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();
}
}

UI Freezing and Computation Really Slow

I'm writing a program, that should replace or remove some entries from a logfile.txt.
The code is working fine ( at least for small LogFiles). If i use a big file (like 27 MB) its getting very slow and the UI freeze. I cant click anything.
On Button click i execute this method:
private string delete_Lines(string[] lines, string searchString)
{
for (int i = 0; i < lines.Length; i++)
{
if (lines[i].Contains(searchString))
{
rtbLog.Text += "Deleting(row " + (i + 1) + "):\n" + lines[i] + "\n";
progressBar1.Value += 1;
if (cbDB == true)
{
while (is_next_line_block(lines, i) == true)
{
i++;
rtbLog.Text += lines[i] + "\n";
progressBar1.Value += 1;
}
}
}
else
{
res += lines[i]+"\n";
progressBar1.Value += 1;
}
}
tssLbl.Text = "Done!";
rtbLog.Text += "...Deleting finished\n";
return res;
}
Lines is the array of the logfile i am trying to clean up. every entry is a single row . tssLbl is a notification label and rtbLog is a richTextBox, where i'am tracking which row i am deleting.
is_next_line_block is just another method, which is checking of the next lines are part of the block i want to delete. The params of this method are the whole lines array and the line position.
private bool is_next_line_block(string[] lines, int curIndex)
{
if (curIndex < lines.Length-1)
{
if (lines[curIndex + 1].StartsWith(" "))
{
return true;
}
else
{
return false;
}
}
else
{
return false;
}
}
Have anybody any idea, what is causing that freezes and is slowing down the program? I know, that i could speed my code up by parallelizing it, but i cant imagine, that it takes so long to check up a 27 MB txt file without parallelism.

You have several issues here:
You are reading the whole file in buffer (array of string), I am guessing you are calling File.ReadAllLines(). Reading big files in buffer will slow you down, as well as in extreme case run you out of memory.
You are using += operation for your rich textbox Text property. That is time consuming operation as UI has to render the whole rich text box every time you update the text property that way. Better option is to use string builder to load these text, and update rich text box periodically.
To fix this you need to read the file as stream. Progress can be monitored based on bytes read instead of line position. You can run the read operation async and monitor progression on a timer, as shown in example below.
private void RunFileOperation(string inputFile, string search)
{
Timer t = new Timer();
int progress = 0;
StringBuilder sb = new StringBuilder();
// Filesize serves as max value to check progress
progressBar1.Maximum = (int)(new FileInfo(inputFile).Length);
t.Tick += (s, e) =>
{
rtbLog.Text = sb.ToString();
progressBar1.Value = progress;
if (progress == progressBar1.Maximum)
{
t.Enabled = false;
tssLbl.Text = "done";
}
};
//update every 0.5 second
t.Interval = 500;
t.Enabled = true;
// Start async file read operation
System.Threading.Tasks.Task.Factory.StartNew(() => delete_Lines(inputFile, search, ref progress, ref sb));
}
private void delete_Lines(string fileName, string searchString, ref int progress, ref StringBuilder sb)
{
using (var file = File.OpenText(fileName))
{
int i = 0;
while (!file.EndOfStream)
{
var line = file.ReadLine();
progress = (int)file.BaseStream.Position;
if (line.Contains(searchString))
{
sb.AppendFormat("Deleting(row {0}):\n{1}", (i + 1), line);
// Change this algorithm for nextline check
// Do this when it is next line, i.e. in this line.
// "If" check above can check if (line.startswith(" "))...
// instead of having to do it nextline next here.
/*if (cbDB == true)
{
while (is_next_line_block(lines, i) == true)
{
i++;
rtbLog.Text += lines[i] + "\n";
progressBar1.Value += 1;
}
}*/
}
}
}
sb.AppendLine("...Deleting finished\n");
}

As a follow up to your question on Task.Factory.Start() usage, it's done this way (generally):
// you might need to wrap this in a Dispatcher.BeginInvoke (see below)
// if you are not calling from the main UI thread
CallSomeMethodToSetVisualCuesIfYouHaveOne();
Task.Factory.StartNew(() =>
{
// code in this block will run in a background thread...
}
.ContinueWith(task =>
{
// if you called the task from the UI thread, you're probably
// ok if you decide not to wrap the optional method call below
// in a dispatcher begininvoke...
Application.Current.Dispatcher.BeginInvoke(new Action(()=>
{
CallSomeMethodToUnsetYourVisualCuesIfYouHaveAnyLOL();
}));
}
Hope this helps!

Thanks to everybody for the help, especially loopedcode, That's the working version (Took loopedcode's code and made some edit):
private void RunFileOperation(string inputFile, string search)
{
Timer t = new Timer();
StringBuilder sb = new StringBuilder();
{
rtbLog.Text = "Start Deleting...\n";
}
// Filesize serves as max value to check progress
progressBar1.Maximum = (int)(new FileInfo(inputFile).Length);
t.Tick += (s, e) =>
{
rtbLog.Text += sb.ToString();
progressBar1.Value = progress;
if (progress == progressBar1.Maximum)
{
t.Enabled = false;
tssLbl.Text = "done";
}
};
//update every 0.5 second
t.Interval = 500;
t.Enabled = true;
// Start async file read operation
if (rbtnDelete.Checked)
{
if (cbDelete.Checked)
{
System.Threading.Tasks.Task.Factory.StartNew(() => delete_Lines(inputFile, search, ref progress, ref sb, ref res1));
}
}
else
{
//..do something
}
private void delete_Lines(string fileName, string searchString, ref int progress, ref StringBuilder sb, ref StringBuilder res1)
{
bool checkNextLine=false;
using (var file = File.OpenText(fileName))
{
int i = 0;
while (!file.EndOfStream)
{
i++;
var line = file.ReadLine();
progress = (int)file.BaseStream.Position;
if (line.Contains(searchString))
{
sb.AppendFormat("Deleting(row {0}):\n{1}\n", (i), line);
checkNextLine = true;
}
else
{
if (cbDB && checkNextLine && line.StartsWith(" "))
{
sb.AppendFormat("{0}\n", line);
}
else
{
checkNextLine = false;
res1.AppendLine(line);
}
}
}
}
sb.AppendLine("\n...Deleting finished!);
}

why do other events cannot be fired while "for loop" is in process?

I have a for loop and when the loop is being processed, I cant access any other function or event like clicking button it doesn't work till the for loop ends. Is there any way to overcome this Issue and hope I can get answer soon.
for (int i = 0; i < sizes - 2; i++)
{
if (pictureBox1.Image != null)
{
trackBar1.Value = trackBar1.Value + 1;
DisplayImage(_image);
}
}
Thanks in advance.

hi if you using framework 4.5
you can to the next :
Task.Run(() =>
{
for (int i = 0; i < sizes - 2; i++)
{
if (pictureBox1.Image != null)
{
trackBar1.Value = trackBar1.Value + 1;
DisplayImage(_image);
}
}
});
if not you can try this using thread :
Thread thread = new Thread(NewMethod);
thread.Start();
private void NewMethod()
{
for (int i = 0; i < sizes - 2; i++)
{
if (pictureBox1.Image != null)
{
trackBar1.Value = trackBar1.Value + 1;
DisplayImage(_image);
}
}
}
you can upgrade but you need to do it with delegate try this if you have cross thread operation error when update ui :
create delegate void function
delegate void Function();
then in your for make this :
Invoke(new Function(delegate()
{
label.text = "some text" ;
}));

This example shows how to create a new thread in .NET Framework. First, create a new ThreadStart delegate. The delegate points to a method that will be executed by the new thread. Pass this delegate as a parameter when creating a new Thread instance. Finally, call the Thread.Start method to run your method (in this case WorkThreadFunction) on background.
using System.Threading;
Thread thread = new Thread(new ThreadStart(WorkThreadFunction));
thread.Start();
The WorkThreadFunction could be defined as follows.
public void WorkThreadFunction()
{
try
{
// do any background work
}
catch (Exception ex)
{
// log errors
}
}

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.

ThreadStart with Parameter method

I am trying to learn Threading in .Net.
Many of you must have seen this:
private void button1_Click(object sender, EventArgs e)
{
Thread t = new Thread(new ThreadStart(loop));
t.Start();
}
private void loop()
{
for (int i = 0; i < 100000; i++)
{
textBox1.Text = i.ToString();
}
}
It works fine, but what if my loop method has parameters in it, like:
private void loop(string str)
{
for (int i = 0; i < 100000; i++)
{
textBox1.Text = i + str;
}
}
Then how to call this method in my ThreadStart as ThreadStart accepts just the method name. Then how to call loop method in a different thread?

Thread t = new Thread(new ParameterizedThreadStart(loop));
t.Start("Hello world");
private void loop(object obj)
{
string str = (string)obj;
for (int i = 0; i < 100000; i++)
{
// Don't do this: you can't change a control from another thread. Danger Will Robinson!
textBox1.Text = i + str;
}
}
Note that the loop method must accept an object parameter, so you'll have to upcast the object to your type. If you don't want, you can use a closure and an anonymous method:
string str = "Hello world";
Thread t = new Thread(() => {
for (int i = 0; i < 100000; i++)
{
// Don't do this: you can't change a control from another thread. Danger Will Robinson!
textBox1.Text = i + str;
}
});
t.Start();
In this way the anonymous method will "close" around str and it will be similar as if you had passed the parameter. Similar because there are differences/problems on closing variables. In reality I would write something similar to:
string str = "Hello world";
{
string str2 = str;
Thread t = new Thread(() => {
for (int i = 0; i < 100000; i++)
{
// Don't do this: you can't change a control from another thread. Danger Will Robinson!
textBox1.Text = i + str2;
}
});
t.Start();
}
so that no one else can "touch" str2.
If you need I can find some answer on SO that explain this "problem"

You'd use ParameterizedThreadStart instead: http://msdn.microsoft.com/en-us/library/system.threading.parameterizedthreadstart.aspx
Thread t = new Thread(new ParameterizedThreadStart(loop));
t.Start("Foo");
// Note the use of Object here to match the delegate signature
private void loop(Object state)
{
var str = state as String;
for (int i = 0; i < 100000; i++)
{
// For what it is worth, this is illegal:
// textBox1.Text = i + str;
// You need to Invoke back to the UI thread to access a control's properties:
textBox1.Invoke(()=> { textBox1.Text = i + str; });
}
}

There is a ParameterizedThreadStart class that Delegates with a single parameter can be cast to when instantiating a Thread:
private void button1_Click(object sender, EventArgs e)
{
Thread t = new Thread(new ParameterizedThreadStart(loop));
t.Start(str);
}
private void loop(string str)
{
for (int i = 0; i < 100000; i++)
{
//the code you had is a no-no when you are multithreading;
//all UI updates must occur on the main thread
//textBox1.Text = i + str;
UpdateTextBoxText(textBox1, i+str);
}
}
private void UpdateTextBoxText(TextBox textBox, string text)
{
//the method will invoke itself on the main thread if it isn't already running there
if(InvokeRequired)
{
this.Invoke((MethodInvoker)(()=>UpdateTextBoxText(TextBox textBox, string text)));
return;
}
textBox.Text = text;
}
If you don't need very fine-grained control over when the thread starts and stops, you can leave it to the ThreadPool and use Delegate.BeginInvoke:
private void button1_Click(object sender, EventArgs e)
{
Action<string> method = loop;
method.BeginInvoke(str, null, null);
}
private void loop(string str)
{
for (int i = 0; i < 100000; i++)
{
//textBox1.Text = i + str;
UpdateTextBoxText(textBox1, i+str);
}
}
private void UpdateTextBoxText(TextBox textBox, string text)
{
//the method will invoke itself on the main thread if it isn't already running there
if(InvokeRequired)
{
this.Invoke((MethodInvoker)(()=>UpdateTextBoxText(textBox, text)));
return;
}
textBox.Text = text;
}

Like this:
new Thread(() => loop("MyString")).Start();
You don't even have to mess with ThreadStart/ParameterizedThreadStart.

Take a look at ParameterizedThreadStart, it allows you to pass parameters into your thread start function.