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Multi-threading - Parallel Syncronization

caksabre231-Mar-09 4:12

31-Mar-09 4:12

Hello,

I have a program that opens multiple user controls, each one needing to run 3 parallel processes. It needs to run all 3 simultaneously, and then when all 3 are complete run a process. This needs to occur every second.

What I have done, is create 3 threads, one main thread which when it starts running it calls two .Set() methods for manualevent handlers which then sets the other two threads running. I then have a waitall in the main thread (after the point where it has done its work) which waits for the other two threads to complete. At the end of the two threads I have a waitall which waits for a different manualevent to be reset (which happens when the main thread finishes).

Now this all seems to work fine, but when running 4 user controls at once, approximetly every minute the threads somehow get confused and one of the waitall's for the two sub threads get stuck. So I have put a timeout parameter here which is a hack, and doesn't really solve why it is locking up. I can't put all the code in but below is an example of it working.

Can anyone help come up with why this is occurring, or a better way of doing this?

//Thread Ones Run Method
public void ThreadOne()
{
while(true)
{

ogEvents[0] = new ManualResetEvent(false);
ogEvents[1] = new ManualResetEvent(false);

//Do a task here
//Wait for the other 2 threads to finish
bool blSuccess = WaitHandle.WaitAll(ogEvents, 4000, false);

//Do some calcs

Thread.Sleep(1000);
ogThreadTwo[0].Set();
ogThreadThree[0].Set();
}
}

//Thread Two's Run Method
public void ThreadTwo()
{
while(true)
{
//Do some task
//Task Finished
ogEvents[0].Set();
ogThreadTwo[0] = new ManualResetEvent(false);
bool blSuccess = WaitHandle.WaitAll(ogThreadTwo, 4000, false);
}
}

//Thread Three's Run Method
public void ThreadThree()
{
while(true)
{
//Do some task

//Task Finished
ogEvents[0].Set();
ogThreadThree[0] = new ManualResetEvent(false);
bool blSuccess = WaitHandle.WaitAll(ogThreadThree, 4000, false);
}
}

Re: Multi-threading - Parallel Syncronization

Luc Pattyn31-Mar-09 4:54

Luc Pattyn

31-Mar-09 4:54

Hi,

why are you creating new ManualResetEvents all the time? I would create them once, and resuse them, i.a. call Set(), Reset() and Wait/WaitAll() as required, no more no less. Replacing one ManualResetEvent by another you are risking signaling or waitinf for one that isn't actually in business any more.

Whatever you do, you must allow for any or all of your threads not to get any CPU cycles at all for some time, e.g. because some high-priority thing suddenly happens.

Smile | :)

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Re: Multi-threading - Parallel Syncronization

Ian Shlasko31-Mar-09 5:02

Ian Shlasko

31-Mar-09 5:02

Purely for organizational purposes, I would actually have a fourth thread controlling the other three, if possible. Threading problems can be difficult to debug, so keeping the code clean can sometimes be a big help...

Also, I would probably go with just basic EventWaitHandles

EventWaitHandle workerThreadStart[] = new EventWaitHandle[3];
EventWaitHandle workerThreadFinish[] = new EventWaitHandle[3];

// Controller thread:

while (true)
{
  for (int x = 0; x < 3; x++) workerThreadStart[x].Set();
  WaitHandle.WaitAll(workerThreadFinish);

  // Insert a delay if desired
}

// Each worker thread (# = 0, 1, or 2 for threads one, two, three):

while (true)
{
  workerThreadStart[#].WaitOne();

  try
  {
    // Do some task
  }
  catch (...)
  {
    // Remember, if you get an exception on a background thread, it may not display
  }
  finally 
  {
    // Even if we get an error, we want to set the EWH so as not to stall everything
    workerThreadFinish[#].Set();
  }
}

(Note: Just typed this out in here, not in a code editor, so might have typos or syntax problems - Just trying to give a rough idea anyway)

EDIT: Oh, and when you instantiate the EWH's, bring 'em up unsignaled and AutoReset.

Re: Multi-threading - Parallel Syncronization

Alan N31-Mar-09 5:17

Alan N

31-Mar-09 5:17

Hi,
I'm not sure why you are continually reallocating the event objects. Doing so may have created a situation where you are waiting for a signal on an event object that is no longer referenced in your code.

It is quite possible that ThreadOne could set ogThreadTwo or ogThreadThree prior to reallocation in ThreadTwo or ThreadThree. If that happens the WaitAll methods will block as they are waiting for the reallocated events to be signalled.

//Task Finished
ogEvents[0].Set();
ogThreadThree[0] = new ManualResetEvent(false);
bool blSuccess = WaitHandle.WaitAll(ogThreadThree, 4000, false);

should be reordered

ogThreadThree[0] = new ManualResetEvent(false);
ogEvents[0].Set();
bool blSuccess = WaitHandle.WaitAll(ogThreadThree, 4000, false);

so that ogThreadThree event is rellocated BEFORE you release ThreadOne.

Alan.

Re: Multi-threading - Parallel Syncronization

caksabre231-Mar-09 5:37

caksabre2

31-Mar-09 5:37

Thanks for the reply's. I have changed the code to have 4 threads, and have stopped reallocating the event and it seems to have fixed any sync issues.

Thanks

why button_click event raising 2 times?

Narendra Reddy Vajrala31-Mar-09 3:43

Narendra Reddy Vajrala

31-Mar-09 3:43

Hi all,
in my C#.net 3.5 windows application, i have a insert statement in my button_Click event.
but this is raising 2 times, so 2 rows with same data inserting instead of 1.
i checked in debugmode after reaching last statement it is moving to first statement again.
why this is happening?

Please give some solution

Thanks in Advance
--Naren
Blush | :O

Re: why button_click event raising 2 times?

stancrm31-Mar-09 3:47

stancrm

31-Mar-09 3:47

Probably you called :

button.Click += new EventHandler(button_Click);

2 times...

Re: why button_click event raising 2 times?

Narendra Reddy Vajrala31-Mar-09 3:57

Narendra Reddy Vajrala

31-Mar-09 3:57

no..!
it was 1 time only

Re: why button_click event raising 2 times?

Ian Shlasko31-Mar-09 4:02

Ian Shlasko

31-Mar-09 4:02

You might want to run a Find in your solution for "BtnOk_Click", just to be certain of that. Remember, the designer will add one event hook and hide it in the InitializeComponent() method.

This may or may not be the problem, but it's best to eliminate the easy solutions first.

Re: why button_click event raising 2 times?

Narendra Reddy Vajrala31-Mar-09 4:12

Narendra Reddy Vajrala

31-Mar-09 4:12

hmmmmmmm
i did but it is showing single time only
Frown | :(

Re: why button_click event raising 2 times?

musefan31-Mar-09 3:54

musefan

31-Mar-09 3:54

Gonna have to see some code to help with this one

Life goes very fast. Tomorrow, today is already yesterday.

Re: why button_click event raising 2 times?

Narendra Reddy Vajrala31-Mar-09 3:57

Narendra Reddy Vajrala

31-Mar-09 3:57

private void BtnOk_Click(object sender, EventArgs e)
{
if (TxtTotMins.Text != TxtUCmins.Text)
return;

DateTime dt = Convert.ToDateTime(System.DateTime.Now.ToString());
DateTime Wo_dt = Convert.ToDateTime(System.DateTime.Now.ToShortDateString());
DateTime mod_time=Convert.ToDateTime(System.DateTime.Now.ToLongTimeString());
string QueueId = ClientInfo.Application + "!" + Wo_dt.ToShortDateString() + "!" + TransId;
string Upload = "N";

for (int i = 1; i <= OeCnt; i++)
{
string[] Level1 = OeControl[i].Level2.Tag.ToString().Split(':');
string Level1Code = Level1[1].ToString();
string Level2Code;
string Level3Code;

if (!(string.IsNullOrEmpty(OeControl[i].Level2.Text)))
{
string[] Level2 = OeControl[i].Level3.Tag.ToString().Split(':');
Level2Code = Level2[1].ToString();
}
else
Level2Code = null;

if (!(string.IsNullOrEmpty(OeControl[i].Level3.Text)))
{
string[] Level3 = OeControl[i].Level1.Tag.ToString().Split(':');
Level3Code = Level3[1].ToString();
}
else
Level3Code=null;

string Timespent=OeControl[i].TimeText.Text;

string Query = string.Format(@"insert into SIS_OEE(T_STAMP,oper,L2_Code,L3_Code,L4_Code,time_spent,
total_time,cono,cctr,emp,job,work_date,work_shift,mod_date,mod_time,
mod_user,sfis_trans_id,queue_id,upload) values ('{0}','{1}','{2}','{3}','{4}','{5}',
'{6}','{7}','{8}','{9}','{10}','{11}','{12}','{13}','{14}','{15}',{16},'{17}','{18}')", dt, TxtOperation.Text,
Level1Code, Level2Code, Level3Code, Timespent, TxtTotMins.Text, Cono, TxtCctr.Text,
Emp, TxtJob.Text, Wo_dt, Shift, Wo_dt, mod_time, Emp, TransId, QueueId, Upload);
Utility.SFISConnection.ExecuteNonQuery(Query);

}

this.Close();

}

this is mycode inside buttonclick

Re: why button_click event raising 2 times?

musefan31-Mar-09 4:02

musefan

31-Mar-09 4:02

well your query code if in a for loop so i can only assume that loop is running twice. Is this what you have indended?

Life goes very fast. Tomorrow, today is already yesterday.

Re: why button_click event raising 2 times?

Narendra Reddy Vajrala31-Mar-09 4:16

Narendra Reddy Vajrala

31-Mar-09 4:16

no no
for loop running fine but
it is coming again to
{ which is the first line under btn_click event
Frown | :(

Re: why button_click event raising 2 times?

musefan31-Mar-09 4:21

musefan

31-Mar-09 4:21

and then returns after the first if statement?

if you event is being called twice then it would suggest that you hav added it to the buttons Click event more than once, are there any other events attached to the button such as MouseClick, Enter etc.

Life goes very fast. Tomorrow, today is already yesterday.

Re: why button_click event raising 2 times?

Narendra Reddy Vajrala31-Mar-09 4:32

Narendra Reddy Vajrala

31-Mar-09 4:32

nowhere in my project btnOK_Click event twice, i checked in design page also.

Re: why button_click event raising 2 times?

musefan31-Mar-09 4:34

musefan

31-Mar-09 4:34

Ok, well Colin's suggestion below sounds good, give that a try

Life goes very fast. Tomorrow, today is already yesterday.

Re: why button_click event raising 2 times?

Colin Angus Mackay31-Mar-09 4:30

Colin Angus Mackay

31-Mar-09 4:30

Narendra Reddy Vajrala wrote:
it is coming again to
{ which is the first line under btn_click event

So what is in the call stack? It will show you what called the method. Is the call stack different from the first time the method gets called? What called the method the second time around?

*Developer Day Scotland - Free community conference Delegate Registration Open

Re: why button_click event raising 2 times?

Narendra Reddy Vajrala31-Mar-09 4:40

Narendra Reddy Vajrala

31-Mar-09 4:40

InitializeComponent();

BtnOk.Click += new EventHandler(BtnOk_Click);

and my clickevent is
private void BtnOk_Click(object sender, EventArgs e)
{
//This Event Raising 2 times.....?
}

and design.cs

this.BtnOk.Click += new System.EventHandler(this.BtnOk_Click);

Re: why button_click event raising 2 times?

Ian Shlasko31-Mar-09 4:44

Ian Shlasko

31-Mar-09 4:44

So like stancrm said initially, you're hooking the event twice.

You hooked it once in the designer, and another time in your design.cs. Either unhook it in the designer, or remove that line from design.cs.

Re: why button_click event raising 2 times?

Narendra Reddy Vajrala31-Mar-09 5:18

Narendra Reddy Vajrala

31-Mar-09 5:18

yesssssssssssssssssssss
finally i got on deleting instance in designer.cs

so Thanks to everybody

Big Grin | :-D

Re: why button_click event raising 2 times?

Colin Angus Mackay31-Mar-09 4:48

Colin Angus Mackay

31-Mar-09 4:48

You have not provided much context for the code snippets. Where are they coming from?

Are you saying that you have

BtnOk.Click += new EventHandler(BtnOk_Click);

in your form's constructor, and

this.BtnOk.Click += new System.EventHandler(this.BtnOk_Click);

in your form's design.cs file?

If this is the case it looks like you have added the event handler twice to the button click event. I would recommend removing the one in the constructor because the designer will take care of the one in the form's design.cs class.

Also, what is in the call stack when the BtnOk_Click method is called? (If you don't know where to get the call stack it is probably in Debug-->Windows-->Call Stack)

*Developer Day Scotland - Free community conference Delegate Registration Open

Re: why button_click event raising 2 times?

Greg Chelstowski31-Mar-09 4:57

Greg Chelstowski

31-Mar-09 4:57

How very javascriptish--

anyway, check your Form.designer.cs file for BtnOk.Click+=new EventHandler(object sender, Eventargs e);
and then check your Form.cs file for the same. Get rid of one.
If you want to register that EventHandler always, leave it in the designer file, if you want to attach it if some condition is met - take it out and do it in the form.

var question = (_2b || !(_2b));

Re: why button_click event raising 2 times?

Xmen Real 31-Mar-09 4:08

Xmen Real

31-Mar-09 4:08

Narendra Reddy Vajrala wrote:
Please give some solution

Its quite simple...add another button in a new project, put breakpoint and check is it calling twice or not. If it is then something wrong with your windows or your mouse is dying.

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Re: why button_click event raising 2 times?

Narendra Reddy Vajrala31-Mar-09 4:18

Narendra Reddy Vajrala

31-Mar-09 4:18

yes,
from some other form am comming to this form and no where in my project it doesnt happend but y here only....!?

Frown | :(

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