initial commit of EdgeCloudSim

EdgeCloudSim with default network model, mobility model,  load generator
model, edge orchestrator, and VM CPU utilization model

src/edu/boun/edgecloudsim/utils/PoissonDistr.java

@@ -0,0 +1,63 @@
+/*
+ * Title:        EdgeCloudSim - Poisson Distribution
+ * 
+ * Description:  Poisson Distribution implementation
+ * 
+ * Licence:      GPL - http://www.gnu.org/copyleft/gpl.html
+ * Copyright (c) 2017, Bogazici University, Istanbul, Turkey
+ */
+
+package edu.boun.edgecloudsim.utils;
+
+import java.util.Random;
+
+public class PoissonDistr {
+    /** The num gen. */
+    private final Random numGen;
+
+    /** The mean. */
+    private final double mean;
+
+    /**
+     * Creates a new exponential number generator.
+     * 
+     * @param seed the seed to be used.
+     * @param mean the mean for the distribution.
+     */
+    public PoissonDistr(long seed, double mean) {
+        if (mean <= 0.0) {
+            throw new IllegalArgumentException("Mean must be greater than 0.0");
+        }
+        numGen = new Random(seed);
+        this.mean = mean;
+    }
+
+    /**
+     * Creates a new exponential number generator.
+     * 
+     * @param mean the mean for the distribution.
+     */
+    public PoissonDistr(double mean) {
+        if (mean <= 0.0) {
+            throw new IllegalArgumentException("Mean must be greated than 0.0");
+        }
+        numGen = new Random(System.currentTimeMillis());
+        this.mean = mean;
+    }
+
+    /**
+     * Generate a new random number.
+     * 
+     * @return the next random number in the sequence
+     */
+        public double sample() {
+            double L = Math.exp(-mean);
+            int k = 0;
+            double p = 1.0;
+            do {
+                p = p * numGen.nextDouble();
+                k++;
+            } while (p > L);
+            return k - 1;
+    }
+}