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diff --git a/third_party/eigen3/unsupported/Eigen/CXX11/src/Tensor/TensorDimensions.h b/third_party/eigen3/unsupported/Eigen/CXX11/src/Tensor/TensorDimensions.h
new file mode 100644
index 0000000000..8bf5272ec8
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+++ b/third_party/eigen3/unsupported/Eigen/CXX11/src/Tensor/TensorDimensions.h
@@ -0,0 +1,597 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// Copyright (C) 2014 Benoit Steiner <benoit.steiner.goog@gmail.com>
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef EIGEN_CXX11_TENSOR_TENSOR_DIMENSIONS_H
+#define EIGEN_CXX11_TENSOR_TENSOR_DIMENSIONS_H
+
+
+namespace Eigen {
+
+/** \internal
+  *
+  * \class TensorDimensions
+  * \ingroup CXX11_Tensor_Module
+  *
+  * \brief Set of classes used to encode and store the dimensions of a Tensor.
+  *
+  * The Sizes class encodes as part of the type the number of dimensions and the
+  * sizes corresponding to each dimension. It uses no storage space since it is
+  * entirely known at compile time.
+  * The DSizes class is its dynamic sibling: the number of dimensions is known
+  * at compile time but the sizes are set during execution.
+  *
+  * \sa Tensor
+  */
+
+// Can't use std::pairs on cuda devices
+template <typename Index> struct IndexPair {
+  EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE IndexPair() : first(0), second(0) { }
+  EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE IndexPair(Index f, Index s) : first(f), second(s) { }
+  Index first;
+  Index second;
+};
+
+// Boilerplate code
+namespace internal {
+
+template<std::size_t n, typename Dimension> struct dget {
+  static const std::size_t value = get<n, typename Dimension::Base>::value;
+};
+
+
+template<typename Index, std::size_t NumIndices, std::size_t n, bool RowMajor>
+struct fixed_size_tensor_index_linearization_helper
+{
+  template <typename Dimensions> EIGEN_DEVICE_FUNC
+  static inline Index run(array<Index, NumIndices> const& indices,
+                          const Dimensions& dimensions)
+  {
+    return array_get<RowMajor ? n - 1 : (NumIndices - n)>(indices) +
+        dget<RowMajor ? n - 1 : (NumIndices - n), Dimensions>::value *
+        fixed_size_tensor_index_linearization_helper<Index, NumIndices, n - 1, RowMajor>::run(indices, dimensions);
+  }
+};
+
+template<typename Index, std::size_t NumIndices, bool RowMajor>
+struct fixed_size_tensor_index_linearization_helper<Index, NumIndices, 0, RowMajor>
+{
+  template <typename Dimensions> EIGEN_DEVICE_FUNC
+  static inline Index run(array<Index, NumIndices> const& indices,
+                          const Dimensions&)
+  {
+    return 0;
+  }
+};
+
+template<typename Index, std::size_t n>
+struct fixed_size_tensor_index_extraction_helper
+{
+  template <typename Dimensions> EIGEN_DEVICE_FUNC
+  static inline Index run(const Index index,
+                          const Dimensions& dimensions)
+  {
+    const Index mult = (index == n) ? 1 : 0;
+    return array_get<n>(dimensions) * mult +
+        fixed_size_tensor_index_extraction_helper<Index, n - 1>::run(index, dimensions);
+  }
+};
+
+template<typename Index>
+struct fixed_size_tensor_index_extraction_helper<Index, 0>
+{
+  template <typename Dimensions> EIGEN_DEVICE_FUNC
+  static inline Index run(const Index index,
+                          const Dimensions& dimensions)
+  {
+    const Index mult = (index == 0) ? 1 : 0;
+    return array_get<0>(dimensions) * mult;
+  }
+};
+
+}  // end namespace internal
+
+
+// Fixed size
+#ifndef EIGEN_EMULATE_CXX11_META_H
+template <typename std::size_t... Indices>
+struct Sizes : internal::numeric_list<std::size_t, Indices...> {
+  typedef internal::numeric_list<std::size_t, Indices...> Base;
+  static const std::size_t total_size = internal::arg_prod(Indices...);
+
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE size_t rank() const {
+    return Base::count;
+  }
+
+  static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE std::size_t TotalSize() {
+    return internal::arg_prod(Indices...);
+  }
+
+  Sizes() { }
+  template <typename DenseIndex>
+  explicit Sizes(const array<DenseIndex, Base::count>& /*indices*/) {
+    // todo: add assertion
+  }
+#ifdef EIGEN_HAS_VARIADIC_TEMPLATES
+  template <typename... DenseIndex> Sizes(DenseIndex...) { }
+  explicit Sizes(std::initializer_list<std::size_t> /*l*/) {
+    // todo: add assertion
+  }
+#endif
+
+  template <typename T> Sizes& operator = (const T& /*other*/) {
+    // add assertion failure if the size of other is different
+    return *this;
+  }
+
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE std::ptrdiff_t operator[] (const int index) const {
+    return internal::fixed_size_tensor_index_extraction_helper<std::ptrdiff_t, Base::count - 1>::run(index, *this);
+  }
+
+  template <typename DenseIndex> EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
+  size_t IndexOfColMajor(const array<DenseIndex, Base::count>& indices) const {
+    return internal::fixed_size_tensor_index_linearization_helper<DenseIndex, Base::count, Base::count, false>::run(indices, *static_cast<const Base*>(this));
+  }
+  template <typename DenseIndex> EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
+  size_t IndexOfRowMajor(const array<DenseIndex, Base::count>& indices) const {
+    return internal::fixed_size_tensor_index_linearization_helper<DenseIndex, Base::count, Base::count, true>::run(indices, *static_cast<const Base*>(this));
+  }
+};
+
+namespace internal {
+template <typename std::size_t... Indices>
+EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE std::size_t array_prod(const Sizes<Indices...>&) {
+  return Sizes<Indices...>::total_size;
+}
+}
+
+#else
+
+template <std::size_t n>
+struct non_zero_size {
+  typedef internal::type2val<std::size_t, n> type;
+};
+template <>
+struct non_zero_size<0> {
+  typedef internal::null_type type;
+};
+
+template <std::size_t V1=0, std::size_t V2=0, std::size_t V3=0, std::size_t V4=0, std::size_t V5=0> struct Sizes {
+  typedef typename internal::make_type_list<typename non_zero_size<V1>::type, typename non_zero_size<V2>::type, typename non_zero_size<V3>::type, typename non_zero_size<V4>::type, typename non_zero_size<V5>::type >::type Base;
+  static const size_t count = Base::count;
+  static const std::size_t total_size = internal::arg_prod<Base>::value;
+
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE size_t rank() const {
+    return count;
+  }
+
+  static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE size_t TotalSize() {
+    return internal::arg_prod<Base>::value;
+  }
+
+  Sizes() { }
+  template <typename DenseIndex>
+  explicit Sizes(const array<DenseIndex, Base::count>& indices) {
+    // todo: add assertion
+  }
+#ifdef EIGEN_HAS_VARIADIC_TEMPLATES
+  template <typename... DenseIndex> Sizes(DenseIndex... indices) { }
+  explicit Sizes(std::initializer_list<std::size_t> l) {
+    // todo: add assertion
+  }
+#else
+  EIGEN_DEVICE_FUNC explicit Sizes(const DenseIndex i0) {
+  }
+  EIGEN_DEVICE_FUNC explicit Sizes(const DenseIndex i0, const DenseIndex i1) {
+  }
+  EIGEN_DEVICE_FUNC explicit Sizes(const DenseIndex i0, const DenseIndex i1, const DenseIndex i2) {
+  }
+  EIGEN_DEVICE_FUNC explicit Sizes(const DenseIndex i0, const DenseIndex i1, const DenseIndex i2, const DenseIndex i3) {
+  }
+  EIGEN_DEVICE_FUNC explicit Sizes(const DenseIndex i0, const DenseIndex i1, const DenseIndex i2, const DenseIndex i3, const DenseIndex i4) {
+  }
+#endif
+
+  template <typename T> Sizes& operator = (const T& other) {
+    // to do: check the size of other
+    return *this;
+  }
+
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE std::size_t operator[] (const int index) const {
+    switch (index) {
+      case 0:
+        return internal::get<0, Base>::value;
+      case 1:
+        return internal::get<1, Base>::value;
+      case 2:
+        return internal::get<2, Base>::value;
+      case 3:
+        return internal::get<3, Base>::value;
+      case 4:
+        return internal::get<4, Base>::value;
+      default:
+        eigen_assert(false && "index overflow");
+        return static_cast<std::size_t>(-1);
+    }
+  }
+
+  template <typename DenseIndex> EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
+  size_t IndexOfColMajor(const array<DenseIndex, Base::count>& indices) const {
+    return internal::fixed_size_tensor_index_linearization_helper<DenseIndex, Base::count, Base::count, false>::run(indices, *this);
+  }
+  template <typename DenseIndex> EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
+  size_t IndexOfRowMajor(const array<DenseIndex, Base::count>& indices) const {
+    return internal::fixed_size_tensor_index_linearization_helper<DenseIndex, Base::count, Base::count, true>::run(indices, *this);
+  }
+};
+
+namespace internal {
+template <std::size_t V1, std::size_t V2, std::size_t V3, std::size_t V4, std::size_t V5>
+EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE std::size_t array_prod(const Sizes<V1, V2, V3, V4, V5>&) {
+  return Sizes<V1, V2, V3, V4, V5>::total_size;
+}
+}
+
+#endif
+
+// Boilerplate
+namespace internal {
+template<typename Index, std::size_t NumIndices, std::size_t n, bool RowMajor>
+struct tensor_index_linearization_helper
+{
+  static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
+  Index run(array<Index, NumIndices> const& indices, array<Index, NumIndices> const& dimensions)
+  {
+    return array_get<RowMajor ? n : (NumIndices - n - 1)>(indices) +
+      array_get<RowMajor ? n : (NumIndices - n - 1)>(dimensions) *
+        tensor_index_linearization_helper<Index, NumIndices, n - 1, RowMajor>::run(indices, dimensions);
+  }
+};
+
+template<typename Index, std::size_t NumIndices, bool RowMajor>
+struct tensor_index_linearization_helper<Index, NumIndices, 0, RowMajor>
+{
+  static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
+  Index run(array<Index, NumIndices> const& indices, array<Index, NumIndices> const&)
+  {
+    return array_get<RowMajor ? 0 : NumIndices - 1>(indices);
+  }
+};
+}  // end namespace internal
+
+
+
+// Dynamic size
+template <typename DenseIndex, std::size_t NumDims>
+struct DSizes : array<DenseIndex, NumDims> {
+  typedef array<DenseIndex, NumDims> Base;
+  static const std::size_t count = NumDims;
+
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE size_t rank() const {
+    return NumDims;
+  }
+
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE size_t TotalSize() const {
+    return internal::array_prod(*static_cast<const Base*>(this));
+  }
+
+  EIGEN_DEVICE_FUNC DSizes() {
+    for (int i = 0 ; i < NumDims; ++i) {
+      (*this)[i] = 0;
+    }
+  }
+  EIGEN_DEVICE_FUNC DSizes(const array<DenseIndex, NumDims>& a) : Base(a) { }
+
+  EIGEN_DEVICE_FUNC DSizes(const DimensionList<DenseIndex, NumDims>& a) {
+    for (int i = 0 ; i < NumDims; ++i) {
+      (*this)[i] = a[i];
+    }
+  }
+
+#ifndef EIGEN_EMULATE_CXX11_META_H
+  template <typename std::size_t... Indices>
+  EIGEN_DEVICE_FUNC DSizes(const Sizes<Indices...>& a) {
+    for (int i = 0 ; i < NumDims; ++i) {
+      (*this)[i] = a[i];
+    }
+  }
+#else
+  template <std::size_t V1, std::size_t V2, std::size_t V3, std::size_t V4, std::size_t V5>
+  EIGEN_DEVICE_FUNC DSizes(const Sizes<V1, V2, V3, V4, V5>& a) {
+    for (int i = 0 ; i < NumDims; ++i) {
+      (*this)[i] = a[i];
+    }
+  }
+#endif
+
+#ifdef EIGEN_HAS_VARIADIC_TEMPLATES
+  template<typename... IndexTypes> EIGEN_DEVICE_FUNC
+  EIGEN_STRONG_INLINE explicit DSizes(DenseIndex firstDimension, IndexTypes... otherDimensions) {
+    EIGEN_STATIC_ASSERT(sizeof...(otherDimensions) + 1 == NumDims, YOU_MADE_A_PROGRAMMING_MISTAKE)
+    (*this) = array<DenseIndex, NumDims>{{firstDimension, otherDimensions...}};
+  }
+#else
+  EIGEN_DEVICE_FUNC explicit DSizes(const DenseIndex i0) {
+    eigen_assert(NumDims == 1);
+    (*this)[0] = i0;
+  }
+  EIGEN_DEVICE_FUNC explicit DSizes(const DenseIndex i0, const DenseIndex i1) {
+    eigen_assert(NumDims == 2);
+    (*this)[0] = i0;
+    (*this)[1] = i1;
+  }
+  EIGEN_DEVICE_FUNC explicit DSizes(const DenseIndex i0, const DenseIndex i1, const DenseIndex i2) {
+    eigen_assert(NumDims == 3);
+    (*this)[0] = i0;
+    (*this)[1] = i1;
+    (*this)[2] = i2;
+  }
+  EIGEN_DEVICE_FUNC explicit DSizes(const DenseIndex i0, const DenseIndex i1, const DenseIndex i2, const DenseIndex i3) {
+    eigen_assert(NumDims == 4);
+    (*this)[0] = i0;
+    (*this)[1] = i1;
+    (*this)[2] = i2;
+    (*this)[3] = i3;
+  }
+  EIGEN_DEVICE_FUNC explicit DSizes(const DenseIndex i0, const DenseIndex i1, const DenseIndex i2, const DenseIndex i3, const DenseIndex i4) {
+    eigen_assert(NumDims == 5);
+    (*this)[0] = i0;
+    (*this)[1] = i1;
+    (*this)[2] = i2;
+    (*this)[3] = i3;
+    (*this)[4] = i4;
+  }
+#endif
+
+  EIGEN_DEVICE_FUNC DSizes& operator = (const array<DenseIndex, NumDims>& other) {
+    *static_cast<Base*>(this) = other;
+    return *this;
+  }
+
+  // A constexpr would be so much better here
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE size_t IndexOfColMajor(const array<DenseIndex, NumDims>& indices) const {
+    return internal::tensor_index_linearization_helper<DenseIndex, NumDims, NumDims - 1, false>::run(indices, *static_cast<const Base*>(this));
+  }
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE size_t IndexOfRowMajor(const array<DenseIndex, NumDims>& indices) const {
+    return internal::tensor_index_linearization_helper<DenseIndex, NumDims, NumDims - 1, true>::run(indices, *static_cast<const Base*>(this));
+  }
+};
+
+
+
+
+// Boilerplate
+namespace internal {
+template<typename Index, std::size_t NumIndices, std::size_t n, bool RowMajor>
+struct tensor_vsize_index_linearization_helper
+{
+  static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
+  Index run(array<Index, NumIndices> const& indices, std::vector<DenseIndex> const& dimensions)
+  {
+    return array_get<RowMajor ? n : (NumIndices - n - 1)>(indices) +
+      array_get<RowMajor ? n : (NumIndices - n - 1)>(dimensions) *
+        tensor_vsize_index_linearization_helper<Index, NumIndices, n - 1, RowMajor>::run(indices, dimensions);
+  }
+};
+
+template<typename Index, std::size_t NumIndices, bool RowMajor>
+struct tensor_vsize_index_linearization_helper<Index, NumIndices, 0, RowMajor>
+{
+  static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
+  Index run(array<Index, NumIndices> const& indices, std::vector<DenseIndex> const&)
+  {
+    return array_get<RowMajor ? 0 : NumIndices - 1>(indices);
+  }
+};
+}  // end namespace internal
+
+
+template <typename DenseIndex>
+struct VSizes : std::vector<DenseIndex> {
+  typedef std::vector<DenseIndex> Base;
+
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE size_t rank() const {
+    return Base::size();
+  }
+
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE size_t TotalSize() const {
+    return internal::array_prod(*static_cast<const Base*>(this));
+  }
+
+  EIGEN_DEVICE_FUNC VSizes() { }
+  EIGEN_DEVICE_FUNC explicit VSizes(const std::vector<DenseIndex>& a) : Base(a) { }
+
+  template <std::size_t NumDims>
+  EIGEN_DEVICE_FUNC explicit VSizes(const array<DenseIndex, NumDims>& a) {
+    this->resize(NumDims);
+    for (int i = 0; i < NumDims; ++i) {
+      (*this)[i] = a[i];
+    }
+  }
+  template <std::size_t NumDims>
+  EIGEN_DEVICE_FUNC explicit VSizes(const DSizes<DenseIndex, NumDims>& a) {
+    this->resize(NumDims);
+    for (int i = 0; i < NumDims; ++i) {
+      (*this)[i] = a[i];
+    }
+  }
+
+  EIGEN_DEVICE_FUNC explicit VSizes(const DenseIndex i0) {
+    this->resize(1);
+    (*this)[0] = i0;
+  }
+  EIGEN_DEVICE_FUNC explicit VSizes(const DenseIndex i0, const DenseIndex i1) {
+    this->resize(2);
+    (*this)[0] = i0;
+    (*this)[1] = i1;
+  }
+  EIGEN_DEVICE_FUNC explicit VSizes(const DenseIndex i0, const DenseIndex i1, const DenseIndex i2) {
+    this->resize(3);
+    (*this)[0] = i0;
+    (*this)[1] = i1;
+    (*this)[2] = i2;
+  }
+  EIGEN_DEVICE_FUNC explicit VSizes(const DenseIndex i0, const DenseIndex i1, const DenseIndex i2, const DenseIndex i3) {
+    this->resize(4);
+    (*this)[0] = i0;
+    (*this)[1] = i1;
+    (*this)[2] = i2;
+    (*this)[3] = i3;
+  }
+  EIGEN_DEVICE_FUNC explicit VSizes(const DenseIndex i0, const DenseIndex i1, const DenseIndex i2, const DenseIndex i3, const DenseIndex i4) {
+    this->resize(5);
+    (*this)[0] = i0;
+    (*this)[1] = i1;
+    (*this)[2] = i2;
+    (*this)[3] = i3;
+    (*this)[4] = i4;
+  }
+
+  EIGEN_DEVICE_FUNC VSizes& operator = (const std::vector<DenseIndex>& other) {
+    *static_cast<Base*>(this) = other;
+    return *this;
+  }
+  template <std::size_t NumDims>
+  EIGEN_DEVICE_FUNC VSizes& operator = (const array<DenseIndex, NumDims>& a) {
+    this->resize(NumDims);
+    for (int i = 0; i < NumDims; ++i) {
+      (*this)[i] = a[i];
+    }
+    return *this;
+  }
+  template <std::size_t NumDims>
+  EIGEN_DEVICE_FUNC VSizes& operator = (const DSizes<DenseIndex, NumDims>& a) {
+    this->resize(NumDims);
+    for (int i = 0; i < NumDims; ++i) {
+      (*this)[i] = a[i];
+    }
+    return *this;
+  }
+
+  // A constexpr would be so much better here
+  template <std::size_t NumDims>
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE size_t IndexOfColMajor(const array<DenseIndex, NumDims>& indices) const {
+    return internal::tensor_vsize_index_linearization_helper<DenseIndex, NumDims, NumDims - 1, false>::run(indices, *static_cast<const Base*>(this));
+  }
+  template <std::size_t NumDims>
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE size_t IndexOfRowMajor(const array<DenseIndex, NumDims>& indices) const {
+    return internal::tensor_vsize_index_linearization_helper<DenseIndex, NumDims, NumDims - 1, true>::run(indices, *static_cast<const Base*>(this));
+  }
+};
+
+
+// Boilerplate
+namespace internal {
+template <typename DenseIndex>
+EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE DenseIndex array_prod(const VSizes<DenseIndex>& sizes) {
+  DenseIndex total_size = 1;
+  for (int i = 0; i < sizes.size(); ++i) {
+    total_size *= sizes[i];
+  }
+  return total_size;
+};
+}
+
+namespace internal {
+
+template <typename DenseIndex, std::size_t NumDims> struct array_size<const DSizes<DenseIndex, NumDims> > {
+  static const size_t value = NumDims;
+};
+template <typename DenseIndex, std::size_t NumDims> struct array_size<DSizes<DenseIndex, NumDims> > {
+  static const size_t value = NumDims;
+};
+template <typename DenseIndex>
+struct array_size<VSizes<DenseIndex> > {
+  static const ptrdiff_t value = -1;
+};
+#ifndef EIGEN_EMULATE_CXX11_META_H
+template <typename std::size_t... Indices> struct array_size<const Sizes<Indices...> > {
+static const size_t value = Sizes<Indices...>::count;
+};
+template <typename std::size_t... Indices> struct array_size<Sizes<Indices...> > {
+static const size_t value = Sizes<Indices...>::count;
+};
+template <std::size_t n, typename std::size_t... Indices> EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE std::ptrdiff_t array_get(const Sizes<Indices...>&) {
+  return get<n, internal::numeric_list<std::size_t, Indices...> >::value;
+}
+#else
+template <std::size_t V1, std::size_t V2, std::size_t V3, std::size_t V4, std::size_t V5> struct array_size<const Sizes<V1,V2,V3,V4,V5> > {
+  static const size_t value = Sizes<V1,V2,V3,V4,V5>::count;
+};
+template <std::size_t V1, std::size_t V2, std::size_t V3, std::size_t V4, std::size_t V5> struct array_size<Sizes<V1,V2,V3,V4,V5> > {
+  static const size_t value = Sizes<V1,V2,V3,V4,V5>::count;
+};
+template <std::size_t n, std::size_t V1, std::size_t V2, std::size_t V3, std::size_t V4, std::size_t V5> EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE std::ptrdiff_t array_get(const Sizes<V1,V2,V3,V4,V5>& a) {
+  return get<n, typename Sizes<V1,V2,V3,V4,V5>::Base>::value;
+}
+
+#endif
+
+
+template <typename Dims1, typename Dims2, size_t n, size_t m>
+struct sizes_match_below_dim {
+  static inline bool run(Dims1& dims1, Dims2& dims2) {
+    return false;
+  }
+};
+template <typename Dims1, typename Dims2, size_t n>
+struct sizes_match_below_dim<Dims1, Dims2, n, n> {
+  static inline bool run(Dims1& dims1, Dims2& dims2) {
+    return (array_get<n-1>(dims1) == array_get<n-1>(dims2)) &
+        sizes_match_below_dim<Dims1, Dims2, n-1, n-1>::run(dims1, dims2);
+  }
+};
+template <typename Dims1, typename Dims2>
+struct sizes_match_below_dim<Dims1, Dims2, 0, 0> {
+  static inline bool run(Dims1& dims1, Dims2& dims2) {
+    return true;
+  }
+};
+
+} // end namespace internal
+
+
+template <typename Dims1, typename Dims2>
+bool dimensions_match(Dims1& dims1, Dims2& dims2) {
+  return internal::sizes_match_below_dim<Dims1, Dims2, internal::array_size<Dims1>::value, internal::array_size<Dims2>::value>::run(dims1, dims2);
+}
+
+template <typename IndexType, typename Dims2>
+bool dimensions_match(const VSizes<IndexType>& dims1, Dims2& dims2) {
+  if (dims1.size() != internal::array_size<Dims2>::value) {
+    return false;
+  }
+  for (int i = 0; i < internal::array_size<Dims2>::value; ++i) {
+    if (dims1[i] != dims2[i]) {
+      return false;
+    }
+  }
+  return true;
+}
+
+template <typename Dims1, typename IndexType>
+bool dimensions_match(Dims1& dims1, const VSizes<IndexType>& dims2) {
+  if (internal::array_size<Dims1>::value != dims2.size()) {
+    return false;
+  }
+  for (int i = 0; i < internal::array_size<Dims1>::value; ++i) {
+    if (dims1[i] != dims2[i]) {
+      return false;
+    }
+  }
+  return true;
+}
+
+template <typename IndexType>
+bool dimensions_match(const VSizes<IndexType>& dims1, const VSizes<IndexType>& dims2) {
+  return dims1 == dims2;
+}
+
+} // end namespace Eigen
+
+#endif // EIGEN_CXX11_TENSOR_TENSOR_DIMENSIONS_H