imtime.cpp

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// Copyright (c) 2016-2018 Commissariat à l'énergie atomique et aux énergies alternatives (CEA)
// Copyright (c) 2016-2018 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: Philipp Dumitrescu, Michel Ferrero, Olivier Parcollet, Nils Wentzell

 
#include "./imtime.hpp"
#include "../gf/gf_const_view.hpp"
#include "../gf/gf.hpp"
#include "../../mesh/imtime.hpp"
 
#include <cstddef>
 
namespace triqs::gfs {
 
  using nda::array;
 
  //-------------------------------------------------------
  // For Imaginary Time functions
  // ------------------------------------------------------
  gf<mesh::imtime> rebinning_tau(gf_const_view<mesh::imtime> const &g, size_t new_n_tau) {
 
    auto const &old_m = g.mesh();
    gf<mesh::imtime> new_gf{{old_m.beta(), old_m.statistic(), static_cast<long>(new_n_tau)}, g.target_shape()};
    auto const &new_m = new_gf.mesh();
    new_gf.data()()   = 0;
    long prev_index   = 0;
    long norm         = 0;
    for (auto const &tau : old_m) {
      long index = std::lround(static_cast<double>(tau) / new_m.delta());
      if (index == prev_index) {
        norm++;
      } else {
        new_gf[index - 1] /= static_cast<double>(norm);
        prev_index = index;
        norm       = 1;
      }
      new_gf[index] += g[tau];
    }
    if (norm != 1) new_gf[new_m.size() - 1] /= norm;
    return new_gf;
  }
 
} // namespace triqs::gfs