fourier_lattice.cpp

// 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) 2018-2019 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, tayral
 
#include "./fourier_common.hpp"
#include <itertools/itertools.hpp>
 
#include <fftw3.h>
 
namespace triqs_tprf::fourier {
 
  // The implementation is almost the same in both cases...
  template <typename M1, typename M2> fourier_plan __impl_plan(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 = g_in.data().shape()[1];
 
    auto dims     = g_in.mesh().dims();
    auto dims_int = stdutil::make_std_array<int>(dims);
 
    return _fourier_base_plan(g_in.data(), g_out.data(), dims.size(), dims_int.data(), n_others, fftw_backward_forward);
  }
 
  fourier_plan _fourier_plan(triqs::mesh::cyclat const &r_mesh, gf_vec_cvt<brzone> gk) { return __impl_plan(FFTW_FORWARD, r_mesh, gk); }
  fourier_plan _fourier_plan(triqs::mesh::brzone const &k_mesh, gf_vec_cvt<cyclat> gr) { return __impl_plan(FFTW_BACKWARD, k_mesh, gr); }
 
  // ------------------------ DIRECT TRANSFORM --------------------------------------------
 
  gf_vec_t<cyclat> _fourier_impl(triqs::mesh::cyclat const &r_mesh, gf_vec_cvt<brzone> gk, fourier_plan &p) {
 
    auto gr = gf_vec_t<cyclat>{r_mesh, {gk.target_shape()[0]}};
    _fourier_base(gk.data(), gr.data(), p);
 
    gr.data() /= gk.mesh().size();
    return gr;
  }
 
  // ------------------------ INVERSE TRANSFORM --------------------------------------------
 
  gf_vec_t<brzone> _fourier_impl(triqs::mesh::brzone const &k_mesh, gf_vec_cvt<cyclat> gr, fourier_plan &p) {
    auto gk = gf_vec_t<brzone>{k_mesh, {gr.target_shape()[0]}};
    _fourier_base(gr.data(), gk.data(), p);
    return gk;
  }
 
} // namespace triqs_tprf::fourier