Question

What’s the fastest way to enumerate through an integer and return the exponent of each bit that is turned on? Have seen an example using << and another using Math.Pow. Wondering if there is anything else that’s really fast.

Thanks.

Answer 1

I imagine bit-shifting would be the fastest. Untested, but I think the following ought to be fast (as fast as IEnumerables are at least).

IEnumerable<int> GetExponents(Int32 value)
{
    for(int i=0; i<32; i++)
    {
        if(value & 1)
            yield return i;
        value >>= 1;
    }
}

If you want it to be faster, you might consider returning a List<int> instead.