Fast Math.exp

I started on a FastMath class and then caved and started playing with this one. Just thought I'd offer up a fast Math.exp I found from this blog (via StackOverflow):

public static double exp(double val) {
    final long tmp = (long) (1512775 * val + 1072632447);
    return Double.longBitsToDouble(tmp << 32);
}

Probably doesn't matter to most of you, but if you're doing DC with gaussians it might. I actually use a different kernel density in my main gun because 20,000 Math.exp's each time I aim would be pretty slow. (Not sure the above would solve that, but anyway...)