Develop Reference

Executing a function on multiple threads

I am trying to splice the work on multiple threads using ThreadPooling. I wanna use every available thread to assign (and calculate in a different part of the program down the line) the output of an array member to another array members.
It does work, but it is much slower than just adding them on a single thread. Is my usage wrong or is this operation too simple for multithreading?
arrayI and arrayX variables are in classScope, i couldnt pass them as QueueUserWorkItem argument without converting them in setNeuronInput.
if (layerType != 0)
{
for (arrayI = 0; arrayI < layerSize -1 ; arrayI++)
{
for (arrayX = 0; arrayX < network.Layers[layerIndex - 1].layerSize - 1; arrayX++)
{
ThreadPool.QueueUserWorkItem(new WaitCallback(setNeuronInput), null);
//Neurons[i].input[x] = _network.Layers[layerIndex - 1].Neurons[x].output;
}
}
}
//ThreadPool.GetAvailableThreads(out availableThreads, out placeHolder);
//while (availableThreads != maxThreads)
//{
// ThreadPool.GetAvailableThreads(out availableThreads, out placeHolder);
//}
//return;
}
public void setNeuronInput(object o)
{
try
{
//Console.WriteLine("Thread is working");
Neurons[arrayI].input[arrayX] = network.Layers[layerIndex - 1].Neurons[arrayX].output;
}
catch(Exception e)
{
Console.WriteLine(e);
Console.WriteLine("ArrayI is : " + arrayI);
Console.WriteLine("ArrayX is : " + arrayX);
Console.ReadLine();
}
}

Exception of type 'System.OutOfMemoryException' was thrown inside Dispatcher

Please help me to understand what went wrong. I have a progress bar method to start running the progress bar in a task. The Base class is the static class which holds the updated values from another class. Below is my code:
private void startProgressBarBA()
{
int tempBA = 0;
proBing.Maximum = Int32.Parse(cboGeoThreshold.Text);
CancellationTokenSource bingBarToken = new CancellationTokenSource();
Task bingTask = Task.Factory.StartNew(() =>
{
while (!bingBarToken.Token.IsCancellationRequested)
{
if (tempBA != Base.proBaValue)//Reduce the number of same value assigned.
{
try
{
Dispatcher.BeginInvoke(new Action(() =>
{
if (proBing.Value == proBing.Maximum)
{
proBing.Value = 0;
Base.proBaValue = 0;
}
proBing.Value = Base.proBaValue;
tempBA = Base.proBaValue;
baRecord.Content = proBing.Value + "/" + proBing.Maximum;
}
));
}
catch(OutOfMemoryException e)
{
throw e;
}
}
if (Base.checkTaskBA == false)
{
bingBarToken.Cancel();
}
}
},bingBarToken.Token, TaskCreationOptions.LongRunning,TaskScheduler.Default);
}
The exception will occurs after a certain time, and the
Dispatcher.BeginInvoke
has been highlighted. Here is the exception message:
System.OutOfMemoryException was unhandled by user code
HResult=-2147024882
Message=Exception of type 'System.OutOfMemoryException' was thrown.
Source=View
StackTrace:
at View.MainWindow.<>c__DisplayClass21_0.<startProgressBarBA>b__0() in C:\Wade\GeocodingApp\Geocoder_v21_Rev_pcode\View\MainWindow.xaml.cs:line 331
at System.Threading.Tasks.Task.InnerInvoke()
at System.Threading.Tasks.Task.Execute()
InnerException:
How to solve this issue? Is it because the
new Action()
causes the OutOfMemoryException? Thanks for everyone's help.

Just a guess here, but it looks like you have no delay in that "while" loop in your task.
That means you are cycling through that loop very quickly, and are creating a huge number of asynchronous "invoke" messages on the Dispatcher queue - no doubt this is eating up all the memory....they aren't being processed fast enough so are building up (i.e. must have 100s thousands/maybe millions of "Action" objects created).
Possible solution....put some kind of "wait" in your while loop e.g. a Thread.Sleep(100) - you don't need to send them out that often to indicate the progress.
private void startProgressBarBA()
{
int tempBA = 0;
proBing.Maximum = Int32.Parse(cboGeoThreshold.Text);
CancellationTokenSource bingBarToken = new CancellationTokenSource();
Task bingTask = Task.Factory.StartNew(() =>
{
while (!bingBarToken.Token.IsCancellationRequested)
{
if (tempBA != Base.proBaValue)//Reduce the number of same value assigned.
{
try
{
Dispatcher.BeginInvoke(new Action(() =>
{
if (proBing.Value == proBing.Maximum)
{
proBing.Value = 0;
Base.proBaValue = 0;
}
proBing.Value = Base.proBaValue;
tempBA = Base.proBaValue;
baRecord.Content = proBing.Value + "/" + proBing.Maximum;
}
));
}
catch(OutOfMemoryException e)
{
throw e;
}
}
if (Base.checkTaskBA == false)
{
bingBarToken.Cancel();
}
Thread.Sleep(100);
}
},bingBarToken.Token, TaskCreationOptions.LongRunning,TaskScheduler.Default);
}

Unsubscribe event in reactive extension, Execute a continuasoly

public IDisposable subscription;
public ProcessData(DeviceModel model, string name = "") : base(model, name)
{
BaseAddress = _model.Process.oxyVal.regAddr;
CurrentSampleRate=1000;
subscription = Observable.Interval(TimeSpan.FromMilliseconds(CurrentSampleRate)).Subscribe(async t => await Refresh());
}
public async Task Refresh()
{
Status = "Fetching from device...";
if ((_model == null) || !_model.IsSerialPortOpen || busy)
{
StatusTrans = "Device not connected.";
return;
}
busy = true;
try
{
await ReadFromDevice().ConfigureAwait(false);
StatusTrans = "Completed.";
}
catch (Exception ex)
{
StatusTrans = ex.Message;
Trace.WriteLine(ex.Message);
}
busy = false;
}
protected override async Task ReadFromDevice()
{
var SampleRate_var = await _model.Measurement.sampleRate.sampleRate.GetValue();
CurrentSampleRate = SampleRate_var * 1000;
/*****other code********/
}
public void ChangeSampleRate()
{
subscription?.Dispose();
Observable.Interval(TimeSpan.FromMilliseconds(CurrentSampleRate)).Subscribe(async t => await Refresh());
}
I have been trying to fetching details from device.On the start,i'll subscribe a event 1 sec,in the it try to read from device(ReadFromDevice) and i'll change get the CurrentSampleRate,Onproperty change,that time I'll dispose 1sec subscribe event and i will subscribe new event with current sample rate.But problem is ReadFromDevice happens at every 1 sec.

Try this:
var CurrentSampleRate = 30;
Observable
.Generate(0, x => true, x => x + 1, x => x, x => TimeSpan.FromMilliseconds(CurrentSampleRate))
.Subscribe(x =>
{
if (x == 50)
{
CurrentSampleRate = 1000;
}
Console.Write(".");
});
It's a little nasty in that you're changing some external state to make the observable's interval change - so you may need to use Interlocked.Exchange to make the update safe.

Why my Task.ContinueWith not wait the define time

I am using this method to open specific work with concurrent Threads from my Main UI thread:
private List<MyData> MyCollection;
private static CancellationTokenSource _tokenSource;
private void Start()
{
int concurrentThread = (int)nudConcurrentFiles.Value;
int loops = (int)nudLoops.Value;
var token = _tokenSource.Token;
Task.Factory.StartNew(() =>
{
try
{
while (Iteration.LoopFinished < loops)
{
Parallel.ForEach(PcapList.Files,
new ParallelOptions
{
MaxDegreeOfParallelism = concurrentThread //limit number of parallel threads
},
File=>
{
if (token.IsCancellationRequested)
return;
//do work...
});
Iteration.LoopFinished++;
Task.Delay(10000).ContinueWith(
t =>
{
}, _tokenSource.Token);
}
}
catch (Exception e)
{ }
}, _tokenSource.Token,
TaskCreationOptions.None,
TaskScheduler.Default).ContinueWith(
t =>
{
}
);
}
The problem is that after loop i want to wait 10 secons and Task.Delay(10000).ContinueWith not waiting this 10 seconds but start immedietly another loop.

You need to call Wait() method in order to execute the task
Task.Delay(10000).ContinueWith(
t =>
{
}, _tokenSource.Token).Wait();

ThreadPool and displaying info without form freezing

I have one problem. In my project i need for more then 100 threads, that's why i prefer to use ThreadPool. here is a part of code, but in this case i have got a lot of memory usage and my form is very laggy, cuz of A lot of BeginInvoke calls(i suppose).
Is there any solutions for this problem?
public void launch()
{
while (data.Count > 0)
{
string[] part;
if (data.Count> 1000)
{
part = data.Take(1000).ToArray();
data = data.Skip(1000).ToList();
}
else
{
part = data.Take(data.Count).ToArray(); data = data.Skip(1000).ToList();
}
foreach (var input in part)
{
try
{
char splitter = ':';
if (input.Contains(';')) splitter = ';';
string login = input.Split(splitter)[0];
string pass = input.Split(splitter)[1];
EncryptCore ec = new EncryptCore(new byte[15]);
PacketSend ps = new PacketSend(ec, "");
ps._login = login;
ps._password = pass;
ps.Brutted+=ps_Parsed;
ps.Failed+=ps_Failed;
ThreadPool.QueueUserWorkItem(ps.Parse);
}
catch { Interlocked.Increment(ref curr); }
}
Thread.Sleep(1000);
}
data.Clear();
}
private void ps_Brutted(User Account)
{
toGet.Add(Account);
Interlocked.Increment(ref good);
goodLabl.BeginInvoke(new Action(delegate()
{
goodLabl.Text = "Good: " + good;
}));
Update();
}
private void Update()
{
try
{
Interlocked.Increment(ref curr);
progLabel.BeginInvoke(new Action(delegate()
{
progLabel.Text = (double.Parse(curr.ToString()) / double.Parse(max.ToString())).ToString("#%");
}));
progressBar.BeginInvoke(new Action(delegate()
{
progressBar.Text = (double.Parse(curr.ToString()) / double.Parse(max.ToString()) * 100).ToString("#");
}));
checkedLabl.BeginInvoke(new Action(delegate()
{
checkedLabl.Text = "Checked: " + curr + " / " + max;
}));
}
catch { }
}

So you have thousands of tasks, and each time one of them completes you update the UI by scheduling 4 updates on the UI thread. What you might consider doing is having the UI update on a timer-based schedule (try 100ms or 200ms) based on the integers that are updating.
Aside from that, you've got some strange numeric operations going on. You can just cast an int to a double, you don't have to round-trip through a String.