From 988328cd4918faa0108d6b7f52d77e9067c9fa60 Mon Sep 17 00:00:00 2001
From: Berack96 <giacomobertolazzi7@gmail.com>
Date: Tue, 19 Dec 2023 00:16:37 +0100
Subject: [PATCH] LW - init LikelyhoodWeighting - added NetworkNode helper
 class

---
 .../upo/ai/problem3/LikelyhoodWeighting.java  | 45 +++++++++
 .../berack/upo/ai/problem3/NetworkNode.java   | 92 +++++++++++++++++++
 .../net/berack/upo/ai/problem3/SmileLib.java  |  6 ++
 3 files changed, 143 insertions(+)
 create mode 100644 src/main/java/net/berack/upo/ai/problem3/LikelyhoodWeighting.java
 create mode 100644 src/main/java/net/berack/upo/ai/problem3/NetworkNode.java

diff --git a/src/main/java/net/berack/upo/ai/problem3/LikelyhoodWeighting.java b/src/main/java/net/berack/upo/ai/problem3/LikelyhoodWeighting.java
new file mode 100644
index 0000000..817cb75
--- /dev/null
+++ b/src/main/java/net/berack/upo/ai/problem3/LikelyhoodWeighting.java
@@ -0,0 +1,45 @@
+package net.berack.upo.ai.problem3;
+
+import java.security.SecureRandom;
+import java.util.Objects;
+import smile.Network;
+
+public class LikelyhoodWeighting {
+
+    public final Network net;
+
+    public LikelyhoodWeighting(Network net) {
+        this.net = Objects.requireNonNull(net);
+    }
+
+    public void calculate(int totalRuns) {
+        totalRuns = Math.max(1, totalRuns);
+
+        var nodes = NetworkNode.buildSetFrom(net, totalRuns);
+        var rand = new SecureRandom();
+        var prob = new double[totalRuns];
+        var sum = 0.0d;
+
+        for(var run = 0; run < totalRuns; run++) {
+            prob[run] = 1;
+
+            for(var node: nodes) {
+                if(!node.isEvidence()) node.setSample(rand.nextDouble(), run);
+                else prob[run] *= node.getProbSampleEvidence(run);
+            }
+
+            sum += prob[run];
+        }
+
+        for(var node : nodes) if(!node.isEvidence()) {
+            var values = new double[node.outcomes.length];
+
+            for(var run = 0; run < totalRuns; run++)
+                values[node.samples[run]] += prob[run];
+            for(var i = 0; i < values.length; i++)
+                values[i] /= sum;
+
+            net.setPointValues(node.handle, values);
+        }
+    }
+}
diff --git a/src/main/java/net/berack/upo/ai/problem3/NetworkNode.java b/src/main/java/net/berack/upo/ai/problem3/NetworkNode.java
new file mode 100644
index 0000000..5130cfb
--- /dev/null
+++ b/src/main/java/net/berack/upo/ai/problem3/NetworkNode.java
@@ -0,0 +1,92 @@
+package net.berack.upo.ai.problem3;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Set;
+
+import smile.Network;
+
+public class NetworkNode {
+
+        public static Set<NetworkNode> buildSetFrom(Network net, int totRounds) {
+            var nodes = new HashMap<Integer, NetworkNode>();
+
+            for(var handle : net.getAllNodes()) nodes.put(handle, new NetworkNode(net, handle));
+
+            var retSet = Set.copyOf(nodes.values());
+            for(var node : retSet) {
+                var parentsHandle = net.getParents(node.handle);
+                node.parents = new NetworkNode[parentsHandle.length];
+
+                for(var i = 0; i < parentsHandle.length; i++)
+                    node.parents[i] = nodes.get(parentsHandle[i]);
+
+                if(!node.isEvidence()) {
+                    node.samples = new int[totRounds];
+                    Arrays.fill(node.samples, -1);
+                }
+            }
+
+            return retSet;
+        }
+
+        public static NetworkNode[] topologicalSort(Set<NetworkNode> nodes) {
+            throw new UnsupportedOperationException("TODO implement this function");
+        }
+
+        final int handle;
+        final String[] outcomes;
+        final double[] definition;
+        final int evidence;
+
+        NetworkNode[] parents;
+        int[] samples;
+
+        private NetworkNode(Network net, int handle) {
+            this.handle = handle;
+            this.definition = net.getNodeDefinition(handle);
+            this.outcomes = net.getOutcomeIds(handle);
+            this.evidence = net.isEvidence(handle)? net.getEvidence(handle) : -1;
+        }
+
+        public boolean isEvidence() {
+            return this.evidence > 0 ;
+        }
+
+        public double getProbSampleEvidence(int round) {
+            if(!this.isEvidence()) throw new IllegalArgumentException("Evidence");
+
+            var init = getStartingIndex(round);
+            return this.definition[init + this.evidence];
+        }
+
+        public void setSample(double rand, int round) {
+            var init = getStartingIndex(round);
+            var end = init + this.outcomes.length;
+            var prob = 0;
+
+            for(var i = init; i < end; i++) {
+                prob += this.definition[i];
+
+                if(rand <= prob) {
+                    this.samples[round] = i - init;
+                    break;
+                }
+            }
+        }
+
+        private int getStartingIndex(int round) {
+            var init = 0;
+            var tot = this.definition.length;
+
+            for(var p : this.parents) {
+                var pIndex = p.isEvidence()? p.evidence : p.samples[round];
+                if(pIndex == -1) throw new IllegalArgumentException("Parent");
+
+                tot /= p.outcomes.length;
+                init += tot * pIndex;
+            }
+
+            return init;
+        }
+    }
\ No newline at end of file
diff --git a/src/main/java/net/berack/upo/ai/problem3/SmileLib.java b/src/main/java/net/berack/upo/ai/problem3/SmileLib.java
index 30134d6..af8b279 100644
--- a/src/main/java/net/berack/upo/ai/problem3/SmileLib.java
+++ b/src/main/java/net/berack/upo/ai/problem3/SmileLib.java
@@ -49,6 +49,12 @@ public class SmileLib {
         var net = new Network();
 
         net.readFile(RESOURCE_PATH + "VentureBN.xdsl");
+
+        var nodes = net.getAllNodes();
+        for (var i = 0; i < nodes.length; i++) {
+            System.out.println(nodes[i] + " -> " + net.getNodeId(nodes[i]));
+        }
+
         net.setEvidence("Forecast", "Moderate");
         net.updateBeliefs();