rand_ulab_free_trees.hpp

/*********************************************************************
 *
 * Linear Arrangement Library - A library that implements a collection
 * algorithms for linear arrangments of graphs.
 *
 * Copyright (C) 2019 - 2023
 *
 * 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 (lalemany@cs.upc.edu)
 *         LARCA (Laboratory for Relational Algorithmics, Complexity and Learning)
 *         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)
 *         LARCA (Laboratory for Relational Algorithmics, Complexity and Learning)
 *         CQL (Complexity and Quantitative Linguistics Lab)
 *         Office S124, 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>
#include <map>
 
// lal includes
#include <lal/graphs/free_tree.hpp>
#include <lal/generate/rand_ulab_rooted_trees.hpp>
#include <lal/generate/tree_generator.hpp>
#include <lal/numeric/integer.hpp>
 
namespace lal {
namespace generate {
 
class _rand_ulab_free_trees : public _rand_ulab_rooted_trees {
public:
    /* CONSTRUCTORS */
 
    _rand_ulab_free_trees() noexcept : _rand_ulab_rooted_trees() {
        // add the initial values to m_fn
        init_fn();
    }
 
    _rand_ulab_free_trees(uint64_t n, uint64_t seed = 0) noexcept
        : _rand_ulab_rooted_trees(n, seed)
    {
        // add the initial values to m_fn
        init_fn();
 
        _rand_ulab_free_trees::init(n, seed);
    }
    _rand_ulab_free_trees(const _rand_ulab_free_trees& Gen) = default;
 
    _rand_ulab_free_trees(_rand_ulab_free_trees&& Gen) = default;
 
    ~_rand_ulab_free_trees() = default;
 
    _rand_ulab_free_trees& operator= (const _rand_ulab_free_trees& g) noexcept = default;
    _rand_ulab_free_trees& operator= (_rand_ulab_free_trees&& g) noexcept = default;
 
    /* INITIALIZE */
 
    void init(uint64_t n, uint64_t seed = 0) noexcept {
        _rand_ulab_rooted_trees::init(n, seed);
        // force the addition of the necessary values for m_fn and m_rn
        get_fn(n);
    }
 
    void clear() noexcept {
        _rand_ulab_rooted_trees::clear();
        m_fn.clear();
        m_alpha.clear();
 
        // add the initial values to m_fn
        init_fn();
    }
 
    /* GETTERS */
 
    graphs::free_tree get_tree() noexcept;
 
private:
    std::map<std::pair<uint64_t, uint64_t>, numeric::integer> m_alpha;
 
    std::vector<numeric::integer> m_fn;
 
private:
    uint64_t forest(uint64_t m, uint64_t q, uint64_t nt) noexcept;
 
    void bicenter(uint64_t n) noexcept;
 
    const numeric::integer&
    get_alpha_mq(const uint64_t m, const uint64_t q) noexcept;
 
    void init_fn() noexcept {
        // from the OEIS: https://oeis.org/A000055
        m_fn =
        std::vector<numeric::integer>{
            1ull,
            1ull,
            1ull,
            1ull,
            2ull,
            3ull,
            6ull,
            11ull,
            23ull,
            47ull,
            106ull,
            235ull,
            551ull,
            1301ull,
            3159ull,
            7741ull,
            19320ull,
            48629ull,
            123867ull,
            317955ull,
            823065ull,
            2144505ull,
            5623756ull,
            14828074ull,
            39299897ull,
            104636890ull,
            279793450ull,
            751065460ull,
            2023443032ull,
            5469566585ull,
            14830871802ull
        };
    }
 
    const numeric::integer& get_fn(const uint64_t n) noexcept;
 
    std::pair<uint64_t,uint64_t>
    choose_jd_from_alpha(const uint64_t m, const uint64_t q) noexcept;
};
 
class rand_ulab_free_trees : public _tree_generator<graphs::free_tree> {
public:
    /* CONSTRUCTORS */
 
    rand_ulab_free_trees() noexcept : _tree_generator<graphs::free_tree>() { }
 
    rand_ulab_free_trees(uint64_t n, uint64_t seed = 0) noexcept
        : _tree_generator<graphs::free_tree>(n), m_Gen(n, seed) { }
    rand_ulab_free_trees(const rand_ulab_free_trees& Gen) = default;
 
    rand_ulab_free_trees(rand_ulab_free_trees&& Gen) = default;
 
    ~rand_ulab_free_trees() = default;
 
    rand_ulab_free_trees& operator= (const rand_ulab_free_trees& g) noexcept = default;
    rand_ulab_free_trees& operator= (rand_ulab_free_trees&& g) noexcept = default;
 
    void init(uint64_t n, uint64_t seed = 0) noexcept {
        _tree_generator::init(n);
        m_Gen.init(n, seed);
    }
 
    void clear() noexcept {
        _tree_generator::clear();
        m_Gen.clear();
    }
 
    graphs::free_tree yield_tree() noexcept {
        return get_tree();
    }
 
protected:
    graphs::free_tree __get_tree() noexcept { return m_Gen.get_tree(); }
 
protected:
    _rand_ulab_free_trees m_Gen;
};
 
} // -- namespace generate
} // -- namespace lal