set_maximum_arrangements.hpp

/*********************************************************************
 *
 * Linear Arrangement Library - A library that implements a collection
 * algorithms for linear arrangments of graphs.
 *
 * Copyright (C) 2019 - 2024
 *
 * This file is part of Linear Arrangement Library. The full code is available
 * at:
 *      https://github.com/LAL-project/linear-arrangement-library.git
 *
 * Linear Arrangement Library is free software: you can redistribute it
 * and/or modify it under the terms of the GNU Affero General Public License
 * as published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * Linear Arrangement Library is distributed in the hope that it will be
 * useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with Linear Arrangement Library.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Contact:
 *
 *     Lluís Alemany Puig (lluis.alemany.puig@upc.edu)
 *         LQMC (Quantitative, Mathematical, and Computational Linguisitcs)
 *         CQL (Complexity and Quantitative Linguistics Lab)
 *         Jordi Girona St 1-3, Campus Nord UPC, 08034 Barcelona.   CATALONIA, SPAIN
 *         Webpage: https://cqllab.upc.edu/people/lalemany/
 *
 *     Ramon Ferrer i Cancho (rferrericancho@cs.upc.edu)
 *         LQMC (Quantitative, Mathematical, and Computational Linguisitcs)
 *         CQL (Complexity and Quantitative Linguistics Lab)
 *         Office 220, Omega building
 *         Jordi Girona St 1-3, Campus Nord UPC, 08034 Barcelona.   CATALONIA, SPAIN
 *         Webpage: https://cqllab.upc.edu/people/rferrericancho/
 *
 ********************************************************************/
 
#pragma once
 
// C++ includes
#include <vector>
#if defined DEBUG
#include <cassert>
#endif
 
// lal includes
#include <lal/linear_arrangement.hpp>
#include <lal/graphs/free_tree.hpp>
#include <lal/detail/linarr/level_signature.hpp>
 
namespace lal {
namespace detail {
namespace DMax {
namespace unconstrained {
 
class set_maximum_arrangements {
private:
    static constexpr level_signature_type per_position = level_signature_type::per_position;
 
public:
    set_maximum_arrangements(const graphs::free_tree& t) noexcept : m_t(t) { }
 
    ~set_maximum_arrangements() noexcept { }
 
    void init() noexcept {
        m_max_value = 0;
    }
 
    /* GETTERS */
 
    [[nodiscard]] uint64_t get_max_value() const noexcept
    { return m_max_value; }
 
    [[nodiscard]] std::size_t get_num_representatives() const noexcept
    { return m_representatives.size(); }
 
    [[nodiscard]] std::vector<linear_arrangement>&& retrieve_all_representatives()
    noexcept
    {
        return std::move(m_representatives);
    }
 
    [[nodiscard]] std::size_t get_size_class(const std::size_t i) const noexcept {
#if defined DEBUG
        assert(i < m_amount.size());
#endif
        return m_amount[i];
    }
 
    [[nodiscard]] const linear_arrangement& get_representative(const std::size_t i)
    const noexcept
    {
#if defined DEBUG
        assert(i < m_representatives.size());
#endif
        return m_representatives[i];
    }
 
    [[nodiscard]] const level_signature_per_position& get_level_signature
    (const std::size_t i)
    const noexcept
    {
#if defined DEBUG
        assert(i < m_level_signatures.size());
#endif
        return m_level_signatures[i];
    }
 
    /* MODIFIERS */
 
    void add(const uint64_t value, const linear_arrangement& arr) noexcept {
        if (m_max_value < value) {
            m_max_value = value;
 
            m_representatives.clear();
            m_mirrored_level_signatures.clear();
            m_level_signatures.clear();
            m_amount.clear();
 
            level_signature_per_position L = calculate_level_signature<per_position>(m_t, arr);
 
            m_representatives.push_back(arr);
            m_mirrored_level_signatures.push_back(mirror_level_signature(L));
            m_level_signatures.push_back(std::move(L));
            m_amount.push_back(1);
        }
        else if (m_max_value == value) {
            level_signature_per_position L = calculate_level_signature<per_position>(m_t, arr);
            const std::size_t idx_repr = find_representative(L);
 
            if (idx_repr == m_representatives.size()) {
                m_representatives.push_back(arr);
                m_mirrored_level_signatures.push_back(mirror_level_signature(L));
                m_level_signatures.push_back(std::move(L));
                m_amount.push_back(1);
            }
            else {
                ++m_amount[idx_repr];
            }
        }
    }
 
    void merge(set_maximum_arrangements&& max_arrs) noexcept {
        // nothing to do
        if (m_max_value > max_arrs.m_max_value) {
            return;
        }
 
        // just copy the contents of 'max_arrs'
        if (m_max_value < max_arrs.m_max_value) {
            m_representatives.clear();
            m_mirrored_level_signatures.clear();
            m_level_signatures.clear();
            m_amount.clear();
 
            m_max_value = max_arrs.m_max_value;
            m_representatives = std::move(max_arrs.m_representatives);
            m_mirrored_level_signatures = std::move(max_arrs.m_mirrored_level_signatures);
            m_level_signatures = std::move(max_arrs.m_level_signatures);
            m_amount = std::move(max_arrs.m_amount);
            return;
        }
 
        // actually merge the two sets
        for (std::size_t i = 0; i < max_arrs.m_representatives.size(); ++i) {
            // find the representative's index in this set of arrangements
            const std::size_t idx_repr = find_representative(max_arrs.m_level_signatures[i]);
 
            // update collection
            if (idx_repr < m_representatives.size()) {
                ++m_amount[idx_repr];
            }
            else {
                m_representatives.push_back(std::move(max_arrs.m_representatives[i]));
                m_mirrored_level_signatures.push_back(std::move(max_arrs.m_mirrored_level_signatures[i]));
                m_level_signatures.push_back(std::move(max_arrs.m_level_signatures[i]));
                m_amount.push_back(max_arrs.m_amount[i]);
            }
        }
    }
 
private:
    [[nodiscard]] std::size_t find_representative
    (const level_signature_per_position& L)
    const noexcept
    {
        // The isomorphism to use is based on 'simple' arrangement isomorphism
        for (std::size_t i = 0; i < m_representatives.size(); ++i) {
 
            const bool isomorphic =
                (m_level_signatures[i] == L) or
                (m_mirrored_level_signatures[i] == L);
 
            if (isomorphic) { return i; }
        }
 
        return m_representatives.size();
    }
 
private:
    const graphs::free_tree& m_t;
 
    uint64_t m_max_value;
    std::vector<linear_arrangement> m_representatives;
    std::vector<level_signature_per_position> m_mirrored_level_signatures;
    std::vector<level_signature_per_position> m_level_signatures;
    std::vector<uint64_t> m_amount;
};
 
} // -- namespace unconstrained
} // -- namespace DMax
} // -- namespace detail
} // -- namespace lal