Refactor Net and ServerNodeState classes to improve child node handling and simplify simulation initialization

src/main/java/net/berack/upo/valpre/sim/Net.java

@@ -17,8 +17,6 @@ import com.esotericsoftware.kryo.KryoException;
 import com.esotericsoftware.kryo.io.Input;
 import com.esotericsoftware.kryo.io.Output;
 
-import net.berack.upo.valpre.rand.Rng;
-
 /**
  * A class that represents a network of queues, each with its own servers.
  * The network in question is created by adding a node and then establishing
@@ -141,26 +139,6 @@ public final class Net implements Iterable<ServerNode> {
         return this.servers.get(index);
     }
 
-    /**
-     * Get one of the child nodes from the parent specified. If the index is out of
-     * bounds then an exception is thrown. If the node has no child then -1 is
-     * returned.
-     * 
-     * @param parent the parent node
-     * @param rng    the random number generator used for getting one of the child
-     * @throws IndexOutOfBoundsException If the index is not in the range
-     * @return the resultig node
-     */
-    public int getChildOf(int parent, Rng rng) {
-        var random = rng.random();
-        for (var conn : this.connections.get(parent)) {
-            random -= conn.weight;
-            if (random <= 0)
-                return conn.index;
-        }
-        return -1;
-    }
-
     /**
      * Get a list of all the children of the parent.
      * In the list there is the node and the weight associated with.

src/main/java/net/berack/upo/valpre/sim/ServerNodeState.java

@@ -1,8 +1,10 @@
 package net.berack.upo.valpre.sim;
 
 import java.util.ArrayDeque;
+import java.util.List;
 
 import net.berack.upo.valpre.rand.Rng;
+import net.berack.upo.valpre.sim.Net.Connection;
 import net.berack.upo.valpre.sim.stats.NodeStats;
 
 /**
@@ -17,9 +19,9 @@ public class ServerNodeState {
     public final ArrayDeque<Double> queue = new ArrayDeque<>();
 
     public final int index;
-    public final Net net;
     public final ServerNode node;
     public final NodeStats stats = new NodeStats();
+    public final List<Connection> children;
 
     /**
      * Create a new node state based on the index and the net passed as input
@@ -29,8 +31,8 @@ public class ServerNodeState {
      */
     ServerNodeState(int index, Net net) {
         this.index = index;
-        this.net = net;
         this.node = net.getNode(index);
+        this.children = net.getChildren(index);
     }
 
     /**
@@ -166,9 +168,14 @@ public class ServerNodeState {
      *         otherwise
      */
     public Event spawnArrivalToChild(double time, Rng rng) {
-        var childIndex = this.net.getChildOf(this.index, rng);
+        if (!this.children.isEmpty()) {
-        if (childIndex >= 0)
+            var random = rng.random();
-            return Event.newArrival(childIndex, time);
+            for (var child : this.children) {
+                random -= child.weight;
+                if (random <= 0)
+                    return Event.newArrival(child.index, time);
+            }
+        }
         return null;
     }
 }

src/main/java/net/berack/upo/valpre/sim/Simulation.java

@@ -24,10 +24,15 @@ public final class Simulation {
     private long eventProcessed = 0;
 
     /**
-     * Creates a new run of the simulation with the given nodes and random number
+     * Creates a new simulation for the given network.
-     * generator.
+     * The random number generator is used to generate random numbers for the
+     * simulation.
+     * The simulation will end when the given criteria are met.
+     * NOTE: the network passed is only used to create the initial states of the
+     * nodes, so the simulation is not affected by changes to the network after
+     * the creation of this object.
      * 
-     * @param states    The nodes in the network.
+     * @param net       The network to simulate.
      * @param rng       The random number generator to use.
      * @param criterias when the simulation has to end.
      */

src/test/java/net/berack/upo/valpre/sim/TestSimulation.java

@@ -121,7 +121,7 @@ public class TestSimulation {
         net.addConnection(0, 1, 1.0);
         var conn = net.getChildren(0);
         assertEquals(1, conn.size());
-        assertEquals(node1, conn.get(0).child);
+        assertEquals(1, conn.get(0).index);
         assertEquals(1.0, conn.get(0).weight, DELTA);
         conn = net.getChildren(1);
         assertEquals(0, conn.size());
@@ -131,8 +131,8 @@ public class TestSimulation {
         net.addConnection(0, 2, 1.0);
         conn = net.getChildren(0);
         assertEquals(2, conn.size());
-        assertEquals(node1, conn.get(0).child);
+        assertEquals(1, conn.get(0).index);
-        assertEquals(node2, conn.get(1).child);
+        assertEquals(2, conn.get(1).index);
         assertEquals(1.0, conn.get(0).weight, DELTA);
         assertEquals(1.0, conn.get(1).weight, DELTA);
         conn = net.getChildren(1);
@@ -143,18 +143,14 @@ public class TestSimulation {
         net.normalizeWeights();
         conn = net.getChildren(0);
         assertEquals(2, conn.size());
-        assertEquals(node1, conn.get(0).child);
+        assertEquals(1, conn.get(0).index);
-        assertEquals(node2, conn.get(1).child);
+        assertEquals(2, conn.get(1).index);
         assertEquals(0.5, conn.get(0).weight, DELTA);
         assertEquals(0.5, conn.get(1).weight, DELTA);
         conn = net.getChildren(1);
         assertEquals(0, conn.size());
         conn = net.getChildren(2);
         assertEquals(0, conn.size());
-
-        var sample = net.getChildOf(0, rigged);
-        assertEquals(1, sample);
-        assertEquals(node1, net.getNode(sample));
     }
 
     @Test
@@ -162,7 +158,6 @@ public class TestSimulation {
         var state = new ServerNodeState(1, simpleNet);
 
         assertEquals(1, state.index);
-        assertEquals(simpleNet, state.net);
         assertEquals(node1, state.node);
         assertEquals(0, state.numServerBusy);
         assertEquals(0, state.numServerUnavailable);