Parallel For loops in C# performance 3

Question

0.00/5 (No votes)

See more:

Can anyone show me an example of taking a list, doing some operation in each element in the list's property using a parallel for loop and then returning the original list? For example

C#

List<t> someList = new List<t>
for(int i= 0; i < originallist.count;i++)
{
    Do operation on originallist[i].somevariable
    someList.add(originallist[i])
}
return someList

In other words. HOW would I parallelize this???

Posted 4-Dec-12 18:35pm

shekarchee

Updated 4-Dec-12 18:45pm

Wendelius

v2

Add a Solution

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

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

Programm3r · Answer 1 · 2012-12-04T18:49:00

Hi,

Please refer to the following document: How to: Write a Simple Parallel.For Loop[^]

Here is a code snippet:

C#

static void MultiplyMatricesParallel(double[,] matA, double[,] matB, double[,] result)
{
    int matACols = matA.GetLength(1);
    int matBCols = matB.GetLength(1);
    int matARows = matA.GetLength(0);

    // A basic matrix multiplication.
    // Parallelize the outer loop to partition the source array by rows.
    Parallel.For(0, matARows, i =&gt;
    {
        for (int j = 0; j &lt; matBCols; j++)
        {
            // Use a temporary to improve parallel performance.
            double temp = 0;
            for (int k = 0; k &lt; matACols; k++)
            {
                temp += matA[i, k] * matB[k, j];
            }
            result[i, j] = temp;
        }
    }); // Parallel.For
}

Kind regards,

Wendelius · Answer 2 · 2012-12-04T18:47:00

Solution 1

I suggest going through this article Task Parallel Library: 3 of n[^]. Also note that the whole serie is a really good read.

Posted 4-Dec-12 18:47pm

Wendelius

Updated 11-Dec-12 18:17pm

v2

Comments

Espen Harlinn 11-Dec-12 17:50pm

5'ed!

Wendelius 12-Dec-12 0:17am

Thanks :)