dlr_imfreq.hpp

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// Copyright (c) 2023 Simons Foundation
// Copyright (c) 2023 Hugo Strand
//
// 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: Alexander Hampel, Olivier Parcollet, Hugo Strand, Nils Wentzell

 
#pragma once
 
#include "./matsubara_freq.hpp"
#include "./mesh_iterator.hpp"
#include "./utils.hpp"
#include "./dlr.hpp"
#include "../utility/macros.hpp"
 
#include <cppdlr/cppdlr.hpp>
#include <h5/h5.hpp>
#include <fmt/format.h>
#include <itertools/itertools.hpp>
#include <nda/nda.hpp>
 
#include <cstdint>
#include <iostream>
#include <memory>
#include <string>
#include <string_view>
#include <utility>
 
namespace triqs::mesh {


  class C2PY_RENAME(MeshDLRImFreq) dlr_imfreq {
    public:
    using value_t = matsubara_freq;

    using index_t = long;

    using data_index_t = long;

    class C2PY_IGNORE mesh_point_t : public matsubara_freq {
      public:
      using mesh_t = dlr_imfreq;

      mesh_point_t() = default;

      mesh_point_t(double b, statistic_enum stat, long n_l, long d, uint64_t mhash)
         : matsubara_freq(n_l, b, stat), data_index_(d), mesh_hash_(mhash) {}

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

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

      [[nodiscard]] matsubara_freq const &value() const { return *this; }

      [[nodiscard]] uint64_t mesh_hash() const noexcept { return mesh_hash_; }
 
      private:
      long data_index_    = 0;
      uint64_t mesh_hash_ = 0;
    };
 
    private:
    // Construct an imaginary frequency DLR mesh with a given set of DLR frequencies.
    dlr_imfreq(double beta, statistic_enum statistic, double w_max, double eps, bool symmetrize, nda::vector<double> const &dlr_freq)
       : dlr_imfreq(beta, statistic, w_max, eps, symmetrize,
                    detail::dlr_ops{.freq = dlr_freq,
                                    .imt  = {w_max * beta, dlr_freq, symmetrize},
                                    .imf  = {w_max * beta, dlr_freq, static_cast<cppdlr::statistic_t>(statistic), symmetrize}}) {}
 
    // Construct an imaginary frequency DLR mesh with given DLR operations.
    dlr_imfreq(double beta, statistic_enum statistic, double w_max, double eps, bool symmetrize, detail::dlr_ops dlr)
       : beta_(beta),
         stat_(statistic),
         w_max_(w_max),
         eps_(eps),
         symmetrize_(symmetrize),
         mesh_hash_(hash(beta, statistic, w_max, eps, symmetrize, hash_bytes(dlr.imf.get_ifnodes()), std::string_view{"dlr_imfreq"})),
         dlr_{std::make_shared<detail::dlr_ops>(std::move(dlr))} {}
 
    public:
    dlr_imfreq() = default;

    dlr_imfreq(double beta, statistic_enum statistic, double w_max, double eps, bool symmetrize = true)
       : dlr_imfreq(beta, statistic, w_max, eps, symmetrize, cppdlr::build_dlr_rf(w_max * beta, eps, symmetrize)) {}

    template <nda::AnyOf<dlr_imtime, dlr> M>
    explicit dlr_imfreq(M const &m)
       : beta_(m.beta_),
         stat_(m.stat_),
         w_max_(m.w_max_),
         eps_(m.eps_),
         symmetrize_(m.symmetrize_),
         mesh_hash_(hash(beta_, stat_, w_max_, eps_, symmetrize_, hash_bytes(m.dlr_->imf.get_ifnodes()), std::string_view{"dlr_imfreq"})),
         dlr_(m.dlr_) {}

    bool operator==(dlr_imfreq const &m) const { return mesh_hash_ == m.mesh_hash_; }

    [[nodiscard]] bool is_index_valid(long l) const noexcept { return 0 <= l and l < size(); }

    [[nodiscard]] long to_data_index(long l) const noexcept {
      EXPECTS(is_index_valid(l));
      return l;
    }

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

    [[nodiscard]] mesh_point_t operator[](long d) const { return (*this)(d); }

    [[nodiscard]] mesh_point_t operator()(long l) const {
      EXPECTS(is_index_valid(l));
      return {beta_, stat_, dlr_->imf.get_ifnodes()[l], l, mesh_hash_};
    }

    [[nodiscard]] matsubara_freq to_value(long l) const noexcept {
      EXPECTS(is_index_valid(l));
      return {dlr_->imf.get_ifnodes()[l], beta_, stat_};
    }

    [[nodiscard]] C2PY_PROPERTY_GET(beta) double beta() const noexcept { return beta_; }

    [[nodiscard]] C2PY_PROPERTY_GET(statistic) statistic_enum statistic() const noexcept { return stat_; }

    [[nodiscard]] C2PY_PROPERTY_GET(w_max) double w_max() const noexcept { return w_max_; }

    [[nodiscard]] C2PY_PROPERTY_GET(eps) double eps() const noexcept { return eps_; }

    [[nodiscard]] C2PY_PROPERTY_GET(symmetrize) bool symmetrize() const noexcept { return symmetrize_; }

    [[nodiscard]] C2PY_PROPERTY_GET(dlr_freq) auto const &dlr_freq() const { return dlr_->freq; }

    [[nodiscard]] C2PY_IGNORE auto const &dlr_it() const { return dlr_->imt; }

    [[nodiscard]] C2PY_IGNORE auto const &dlr_if() const { return dlr_->imf; }

    [[nodiscard]] C2PY_PROPERTY_GET(mesh_hash) uint64_t mesh_hash() const noexcept { return mesh_hash_; }

    [[nodiscard]] auto min_max_frequencies() const noexcept {
      return std::pair<matsubara_freq, matsubara_freq>{(*this)(0).value(), (*this)(size() - 1).value()};
    }

    [[nodiscard]] long size() const noexcept { return (dlr_ ? dlr_->imf.get_ifnodes().size() : 0); }

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

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

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

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

    friend std::ostream &operator<<(std::ostream &sout, dlr_imfreq const &m) {
      auto stat_cstr = (m.stat_ == Boson ? "Boson" : "Fermion");
      return sout << fmt::format("DLR imaginary frequency mesh of size {} with beta = {}, statistics = {}, w_max = {}, eps = {}, symmetrized = {}",
                                 m.size(), m.beta_, stat_cstr, m.w_max_, m.eps_, m.symmetrize_);
    }

    void serialize(auto &ar) const {
      EXPECTS(dlr_);
      ar & beta_ & stat_ & w_max_ & eps_ & symmetrize_ & mesh_hash_ & dlr_->freq;
      dlr_->imt.serialize(ar);
      dlr_->imf.serialize(ar);
    }

    void deserialize(auto &ar) {
      nda::vector<double> freq;
      cppdlr::imtime_ops imt;
      cppdlr::imfreq_ops imf;
      ar & beta_ & stat_ & w_max_ & eps_ & symmetrize_ & mesh_hash_ & freq;
      imt.deserialize(ar);
      imf.deserialize(ar);
      dlr_ = std::make_shared<detail::dlr_ops>(freq, imt, imf);
    }

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

    friend void h5_write(h5::group g, std::string const &name, dlr_imfreq const &m) {
      h5::group gr = g.create_group(name);
      h5::write_hdf5_format(gr, m); // NOLINT (downcasting to base class)
      h5::write(gr, "beta", m.beta_);
      h5::write(gr, "statistic", (m.stat_ == Fermion ? "F" : "B"));
      h5::write(gr, "w_max", m.w_max_);
      h5::write(gr, "eps", m.eps_);
      h5::write(gr, "symmetrize", m.symmetrize_);
      h5::write(gr, "dlr_freq", m.dlr_freq());
      h5::write(gr, "dlr_it", m.dlr_it());
      h5::write(gr, "dlr_if", m.dlr_if());
    }

    friend void h5_read(h5::group g, std::string const &name, dlr_imfreq &m) {
      h5::group gr = g.open_group(name);
      h5::assert_hdf5_format(gr, m, true); // NOLINT (downcasting to base class)
      auto b       = h5::read<double>(gr, "beta");
      auto stat    = (h5::read<std::string>(gr, "statistic") == "F" ? Fermion : Boson);
      auto wmax    = h5::read<double>(gr, "w_max");
      auto epsilon = h5::read<double>(gr, "eps");
      bool sym     = false;
      h5::try_read(gr, "symmetrize", sym);
      auto freq = h5::read<nda::vector<double>>(gr, "dlr_freq");
      auto imt  = h5::read<cppdlr::imtime_ops>(gr, "dlr_it");
      auto imf  = h5::read<cppdlr::imfreq_ops>(gr, "dlr_if");
      m         = dlr_imfreq(b, stat, wmax, epsilon, sym, {.freq = freq, .imt = imt, .imf = imf});
    }
 
    // Friend declarations.
    friend class dlr_imtime;
    friend class dlr;
 
    private:
    double beta_                                = 1.0;
    statistic_enum stat_                        = Fermion;
    double w_max_                               = 0.0;
    double eps_                                 = 1e-10;
    bool symmetrize_                            = false;
    uint64_t mesh_hash_                         = 0;
    std::shared_ptr<const detail::dlr_ops> dlr_ = {};
  };

  double evaluate(dlr_imfreq const &m, ...) = delete;

 
} // namespace triqs::mesh