how to use thread in for loop in c#

superselector

Hi i have a method which takes around 10sec to excute(sometimes more time) and store the data in datatable. i am calling this metod inside a for loop so the process is taking longer time. Please suggest a way to speed up the process. This method takes a input and generate a datarow and add that row to the global datatable. so there is same datatable which is being used throughout the for loop iterations. Please suggest how can i use thread in this case specially when we don't know how much time the method is going to take.

Mycroft Holmes

You need to identify if it is the building of the row or writing the row to the database that is causing the bottleneck. They require different solutions.

Never underestimate the power of human stupidity RAH

superselector

No i am creating a datarow.there is no database. i am creating the datatable using that row.

public void GetData(DataTable dtAssetValues)
{

DataRow objdr = dtAssetValues.NewRow();
try { objdr["OSName"] = GetValues(strKey);
dtAssetValues.Rows.Add(objdr)
}
catch { }
}

here in this case the GetValues method has a Thread.Sleep(1000) of 1 sec. so there are 5-6 columns in the datatable for which i am calling this GetValues method to retrieve the column value. I am calling this GetData method inside a for loop. Hope this helps.

GuyThiebaut

superselector wrote:

he GetValues method has a Thread.Sleep(1000) of 1 sec

You've now got my curiosity - why do you sleep the thread? Also as a rule it is best not to catch exceptions without handling them - otherwise you may get undesired data/behaviour within the database.

“That which can be asserted without evidence, can be dismissed without evidence.”

― Christopher Hitchens

Pete OHanlon

Well, that Thread.Sleep will explain why this takes so long. When you do Thread.Sleep, you block that thread and put it to sleep. What effect are you trying to achieve here?

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superselector

Thanks. Actually in that method, the response from a remote machine takes some time, hence i have added some delay in that method.

GuyThiebaut

I still don't understand why you need a sleep, since if the response is taking some time the method will hold the thread - so there should be no need for a sleep. Can you post the method that has the sleep to give me more of an idea of what you are trying to accomplish.

“That which can be asserted without evidence, can be dismissed without evidence.”

― Christopher Hitchens

Abhinav S

If you have a multi-core processor you can consider using Parallel.ForEach. It could lead to another set of issues with concurrency, but you will be able to run a loop faster.

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Simon_Whale

Question. Why are you calling a method that generates an individual row? Yhy not get all the data required at once and then populate the datatable?

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Lost User

Thread.Sleep is probably not the solution.

superselector

HI everyone, Thanks for you replies.I had never used thread before hence i had very little idea about multi-threding.I have removed the sleep inside the method as i found that it is not helping the cause.

superselector

the requirement goes like this ... I have set of ip's . i am looping through the IP list and for each ip i am checking whether i can ping them , i have given a time out of 4 seconds for ping reply. and am storing the result in a datatable.Pleas let me know how it can be implemented using threading to make the looping faster without losing any data as most of the ips are taking 3-4 seconds for reply.

Lost User

Ok, it's a little tricky. The simplest way, not very good is: make one thread for every ping action, start them all, then Join them all. Is that good enough for you? Otherwise, use ping.SendAsync, and make very sure that PingCompletedEventHandler is thread-safe. The handler will have to 1) save the result (safely! may involve locking) and 2) signal a waithandle (after saving the result). Then you can do a WaitAll over all the waithandles to continue when all the pings are done.

superselector

if i follow the first option, Do in need to specify any timeout in Thread.Join method.

Lost User

If the pings have a timeout, that should not be necessary, though it wouldn't be a problem either (as long as it's high enough to give the pings time to succeed).

superselector

i think i need to specify timeout in join with more that 2500 ms as i have specified a time out of 2 sec. without any time out its very slow.

Lost User

But sometimes the pings took 4 seconds, right?

superselector wrote:

without any time out its very slow.

Well that's weird, it shouldn't take significantly longer than the longest running ping. Could you show the code?

superselector

yes the time out takes 4 secs, i have given 2 secs for testing ... actually on successful ping checking for ping i am trying to get some basic details of that ip using WMI.WMI is taking some time also if its not enabled.

for (int index = startIP; index <= EndIP; index++)
{
ipVal = startSubnet + "." + index.ToString();

               Thread wmithread = new Thread(() => PerformWMIOperation(ipVal.ToString().Trim(), txtUserName.Text.ToString().Trim(), txtPassword.Text.ToString(), txtDomain.Text.ToString(), dtAssetValues, chkImpersonate.Checked, recordnumber));
                wmithread.Start();
                wmithread.Join(2500);
            }

Lost User

Ok, not like that. Don't, "for every thread, start it, then join it". That just runs everything in serial. Do, "for every thread, start it. Then, for every thread, join it." That's how I said it: start them all then join them all.

superselector

Hi i did not understand do you want the code to be changed to for (int index = startIP; index <= EndIP; index++) { ipVal = startSubnet + "." + index.ToString(); Thread wmithread = new Thread(() => PerformWMIOperation(ipVal.ToString().Trim(), txtUserName.Text.ToString().Trim(), txtPassword.Text.ToString(), txtDomain.Text.ToString(), dtAssetValues, chkImpersonate.Checked, recordnumber)); wmithread.Start(); wmithread.Join(); }