Added ThreadedJuliaSetCalculator

src/ForkJoinJuliaSetCalculator.java

@@ -55,7 +55,10 @@ public class ForkJoinJuliaSetCalculator implements JuliaSetCalculator {
                     int middle = (startInclusive + endExclusive) / 2;
                     JuliaTask task1 = new JuliaTask(startInclusive, middle);
                     JuliaTask task2 = new JuliaTask(middle, endExclusive);
-                    invokeAll(task1, task2);
+                    //invokeAll(task1, task2);
+                    task1.fork();
+                    task2.compute();
+                    task1.join(); // Interestingly, if I comment out this join, it seems to work ok???
                 }
             }
         }

src/JuliaSetPanel.java

@@ -11,7 +11,7 @@ public class JuliaSetPanel extends JPanel {
 
     public JuliaSetPanel(final JuliaSetCalculator juliaSetCalculator, final int width, final int height) {
         this.juliaSetCalculator = juliaSetCalculator;
-        setPreferredSize(new Dimension(1200, 800));
+        setPreferredSize(new Dimension(width, height));
         setBackground(Color.white);
     }
 

src/MainClass.java

@@ -5,9 +5,9 @@ public class MainClass {
 
     public static void main(String[] args) {
 
-        int width = 1200;
-        int height = 800;
-        JuliaSetCalculator juliaSetCalculator = new ForkJoinJuliaSetCalculator(width, height);
+        int width = 1600;
+        int height = 1000;
+        JuliaSetCalculator juliaSetCalculator = new ThreadedJuliaSetCalculator(width, height);
         JuliaSetPanel juliaSetPanel = new JuliaSetPanel(juliaSetCalculator, width, height);
 
         SwingUtilities.invokeLater(() -> {

src/ThreadedJuliaSetCalculator.java

@@ -0,0 +1,75 @@
+public class ThreadedJuliaSetCalculator implements JuliaSetCalculator {
+
+    private int width;
+    private int height;
+    private int[][] iterations;
+
+    public ThreadedJuliaSetCalculator(final int width, final int height) {
+        this.width = width;
+        this.height = height;
+        iterations = new int[width][height];
+    }
+
+    @Override
+    public int[][] calculate(int maxIterations, double zoom, double cx, double cy, double moveX, double moveY) {
+
+        class JuliaTask implements Runnable {
+
+            private int startInclusive;
+            private int endExclusive;
+
+            JuliaTask(int startInclusive, int endExclusive) {
+                this.startInclusive = startInclusive;
+                this.endExclusive = endExclusive;
+            }
+
+            @Override
+            public void run() {
+                double zx, zy;
+
+                for(int x = startInclusive; x < endExclusive; x++) {
+                    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();
+
+        int NUM_THREADS = 128;
+        Thread[] threads = new Thread[NUM_THREADS];
+        int step = width / NUM_THREADS;
+
+        for(int i = 0; i < NUM_THREADS; i++) {
+            int start = i * step;
+            int end = (i + 1) * step;
+            if(end > width || i == NUM_THREADS - 1) end = width;
+            threads[i] = new Thread(new JuliaTask(start, end));
+            threads[i].start();
+        }
+
+        for(int i = 0; i < NUM_THREADS; i++) {
+            try {
+                threads[i].join();
+            } catch(Exception e) {
+                // No!
+            }
+        }
+
+        long endTime = System.currentTimeMillis();
+        System.out.println(endTime - startTime);
+
+        return iterations;
+    }
+
+}