How to maintain consistency in a variable that is shared among several threads in Task parallel library?

Question

How to maintain consistency in a variable that is shared among several threads in Task parallel library?

Description:I am using task parallel library to run a for loop on all of my CPU cores, but I am just thinking that the resultant of all the operation performed is not going to be what I want? Is there a way to perform operations on a class level variable shared with multiple threads so that the answer of Parallel.For() doesn't return inconsistent value!
For learning purpose I have written a simple code chunk as follows which is always returning less than 10000000


            int total = 0;
            Parallel.For(0, 10000000, (i) =>
                {
                    total++;
                });
            Console.WriteLine(total);
            Console.ReadKey();

Posted by: Peter Andre | Posted on: Mar 15, 2019

1 answers

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3

I assume that you wrote this code for learning the concept only otherwise its not a very good example to use multithreading but what I understand from your code is that your total variable here having a race condition to avoid this you can simply use Interlocked's class add method which will access your global variable in a thread safe manner so your code will look like the following one.


            int total = 0;
            Parallel.For(0, 10000000, (i) =>
                {
                    //total++;
                    Interlocked.Add(ref total, 1)
                });
            Console.WriteLine(total);
            Console.ReadKey();

Replied by: Tabish Usman | Replied on: Mar 19, 2019

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How to maintain consistency in a variable that is shared among several threads in Task parallel library?

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