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Working with ThreadPool

, 6 Nov 2011 CPOL 9K 5
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A workaround for using more than 64 threads with ThreadPool and WaitHandle class.
Before going further, please check the MSDN link How to: Use a Thread Pool [^]. The above link will give you an idea on how to use Thread Pool.

Now in code given at the above link, in Main() method if you make a small change as given below:

const int FibonacciCalculations = 100; //Change its value to 100 from 10
The program will throw a NotSupportedException.

This is because a program can pass only 64 handles to WaitHandle class. So if you want to work with more than 64 threads simultaneously, this program won't work.

I worked out the above program to fulfill my requirement of creating more threads. I made few changes only in the Main() method.
Take a look:

static void Main()
            const int FibonacciCalculations = 100;
            // One event is used for each Fibonacci object
            List<ManualResetEvent> doneEvents = null;
            Fibonacci[] fibArray = new Fibonacci[FibonacciCalculations];
            Random r = new Random();
            int totalCount = 0;
            // Configure and launch threads using ThreadPool:
            Console.WriteLine("launching {0} tasks...", FibonacciCalculations);
            doneEvents = new List<ManualResetEvent>();
            for (int i = totalCount, j = 0; i < FibonacciCalculations && j < 64; i++, j++)
                doneEvents.Add(new ManualResetEvent(false));
                Fibonacci f = new Fibonacci(r.Next(20, 40), doneEvents[j]);
                fibArray[i] = f;
                ThreadPool.QueueUserWorkItem(f.ThreadPoolCallback, i);
            // Wait for all threads in pool to calculation...
            if (totalCount < FibonacciCalculations)
                goto ProcessThread;
            Console.WriteLine("All calculations are complete.");
            // Display the results...
            for (int i = 0; i < FibonacciCalculations; i++)
                Fibonacci f = fibArray[i];
                Console.WriteLine("Result {2} : Fibonacci({0}) = {1}", f.N, f.FibOfN, i);
Now run the program and it will work fine for 100 threads. In this manner, you can work with more than 64 threads.

I have used this method to achieve my goal, but if anyone else has a better way to achieve this, please share it with us.

Note: ManualResetEvent closing tag seen at the end of the code snippet is not part of the code snippet. I am not been able to remove those closing tags.



This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


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Comments and Discussions

Generalah, its a limitation on the WaitHandle. Have a look at http:... Pin
Doc Lobster3-Nov-11 20:50
memberDoc Lobster3-Nov-11 20:50 
GeneralI think thats strange. There's no limit named by MSDN for qu... Pin
Doc Lobster3-Nov-11 6:57
memberDoc Lobster3-Nov-11 6:57 
GeneralRe: There is a limit of 64 handles given by MSDN. Please check R... Pin
nagendrathecoder3-Nov-11 19:12
membernagendrathecoder3-Nov-11 19:12 

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