Inconsistent multiplication performance with floats

Question

While testing the performance of floats in .NET, I stumbled unto a weird case: for certain values, multiplication seems way slower than normal. Here is the test case:

Answer 1

I suspect this has something to do with denormal values (fp values smaller than ~ 1e-38) and the cost associated with processing them.

If you test for denormal values and remove them, sanity is restored.

    static void float32Multiply(float param) {
        float n = 1000f;
        int zeroCount=0;
        for (int i = 0; i < 1000000; ++i) {
            n = n * param;
            if(n<1e-38)n=0;
        }
        // Write result to prevent the compiler from optimizing the entire method away
        Console.Write(n);
    }