commit 1a0cd2fe699703eef00e4b675216ecb3fddbe08b
Author: Alberto Venturini <aventurini@gmail.com>
Date:   Sat Sep 9 19:57:41 2017 +0200

    Multi-threaded Julia set calculator

diff --git a/.gitignore b/.gitignore
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index 0000000..89c8f39
--- /dev/null
+++ b/.gitignore
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+# Compiled class file
+*.class
+
+# Log file
+*.log
+
+# BlueJ files
+*.ctxt
+
+# Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+# Package Files #
+*.jar
+*.war
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+
+*.iml
+.idea
diff --git a/src/JuliaSetCalculator.java b/src/JuliaSetCalculator.java
new file mode 100644
index 0000000..9910788
--- /dev/null
+++ b/src/JuliaSetCalculator.java
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+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+
+public class JuliaSetCalculator {
+    private int width;
+    private int height;
+    private int[][] iterations;
+
+    public JuliaSetCalculator(final int width, final int height) {
+        this.width = width;
+        this.height = height;
+        iterations = new int[width][height];
+    }
+
+    public int[][] calculate(
+            final int maxIterations,
+            final double zoom,
+            final double cx,
+            final double cy,
+            final double moveX,
+            final double moveY) {
+
+        class JuliaTask implements Runnable {
+
+            private int x;
+
+            JuliaTask(int x) {
+                this.x = x;
+            }
+
+            @Override
+            public void run() {
+                double zx, zy;
+                for(int y = 0; y < height; y++) {
+                    zx = 1.5 * (x - width / 2) / (0.5 * zoom * width) + moveX;
+                    zy = (y - height / 2) / (0.5 * zoom * height) + moveY;
+                    int i = maxIterations;
+                    while (zx * zx + zy * zy < 4 && i > 0) {
+                        double tmp = zx * zx - zy * zy + cx;
+                        zy = 2.0 * zx * zy + cy;
+                        zx = tmp;
+                        i--;
+                    }
+                    iterations[x][y] = i;
+                }
+            }
+        }
+
+        long startTime = System.currentTimeMillis();
+
+        ExecutorService executorService = Executors.newWorkStealingPool(8);
+        for(int x = 0; x < width; x++) {
+            JuliaTask task = new JuliaTask(x);
+            executorService.submit(task);
+        }
+
+        executorService.shutdown();
+
+        try {
+            executorService.awaitTermination(5, TimeUnit.SECONDS);
+        } catch (Exception ex) {
+            System.out.println(ex);
+        }
+
+
+        long endTime = System.currentTimeMillis();
+
+        System.out.println(endTime - startTime);
+
+        return iterations;
+    }
+
+
+
+}
diff --git a/src/JuliaSetPanel.java b/src/JuliaSetPanel.java
new file mode 100644
index 0000000..e3627ae
--- /dev/null
+++ b/src/JuliaSetPanel.java
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+import javax.swing.*;
+import java.awt.*;
+import java.awt.image.BufferedImage;
+
+public class JuliaSetPanel extends JPanel {
+    private static int maxIter = 1000;
+    private static double zoom = 1;
+    private double cY, cX;
+
+    private JuliaSetCalculator juliaSetCalculator;
+
+    public JuliaSetPanel(final JuliaSetCalculator juliaSetCalculator, final int width, final int height) {
+        this.juliaSetCalculator = juliaSetCalculator;
+        setPreferredSize(new Dimension(1200, 800));
+        setBackground(Color.white);
+    }
+
+    void drawJuliaSet(Graphics2D g) {
+        int width = getWidth();
+        int height = getHeight();
+        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
+
+        cX = -0.7;
+        cY = 0.27015;
+        double moveX = 0, moveY = 0;
+
+        int[][] iterations = juliaSetCalculator.calculate(maxIter, zoom, cX, cY, moveX, moveY);
+
+        for(int x = 0; x < width; x++) {
+            for(int y = 0; y < height; y++) {
+                float i = iterations[x][y];
+                int color = Color.HSBtoRGB(((maxIter / i) + 0.5f) % 1, 1, i > 0 ? 1 : 0);
+                image.setRGB(x, y, color);
+            }
+        }
+
+        g.drawImage(image, 0, 0, null);
+    }
+
+    @Override
+    public void paintComponent(Graphics gg) {
+        super.paintComponent(gg);
+        Graphics2D g = (Graphics2D) gg;
+        g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
+                RenderingHints.VALUE_ANTIALIAS_ON);
+        drawJuliaSet(g);
+    }
+
+}
\ No newline at end of file
diff --git a/src/MainClass.java b/src/MainClass.java
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index 0000000..97d3e88
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+++ b/src/MainClass.java
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+import javax.swing.*;
+import java.awt.*;
+
+public class MainClass {
+
+    public static void main(String[] args) {
+
+        int width = 1200;
+        int height = 800;
+        JuliaSetCalculator juliaSetCalculator = new JuliaSetCalculator(width, height);
+        JuliaSetPanel juliaSetPanel = new JuliaSetPanel(juliaSetCalculator, width, height);
+
+        SwingUtilities.invokeLater(() -> {
+            JFrame f = new JFrame();
+            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+            f.setTitle("Julia Set");
+            f.setResizable(false);
+            f.add(juliaSetPanel, BorderLayout.CENTER);
+            f.pack();
+            f.setLocationRelativeTo(null);
+            f.setVisible(true);
+        });
+    }
+
+}