Adding Monte Carlo calculation of Pi example

pavanky · pavanky · commit 793de5aa3dc7 · 2014-03-03T18:11:33.000-05:00
diff --git a/examples/MonteCarloPi.java b/examples/MonteCarloPi.java
@@ -0,0 +1,64 @@
+import java.util.Random;
+import com.arrayfire.Array;
+
+public class MonteCarloPi {
+
+    public static double hostCalcPi(int size) {
+        Random rand = new Random();
+        int count = 0;
+        for (int i = 0; i < size; i++) {
+            float x = rand.nextFloat();
+            float y = rand.nextFloat();
+            boolean lt1 = (x * x + y * y) < 1;
+            if (lt1) count++;
+        }
+
+        return 4.0 * ((double)(count)) / size;
+    }
+
+    public static double deviceCalcPi(int size) throws Exception {
+        int[] dims =  new int[] {size, 1};
+
+        Array x = Array.randu(dims, Array.FloatType);
+        Array y = Array.randu(dims, Array.FloatType);
+
+        Array x2 = Array.mul(x, x);
+        Array y2 = Array.mul(y, y);
+        Array res = Array.lt(Array.add(x2, y2), 1);
+
+        double count = Array.sumAll(res);
+        return 4.0 * ((double)(count)) / size;
+    }
+
+    public static void main(String[] args) {
+
+        try {
+            int size = 5000000;
+            int iter = 100;
+            double hostPi = hostCalcPi(size);
+            double devicePi = deviceCalcPi(size);
+
+            System.out.println("Results from host: " + hostPi);
+            System.out.println("Results from device: " + devicePi);
+
+            long hostStart = System.currentTimeMillis();
+            for (int i = 0; i < iter; i++) {
+                hostPi = hostCalcPi(size);
+            }
+            double hostElapsed = (double)(System.currentTimeMillis() - hostStart)/iter;
+
+            long deviceStart = System.currentTimeMillis();
+            for (int i = 0; i < iter; i++) {
+                devicePi = deviceCalcPi(size);
+            }
+            double deviceElapsed = (double)(System.currentTimeMillis() - deviceStart)/iter;
+
+            System.out.println("Time taken for host (ms): " + hostElapsed);
+            System.out.println("Time taken for device (ms): " + deviceElapsed);
+            System.out.println("Speedup: " + Math.round((hostElapsed) / (deviceElapsed)));
+
+        } catch (Exception e) {
+            System.out.println(e.getMessage());
+        }
+    }
+}
