Distributions

- added all distributions required
- introduced tests

src/test/java/net/berack/upo/valpre/rand/TestRandom.java

@@ -0,0 +1,29 @@
+package net.berack.upo.valpre.rand;
+
+import static org.junit.Assert.assertTrue;
+
+import java.util.Arrays;
+
+import org.junit.jupiter.api.Test;
+
+public class TestRandom {
+    @Test
+    public void testRng() {
+        var numbers = new int[5000];
+        var rng = new Rng(4656);
+
+        for (var i = 0; i < 1000000; i++) {
+            var sample = rng.random();
+            var index = (int) (sample * numbers.length);
+            numbers[index] += 1;
+        }
+
+        var avg = (double) Arrays.stream(numbers).sum() / numbers.length;
+        var variance = Arrays.stream(numbers).mapToDouble(num -> Math.pow(num - avg, 2)).sum() / numbers.length;
+        var stdDev = Math.sqrt(variance);
+        var expected = Math.sqrt((double) numbers.length / 12);
+        expected *= 1.1; // adding a bit of margin
+
+        assertTrue("Standard Dev must be less than [" + expected + "] -> [" + stdDev + "]", stdDev < expected);
+    }
+}