fourier_lattice.cpp

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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) 2018-2021 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, Nils Wentzell

 
#include "./fourier.hpp"
#include "./fourier_common.hpp"
 
#include <array>
 
namespace triqs::gfs {
 
  // Shared driver for both lattice transform directions: batched multi-dimensional FFT of g_in onto out_mesh.
  template <typename M1, typename M2> gf_vec_t<M1> fourier_lattice_impl(int fftw_backward_forward, M1 const &out_mesh, gf_vec_cvt<M2> g_in) {
 
    auto g_out    = gf_vec_t<M1>{out_mesh, std::array{g_in.target_shape()[0]}};
    long n_others = second_dim(g_in.data());
 
    auto dims     = g_in.mesh().dims();
    auto dims_int = stdutil::make_std_array<int>(dims);
 
    _fourier_base(g_in.data(), g_out.data(), dims.size(), dims_int.data(), n_others, fftw_backward_forward);
 
    return g_out;
  }
 
  // ------------------------ DIRECT TRANSFORM --------------------------------------------
 
  gf_vec_t<mesh::cyclat> _fourier_impl(mesh::cyclat const &r_mesh, gf_vec_cvt<mesh::brzone> gk) {
    auto gr = fourier_lattice_impl(FFTW_FORWARD, r_mesh, gk);
    gr.data() /= gk.mesh().size();
    return gr;
  }
 
  // ------------------------ INVERSE TRANSFORM --------------------------------------------
 
  gf_vec_t<mesh::brzone> _fourier_impl(mesh::brzone const &k_mesh, gf_vec_cvt<mesh::cyclat> gr) {
    return fourier_lattice_impl(FFTW_BACKWARD, k_mesh, gr);
  }
 
} // namespace triqs::gfs