CODEWITHSUNDEEP
c#multithreading
sooprise
sooprise

Reputation: 23177

When All Threads Are Complete

This is my first real attempt at using multithreading, I want to know how I can tell when all of my tasks groups are done running:

for (int i = 0; i < taskGroups.Count(); i++) {
    ThreadStart t = delegate { RunThread(taskGroups[i]); };
    new Thread(t).Start();
}
if(allThreadsComplete){ //???

}

Any help would be much appreciated

Addendum:

ThreadStart[] threads = new ThreadStart[taskGroups.Count()];
for (int i = 0; i < taskGroups.Count(); i++) {
    threads[i] = new ThreadStart[]
    threads[i] = delegate { RunThread(taskGroups[i]); };
    new Thread(t).Start();
}
bool threadsComplete = false;
while(!threadsComplete){
    for(int i=0;i<taskGroups.Count();i++){
        if(threads[i].State == complete)
        threadsComplete = true;
    }
}

Upvotes: 3

Views: 4567

Answers (6)

Kiril
Kiril

Reputation: 40345

If you're using 3.5 then you can write your own CountdownEvent, if you're using 4.0 then you can use the built in CountdownEvent to do something like this:

CountdownEvent = new CountdownEvent(taskGroups.Count());

for (int i = 0; i < taskGroups.Count(); i++) 
{
    int item = i; // copy i locally
    ThreadStart t = delegate 
    { 
        RunThread(taskGroups[item]); 
        latch.Signal();
    };
    new Thread(t).Start();
}

latch.Wait();

The latch.Wait() will cause your code to block until the threads have all finished. Furthermore, you might want to change the way you start your thread a bit:

CountdownEvent = new CountdownEvent(taskGroups.Count());

for (int i = 0; i < taskGroups.Count(); i++) 
{
    int item = i; // copy i locally
    Thread t = new Thread(()=>
    { 
        RunThread(taskGroups[item]); 
        latch.Signal();
    });
    t.IsBackground = true;
    t.Start();
}

latch.Wait();

Note that I'm setting the thread to background: this your application from hanging when exit and not all threads have finished (i.e. prevents ghost or daemon threads).

Upvotes: 1

jonathanpeppers
jonathanpeppers

Reputation: 26485

You need to store all your threads, and then call Thread.Join().

Something like this:

List<Thread> threads = new List<Thread>();
for (int i = 0; i < taskGroups.Count(); i++) {
   int temp = i; //This fixes the issue with i being shared
   Thread thread = new Thread(() => RunThread(taskGroups[temp]));
   threads.Add(thread);
   thread.Start();
}

foreach (var thread in threads) {
    thread.Join();
}

Upvotes: 4

SLaks
SLaks

Reputation: 887225

You can check the ThreadState property of each Thread object.

Upvotes: 0

as-cii
as-cii

Reputation: 13019

First of all consider switching to the new asynchronous pattern using Task.

Anyway if you want to wait for all your threads you can call Thread.Join:

var threads = new List<Thread>();    
for (int i = 0; i < taskGroups.Count(); i++) {
    ThreadStart t = delegate { RunThread(taskGroups[i]); };
    var thread = new Thread(t);
    threads.Add(thread);
    thread.Start();
}

threads.ForEach(a => a.Join());

Remember that you can also pass a timeout parameter that will wait until the thread finishes only if it doesn't takes more than the time you passed in.

Upvotes: 0

Shadow Wizard
Shadow Wizard

Reputation: 66399

You can add public static integer field to the main thread, in each child thread increase it by one when it's completed then in the main thread wait (in a loop) until that variable is equal to the taskGroups.Count().

Upvotes: 0

Dror Helper
Dror Helper

Reputation: 30780

You can use Thread.Join to make sure that each individual thread has finished running.

Upvotes: 0

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