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muSpectre/src/libmugrid/T4_map_proxy.hh
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T4_map_proxy.hh
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/**
* @file T4_map_proxy.hh
*
* @author Till Junge <till.junge@altermail.ch>
*
* @date 19 Nov 2017
*
* @brief Map type to allow fourth-order tensor-like maps on 2D matrices
*
* Copyright © 2017 Till Junge
*
* µGrid is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation, either version 3, or (at
* your option) any later version.
*
* µGrid 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 should have received a copy of the GNU Lesser General Public License
* along with µGrid; see the file COPYING. If not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* * Boston, MA 02111-1307, USA.
*
* Additional permission under GNU GPL version 3 section 7
*
* If you modify this Program, or any covered work, by linking or combining it
* with proprietary FFT implementations or numerical libraries, containing parts
* covered by the terms of those libraries' licenses, the licensors of this
* Program grant you additional permission to convey the resulting work.
*/
#ifndef SRC_LIBMUGRID_T4_MAP_PROXY_HH_
#define SRC_LIBMUGRID_T4_MAP_PROXY_HH_
#include "eigen_tools.hh"
#include <Eigen/Dense>
#include <Eigen/src/Core/util/Constants.h>
#include <type_traits>
namespace muGrid {
/**
* simple adapter function to create a matrix that can be mapped as a tensor
*/
template <typename T, Dim_t Dim>
using T4Mat = Eigen::Matrix<T, Dim * Dim, Dim * Dim>;
/**
* Map onto `muGrid::T4Mat`
*/
template <typename T, Dim_t Dim, bool ConstMap = false>
using T4MatMap = std::conditional_t<ConstMap, Eigen::Map<const T4Mat<T, Dim>>,
Eigen::Map<T4Mat<T, Dim>>>;
template <class Derived>
struct DimCounter {};
template <class Derived>
struct DimCounter<Eigen::MatrixBase<Derived>> {
private:
using Type = Eigen::MatrixBase<Derived>;
constexpr static Dim_t Rows{Type::RowsAtCompileTime};
public:
static_assert(Rows != Eigen::Dynamic, "matrix type not statically sized");
static_assert(Rows == Type::ColsAtCompileTime, "matrix type not square");
constexpr static Dim_t value{ct_sqrt(Rows)};
static_assert(value * value == Rows,
"Only integer numbers of dimensions allowed");
};
/**
* provides index-based access to fourth-order Tensors represented
* by square matrices
*/
template <typename T4>
inline auto get(const Eigen::MatrixBase<T4> & t4, Dim_t i, Dim_t j, Dim_t k,
Dim_t l) -> decltype(auto) {
constexpr Dim_t Dim{DimCounter<Eigen::MatrixBase<T4>>::value};
const auto myColStride{(t4.colStride() == 1) ? t4.colStride()
: t4.colStride() / Dim};
const auto myRowStride{(t4.rowStride() == 1) ? t4.rowStride()
: t4.rowStride() / Dim};
return t4(i * myRowStride + j * myColStride,
k * myRowStride + l * myColStride);
}
template <typename T4>
inline auto get(Eigen::MatrixBase<T4> & t4, Dim_t i, Dim_t j, Dim_t k,
Dim_t l) -> decltype(t4.coeffRef(i, j)) {
constexpr Dim_t Dim{DimCounter<Eigen::MatrixBase<T4>>::value};
const auto myColStride{(t4.colStride() == 1) ? t4.colStride()
: t4.colStride() / Dim};
const auto myRowStride{(t4.rowStride() == 1) ? t4.rowStride()
: t4.rowStride() / Dim};
return t4.coeffRef(i * myRowStride + j * myColStride,
k * myRowStride + l * myColStride);
}
} // namespace muGrid
#endif // SRC_LIBMUGRID_T4_MAP_PROXY_HH_
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