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      1 // This file is part of Eigen, a lightweight C++ template library
      2 // for linear algebra.
      3 //
      4 // Copyright (C) 2014 Benoit Steiner <benoit.steiner.goog (at) gmail.com>
      5 //
      6 // This Source Code Form is subject to the terms of the Mozilla
      7 // Public License v. 2.0. If a copy of the MPL was not distributed
      8 // with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
      9 
     10 #ifndef EIGEN_CXX11_TENSOR_TENSOR_INITIALIZER_H
     11 #define EIGEN_CXX11_TENSOR_TENSOR_INITIALIZER_H
     12 
     13 #if EIGEN_HAS_VARIADIC_TEMPLATES
     14 
     15 #include <initializer_list>
     16 
     17 namespace Eigen {
     18 
     19 /** \class TensorInitializer
     20   * \ingroup CXX11_Tensor_Module
     21   *
     22   * \brief Helper template to initialize Tensors from std::initializer_lists.
     23   */
     24 namespace internal {
     25 
     26 template <typename Derived, int N>
     27 struct Initializer {
     28   typedef std::initializer_list<
     29     typename Initializer<Derived, N - 1>::InitList> InitList;
     30 
     31   static void run(TensorEvaluator<Derived, DefaultDevice>& tensor,
     32                   Eigen::array<typename traits<Derived>::Index, traits<Derived>::NumDimensions>* indices,
     33                   const InitList& vals) {
     34     int i = 0;
     35     for (auto v : vals) {
     36       (*indices)[traits<Derived>::NumDimensions - N] = i++;
     37       Initializer<Derived, N - 1>::run(tensor, indices, v);
     38     }
     39   }
     40 };
     41 
     42 template <typename Derived>
     43 struct Initializer<Derived, 1> {
     44   typedef std::initializer_list<typename traits<Derived>::Scalar> InitList;
     45 
     46   static void run(TensorEvaluator<Derived, DefaultDevice>& tensor,
     47                   Eigen::array<typename traits<Derived>::Index, traits<Derived>::NumDimensions>* indices,
     48                   const InitList& vals) {
     49     int i = 0;
     50     // There is likely a faster way to do that than iterating.
     51     for (auto v : vals) {
     52       (*indices)[traits<Derived>::NumDimensions - 1] = i++;
     53       tensor.coeffRef(*indices) = v;
     54     }
     55   }
     56 };
     57 
     58 template <typename Derived>
     59 struct Initializer<Derived, 0> {
     60   typedef typename traits<Derived>::Scalar InitList;
     61 
     62   static void run(TensorEvaluator<Derived, DefaultDevice>& tensor,
     63                   Eigen::array<typename traits<Derived>::Index, traits<Derived>::NumDimensions>*,
     64                   const InitList& v) {
     65     tensor.coeffRef(0) = v;
     66   }
     67 };
     68 
     69 
     70 template <typename Derived, int N>
     71 void initialize_tensor(TensorEvaluator<Derived, DefaultDevice>& tensor,
     72                        const typename Initializer<Derived, traits<Derived>::NumDimensions>::InitList& vals) {
     73   Eigen::array<typename traits<Derived>::Index, traits<Derived>::NumDimensions> indices;
     74   Initializer<Derived, traits<Derived>::NumDimensions>::run(tensor, &indices, vals);
     75 }
     76 
     77 }  // namespace internal
     78 }  // namespace Eigen
     79 
     80 #endif  // EIGEN_HAS_VARIADIC_TEMPLATES
     81 
     82 #endif  // EIGEN_CXX11_TENSOR_TENSOR_INITIALIZER_H
     83