Rewrite

- rewritten all the sim code in a way to make easier to read and collect stats

src/main/java/net/berack/upo/valpre/rand/Distribution.java

@@ -0,0 +1,59 @@
+package net.berack.upo.valpre.rand;
+
+public interface Distribution {
+    public double sample(Rng rng);
+
+    public static class Exponential implements Distribution {
+        private final double lambda;
+
+        public Exponential(double lambda) {
+            this.lambda = lambda;
+        }
+
+        @Override
+        public double sample(Rng rng) {
+            return -Math.log(rng.random()) / lambda;
+        }
+    }
+
+    public static class Normal implements Distribution {
+        private final double mean;
+        private final double sigma;
+
+        public Normal(double mean, double sigma) {
+            this.mean = mean;
+            this.sigma = sigma;
+        }
+
+        @Override
+        public double sample(Rng rng) {
+            var sample = rng.random();
+            return mean + sigma * Math.sqrt(-2 * Math.log(sample)) * Math.cos(2 * Math.PI * sample);
+        }
+    }
+
+    public static class NormalBoxMuller implements Distribution {
+        private final double mean;
+        private final double sigma;
+        private double next = Double.NaN;
+
+        public NormalBoxMuller(double mean, double sigma) {
+            this.mean = mean;
+            this.sigma = sigma;
+        }
+
+        @Override
+        public double sample(Rng rng) {
+            if (!Double.isNaN(next)) {
+                var sample = next;
+                next = Double.NaN;
+                return sample;
+            }
+
+            var sample1 = rng.random();
+            var sample2 = rng.random();
+            next = mean + sigma * Math.sqrt(-2 * Math.log(sample1)) * Math.sin(2 * Math.PI * sample2);
+            return mean + sigma * Math.sqrt(-2 * Math.log(sample1)) * Math.cos(2 * Math.PI * sample2);
+        }
+    }
+}