1 files changed, 124 insertions, 0 deletions
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/GossipGirlStrategies.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/GossipGirlStrategies.java
new file mode 100644
index 0000000..4cd534e
--- /dev/null
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/GossipGirlStrategies.java
@@ -0,0 +1,124 @@
+package pl.edu.mimuw.cloudatlas.agent.modules;
+
+import org.apache.commons.math3.distribution.EnumeratedDistribution;
+import org.apache.commons.math3.util.Pair;
+import pl.edu.mimuw.cloudatlas.model.PathName;
+
+import java.util.*;
+
+/**
+ round robin with the same frequency for all levels,
+ round robin with the frequency exponentially decreasing with level,
+ random with the same selection probability for all levels,
+ random with the selection probability decreasing exponentially with level.
+ */
+
+public class GossipGirlStrategies {
+    private int roundRobinSameIt;
+    private ArrayList<Pair<String, Integer>> roundRobinExpFreqs;
+    private List<String> fullPathComponents;
+    private int fullPathLength;
+    private EnumeratedDistribution<String> expDist;
+    private EnumeratedDistribution<String> uniformDist;
+
+    public GossipGirlStrategies(PathName fullPath) {
+        fullPathComponents = fullPath.getComponents();
+        fullPathLength = fullPath.getComponents().size();
+        initUniformZoneProbabilities();
+        initExpZoneProbabilities();
+        roundRobinSameIt = 0;
+        initRoundRobinExpFreqs();
+    }
+
+    private void initExpZoneProbabilities() {
+        ArrayList<Pair<String, Double>> zoneProbabilities;
+        zoneProbabilities = new ArrayList<>(fullPathLength);
+
+        // TODO check if we decrease in good direction
+        for (int i = 0; i < fullPathLength; i++) {
+            Pair<String, Double> probPair = new Pair<String, Double>(fullPathComponents.get(i), Math.exp((double) i+1));
+            zoneProbabilities.add(probPair);
+        }
+
+        expDist = new EnumeratedDistribution<String>(zoneProbabilities);
+    }
+
+    private void initUniformZoneProbabilities() {
+        ArrayList<Pair<String, Double>> zoneProbabilities;
+        zoneProbabilities = new ArrayList<>(fullPathLength);
+        Double uniformProb = 1.0/fullPathLength;
+
+        // TODO good direction
+        for (int i = 0; i < fullPathLength; i++) {
+            Pair<String, Double> probPair = new Pair<String, Double>(fullPathComponents.get(i), uniformProb);
+            zoneProbabilities.add(probPair);
+        }
+
+        uniformDist = new EnumeratedDistribution<String>(zoneProbabilities);
+    }
+
+    private void initRoundRobinExpFreqs() {
+        roundRobinExpFreqs = new ArrayList<>();
+        for (String component : fullPathComponents) {
+            roundRobinExpFreqs.add(new Pair<String, Integer>(component, 0));
+        }
+    }
+
+    public enum ZoneSelectionStrategy {
+        ROUND_ROBIN_SAME_FREQ,
+        ROUND_ROBIN_EXP_FREQ,
+        RANDOM_UNFIORM,
+        RANDOM_DECR_EXP
+    }
+
+    private String updateRoundRobinExpFreqs() {
+        // TODO good direction
+        for (int i = roundRobinExpFreqs.size() - 1; i > 0; i--) {
+            Pair<String, Integer> p = roundRobinExpFreqs.get(i);
+            Pair<String, Integer> nextP = roundRobinExpFreqs.get(i-1);
+
+            if (2 * p.getSecond() < nextP.getSecond()) {
+                roundRobinExpFreqs.set(i, new Pair<String, Integer>(p.getFirst(), p.getSecond() + 1));
+                return p.getFirst();
+            }
+        }
+
+        Pair<String, Integer> rootPath = roundRobinExpFreqs.get(0);
+        roundRobinExpFreqs.set(0, new Pair<String, Integer>(rootPath.getFirst(), rootPath.getSecond() + 1));
+        return rootPath.getFirst();
+    }
+
+    private String formNewPath(String selectedPath) {
+        String newPath = "";
+        for (String pathEl : fullPathComponents) {
+            newPath = newPath.concat("/" + pathEl);
+            if (pathEl.equals(selectedPath))
+                break;
+        }
+        return newPath;
+    }
+
+    public PathName selectStrategy(ZoneSelectionStrategy selectionStrategy) {
+        String selectedPath = null;
+
+        switch(selectionStrategy) {
+            case ROUND_ROBIN_SAME_FREQ:
+                selectedPath = fullPathComponents.get(roundRobinSameIt);
+                roundRobinSameIt = (roundRobinSameIt + 1) % fullPathLength;
+                break;
+            case ROUND_ROBIN_EXP_FREQ:
+                selectedPath = updateRoundRobinExpFreqs();
+                break;
+            case RANDOM_UNFIORM:
+                selectedPath = uniformDist.sample();
+                break;
+            case RANDOM_DECR_EXP:
+                selectedPath = expDist.sample();
+                break;
+            default:
+                throw new UnsupportedOperationException("Such strategy doesn't exist");
+        }
+
+        return new PathName(formNewPath(selectedPath));
+    }
+}