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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
*
* µSpectre 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, or (at
* your option) any later version.
*
* µSpectre 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 General Public License
* along with GNU Emacs; see the file COPYING. If not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
#ifndef T4_MAP_PROXY_H
#define T4_MAP_PROXY_H
#include "common/eigen_tools.hh"
#include <Eigen/Dense>
#include <Eigen/src/Core/util/Constants.h>
#include <type_traits>
namespace muSpectre {
/**
* 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 `muSpectre::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>>>;
/**
* provides index-based access to fourth-order Tensors represented
* by square matrices
*/
template <typename T4>
inline auto get(T4&& t4, Dim_t i, Dim_t j, Dim_t k, Dim_t l)
-> decltype(t4.coeffRef(i,j)) {
constexpr Dim_t Dim{EigenCheck::tensor_4_dim<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);
}
// /* ---------------------------------------------------------------------- */
// /** Proxy class mapping a fourth-order tensor onto a 2D matrix (in
// order to avoid the use of Eigen::Tensor. This class is, however
// byte-compatible with Tensors (i.e., you can map this onto a
// tensor instead of a matrix)
// **/
// template <typename T, Dim_t Dim, bool MapConst=false, bool Symmetric=false,
// int MapOptions=Eigen::Unaligned,
// typename StrideType=Eigen::Stride<0, 0>>
// class T4Map:
// public Eigen::MapBase<T4Map<T, Dim, MapConst, Symmetric,
// MapOptions, StrideType>>
// {
// public:
// typedef Eigen::MapBase<T4Map> Base;
// EIGEN_DENSE_PUBLIC_INTERFACE(T4Map);
// using matrix_type = Eigen::Matrix<T, Dim*Dim, Dim*Dim>;
// using PlainObjectType =
// std::conditional_t<MapConst,
// const matrix_type, matrix_type>;
// using ConstType = T4Map<T, Dim, true, Symmetric, MapOptions, StrideType>;
// using Base::colStride;
// using Base::rowStride;
// using Base::IsRowMajor;
// typedef typename Base::PointerType PointerType;
// typedef PointerType PointerArgType;
// using trueScalar = std::conditional_t<MapConst, const Scalar, Scalar>;
// EIGEN_DEVICE_FUNC
// inline PointerType cast_to_pointer_type(PointerArgType ptr) { return ptr; }
// EIGEN_DEVICE_FUNC
// inline Eigen::Index innerStride() const
// {
// return StrideType::InnerStrideAtCompileTime != 0 ? m_stride.inner() : 1;
// }
// template <class Derived>
// inline T4Map & operator=(const Eigen::MatrixBase<Derived> & other) {
// this->map = other;
// return *this;
// }
// EIGEN_DEVICE_FUNC
// inline Eigen::Index outerStride() const
// {
// return StrideType::OuterStrideAtCompileTime != 0 ? m_stride.outer()
// : IsVectorAtCompileTime ? this->size()
// : int(Flags)&Eigen::RowMajorBit ? this->cols()
// : this->rows();
// }
// /** Constructor in the fixed-size case.
// *
// * \param dataPtr pointer to the array to map
// * \param stride optional Stride object, passing the strides.
// */
// EIGEN_DEVICE_FUNC
// explicit inline T4Map(PointerArgType dataPtr, const StrideType& stride = StrideType())
// : Base(cast_to_pointer_type(dataPtr)), m_stride(stride),
// map(cast_to_pointer_type(dataPtr))
// {
// PlainObjectType::Base::_check_template_params();
// }
// EIGEN_INHERIT_ASSIGNMENT_OPERATORS(T4Map);
// /** My accessor to mimick tensorial access
// **/
// inline const Scalar& operator()(Dim_t i, Dim_t j, Dim_t k, Dim_t l ) const {
// const auto myColStride{
// (colStride() == 1) ? colStride(): colStride()/Dim};
// const auto myRowStride{
// (rowStride() == 1) ? rowStride(): rowStride()/Dim};
// return this->map.coeff(i * myRowStride + j * myColStride,
// k * myRowStride + l * myColStride);
// }
// inline trueScalar& operator()(Dim_t i, Dim_t j, Dim_t k, Dim_t l ) {
// const auto myColStride{
// (colStride() == 1) ? colStride(): colStride()/Dim};
// const auto myRowStride{
// (rowStride() == 1) ? rowStride(): rowStride()/Dim};
// return this->map.coeffRef(i * myRowStride + j * myColStride,
// k * myRowStride + l * myColStride);
// }
// protected:
// StrideType m_stride;
// Eigen::Map<PlainObjectType> map;
// };
} // muSpectre
// namespace Eigen {
// //! forward declarations
// template<typename T> struct traits;
// /* ---------------------------------------------------------------------- */
// namespace internal {
// template<typename T, muSpectre::Dim_t Dim, bool MapConst, bool Symmetric,
// int MapOptions, typename StrideType>
// struct traits<muSpectre::T4Map<T, Dim, MapConst, Symmetric,
// MapOptions, StrideType> >
// : public traits<Matrix<T, Dim*Dim, Dim*Dim>>
// {
// using PlainObjectType = Matrix<T, Dim*Dim, Dim*Dim>;
// typedef traits<PlainObjectType> TraitsBase;
// enum {
// InnerStrideAtCompileTime = StrideType::InnerStrideAtCompileTime == 0
// ? int(PlainObjectType::InnerStrideAtCompileTime)
// : int(StrideType::InnerStrideAtCompileTime),
// OuterStrideAtCompileTime = StrideType::OuterStrideAtCompileTime == 0
// ? int(PlainObjectType::OuterStrideAtCompileTime)
// : int(StrideType::OuterStrideAtCompileTime),
// Alignment = int(MapOptions)&int(AlignedMask),
// Flags0 = TraitsBase::Flags & (~NestByRefBit),
// Flags = is_lvalue<PlainObjectType>::value ? int(Flags0) : (int(Flags0) & ~LvalueBit)
// };
// private:
// enum { Options }; // Expressions don't have Options
// };
// } // namespace internal
// } // namespace Eigen
#endif /* T4_MAP_PROXY_H */

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