AlgRouletteWheel.cpp

#include "ECF_base.h"
#include "AlgRouletteWheel.h"
#include "ECF_macro.h"
 
 
RouletteWheel :: RouletteWheel()
{
    name_ = "RouletteWheel";
 
    selFitPropOp = static_cast<SelFitnessProportionalOpP> (new SelFitnessProportionalOp);
    selRandomOp = static_cast<SelRandomOpP> (new SelRandomOp);
    selBestOp = static_cast<SelBestOpP> (new SelBestOp);
}
 
 
void RouletteWheel :: registerParameters(StateP state)
{
    registerParameter(state, "crxprob", (voidP) new double(0.5), ECF::DOUBLE, "crossover rate");
    registerParameter(state, "selpressure", (voidP) new double(10), ECF::DOUBLE, 
        "selection pressure: how much is the best individual 'better' than the worst");
}
 
 
bool RouletteWheel :: initialize(StateP state)
{
    selFitPropOp->initialize(state);
    selRandomOp->initialize(state);
    selBestOp->initialize(state);
 
    voidP crRateP = getParameterValue(state, "crxprob");
    crxRate_ = *((double*) crRateP.get());
 
    voidP selPressP = getParameterValue(state, "selpressure");
    selPressure_ = *((double*) selPressP.get());
 
    selFitPropOp->setSelPressure(selPressure_);
 
    return true;
}
 
 
bool RouletteWheel :: advanceGeneration(StateP state, DemeP deme)
{
    // elitism: copy current best individual
    IndividualP best = selBestOp->select(*deme);
    best = copy(best);
 
    // select individuals
    std::vector<IndividualP> wheel;
    wheel = selFitPropOp->selectMany(*deme, (uint) deme->size());
 
    // copy selected to new population
    for(uint i = 0; i < wheel.size(); ++i) 
        wheel[i] = copy(wheel[i]);
 
    // replace old population
    for(uint i = 0; i < deme->size(); i++)
        replaceWith((*deme)[i], wheel[i]);
 
    ECF_LOG(state, 5, "Selected individuals:");
    for(uint i = 0; i < deme->size(); i++){
        ECF_LOG(state, 5, dbl2str(deme->at(i)->fitness->getValue()));
    }
 
    // determine the number of crx operations
    uint noCrx = (int)(deme->size() * crxRate_ /2);
 
    // perform crossover
    for(uint i = 0; i < noCrx; i++){
 
        // select parents
        IndividualP parent1 = selRandomOp->select(*deme);
        IndividualP parent2 = selRandomOp->select(*deme);
        ECF_LOG(state, 5, "Parents: " + dbl2str(parent1->fitness->getValue()) + ", " + dbl2str(parent2->fitness->getValue()));
 
        // create children
        IndividualP child1 = copy(parent1);
        IndividualP child2 = copy(parent2);
 
        // perform crx operations
        mate(parent1, parent2, child1);
        mate(parent1, parent2, child2);
 
        // replace parents with children
        replaceWith(parent1, child1);
        replaceWith(parent2, child2);
    }
 
    // perform mutation on whole population
    mutate(*deme);
 
    // evaluate new individuals
    for(uint i = 0; i < deme->size(); i++)
        if(!deme->at(i)->fitness->isValid()) {
            evaluate(deme->at(i));
        }
 
    // elitism: preserve best individual
    IndividualP random = selRandomOp->select(*deme);
    if(best->fitness->isBetterThan(random->fitness))
        replaceWith(random, best);
 
    return true;
}