Improve premature algorithm break

jsprit-core/src/main/java/basics/VehicleRoutingAlgorithm.java

@@ -31,7 +31,10 @@ import basics.algo.AlgorithmEndsListener;
 import basics.algo.AlgorithmStartsListener;
 import basics.algo.IterationEndsListener;
 import basics.algo.IterationStartsListener;
+import basics.algo.IterationWithoutImprovementBreaker;
+import basics.algo.PrematureAlgorithmBreaker;
 import basics.algo.SearchStrategy;
+import basics.algo.SearchStrategy.DiscoveredSolution;
 import basics.algo.SearchStrategyManager;
 import basics.algo.VehicleRoutingAlgorithmListener;
 import basics.algo.VehicleRoutingAlgorithmListeners;
@@ -44,6 +47,8 @@ import basics.algo.VehicleRoutingAlgorithmListeners;
  */
 public class VehicleRoutingAlgorithm {
 	
+	
+	
 	public static final int NOBREAK = Integer.MAX_VALUE;
 
 	private static Logger logger = Logger.getLogger(VehicleRoutingAlgorithm.class);
@@ -52,8 +57,6 @@ public class VehicleRoutingAlgorithm {
 	
 	private int nOfIterations = 100;
 	
-	private int prematureBreak = NOBREAK;
-	
 	private Counter counter = new Counter("iterations ");
 	
 	private SearchStrategyManager searchStrategyManager;
@@ -62,6 +65,15 @@ public class VehicleRoutingAlgorithm {
 	
 	private Collection<VehicleRoutingProblemSolution> initialSolutions;
 	
+	private PrematureAlgorithmBreaker prematureAlgorithmBreaker = new PrematureAlgorithmBreaker() {
+		
+		@Override
+		public boolean isPrematureBreak(DiscoveredSolution discoveredSolution) {
+			return false;
+		}
+		
+	};
+	
 	public VehicleRoutingAlgorithm(VehicleRoutingProblem problem, SearchStrategyManager searchStrategyManager) {
 		super();
 		this.problem = problem;
@@ -93,10 +105,14 @@ public class VehicleRoutingAlgorithm {
 	 * the assigned number of iterations without solution-acceptance.
 	 * 
 	 * 
-	 * @param iterationsWithoutImprovement
+	 * @param nuIterationsWithoutImprovement
 	 */
-	public void setPrematureBreak(int iterationsWithoutImprovement){
+	public void setPrematureBreak(int nuIterationsWithoutImprovement){
-		prematureBreak = iterationsWithoutImprovement;
+		prematureAlgorithmBreaker = new IterationWithoutImprovementBreaker(nuIterationsWithoutImprovement);
+	}
+	
+	public void setPrematureAlgorithmBreaker(PrematureAlgorithmBreaker prematureAlgorithmBreaker){
+		this.prematureAlgorithmBreaker = prematureAlgorithmBreaker;
 	}
 
 	/**
@@ -127,17 +143,14 @@ public class VehicleRoutingAlgorithm {
 		counter.reset();
 		Collection<VehicleRoutingProblemSolution> solutions = new ArrayList<VehicleRoutingProblemSolution>(initialSolutions);
 		algorithmStarts(problem,solutions);
-		int iterWithoutImprovement = 0;
 		logger.info("iterations start");
 		for(int i=0;i<nOfIterations;i++){
 			iterationStarts(i+1,problem,solutions);
 			counter.incCounter();
-			SearchStrategy strat = searchStrategyManager.getRandomStrategy();
+			SearchStrategy strategy = searchStrategyManager.getRandomStrategy();
-			boolean newSolutionFoundAndAccepted = strat.run(problem, solutions);
+			DiscoveredSolution discoveredSolution = strategy.run(problem, solutions);
-			selectedStrategy(strat.getName(),problem, solutions);
+			selectedStrategy(strategy.getName(),problem, solutions);
-			if(newSolutionFoundAndAccepted) iterWithoutImprovement = 0;
+			if(prematureAlgorithmBreaker.isPrematureBreak(discoveredSolution)){
-			else iterWithoutImprovement++;
-			if(iterWithoutImprovement > prematureBreak){
 				logger.info("premature break at iteration "+ (i+1));
 				nuOfIterationsThisAlgoIsRunning = (i+1);
 				break;

jsprit-core/src/main/java/basics/algo/IterationWithoutImprovementBreaker.java

@@ -0,0 +1,26 @@
+package basics.algo;
+
+import basics.algo.SearchStrategy.DiscoveredSolution;
+
+public class IterationWithoutImprovementBreaker implements PrematureAlgorithmBreaker{
+
+	private int nuOfIterationWithoutImprovement;
+	
+	private int iterationsWithoutImprovement = 0;
+	
+	public IterationWithoutImprovementBreaker(int nuOfIterationsWithoutImprovement){
+		this.nuOfIterationWithoutImprovement=nuOfIterationsWithoutImprovement;
+	}
+	
+	@Override
+	public boolean isPrematureBreak(DiscoveredSolution discoveredSolution) {
+		if(discoveredSolution.isAccepted()) iterationsWithoutImprovement = 0;
+		else iterationsWithoutImprovement++;
+		if(iterationsWithoutImprovement > nuOfIterationWithoutImprovement){
+			return true;
+		}
+		return false;
+	}
+
+	
+}

jsprit-core/src/main/java/basics/algo/PrematureAlgorithmBreaker.java

@@ -0,0 +1,9 @@
+package basics.algo;
+
+import basics.algo.SearchStrategy.DiscoveredSolution;
+
+public interface PrematureAlgorithmBreaker {
+	
+	public boolean isPrematureBreak(DiscoveredSolution discoveredSolution);
+
+}

jsprit-core/src/main/java/basics/algo/SearchStrategy.java

@@ -26,11 +26,10 @@ import java.util.Collections;
 
 import org.apache.log4j.Logger;
 
-import basics.VehicleRoutingProblem;
-import basics.VehicleRoutingProblemSolution;
-
 import algorithms.acceptors.SolutionAcceptor;
 import algorithms.selectors.SolutionSelector;
+import basics.VehicleRoutingProblem;
+import basics.VehicleRoutingProblemSolution;
 
 
 
@@ -38,6 +37,32 @@ import algorithms.selectors.SolutionSelector;
 
 public class SearchStrategy {
 	
+	public static class DiscoveredSolution {
+		private VehicleRoutingProblemSolution solution;
+		private boolean accepted;
+		private String strategyName;
+		
+		public DiscoveredSolution(VehicleRoutingProblemSolution solution,boolean accepted, String strategyName) {
+			super();
+			this.solution = solution;
+			this.accepted = accepted;
+			this.strategyName = strategyName;
+		}
+
+		public VehicleRoutingProblemSolution getSolution() {
+			return solution;
+		}
+
+		public boolean isAccepted() {
+			return accepted;
+		}
+
+		public String getStrategyName() {
+			return strategyName;
+		}
+		
+	}
+	
 	private static Logger logger = Logger.getLogger(SearchStrategy.class);
 	
 	private Collection<SearchStrategyModule> searchStrategyModules = new ArrayList<SearchStrategyModule>();
@@ -86,14 +111,14 @@ public class SearchStrategy {
 	 * <p>This involves three basic steps: 1) Selecting a solution from solutions (input parameter) according to {@link SolutionSelector}, 2) running the modules 
 	 * ({@link SearchStrategyModule}) on the selectedSolution and 3) accepting the new solution according to {@link SolutionAcceptor}. 
 	 * <p> Note that after 1) the selected solution is copied, thus the original solution is not modified.
-	 * <p> Note also that 3) modifies the input parameter solutions by adding, removing, replacing existing solutions.
+	 * <p> Note also that 3) modifies the input parameter solutions by adding, removing, replacing the existing solutions or whatever is defined in the solutionAcceptor.
 	 *  
 	 * @param vrp
 	 * @param solutions which will be modified 
 	 * @return boolean true if solution has been accepted, false otherwise
 	 * @see SolutionSelector, SearchStrategyModule, SolutionAcceptor 
 	 */
-	public boolean run(VehicleRoutingProblem vrp, Collection<VehicleRoutingProblemSolution> solutions){
+	public DiscoveredSolution run(VehicleRoutingProblem vrp, Collection<VehicleRoutingProblemSolution> solutions){
 		VehicleRoutingProblemSolution solution = solutionSelector.selectSolution(solutions);
 		if(solution == null) throw new IllegalStateException("solution is null. check solutionSelector to return an appropiate solution.");
 		VehicleRoutingProblemSolution lastSolution = VehicleRoutingProblemSolution.copyOf(solution);
@@ -102,7 +127,8 @@ public class SearchStrategy {
 			lastSolution = newSolution;
 		}
 		boolean solutionAccepted = solutionAcceptor.acceptSolution(solutions, lastSolution);
-		return solutionAccepted;
+		DiscoveredSolution discoveredSolution = new DiscoveredSolution(lastSolution, solutionAccepted, getName());
+		return discoveredSolution;
 	}
 
 	

jsprit-core/src/main/java/basics/algo/VariationCoefficientBreaker.java

@@ -0,0 +1,85 @@
+package basics.algo;
+
+import java.util.Collection;
+
+import org.apache.commons.math.stat.StatUtils;
+import org.apache.commons.math.stat.descriptive.moment.Mean;
+import org.apache.commons.math.stat.descriptive.moment.StandardDeviation;
+import org.apache.log4j.Logger;
+
+import basics.VehicleRoutingAlgorithm;
+import basics.VehicleRoutingProblem;
+import basics.VehicleRoutingProblemSolution;
+import basics.algo.SearchStrategy.DiscoveredSolution;
+
+public class VariationCoefficientBreaker implements PrematureAlgorithmBreaker, AlgorithmStartsListener, IterationEndsListener{
+
+	private static Logger logger = Logger.getLogger(VariationCoefficientBreaker.class);
+	
+	private int nuOfIterations;
+	
+	private double variationCoefficientThreshold;
+	
+	private int currentIteration;
+	
+	private double[] solutionValues;
+	
+	private VehicleRoutingProblemSolution lastAccepted = null;
+	
+	public VariationCoefficientBreaker(int nuOfIterations, double variationCoefficientThreshold) {
+		super();
+		this.nuOfIterations = nuOfIterations;
+		this.variationCoefficientThreshold = variationCoefficientThreshold;
+		solutionValues = new double[nuOfIterations];
+	}
+
+	@Override
+	public boolean isPrematureBreak(DiscoveredSolution discoveredSolution) {
+		if(discoveredSolution.isAccepted()){
+			lastAccepted = discoveredSolution.getSolution();
+			solutionValues[currentIteration]=discoveredSolution.getSolution().getCost();
+		}
+		else{
+			if(lastAccepted != null){
+				solutionValues[currentIteration]=lastAccepted.getCost();
+			}
+			else solutionValues[currentIteration]=Double.MAX_VALUE; 
+		}
+		if(lastAccepted !=null) {
+//			logger.info(lastAccepted.getCost());
+//			logger.info("inArr,"+(currentIteration)+","+solutionValues[currentIteration]);
+		}
+		if(currentIteration == (nuOfIterations-1)){
+			double mean = StatUtils.mean(solutionValues);
+			double stdDev = new StandardDeviation(true).evaluate(solutionValues, mean);
+			double variationCoefficient = stdDev/mean;
+//			logger.info("[mean="+mean+"][stdDev="+stdDev+"][variationCoefficient="+variationCoefficient+"]");
+			if(variationCoefficient < variationCoefficientThreshold){
+				return true;
+			}
+		}
+		return false;
+	}
+	
+	private void reset(){
+		currentIteration=0;
+	}
+
+	@Override
+	public void informAlgorithmStarts(VehicleRoutingProblem problem,VehicleRoutingAlgorithm algorithm,Collection<VehicleRoutingProblemSolution> solutions) {
+		reset();
+	}
+
+	@Override
+	public void informIterationEnds(int i, VehicleRoutingProblem problem, Collection<VehicleRoutingProblemSolution> solutions) {
+		if(currentIteration == (nuOfIterations-1)){
+			reset();
+		}
+		else{
+			currentIteration++;
+		}
+	}
+
+	
+
+}