1 files changed, 42 insertions, 25 deletions

diff --git a/src/jcgp/backend/modules/es/MuPlusLambda.java b/src/jcgp/backend/modules/es/MuPlusLambda.java
index 6a3883b..50bf265 100644
--- a/src/jcgp/backend/modules/es/MuPlusLambda.java
+++ b/src/jcgp/backend/modules/es/MuPlusLambda.java
@@ -9,41 +9,59 @@ import jcgp.backend.resources.parameters.Parameter;
 import jcgp.backend.resources.parameters.ParameterStatus;
 
 /**
- * (μ + λ) EA.
- * 
+ * (μ + λ)-ES
+ * <br><br>
+ * This strategy selects the μ fittest chromosomes from the population.
+ * The promoted individuals are copied into the new population and mutated
+ * λ times, but also carried forward unchanged. The total population size
+ * is μ + λ. 
+ * <br><br>
+ * Two integer parameters are used to control this strategy: parents
+ * and offspring. They are constrained in that they must always add up to
+ * the population size, and must never be smaller than 1.
+ * <br>
+ * One additional parameter, report, controls whether a detailed log of the
+ * algorithm's operation is to be printed or not. Reports respect the report
+ * interval base parameter.
  * 
+ * @see EvolutionaryStrategy
  * @author Eduardo Pedroni
  *
  */
 public class MuPlusLambda implements EvolutionaryStrategy {
 	
-	private IntegerParameter parents, offspring;
+	private IntegerParameter mu, lambda;
 	private BooleanParameter report;
 		
+	/**
+	 * Creates a new instance of MuPlusLambda. 
+	 * 
+	 * @param resources a reference to the experiment's resources.
+	 */
 	public MuPlusLambda(final Resources resources) {
-		parents = new IntegerParameter(1, "Parents") {
+		mu = new IntegerParameter(1, "Parents (μ)") {
 			@Override
 			public void validate(Number newValue) {
-				if (newValue.intValue() + offspring.get() != resources.populationSize()) {
+				if (newValue.intValue() + lambda.get() != resources.populationSize()) {
 					status = ParameterStatus.INVALID;
 					status.setDetails("Parents + offspring must equal population size.");
 				} else if (newValue.intValue() <= 0) {
 					status = ParameterStatus.INVALID;
-					status.setDetails("EA needs at least 1 parent.");
+					status.setDetails("ES needs at least 1 parent.");
 				} else {
 					status = ParameterStatus.VALID;
 				}
 			}
 		};
-		offspring = new IntegerParameter(4, "Offspring") {
+		lambda = new IntegerParameter(4, "Offspring (λ)") {
 			@Override
 			public void validate(Number newValue) {
-				if (newValue.intValue() + parents.get() != resources.populationSize()) {
+				if (newValue.intValue() + mu.get() != resources.populationSize()) {
 					status = ParameterStatus.INVALID;
 					status.setDetails("Parents + offspring must equal population size.");
 				} else if (newValue.intValue() <= 0) {
 					status = ParameterStatus.INVALID;
-					status.setDetails("EA needs at least 1 offspring.");
+					status.setDetails("ES needs at least 1 offspring.");
 				} else {
 					status = ParameterStatus.VALID;
 				}
@@ -58,32 +76,31 @@ public class MuPlusLambda implements EvolutionaryStrategy {
 	}
 	
 	@Override
-	public void evolve(Population population, Mutator mutator, Resources resources) {
-		// select fittest chromosomes
-		if (report.get()) resources.reportln("[ES] Selected chromosome: " + population.getFittestIndex());
-		
-		// create copies of fittest chromosome, mutate them
-		for (int i = 0; i < resources.populationSize(); i++) {
-			if (i != population.getFittestIndex()) {
-				if (report.get()) resources.reportln("[ES] Copying fittest chromosome to population position " + i);
-				population.copyChromosome(population.getFittestIndex(), i);
-				if (report.get()) resources.reportln("[ES] Mutating copied chromosome");
-				mutator.mutate(population.getChromosome(i), resources);
-			}
+	public void evolve(Population population, Mutator mutator, Resources resources) {		
+		/* Population is sorted in ascending order of fitness, so leave the last
+		 * mu chromosomes intact
+		 */
+		for (int i = 0; i < resources.populationSize() - mu.get(); i++) {
+			// select a random parent out of the lambda offspring individuals
+			int randomParent = resources.populationSize() - 1 - resources.getRandomInt(mu.get());
+			if (report.get()) resources.reportln("[ES] Copying Chr " + randomParent + " to population position " + i);
+			population.copyChromosome(randomParent, i);
+			
+			// mutate selected chromosome
+			if (report.get()) resources.reportln("[ES] Mutating copied chromosome");
+			mutator.mutate(population.getChromosome(i), resources);
 		}
 		
-		if (report.get()) resources.reportln("[ES] Generation is complete.");
-		
+		if (report.get()) resources.reportln("[ES] Generation is complete");
 	}
 
 	@Override
 	public Parameter<?>[] getLocalParameters() {
-		return new Parameter[] {parents, offspring, report};
+		return new Parameter[] {mu, lambda, report};
 	}
 
 	@Override
 	public String toString() {
 		return "(μ + λ)";
 	}
-	
 }