discrete.hpp

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// Copyright (c) 2022-2023 Simons Foundation
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program 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 General Public License for more details.
//
// You may obtain a copy of the License at
//     https://www.gnu.org/licenses/gpl-3.0.txt
//
// Authors: Olivier Parcollet, Nils Wentzell

 
#pragma once
 
#include "./mesh_iterator.hpp"
#include "../utility/macros.hpp"
 
#include <h5/h5.hpp>
#include <itertools/itertools.hpp>
#include <nda/nda.hpp>
 
#include <cstdint>
#include <iostream>
#include <string>
 
namespace triqs::mesh {

  class C2PY_IGNORE discrete {
    public:
    using index_t = long;

    using data_index_t = long;

    class mesh_point_t {
      public:
      using mesh_t = discrete;

      mesh_point_t() = default;

      mesh_point_t(long n, long d, uint64_t mhash) : index_(n), data_index_(d), mesh_hash_(mhash) {}

      [[nodiscard]] long index() const { return index_; }

      [[nodiscard]] long data_index() const { return data_index_; }

      [[nodiscard]] uint64_t mesh_hash() const noexcept { return mesh_hash_; }
 
      private:
      long index_         = 0;
      long data_index_    = 0;
      uint64_t mesh_hash_ = 0;
    };

    discrete(long N = 0) : N_(N), mesh_hash_(N) { EXPECTS(N >= 0); }

    bool operator==(discrete const &) const = default;

    [[nodiscard]] bool is_index_valid(index_t n) const noexcept { return 0 <= n and n < N_; }

    [[nodiscard]] data_index_t to_data_index(index_t n) const noexcept {
      EXPECTS(is_index_valid(n));
      return n;
    }

    [[nodiscard]] index_t to_index(long d) const noexcept {
      EXPECTS(is_index_valid(d));
      return d;
    }

    [[nodiscard]] mesh_point_t operator[](long d) const { return {to_index(d), d, mesh_hash_}; }

    [[nodiscard]] mesh_point_t operator()(index_t n) const { return {n, to_data_index(n), mesh_hash_}; }

    [[nodiscard]] uint64_t mesh_hash() const { return mesh_hash_; }

    [[nodiscard]] long size() const { return N_; }

    [[nodiscard]] auto begin() const { return mesh_iterator<discrete>{.mesh_ptr = this, .data_index = 0}; }

    [[nodiscard]] auto cbegin() const { return begin(); }

    [[nodiscard]] auto end() const { return mesh_iterator<discrete>{.mesh_ptr = this, .data_index = size()}; }

    [[nodiscard]] auto cend() const { return end(); }

    friend std::ostream &operator<<(std::ostream &sout, discrete const &m) { return sout << "Discrete mesh of size " << m.size(); }

    void serialize(auto &ar) const { ar & N_ & mesh_hash_; }

    void deserialize(auto &ar) { ar & N_ & mesh_hash_; }

    [[nodiscard]] static std::string hdf5_format() { return "MeshIndex"; }

    friend void h5_write(h5::group g, std::string const &name, discrete const &m) {
      h5::group gr = g.create_group(name);
      h5::write_hdf5_format(gr, m); // NOLINT (downcasting to base class)
      h5::write(gr, "size", m.size());
    }

    friend void h5_read(h5::group g, std::string const &name, discrete &m) {
      h5::group gr = g.open_group(name);
      h5::assert_hdf5_format(gr, m, true); // NOLINT (downcasting to base class)
      long L = h5::read<long>(gr, "size");
      m      = discrete(L);
    }
 
    private:
    long N_;
    uint64_t mesh_hash_ = 0;
  };
 
} // namespace triqs::mesh