mandelbrot_2.java

/* The Computer Language Benchmarks Game
 * https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
 *
 * contributed by Stefan Krause
 * slightly modified by Chad Whipkey
 * parallelized by Colin D Bennett 2008-10-04
 * reduce synchronization cost by The Anh Tran
 * optimizations and refactoring by Enotus 2010-11-11
 * optimization by John Stalcup 2012-2-19
 */


import java.io.*;
import java.util.concurrent.atomic.*;

public final class mandelbrot_2 {
    static byte[][] out;
    static AtomicInteger yCt;
    static double[] Crb;
    static double[] Cib;

    static int getByte(int x, int y){
        int res=0;
        for(int i=0;i<8;i+=2){
            double Zr1=Crb[x+i];
            double Zi1=Cib[y];

            double Zr2=Crb[x+i+1];
            double Zi2=Cib[y];

            int b=0;
            int j=49;do{
                double nZr1=Zr1*Zr1-Zi1*Zi1+Crb[x+i];
                double nZi1=Zr1*Zi1+Zr1*Zi1+Cib[y];
                Zr1=nZr1;Zi1=nZi1;

                double nZr2=Zr2*Zr2-Zi2*Zi2+Crb[x+i+1];
                double nZi2=Zr2*Zi2+Zr2*Zi2+Cib[y];
                Zr2=nZr2;Zi2=nZi2;

                if(Zr1*Zr1+Zi1*Zi1>4){b|=2;if(b==3)break;}
                if(Zr2*Zr2+Zi2*Zi2>4){b|=1;if(b==3)break;}
            }while(--j>0);
            res=(res<<2)+b;
        }
        return res^-1;
    }

    static void putLine(int y, byte[] line){
        for (int xb=0; xb<line.length; xb++)
            line[xb]=(byte)getByte(xb*8,y);
    }

    public static void main(String[] args) throws Exception {
        int N=6000;
        if (args.length>=1) N=Integer.parseInt(args[0]);

        Crb=new double[N+7]; Cib=new double[N+7];
        double invN=2.0/N; for(int i=0;i<N;i++){ Cib[i]=i*invN-1.0; Crb[i]=i*invN-1.5; }
        yCt=new AtomicInteger();
        out=new byte[N][(N+7)/8];

        Thread[] pool=new Thread[2*Runtime.getRuntime().availableProcessors()];
        for (int i=0;i<pool.length;i++)
            pool[i]=new Thread(){
                public void run() {
                    int y; while((y=yCt.getAndIncrement())<out.length) putLine(y,out[y]);
                }
            };
        for (Thread t:pool) t.start();
        for (Thread t:pool) t.join();

        OutputStream stream = new BufferedOutputStream(System.out);
        stream.write(("P4\n"+N+" "+N+"\n").getBytes());
        for(int i=0;i<N;i++) stream.write(out[i]);
        stream.close();
    }
}