Parallel For loops in C# performance 3

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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

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Wendelius · Answer 1 · 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 :)

Programm3r · Answer 2 · 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,