diff options
Diffstat (limited to 'src/jcgp/backend/modules')
| -rw-r--r-- | src/jcgp/backend/modules/es/MuPlusLambda.java | 66 | ||||
| -rw-r--r-- | src/jcgp/backend/modules/problem/DigitalCircuitProblem.java | 8 |
2 files changed, 67 insertions, 7 deletions
diff --git a/src/jcgp/backend/modules/es/MuPlusLambda.java b/src/jcgp/backend/modules/es/MuPlusLambda.java index 3743ee6..6a6870f 100644 --- a/src/jcgp/backend/modules/es/MuPlusLambda.java +++ b/src/jcgp/backend/modules/es/MuPlusLambda.java @@ -77,21 +77,77 @@ public class MuPlusLambda extends EvolutionaryStrategy { @Override public void evolve(Population population, Mutator mutator) { - // sort the population in order of best fitness - population.sort(); + // sort the population neutrally + sort(population); - // population is now sorted in ascending order of fitness, the last chromosomes are the fittest + // population is now sorted such that the new parents are in the last mu positions for (int i = 0; i < getResources().populationSize() - mu.get(); i++) { - // select a random parent out of the lambda offspring individuals + // select a random parent out of the mu population parents int randomParent = getResources().populationSize() - 1 - getResources().getRandomInt(mu.get()); if (report.get()) getResources().reportln("[ES] Copying Chr " + randomParent + " to population position " + i); + + // copy it into the offspring position population.copyChromosome(randomParent, i); - // mutate selected chromosome + // mutate the new offspring chromosome if (report.get()) getResources().reportln("[ES] Mutating copied chromosome"); mutator.mutate(population.get(i)); } if (report.get()) getResources().reportln("[ES] Generation is complete"); } + + /** + * Neutrally sorts the specified population. + * <br><br> + * Optimised sorting methods tend to be stable, meaning + * the order of elements which are already ordered is not + * changed. While performing faster, such sorting algorithms + * do not promote neutral drift, an important aspect of CGP. + * <br><br> + * This sort iterates through the population offspring (first lambda + * elements) and compares each with each of the parents (last mu + * elements), overwriting the parent if the offspring's fitness + * is greater than or equal to the parent's. + * It is biased towards offspring: parents are replaced with + * equally fit offspring as often as possible. + * + * @param population the population to sort. + */ + private void sort(Population population) { + /* Create an array with the index of each of the current parents. + * This is done to speed up the sort. No deep chromosome copies are + * made until the algorithm is finished; instead, only indices are copied. + */ + int[] parents = new int[mu.get()]; + for (int i = 0; i < parents.length; i++) { + parents[i] = lambda.get() + i; + } + + // cycle through the offspring, i.e. the first lambda elements of the population + for (int o = 0; o < getResources().populationSize() - mu.get(); o++) { + // compare each offspring with each parent, as stored in parents + for (int p = 0; p < parents.length; p++) { + /* replace parent if the offspring fitness and greater than or equal to its own + * if it is equal to, only replace if it is an old parent, if it is greater than, + * replace regardless + */ + if ((population.get(o).getFitness() == population.get(parents[p]).getFitness() && parents[p] >= lambda.get()) + || population.get(o).getFitness() >= population.get(parents[p]).getFitness()) { + parents[p] = o; + // offspring has been selected, check the next one + break; + } + } + } + + /* selection is complete, parents now contains the indices of each selected offspring + * time to perform the deep copies + */ + for (int c = 0; c < parents.length; c++) { + // copy each selected index in parent to each parent position in the population + population.copyChromosome(parents[c], lambda.get() + c); + } + + } } diff --git a/src/jcgp/backend/modules/problem/DigitalCircuitProblem.java b/src/jcgp/backend/modules/problem/DigitalCircuitProblem.java index b615675..e2f17c3 100644 --- a/src/jcgp/backend/modules/problem/DigitalCircuitProblem.java +++ b/src/jcgp/backend/modules/problem/DigitalCircuitProblem.java @@ -45,13 +45,17 @@ public class DigitalCircuitProblem extends TestCaseProblem<UnsignedInteger> { Integer output = ((UnsignedInteger) population.get(i).getOutput(o).calculate()).get(); Integer matches = ~(output ^ testCases.get(t).getOutput(o).get()); // check only the relevant bits - int bits = (int) Math.pow(2.0, (double) resources.inputs()); + int bits; + if (resources.inputs() < 5) { + bits = (int) Math.pow(2.0, (double) resources.inputs()); + } else { + bits = 32; + } for (int b = 0; b < bits; b++) { fitness += (matches >>> b) & 1; } } } - // assign the resulting fitness to the respective individual population.get(i).setFitness(fitness); } |