it when you're done with it.
I am coding in VB.Net, VS 2008.
I wrote a console app that consumes 2 web methods from a web site application. I need to enhance this console app so that it launches the web methods continuously, perhaps every x minutes (during business hours), but never before the last invocation has terminated, whose duration may vary, depending on how many accounts there are to process.
Originally, I scheduled the application using Task Scheduler, but I think this doesn't prevent two invocations at the same time.
Although I have seen many posts on using timers, I haven't found exactly what I need.
So far I have:
Dim aTimer As New System.Timers.Timer()
AddHandler aTimer.Elapsed, AddressOf TriggerWebMethods
' Set the Interval to 10 minutes:
aTimer.Interval = 1000 * 60 * 10 '(1 second * 60 = 1 minute * 10 = 10 minutes)
aTimer.Enabled = True
aTimer.AutoReset = True
When should Timer.Elapsed be used vs. Timer.Tick?
What is the difference between Timer.Enabled vs Timer.Start, and should I be selecting just one?
I would like the 2nd web method to kick off when the first one is done.
I'd like to keep this as simple as possible. Thank you for all help.
If you are dealing with a System.Timers.Timer, then you'd only have the Elapsed event available. If a System.Windows.Forms.Timer, then you'd use the Tick event. You're not writing a WinForms app so you would be using the System.Timers.Timer.
Personally, I would only use the Enabled property to see if the timer has been started. I wouldn't use it to start or stop it. Using the Start() or Stop() method makes it very clear what's happening to the timer.
If your web methods execute synchronously, you could just call them one after the other in your TriggerWebMethods() method. The second will not be called until the first completes.
Sub TriggerWebMethods(source As Object, e As ElapsedEventArgs)
FirstWebMethod()
SecondWebMethod()
End Sub
If asynchronously, you'd have to register a callback on the first web method to execute the second when it completes. In VB, I believe you can use the second directly as the callback, depending on how you make the asynchronous call. (Sorry, my VB is very rusty now so might not be 100% correct syntax)
Sub FirstWebMethod()
' ...
End Sub
Sub SecondWebMethod()
' ...
End Sub
Sub TriggerWebMethods(source As Object, e As ElapsedEventArgs)
Dim first As Action = AddressOf FirstWebMethod
first.BeginInvoke(AddressOf SecondWebMethod, first)
End Sub
Just to add a little to Jeff M's answer. The Timer.Elapsed Event has the following note.
If the SynchronizingObject property is null, the Elapsed event is
raised on a ThreadPool thread. If the
processing of the Elapsed event lasts
longer than Interval, the event might
be raised again on another ThreadPool
thread. In this situation, the event
handler should be reentrant.
Since you're in a Console app you can either hand roll you own SynchronizingObject or you can set the AutoReset to False, and change your TriggerWebMethods to have a start at the end. You may even want to offset the interval to take into consideration the amount of processing time.
e.g.
Dim start As Date = Now
'do stuff
Dim ts As TimeSpan = Now - start
Dim i As Integer = (1000 * 60 * 10) - ts.TotalMilliseconds
Dim aTimer As Timers
aTimer.Interval = i
So I'm kind of new to VB and am just playing around with a little project, I currently need a loop that is constantly checking the systems clock to see if it's equal to a certain time.
While Not myTime.Hour = 24
If TimeOfDay = newTime Then
nfi.ShowBalloonTip(15)
intRandNumb = RandomNumber(1, 15)
dblAddMinutes = intTime + intRandNumb
newTime = TimeOfDay.AddMinutes(dblAddMinutes)
End If
End While
I have this right now, but obviously it's grinding everything to a halt and using 50% of my cpu in the process, I just would like to know what I can substitute in or change to make this loop run better and perform how I need it to.
you can add
Threading.Thread.Sleep(0),
this will cause a context switch and greatly reduce the CPU usage
Also consider using a timer object to be called every 10 or 100 ms, this will also be better in usage then having a loop
You can use
Threading.Thread.Sleep(0)
This will cause the working thread to yield the rest of it's current timeslice which will reduce the cpu usage quite a bit. However you should consider whether you really nead busy waiting for the time or if you could get away with setting a timer to count down the difference between the current time and the expected time, e.g.:
var t = new System.Timers.Timer((DateTime.Now - DateTime.Now).TotalMilliseconds);
t.Elapsed = DoSomething;
t.Start();
checking the systems clock to see if it's equal to a certain time.
There are two "correct" ways to do this:
Build a normal app that doesn't care what time it is, and set it up in windows as a schedule task.
Check the time once and calculate how long until the desired time. Then set up a timer to wait for that exact duration.
Under no circumstance should you keep polling the system clock for something like this that will just run once.
As Joel pointed out, you should try using a timer instead. I'm not sure if your app is a form or console or other, so I'll try to be generic and use System.Timers.Timer.
The code here (interval is set at 10ms, change to a value of your need):
Private timer1 As System.Timers.Timer
Const interval As Integer = 10
Sub initTimer()
timer1 = New System.Timers.Timer(10)
AddHandler timer1.Elapsed, AddressOf Me.timer_Elapsed
timer1.Start()
End Sub
Sub timer_Elapsed(ByVal sender As Object, ByVal e As System.Timers.ElapsedEventArgs)
'do your stuff here
'Console.WriteLine(e.SignalTime.ToString())
End Sub
How do you limit the CPU of a while loop?
In this case, the code which is inside the while loop:
Private Sub wait(ByVal time)
Dim sw As New Stopwatch
sw.Start()
Do While sw.ElapsedMilliseconds < time And StillOpen = True
Application.DoEvents()
Loop
sw.Stop()
End Sub
But now, here is the issue. This loop is allowing the while loop to run every second, once a second, and the wait sub is causing this delay, as it should.
How can I limit the CPU that this is taking up? For some reason, my task manager says it is taking 50 CPUs to run this simple task, yet it should probably take no more than 1 or 2. Though the manager says it is taking that much CPU, my computer speed is not being affected at all, which is odd considering it is a two-year-old laptop.
I don't want any users to freak out about it, but knowing how people are these days....
Anyway, the language is vb.net. Can someone please help me?
Thanks!
EDIT: To clarify, that code is not inside the while loop itself, but a call for the subroutine is, i.e. wait(1000)
Use a timer event !!! Nearly no cpu effort.
You could always perform some kind of sleep between iterations of the loop...
I'm not familiar with VB.NET but a duration of 100-200ms will probably be more than enough to drop the CPU usage.
Eg:
Do while (...)
Application.blah();
System.Threading.Thread.Sleep(150);
End
Edit After some research, I think the function you want is: System.Threading.Thread.Sleep()
Your code is executing Application.DoEvents() constantly in the while loop, for the time duration specified in your time parameter. This will consume one core of your CPU, which is why you're seeing 50% processor usage (you have a dual-core processor, correct?). This is an ugly way to wait. You could instead call Thread.Sleep(), passing it the number of milliseconds you'd like your thread to wait.
If you'd like your application to stay responsive, you might also spin off a timer, and block the UI from any action until the timer triggers. Something like (lightly tested):
// constructor or designer code
System.Windows.Forms.Timer timer = new System.Windows.Forms.Timer();
timer.Tick += new EventHandler(timer_Tick);
void Wait(int interval)
{
timer.Interval = interval;
timer.Start();
BlockUIOperations(); // implement yourself
}
void timer_Tick(object sender, EventArgs e)
{
timer.Stop();
EnableUIOperations(); // implement yourself
}
Here's my attempt at a translation into VB:
'' Add a Timer object to the form named "Timer".
'' Hook its Tick event to Timer_Tick
Private Sub Wait(ByVal interval As Integer)
Timer.Interval = interval
Timer.Start()
BlockUIOperations() '' implement yourself
End Sub
Private Sub Timer_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer.Tick
Timer.Stop()
EnableUIOperations() '' implement yourself
End Sub
Well, the CPU is always running at 100% when it's running, so the only practical way to limit the CPU usage is to run bursts or loop and sleeping in between.
Laptop CPUs usually have some SpeedStep technology or equievalent that will slow down the CPU when it's not working hard, but it's not reasonable to assume that your application would have access to control that, at least not directly. You might be able to affect it indirectly by measuring the CPU usage and adjust the length of the work and sleep cycles to get the desired result.
If you don't mind blocking the current thread, you could use a WaitHandle.
Public Sub Wait(ByVal ms As Integer)
Using wh As New ManualResetEvent(False)
wh.WaitOne(ms)
End Using
End Sub
Sub Main()
Console.WriteLine("Hello World!")
Wait(5000)
Console.WriteLine("Good-Bye!")
End Sub
Of course, something more complex can be constructed depending on what you are trying to accomplish.
This is perfect as a VB.net sleep replacement. Now my console app is NOT reported as non responsive since I have no sleep commands!
Just add Imports System.Threading above your module and place this just above your sub main
Public Sub Wait(ByVal ms As Integer)
Using wh As New ManualResetEvent(False)
wh.WaitOne(ms)
End Using
End Sub
Then, in your sub main, use
wait(100)
to pause your app for 100 miliseconds.
Have fun
You should take note of if you are doing this in the main UI Thread or a thread you have spun off.
For Threads the easiest way is to just Thread.Sleep(x miliseconds)
On the main UI thread I tend to use a DoEvents function in vb.net and vb6 like this
Public Sub TimeKiller(byval secondstowait as integer)
dim tmptime as datetime = datetime.now
do while datetime.now < dateadd("s",secondstowait,tmptime)
Application.Doevents
end while
End Sub
On the question of CPU usage I look at it like this.... if you make just a hard loop that like
while true
end while
I would expect to see very high cpu usage over 50% because the UI thread is hard blocking on this.... in most cases the windows system will limit the cpu usage of any given program so that its threads dont block the entire system.
The DoEvents ensure that windows message pumps fire correct and respond to correct. It also ensures that the garbage collector fires on time.
Also if you have other threads spun up off of your UI.Thread your UI.Thread can respond to events fired from these other threads....
In such cases where your calling form controls from other threads and do form.InvokeRequired routines will be able to respond correctly.
Also The only time you should be hard looping on the MainUI thread is when it is in response to some user activity and you need to put waits in for the user to see progress of something....
If it is some kind of automated process that is always running... look to moving it to another thread.
Or if its something that runs periodically on a timer or a time that kicks off a thread.
Somebody please tell me if I am wrong on these assumptions....
Not sure about the Using wh As New ManualResetEvent(False) wh.WaitOne(ms) as I have never heard of that and have no idea what that does.