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-rw-r--r--src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/GossipGirlStrategies.java124
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));
+ }
+}