density.hpp

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// Copyright (c) 2014-2018 Commissariat à l'énergie atomique et aux énergies alternatives (CEA)
// Copyright (c) 2014-2018 Centre national de la recherche scientifique (CNRS)
// Copyright (c) 2018-2023 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: Michel Ferrero, Olivier Parcollet, Hugo U. R. Strand, Nils Wentzell

 
#pragma once
 
#include "../block/block_gf.hpp"
 
#include "../../mesh/dlr.hpp"
#include "../../mesh/dlr_imfreq.hpp"
#include "../../mesh/dlr_imtime.hpp"
#include "../../mesh/imfreq.hpp"
#include "../../mesh/legendre.hpp"
#include "../../mesh/refreq.hpp"
#include "../../utility/exceptions.hpp"
 
#include <itertools/itertools.hpp>
 
#include <type_traits>
#include <vector>
 
namespace triqs::gfs {
 
  // Names elevated from nda for the declarations below.
  using nda::array;
  using nda::array_const_view;

 
  //-------------------------------------------------------
  // For Imaginary Matsubara Frequency functions
  // ------------------------------------------------------

  nda::matrix<dcomplex> density(gf_const_view<mesh::imfreq> g, array_const_view<dcomplex, 3> known_moments = {});

  dcomplex density(gf_const_view<mesh::imfreq, scalar_valued> g, array_const_view<dcomplex, 1> known_moments = {});

  nda::matrix<dcomplex> density(gf_const_view<mesh::legendre> g);

  dcomplex density(gf_const_view<mesh::legendre, scalar_valued> g);
 
  //-------------------------------------------------------
  // DLR
  // ------------------------------------------------------

  auto density(MemoryGf<mesh::dlr> auto const &g) {
    auto res = make_regular(-g(g.mesh().beta()));
    // Transpose to get <cdag_i c_j> instead of <cdag_j c_i>
    if constexpr (requires { transpose(res); }) {
      res = transpose(res);
      return res;
    } else
      return res;
  }

  auto density(MemoryGf<mesh::dlr_imtime> auto const &g) { return density(make_gf_dlr(g)); }

  auto density(MemoryGf<mesh::dlr_imfreq> auto const &g) { return density(make_gf_dlr(g)); }
 
  //-------------------------------------------------------
  // For Real Frequency functions
  // ------------------------------------------------------

  nda::matrix<dcomplex> density(gf_const_view<mesh::refreq> g, double beta);

  dcomplex density(gf_const_view<mesh::refreq, scalar_valued> g, double beta);

  nda::matrix<dcomplex> density(gf_const_view<mesh::refreq> g);

  dcomplex density(gf_const_view<mesh::refreq, scalar_valued> g);
 
  //-------------------------------------------------------
  // General Version for Block Gf
  // ------------------------------------------------------

  template <typename BGf, int R>
  auto density(BGf const &gin, std::vector<array<dcomplex, R>> const &known_moments)
    requires(is_block_gf_v<BGf>)
  {
 
    using mesh_t = typename BGf::mesh_t;
    static_assert(std::is_same_v<mesh_t, mesh::imfreq> or std::is_same_v<mesh_t, mesh::refreq>,
                  "Density Function must be called with either an imfreq or a refreq Green Function");
 
    using r_t = decltype(density(gin[0], known_moments[0]));
    std::vector<r_t> dens_vec;
 
    TRIQS_ASSERT2(gin.size() == known_moments.size(), "Density: Require equal number of blocks in block_gf and known_moments vector");
 
    for (auto [gin_bl, km_bl] : itertools::zip(gin, known_moments)) dens_vec.push_back(density(gin_bl, km_bl));
    return dens_vec;
  }

 
} // namespace triqs::gfs
 
namespace nda::clef {
  // Make density usable inside lazy CLEF expressions.
  TRIQS_CLEF_MAKE_FNT_LAZY(density);
} // namespace nda::clef