Scale free optimization

Community Lounge
1

Kinda discussing scale free optimization again over here:
http://www.freebasic.net/forum/viewtopic.php?f=5&t=25133
Very simple and effective. It should only take an hour to convert to Java if you wanted to using the Float class methods.

2

package neonandroid;

public class Opt {

private static long s0, s1;

//http://xoroshiro.di.unimi.it/
private static long nextLong() {
final long s0 = Opt.s0;
long s1 = Opt.s1;
final long result = s0 + s1;
s1 ^= s0;
Opt.s0 = Long.rotateLeft(s0, 55) ^ s1 ^ s1 << 14;
Opt.s1 = Long.rotateLeft(s1, 36);
return result;
}

public static float mutateSymP127(float x){
    float m=x+Float.intBitsToFloat((int)nextLong() & 0xbfffffff);
    if((m>1f) || (m<-1f) ) return x;
    return m;
}

//https://en.wikipedia.org/wiki/Test_functions_for_optimization
//Lévi function N.13
public static double levi(double x,double y){
x*=10; // -10 to 10
y*=10; // -10 to 10
return Math.sin(3Math.PIx)Math.sin(3Math.PIx)+(x-1)(x-1)(1+Math.sin(3Math.PIy)Math.sin(3Math.PIy))+(y-1)(y-1)(1+Math.sin(2Math.PIy)Math.sin(2Math.PI*y));
}

public static void main(String[] args) {
    float x=0,y=0,cx,cy,cost=Float.POSITIVE_INFINITY;
    for(int i=0;i<5000;i++){
        cx=mutateSymP127(x);
        cy=mutateSymP127(y);
        float newcost=(float)levi(cx,cy);
        if(newcost<cost){
            cost=newcost;
            x=cx;
            y=cy;
        }
    }
    System.out.println("Cost: "+cost);
    System.out.println("At: "+10*x+"  "+10*y);
    System.out.println("Should be 0 at 1,1");
}

static {
    s0=System.nanoTime();
    s1=s0+1;
}

}