worst_r_policy.cpp

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#include <algorithm>
#include <boost/numeric/conversion/cast.hpp>
#include <utility>
#include <vector>

#include "../population.h"
#include "base.h"
#include "base_r_policy.h"
#include "worst_r_policy.h"

namespace pagmo { namespace migration {


worst_r_policy::worst_r_policy(const double &rate, rate_type type):base_r_policy(rate,type) {}

base_r_policy_ptr worst_r_policy::clone() const
{
        return base_r_policy_ptr(new worst_r_policy(*this));
}

// Helper object used to sort arrays of indices of object placed in another container.
template <class Container>
struct indirect_individual_sorter
{
        indirect_individual_sorter(const Container &container, const population &pop):
                m_container(container),m_pop(pop) {}
        template <class Idx>
        bool operator()(const Idx &idx1, const Idx &idx2) const
        {
                typedef typename Container::const_iterator::difference_type diff_type;
                return m_pop.n_dominated(*(m_container.begin() + boost::numeric_cast<diff_type>(idx1))) >
                        m_pop.n_dominated(*(m_container.begin() + boost::numeric_cast<diff_type>(idx2)));
        }
        // The original container.
        const Container         &m_container;
        const population        &m_pop;
};

// Selection implementation.
std::vector<std::pair<population::size_type,std::vector<population::individual_type>::size_type> >
        worst_r_policy::select(const std::vector<population::individual_type> &immigrants, const population &dest) const
{
        const population::size_type rate_limit = std::min<population::size_type>(get_n_individuals(dest),boost::numeric_cast<population::size_type>(immigrants.size()));
        // Temporary vectors to store sorted indices of the populations.
        std::vector<population::size_type> immigrants_idx(boost::numeric_cast<std::vector<population::size_type>::size_type>(immigrants.size()));
        std::vector<population::size_type> dest_idx(boost::numeric_cast<std::vector<population::size_type>::size_type>(dest.size()));
        // Fill in the arrays of indices.
        iota(immigrants_idx.begin(),immigrants_idx.end(),population::size_type(0));
        iota(dest_idx.begin(),dest_idx.end(),population::size_type(0));
        // Sort the arrays of indices.
        // From best to worst.
        std::sort(immigrants_idx.begin(),immigrants_idx.end(),indirect_individual_sorter<std::vector<population::individual_type> >(immigrants,dest));
        // From worst to best.
        std::sort(dest_idx.begin(),dest_idx.end(),indirect_individual_sorter<population>(dest,dest));
        std::reverse(dest_idx.begin(),dest_idx.end());
        // Create the result.
        std::vector<std::pair<population::size_type,std::vector<population::individual_type>::size_type> > result;
        for (population::size_type i = 0; i < rate_limit; ++i) {
                // Similar to fair policy, but replace unconditionally, without checking if the incoming individuals are better.
                result.push_back(std::make_pair(dest_idx[i],immigrants_idx[i]));
        }
        return result;
}

}}

BOOST_CLASS_EXPORT_IMPLEMENT(pagmo::migration::worst_r_policy)