level_signature.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
#if defined DEBUG
#include <cassert>
#endif
 
// lal includes
#include <lal/iterators/E_iterator.hpp>
#include <lal/linear_arrangement.hpp>
#include <lal/properties/branchless_path.hpp>
 
namespace lal {
namespace detail {
 
enum class level_signature_type {
    per_vertex,
    per_position
};
 
template <level_signature_type t>
class level_signature {
public:
    level_signature() noexcept = default;
    level_signature(const level_signature&) noexcept = default;
    level_signature(level_signature&&) noexcept = default;
    level_signature& operator=(const level_signature&) noexcept = default;
    level_signature& operator=(level_signature&&) noexcept = default;
 
    level_signature(const std::size_t n) noexcept : m_data(n, 0) { }
 
    void init(const std::size_t n) noexcept {
        m_data.resize(n, 0);
    }
 
    template <typename T>
    [[nodiscard]] int64_t operator[] (const T i) const noexcept {
        if constexpr (t == level_signature_type::per_position) {
            static_assert(std::is_same_v<T, position_t>);
        }
        else {
            static_assert(std::is_same_v<T, node_t>);
        }
        return m_data[*i];
    }
    template <typename T>
    [[nodiscard]] int64_t& operator[] (const T i) noexcept {
        if constexpr (t == level_signature_type::per_position) {
            static_assert(std::is_same_v<T, position_t>);
        }
        else {
            static_assert(std::is_same_v<T, node_t>);
        }
        return m_data[*i];
    }
 
    template <level_signature_type st = t>
    [[nodiscard]] bool operator== (const level_signature<st>& L) const noexcept {
        static_assert(st == t);
        for (std::size_t i = 0; i < m_data.size(); ++i) {
            if (m_data[i] != L.m_data[i]) { return false; }
        }
        return true;
    }
 
    template <
        level_signature_type st = t,
        std::enable_if_t<st == level_signature_type::per_vertex, bool> = true
    >
    [[nodiscard]] int64_t get_vertex_level(const node u) const noexcept {
        return m_data[u];
    }
    template <
        level_signature_type st = t,
        std::enable_if_t<st == level_signature_type::per_vertex, bool> = true
    >
    void set_vertex_level(const node u, const int64_t l) noexcept {
        m_data[u] = l;
    }
 
    template <
        level_signature_type st = t,
        std::enable_if_t<st == level_signature_type::per_position, bool> = true
    >
    [[nodiscard]] int64_t get_position_level(const position p) const noexcept {
        return m_data[p];
    }
    template <
        level_signature_type st = t,
        std::enable_if_t<st == level_signature_type::per_position, bool> = true
    >
    void set_position_level(const position p, const int64_t l) noexcept {
        m_data[p] = l;
    }
 
    void mirror() noexcept {
        if constexpr (t == level_signature_type::per_position) {
            const std::size_t n = m_data.size();
            for (position p = 0ull; p < n/2; ++p) {
                m_data[p] = -m_data[p];
                m_data[n - 1ull - p] = -m_data[n - 1ull - p];
                std::swap( m_data[p], m_data[n - 1ull - p] );
            }
            if (n%2 == 1) {
                m_data[n/2] = -m_data[n/2];
            }
        }
        else {
            for (node u = 0ull; u < m_data.size(); ++u) {
                m_data[u] = -m_data[u];
            }
        }
    }
 
private:
    array<int64_t> m_data;
};
 
[[nodiscard]] inline constexpr bool is_per_vertex(const level_signature_type& t)
noexcept
{
    return t == level_signature_type::per_vertex;
}
[[nodiscard]] inline constexpr bool is_per_position(const level_signature_type& t)
noexcept
{
    return t == level_signature_type::per_position;
}
 
typedef level_signature<level_signature_type::per_vertex> level_signature_per_vertex;
typedef level_signature<level_signature_type::per_position> level_signature_per_position;
 
template <level_signature_type t, class graph_t>
[[nodiscard]] bool is_thistle_vertex
(
    const graph_t& g,
    const level_signature<t>& levels,
    const node_t u,
    const linear_arrangement& arr = {}
)
noexcept
{
    int64_t l;
    if constexpr (t == level_signature_type::per_vertex) {
        l = levels[u];
    }
    else {
        l = (arr.size() == 0 ? levels[position_t{*u}] : levels[position_t{arr[u]}]);
    }
    return static_cast<uint64_t>( std::abs(l) ) != g.get_degree(*u);
}
 
template <level_signature_type t, class graph_t>
void calculate_level_signature
(
    const graph_t& g,
    const linear_arrangement& arr,
    level_signature<t>& L
)
noexcept
{
    iterators::E_iterator it(g);
    while (not it.end()) {
        const auto [u, v] = it.yield_edge_t();
        const position_t pu = (arr.size() == 0 ? *u : arr[u]);
        const position_t pv = (arr.size() == 0 ? *v : arr[v]);
        if constexpr (t == level_signature_type::per_vertex) {
            if (pu < pv) {
                ++L[u];
                --L[v];
            }
            else {
                --L[u];
                ++L[v];
            }
        }
        else {
            if (pu < pv) {
                ++L[pu];
                --L[pv];
            }
            else {
                --L[pu];
                ++L[pv];
            }
        }
    }
}
 
template <level_signature_type t, class graph_t>
[[nodiscard]] level_signature<t> calculate_level_signature
(const graph_t& g, const linear_arrangement& arr)
noexcept
{
    const auto n = g.get_num_nodes();
    level_signature<t> L(n);
    if constexpr (t == level_signature_type::per_vertex) {
        for (node_t u = 0ull; u < n; ++u) { L[u] = 0; }
    }
    else {
        for (position_t p = 0ull; p < n; ++p) { L[p] = 0; }
    }
 
    calculate_level_signature(g, arr, L);
    return L;
}
 
template <class level_signature_t>
[[nodiscard]] level_signature_t mirror_level_signature(const level_signature_t& L)
noexcept
{
    level_signature_t L2 = L;
    L2.mirror();
    return L2;
}
 
} // -- namespace detail
} // -- namespace lal