Fast Exponential Function in Java
The paper “A Fast, Compact Approximation of the Exponential Function” describes a C macro that does a good job at exploiting the IEEE 754 floating-point representation to calculate e^x. I have transformed the macro into Java code:
public static double exp(double val) {
final long tmp = (long) (1512775 * val + 1072632447);
return Double.longBitsToDouble(tmp « 32);
}
This code is 5.3 times faster than Math.exp() on my computer. Beware that it is only an approximation, for a detailed analysis read the paper.
