random_r_policy.cpp

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 *   Copyright (C) 2004-2015 The PaGMO development team,                     *
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#include <algorithm>
#include <boost/numeric/conversion/cast.hpp>
#include <utility>
#include <vector>

#include "../population.h"
#include "../rng.h"
#include "base.h"
#include "base_r_policy.h"
#include "random_r_policy.h"

namespace pagmo { namespace migration {


random_r_policy::random_r_policy(const double &rate, rate_type type):base_r_policy(rate,type),m_urng(rng_generator::get<rng_uint32>()) {}

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

std::vector<std::pair<population::size_type,std::vector<population::individual_type>::size_type> >
        random_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));
        // Permute the indices (immigrants).
        for (population::size_type i = 0; i < rate_limit; ++i) {
                population::size_type next_idx = i + (m_urng() % (rate_limit - i));
                if (next_idx != i) {
                        std::swap(immigrants_idx[i], immigrants_idx[next_idx]);
                }
        }
        // Permute the indices (destination).
        for (population::size_type i = 0; i < rate_limit; ++i) {
                population::size_type next_idx = i + (m_urng() % (dest.size() - i));
                if (next_idx != i) {
                        std::swap(dest_idx[i], dest_idx[next_idx]);
                }
        }
        // Return value.
        std::vector<std::pair<population::size_type,std::vector<population::individual_type>::size_type> >
                retval;
        for (population::size_type i = 0; i < rate_limit; ++i) {
                retval.push_back(std::make_pair(dest_idx[i],immigrants_idx[i]));
        }
        return retval;
}

} }

BOOST_CLASS_EXPORT_IMPLEMENT(pagmo::migration::random_r_policy)