Parallel.For step size

Question

Does anyone know if there's any overload that would allow me to specify a step size in a Parallel.For loop? Samples in either C# or VB.Net would be great.

Brufsky

Answer 1

Google for "enumerable.range step" and you should be able to come upon alternate implementations of Enumerable.Range that provide stepped ranges. Then you can just do a

Parallel.ForEach(BetterEnumerable.SteppedRange(fromInclusive, toExclusive, step), ...)

If google isn't working, implementation should be something like this:

public static class BetterEnumerable {
    public static IEnumerable<int> SteppedRange(int fromInclusive, int toExclusive, int step) {
        for (var i = fromInclusive; i < toExclusive; i += step) {
            yield return i;
        }
    }
}

Alternately if "yield return" gives one the heebie jeebies, you can always just create a regular old list in-place:

var list = new List<int>();
for (int i = fromInclusive; i < toExclusive; i += step) {
    list.Add(i);
}
Parallel.ForEach(list, ...);

This should be easily translatable to VB if that's a requirement.

Veronikaveronike

Thanks Dax. Would it be too much extra work if i'm trying to do this in VB.Net where there's no yield return? – Brufsky

No VB experience, but you should be able to use a for loop to make a List Of Integer with the integers you need, and then use Parallel.ForEach with that list. – Veronikaveronike

@Gonzalo: The async CTP enables the use of iterators in VB.NET. – Manners