User:Rednaxela/FastTrig

A little class for fast trig lookups. Tests show that:

• When used with the sin/cos static methods, it ranges from twice as slow, to three times as fast, depending on how much of a chance the JIT has to optimize
• When you inline the index-calculation code into your own code (see usage in the main method) instead of using static methods, it ranges from just slightly faster, up to three times as fast.
• Increasing the number of divisions has no impact on runtime performance, only initialization time and memory consumption.

This could provide some measurable speedup to intensive play-it-forward guns or precise prediction in surfers. Cheers!

package ags.util;

public class FastTrig {
	public static final int DIVISIONS = 2880;
	public static final double[] sineTable = new double[DIVISIONS];
	public static final double[] cosineTable = new double[DIVISIONS];
	
	public static final void init() {
		for (int i=0; i<DIVISIONS; i++) {
			double value = i*Math.PI*2/DIVISIONS;
			sineTable[i] = Math.sin(value);
			cosineTable[i] = Math.cos(value);
		}
	}
	
	public static final double sin(double value) {
		return sineTable[(int)(value/(Math.PI*2/DIVISIONS) + 0.5) % DIVISIONS];
	}
	
	public static final double cos(double value) {
		return cosineTable[(int)(value/(Math.PI*2/DIVISIONS) + 0.5) % DIVISIONS];
	}
	
	/*
	public static void main(String[] args) {
		init();
		
		double v=12.23;
		long ms;
		ms = -System.nanoTime();
		for (int i=0; i<100000; i++)
			v += Math.sin(i*Math.PI*2/1000);
		ms += System.nanoTime();
		System.out.println(String.format("Done in %4.4f seconds", ms/1E9));
		
		ms = -System.nanoTime();
		for (int i=0; i<100000; i++) {
			double value = i*Math.PI/1000;
			v += sineTable[(int)(value/(Math.PI*2/DIVISIONS) + 0.5) % DIVISIONS];
		}
		ms += System.nanoTime();
		System.out.println(String.format("Done in %4.4f seconds", ms/1E9));
	}
	*/
}

--Rednaxela 09:18, 3 March 2009 (UTC)