random_s_policy.cpp

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#include <algorithm>
#include <vector>

#include "../population.h"
#include "base.h"
#include "base_s_policy.h"
#include "random_s_policy.h"
#include "../exceptions.h"

namespace pagmo { namespace migration {


random_s_policy::random_s_policy(const double &rate, rate_type type):base_s_policy(rate,type) {}

base_s_policy_ptr random_s_policy::clone() const
{
        return base_s_policy_ptr(new random_s_policy(*this));
}

std::vector<population::individual_type> random_s_policy::select(population &pop) const
{
        pagmo_assert(get_n_individuals(pop) <= pop.size());
        // Gets the number of individuals to select
        const population::size_type migration_rate = get_n_individuals(pop);
        
        // Create a temporary array of individuals.
        std::vector<population::individual_type> result;
        
        // Create an array of indices
        std::vector<population::size_type> candidates_idx(boost::numeric_cast<std::vector<population::size_type>::size_type>(pop.size()));
        
        // Fill it with indices
        iota(candidates_idx.begin(),candidates_idx.end(),population::size_type(0));

        // shuffle
        random_shuffle(candidates_idx.begin(),candidates_idx.end());
        
        // Selects the n first individuals
        for (population::size_type i = 0; i< migration_rate; ++i) {
                result.push_back(pop.get_individual(candidates_idx[i]));
        }
        
        return result;
}

}}

BOOST_CLASS_EXPORT_IMPLEMENT(pagmo::migration::random_s_policy)