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eigen_tools.hh
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/**
* file eigen_tools.hh
*
* @author Till Junge <till.junge@epfl.ch>
*
* @date 20 Sep 2017
*
* @brief small tools to be used with Eigen
*
* @section LICENCE
*
* 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 EIGEN_TOOLS_H
#define EIGEN_TOOLS_H
#include "common/common.hh"
#include <unsupported/Eigen/CXX11/Tensor>
#include <utility>
#include <type_traits>
namespace muSpectre {
/* ---------------------------------------------------------------------- */
//! Creates a Eigen::Sizes type for a Tensor defined by an order and dim
namespace internal {
template <Dim_t order, Dim_t dim, Dim_t... dims>
struct SizesByOrderHelper {
using Sizes = typename SizesByOrderHelper<order-1, dim, dim, dims...>::Sizes;
};
template <Dim_t dim, Dim_t... dims>
struct SizesByOrderHelper<0, dim, dims...> {
using Sizes = Eigen::Sizes<dims...>;
};
} // internal
template <Dim_t order, Dim_t dim>
struct SizesByOrder {
static_assert(order > 0, "works only for order greater than zero");
using Sizes = typename
internal::SizesByOrderHelper<order-1, dim, dim>::Sizes;
};
/* ---------------------------------------------------------------------- */
//! Call a passed lambda with the unpacked sizes as arguments
namespace internal {
/* ---------------------------------------------------------------------- */
template<Dim_t order, typename Fun_t, Dim_t dim, Dim_t ... args>
struct CallSizesHelper {
static decltype(auto) call(Fun_t && fun) {
static_assert(order > 0, "can't handle empty sizes b)");
return CallSizesHelper<order-1, Fun_t, dim, dim, args...>::call
(fun);
}
};
/* ---------------------------------------------------------------------- */
template<typename Fun_t, Dim_t dim, Dim_t ... args>
struct CallSizesHelper<0, Fun_t, dim, args...> {
static decltype(auto) call(Fun_t && fun) {
return fun(args...);
}
};
} // internal
template<Dim_t order, Dim_t dim, typename Fun_t>
inline decltype(auto) call_sizes(Fun_t && fun) {
static_assert(order > 1, "can't handle empty sizes");
return internal::CallSizesHelper<order-1, Fun_t, dim, dim>::
call(std::forward<Fun_t>(fun));
}
//compile-time square root
static constexpr Dim_t ct_sqrt(Dim_t res, Dim_t l, Dim_t r){
if(l == r){
return r;
} else {
const auto mid = (r + l) / 2;
if(mid * mid >= res){
return ct_sqrt(res, l, mid);
} else {
return ct_sqrt(res, mid + 1, r);
}
}
}
static constexpr Dim_t ct_sqrt(Dim_t res){
return ct_sqrt(res, 1, res);
}
/**
* Structure to determine whether an expression can be evaluated into a Matrix, Array, etc. and which helps determine compile-time size
*/
namespace EigenCheck {
template <class Derived>
struct is_matrix {
using T = std::remove_reference_t<Derived>;
constexpr static bool value{std::is_same<typename Eigen::internal::traits<T>::XprKind,
Eigen::MatrixXpr>::value};
};
template <class Derived>
struct is_fixed {
using T = std::remove_reference_t<Derived>;
constexpr static bool value{T::SizeAtCompileTime != Eigen::Dynamic};
};
template <class Derived>
struct is_square {
using T = std::remove_reference_t<Derived>;
constexpr static bool value{
(T::RowsAtCompileTime == T::ColsAtCompileTime) &&
is_fixed<T>::value};
};
template <class Derived>
struct tensor_dim {
using T = std::remove_reference_t<Derived>;
static_assert(is_matrix<T>::value, "The type of t is not understood as an Eigen::Matrix");
static_assert(is_square<T>::value, "t's matrix isn't square");
constexpr static Dim_t value{T::RowsAtCompileTime};
};
template <class Derived>
struct tensor_4_dim {
using T = std::remove_reference_t<Derived>;
static_assert(is_matrix<T>::value, "The type of t is not understood as an Eigen::Matrix");
static_assert(is_square<T>::value, "t's matrix isn't square");
constexpr static Dim_t value{ct_sqrt(T::RowsAtCompileTime)};
static_assert(value*value == T::RowsAtCompileTime,
"This is not a fourth-order tensor mapped on a square "
"matrix");
};
};
} // muSpectre
#endif /* EIGEN_TOOLS_H */

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