mandelbrot Java #3 program

/* 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
  */

//package mandelbrot;

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

public final class mandelbrot
{
    public static void main(String[] args) throws Exception
    {
        int size = 200;
        if (args.length >= 1)
            size = Integer.parseInt(args[0]);
        
        System.out.format("P4\n%d %d\n", size, size);
        
        int width_bytes = size /8 +1;
        byte[][] output_data = new byte[size][width_bytes];
        int[] bytes_per_line = new int[size];
        
        Compute(size, output_data, bytes_per_line);
        
        BufferedOutputStream ostream = new BufferedOutputStream(System.out);
        for (int i = 0; i < size; i++)
            ostream.write(output_data[i], 0, bytes_per_line[i]);
        ostream.close();
    }
    
    private static final void Compute(final int N, final byte[][] output, final int[] bytes_per_line)
    {
        final double inverse_N = 2.0 / N;
        final AtomicInteger current_line = new AtomicInteger(0);
        
        final Thread[] pool = new Thread[Runtime.getRuntime().availableProcessors()];
        for (int i = 0; i < pool.length; i++)
        {
            pool[i] = new Thread()
            {
                public void run()
                {
                    int y;
                    while ((y = current_line.getAndIncrement()) < N)
                    {
                        byte[] pdata = output[y];
                        
                        int bit_num = 0;
                        int byte_count = 0;
                        int byte_accumulate = 0;
                        
                        double Civ = (double)y * inverse_N - 1.0;
                        for (int x = 0; x < N; x++)
                        {
                            double Crv = (double)x * inverse_N - 1.5;
                            
                            double Zrv = Crv;
                            double Ziv = Civ;
                            
                            double Trv = Crv * Crv;
                            double Tiv = Civ * Civ;
                            
                            int i = 49;
                            do
                            {
                                Ziv = (Zrv * Ziv) + (Zrv * Ziv) + Civ;
                                Zrv = Trv - Tiv + Crv;
                                
                                Trv = Zrv * Zrv;
                                Tiv = Ziv * Ziv;
                            } while ( ((Trv + Tiv) <= 4.0) && (--i > 0));

                            byte_accumulate <<= 1;
                            if (i == 0)
                                byte_accumulate++;
                            
                            if (++bit_num == 8)
                            {
                                pdata[ byte_count++ ] = (byte)byte_accumulate;
                                bit_num = byte_accumulate = 0;
                            }
                        } // end foreach column
                        
                        if (bit_num != 0)
                        {
                            byte_accumulate <<= (8 - (N & 7));
                            pdata[ byte_count++ ] = (byte)byte_accumulate;
                        }
                        
                        bytes_per_line[y] = byte_count;
                    } // end while (y < N)
                } // end void run()
            }; // end inner class definition
            
            pool[i].start();
        }
        
        for (Thread t : pool)
        {
            try
            {
                t.join();
            }
            catch (InterruptedException e)
            {
                e.printStackTrace();
            }
        }
    }
}
    

NOTES:
64-bit Ubuntu quad core
openjdk 14 2020-03-17
OpenJDK Runtime Environment (build 14+36-1461)
OpenJDK 64-Bit Server VM (build 14+36-1461, mixed mode, sharing)


Tue, 05 May 2020 02:16:07 GMT

MAKE:
mv mandelbrot.java-3.java mandelbrot.java
/opt/src/openjdk-14/bin/javac -d .  mandelbrot.java

5.84s to complete and log all make actions

COMMAND LINE:
/opt/src/openjdk-14/bin/java   mandelbrot 16000

(BINARY) PROGRAM OUTPUT NOT SHOWN