Parallelizing method with foreach loop C#

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C#

C#4.0

multi-threading

parallel

Hello.

So I am currently working on a project and now I feel the need to try and speed up the execution. I have a method with a foreach loop in it that I wish to parallelize as efficiently as possible.

This is how it looks now:

public void Simulate()
{
    List<Coordinate> Locations = retrieveLocations();

    int min = int.MaxValue;
    int bestX = -1, bestY = -1;

    foreach (Coordinate currPos in Locations)
    {
        string[,] tempMap = new string[globalMap.GetLength(0), globalMap.GetLength(1)];
        matrixCopy(globalMap, tempMap);

        int result = processData(currPos, tempMap);

        if (result < min)
        {
            min = result;
            bestX = currPos.X;
            bestY = currPos.Y;
        }
    }

    MessageBox.Show(bestX + " " + bestY + " " + min);
}

I would like to change the foreach loop to use Parallel.ForEach or perhaps use PLINQ. My concerns are how I can find the minimal value with as little locking as possible. Also I want to preserve some other values than just the minimum.

Another issue is the globalMap, is it good to copy it like I do now? All threads can't work on the original at the same time because they change the data. But perhaps I should do the copy in my processData()-method? Any thoughts?