Question

I have simple code

for( int i = 0 ; i < arr.GetLength(0) ; i++)
{
    for( int j = 0 ; j < arr.GetLength(1) ; j++)
    {
         arr[i, j ] = 0;
    }
}

I need to make this code to be very fast – so i want to use the Tasks.Parallel.For

What will be the most fast and effecint way to use the Parallel.For ?

It can be like this

Parallel.for( int i = 0 ; i < arr.GetLength(0) ; i++)
{
    Parallel.for( int j = 0 ; j < arr.GetLength(1) ; j++)
    {
         arr[i, j ] = 0;
    }
}

or just use one Parallel.for ?

Answer 1

You would be better off using the Parallel.for(...) on the outer loop only.

The idea being that you would have as many cores in parallel execute the inner loop’s iterations.