rand_ulab_rooted_trees.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 <random>
#include <tuple>
 
// lal includes
#include <lal/graphs/rooted_tree.hpp>
#include <lal/generate/tree_generator.hpp>
#include <lal/numeric/integer.hpp>
#include <lal/detail/array.hpp>
 
namespace lal {
namespace generate {
 
class _rand_ulab_rooted_trees {
public:
    /* CONSTRUCTORS */
 
    _rand_ulab_rooted_trees() noexcept {
        // add the initial values to m_rn
        init_rn();
    }
 
    _rand_ulab_rooted_trees(const uint64_t n, const uint64_t seed = 0) noexcept :
        _rand_ulab_rooted_trees()
    {
        // add the initial values to m_rn
        init_rn();
 
        init(n, seed);
    }
 
    _rand_ulab_rooted_trees(const _rand_ulab_rooted_trees& Gen) = default;
 
    _rand_ulab_rooted_trees(_rand_ulab_rooted_trees&& Gen) = default;
 
    virtual ~_rand_ulab_rooted_trees() = default;
 
    _rand_ulab_rooted_trees& operator= (const _rand_ulab_rooted_trees& g) noexcept = default;
    _rand_ulab_rooted_trees& operator= (_rand_ulab_rooted_trees&& g) noexcept = default;
 
    /* INITIALIZE */
 
    void init(const uint64_t n, const uint64_t seed = 0) noexcept {
        // setup memory
        m_n = n;
        m_head_vector.resize(m_n);
 
        if (m_n <= 1) { return; }
 
        // initialize the random number generators
        if (seed == 0) {
            std::random_device rd;
            m_gen = std::mt19937(rd());
        }
        else {
            m_gen = std::mt19937(seed);
        }
        m_unif = std::uniform_real_distribution<double>(0, 1);
 
        // force the addition of the necessary values for m_rn
        std::ignore = get_rn(n);
    }
 
    void clear() noexcept {
        // clear the values in m_rn
        m_rn.clear();
        // add the initial values to m_rn
        init_rn();
        // clear the other memory
        m_head_vector.clear();
    }
 
    /* GETTERS */
 
    [[nodiscard]] graphs::rooted_tree get_tree() noexcept;
 
protected:
    uint64_t m_n;
 
    std::mt19937 m_gen;
    std::uniform_real_distribution<double> m_unif;
 
    std::vector<numeric::integer> m_rn;
 
    std::vector<numeric::integer> m_rn_times_n;
    std::vector<numeric::integer> m_rn_times_n_minus_1;
 
    head_vector m_head_vector;
 
protected:
 
    [[nodiscard]] std::pair<uint64_t,uint64_t> ranrut
    (
        const uint64_t n,
        const uint64_t lr,
        uint64_t nt
    )
    noexcept;
 
    void init_rn() noexcept {
        // from the OEIS: https://oeis.org/A000081
        m_rn =
        std::vector<numeric::integer>{
            0ull,
            1ull,
            1ull,
            2ull,
            4ull,
            9ull,
            20ull,
            48ull,
            115ull,
            286ull,
            719ull,
            1842ull,
            4766ull,
            12486ull,
            32973ull,
            87811ull,
            235381ull,
            634847ull,
            1721159ull,
            4688676ull,
            12826228ull,
            35221832ull,
            97055181ull,
            268282855ull,
            743724984ull,
            2067174645ull,
            5759636510ull,
            16083734329ull,
            45007066269ull,
            126186554308ull,
            354426847597ull
        };
        m_rn_times_n.resize(m_rn.size());
        m_rn_times_n[0] = 0;
        m_rn_times_n_minus_1.resize(m_rn.size());
        m_rn_times_n_minus_1[0] = 0;
        for (uint64_t n = 1; n < m_rn.size(); ++n) {
            m_rn_times_n[n] = m_rn[n]*n;
            m_rn_times_n_minus_1[n] = m_rn_times_n[n] - m_rn[n];
        }
    }
 
    [[nodiscard]] const numeric::integer& get_rn(const uint64_t n) noexcept;
 
    [[nodiscard]] bool has_rn(const uint64_t n) const noexcept { return m_rn.size() >= n + 1; }
 
    [[nodiscard]] std::pair<uint64_t,uint64_t> choose_jd_from_T(const uint64_t n) noexcept;
};
 
class rand_ulab_rooted_trees : public _tree_generator<graphs::rooted_tree> {
public:
    /* CONSTRUCTORS */
 
    rand_ulab_rooted_trees() noexcept { }
 
    rand_ulab_rooted_trees(const uint64_t n, const uint64_t seed = 0) noexcept :
        _tree_generator<graphs::rooted_tree>(n), m_Gen(n, seed) { }
    rand_ulab_rooted_trees(const rand_ulab_rooted_trees& Gen) noexcept = default;
 
    rand_ulab_rooted_trees(rand_ulab_rooted_trees&& Gen) noexcept = default;
 
    ~rand_ulab_rooted_trees() noexcept = default;
 
    rand_ulab_rooted_trees& operator= (const rand_ulab_rooted_trees& g) noexcept = default;
    rand_ulab_rooted_trees& operator= (rand_ulab_rooted_trees&& g) noexcept = default;
 
    void init(const uint64_t n, const uint64_t seed = 0) noexcept {
        _tree_generator::init(n);
        m_Gen.init(n, seed);
    }
 
    void clear() noexcept {
        _tree_generator::clear();
        m_Gen.clear();
    }
 
    [[nodiscard]] graphs::rooted_tree yield_tree() noexcept {
        return get_tree();
    }
 
protected:
    [[nodiscard]] graphs::rooted_tree __get_tree() noexcept { return m_Gen.get_tree(); }
 
protected:
    _rand_ulab_rooted_trees m_Gen;
};
 
} // -- namespace generate
} // -- namespace lal