Added support for tensor references

unsupported/Eigen/CXX11/Tensor

@@ -76,6 +76,8 @@
 #include "unsupported/Eigen/CXX11/src/Tensor/TensorFixedSize.h"
 #include "unsupported/Eigen/CXX11/src/Tensor/TensorMap.h"
 
+#include "unsupported/Eigen/CXX11/src/Tensor/TensorRef.h"
+
 #include "unsupported/Eigen/CXX11/src/Tensor/TensorIO.h"
 
 #include "Eigen/src/Core/util/ReenableStupidWarnings.h"

unsupported/Eigen/CXX11/src/Tensor/TensorForwardDeclarations.h

@@ -15,6 +15,7 @@ namespace Eigen {
 template<typename Scalar_, std::size_t NumIndices_, int Options_ = 0> class Tensor;
 template<typename Scalar_, typename Dimensions, int Options_ = 0> class TensorFixedSize;
 template<typename PlainObjectType, int Options_ = Unaligned> class TensorMap;
+template<typename PlainObjectType> class TensorRef;
 template<typename Derived, int AccessLevel = internal::accessors_level<Derived>::value> class TensorBase;
 
 template<typename NullaryOp, typename PlainObjectType> class TensorCwiseNullaryOp;

unsupported/Eigen/CXX11/src/Tensor/TensorRef.h

@@ -0,0 +1,360 @@
+// 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_REF_H
+#define EIGEN_CXX11_TENSOR_TENSOR_REF_H
+
+namespace Eigen {
+
+namespace internal {
+
+template <typename Dimensions, typename Scalar>
+class TensorLazyBaseEvaluator {
+ public:
+  TensorLazyBaseEvaluator() : m_refcount(0) { }
+  virtual ~TensorLazyBaseEvaluator() { }
+
+  virtual const Dimensions& dimensions() const = 0;
+  virtual const Scalar* data() const = 0;
+
+  virtual const Scalar coeff(DenseIndex index) const = 0;
+  virtual Scalar& coeffRef(DenseIndex index) = 0;
+
+  void incrRefCount() { ++m_refcount; }
+  void decrRefCount() { --m_refcount; }
+  int refCount() const { return m_refcount; }
+
+ private:
+  // No copy, no assigment;
+  TensorLazyBaseEvaluator(const TensorLazyBaseEvaluator& other);
+  TensorLazyBaseEvaluator& operator = (const TensorLazyBaseEvaluator& other);
+
+  int m_refcount;
+};
+
+static char dummy[8];
+
+template <typename Dimensions, typename Expr, typename Device>
+class TensorLazyEvaluatorReadOnly : public TensorLazyBaseEvaluator<Dimensions, typename TensorEvaluator<Expr, Device>::Scalar> {
+ public:
+  //  typedef typename TensorEvaluator<Expr, Device>::Dimensions Dimensions;
+  typedef typename TensorEvaluator<Expr, Device>::Scalar Scalar;
+
+  TensorLazyEvaluatorReadOnly(const Expr& expr, const Device& device) : m_impl(expr, device) {
+    m_dims = m_impl.dimensions();
+    m_impl.evalSubExprsIfNeeded(NULL);
+  }
+  virtual ~TensorLazyEvaluatorReadOnly() {
+    m_impl.cleanup();
+  }
+
+  virtual const Dimensions& dimensions() const {
+    return m_dims;
+  }
+  virtual const Scalar* data() const {
+    return m_impl.data();
+  }
+
+  virtual const Scalar coeff(DenseIndex index) const {
+    return m_impl.coeff(index);
+  }
+  virtual Scalar& coeffRef(DenseIndex index) {
+    eigen_assert(false && "can't reference the coefficient of a rvalue");
+    return *reinterpret_cast<Scalar*>(dummy);
+  };
+
+ protected:
+  TensorEvaluator<Expr, Device> m_impl;
+  Dimensions m_dims;
+};
+
+template <typename Dimensions, typename Expr, typename Device>
+class TensorLazyEvaluatorWritable : public TensorLazyEvaluatorReadOnly<Dimensions, Expr, Device> {
+ public:
+  typedef TensorLazyEvaluatorReadOnly<Dimensions, Expr, Device> Base;
+  typedef typename Base::Scalar Scalar;
+
+  TensorLazyEvaluatorWritable(const Expr& expr, const Device& device) : Base(expr, device) {
+  }
+  virtual ~TensorLazyEvaluatorWritable() {
+  }
+
+  virtual Scalar& coeffRef(DenseIndex index) {
+    return this->m_impl.coeffRef(index);
+  }
+};
+
+template <typename Dimensions, typename Expr, typename Device>
+class TensorLazyEvaluator : public internal::conditional<bool(internal::is_lvalue<Expr>::value),
+                            TensorLazyEvaluatorWritable<Dimensions, Expr, Device>,
+                            TensorLazyEvaluatorReadOnly<Dimensions, const Expr, Device> >::type {
+ public:
+  typedef typename internal::conditional<bool(internal::is_lvalue<Expr>::value),
+                                         TensorLazyEvaluatorWritable<Dimensions, Expr, Device>,
+                                         TensorLazyEvaluatorReadOnly<Dimensions, const Expr, Device> >::type Base;
+  typedef typename Base::Scalar Scalar;
+
+  TensorLazyEvaluator(const Expr& expr, const Device& device) : Base(expr, device) {
+  }
+  virtual ~TensorLazyEvaluator() {
+  }
+};
+
+}  // namespace internal
+
+
+/** \class TensorRef
+  * \ingroup CXX11_Tensor_Module
+  *
+  * \brief A reference to a tensor expression
+  * The expression will be evaluated lazily (as much as possible).
+  *
+  */
+template<typename PlainObjectType> class TensorRef : public TensorBase<TensorRef<PlainObjectType> >
+{
+  public:
+    typedef TensorRef<PlainObjectType> Self;
+    typedef typename PlainObjectType::Base Base;
+    typedef typename Eigen::internal::nested<Self>::type Nested;
+    typedef typename internal::traits<PlainObjectType>::StorageKind StorageKind;
+    typedef typename internal::traits<PlainObjectType>::Index Index;
+    typedef typename internal::traits<PlainObjectType>::Scalar Scalar;
+    typedef typename internal::packet_traits<Scalar>::type Packet;
+    typedef typename NumTraits<Scalar>::Real RealScalar;
+    typedef typename Base::CoeffReturnType CoeffReturnType;
+    typedef Scalar* PointerType;
+    typedef PointerType PointerArgType;
+
+    static const Index NumIndices = PlainObjectType::NumIndices;
+    typedef typename PlainObjectType::Dimensions Dimensions;
+
+    enum {
+      IsAligned = false,
+      PacketAccess = false,
+    };
+
+    EIGEN_STRONG_INLINE TensorRef() : m_evaluator(NULL) {
+    }
+
+    template <typename Expression>
+    EIGEN_STRONG_INLINE TensorRef(const Expression& expr) : m_evaluator(new internal::TensorLazyEvaluator<Dimensions, Expression, DefaultDevice>(expr, DefaultDevice())) {
+      m_evaluator->incrRefCount();
+    }
+
+    template <typename Expression>
+    EIGEN_STRONG_INLINE TensorRef& operator = (const Expression& expr) {
+      unrefEvaluator();
+      m_evaluator = new internal::TensorLazyEvaluator<Dimensions, Expression, DefaultDevice>(expr, DefaultDevice());
+      m_evaluator->incrRefCount();
+      return *this;
+    }
+
+    ~TensorRef() {
+      unrefEvaluator();
+    }
+
+    TensorRef(const TensorRef& other) : m_evaluator(other.m_evaluator) {
+      eigen_assert(m_evaluator->refCount() > 0);
+      m_evaluator->incrRefCount();
+    }
+
+    TensorRef& operator = (const TensorRef& other) {
+      if (this != &other) {
+        unrefEvaluator();
+        m_evaluator = other.m_evaluator;
+        eigen_assert(m_evaluator->refCount() > 0);
+        m_evaluator->incrRefCount();
+      }
+      return *this;
+    }
+
+    EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE Index dimension(Index n) const { return m_evaluator->dimensions()[n]; }
+    EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE const Dimensions& dimensions() const { return m_evaluator->dimensions(); }
+    EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE Index size() const { return m_evaluator->dimensions().TotalSize(); }
+    EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE const Scalar* data() const { return m_evaluator->data(); }
+
+    EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE const Scalar operator()(Index index) const
+    {
+      return m_evaluator->coeff(index);
+    }
+
+#ifdef EIGEN_HAS_VARIADIC_TEMPLATES
+    template<typename... IndexTypes> EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE const Scalar operator()(Index firstIndex, IndexTypes... otherIndices) const
+    {
+      const std::size_t NumIndices = (sizeof...(otherIndices) + 1);
+      const array<Index, NumIndices> indices{{firstIndex, otherIndices...}};
+      return coeff(indices);
+    }
+#else
+
+    EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE const Scalar operator()(Index i0, Index i1) const
+    {
+      array<Index, 2> indices;
+      indices[0] = i0;
+      indices[1] = i1;
+      return coeff(indices);
+    }
+    EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE const Scalar operator()(Index i0, Index i1, Index i2) const
+    {
+      array<Index, 3> indices;
+      indices[0] = i0;
+      indices[1] = i1;
+      indices[2] = i2;
+      return coeff(indices);
+    }
+    EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE const Scalar operator()(Index i0, Index i1, Index i2, Index i3) const
+    {
+      array<Index, 4> indices;
+      indices[0] = i0;
+      indices[1] = i1;
+      indices[2] = i2;
+      indices[3] = i3;
+      return coeff(indices);
+    }
+    EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE const Scalar operator()(Index i0, Index i1, Index i2, Index i3, Index i4) const
+    {
+      array<Index, 5> indices;
+      indices[0] = i0;
+      indices[1] = i1;
+      indices[2] = i2;
+      indices[3] = i3;
+      indices[4] = i4;
+      return coeff(indices);
+    }
+#endif
+
+    template <std::size_t NumIndices> EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE const Scalar coeff(const array<Index, NumIndices>& indices) const
+    {
+      const Dimensions& dims = this->dimensions();
+      Index index = 0;
+      if (PlainObjectType::Options&RowMajor) {
+        index += indices[0];
+        for (int i = 1; i < NumIndices; ++i) {
+          index = index * dims[i] + indices[i];
+        }
+      } else {
+        index += indices[NumIndices-1];
+        for (int i = NumIndices-2; i >= 0; --i) {
+          index = index * dims[i] + indices[i];
+        }
+      }
+      return m_evaluator->coeff(index);
+    }
+
+    EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE const Scalar coeff(Index index) const
+    {
+      return m_evaluator->coeff(index);
+    }
+
+    EIGEN_DEVICE_FUNC
+    EIGEN_STRONG_INLINE Scalar& coeffRef(Index index)
+    {
+      return m_evaluator->coeffRef(index);
+    }
+
+  private:
+    EIGEN_STRONG_INLINE void unrefEvaluator() {
+      if (m_evaluator) {
+        m_evaluator->decrRefCount();
+        if (m_evaluator->refCount() == 0) {
+          delete m_evaluator;
+        }
+      }
+    }
+
+  internal::TensorLazyBaseEvaluator<Dimensions, Scalar>* m_evaluator;
+};
+
+
+// evaluator for rvalues
+template<typename Derived, typename Device>
+struct TensorEvaluator<const TensorRef<Derived>, Device>
+{
+  typedef typename Derived::Index Index;
+  typedef typename Derived::Scalar Scalar;
+  typedef typename Derived::Packet Packet;
+  typedef typename Derived::Scalar CoeffReturnType;
+  typedef typename Derived::Packet PacketReturnType;
+  typedef typename Derived::Dimensions Dimensions;
+
+  enum {
+    IsAligned = false,
+    PacketAccess = false,
+  };
+
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE TensorEvaluator(const TensorRef<Derived>& m, const Device&)
+      : m_ref(m)
+  { }
+
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const Dimensions& dimensions() const { return m_ref.dimensions(); }
+
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE bool evalSubExprsIfNeeded(Scalar*) {
+    return true;
+  }
+
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void cleanup() { }
+
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE CoeffReturnType coeff(Index index) const {
+    return m_ref.coeff(index);
+  }
+
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Scalar& coeffRef(Index index) {
+    return m_ref.coeffRef(index);
+  }
+
+  Scalar* data() const { return m_ref.data(); }
+
+ protected:
+  TensorRef<Derived> m_ref;
+};
+
+
+// evaluator for lvalues
+template<typename Derived, typename Device>
+struct TensorEvaluator<TensorRef<Derived>, Device> : public TensorEvaluator<const TensorRef<Derived>, Device>
+{
+  typedef typename Derived::Index Index;
+  typedef typename Derived::Scalar Scalar;
+  typedef typename Derived::Packet Packet;
+  typedef typename Derived::Scalar CoeffReturnType;
+  typedef typename Derived::Packet PacketReturnType;
+  typedef typename Derived::Dimensions Dimensions;
+
+  typedef TensorEvaluator<const TensorRef<Derived>, Device> Base;
+
+  enum {
+    IsAligned = false,
+    PacketAccess = false,
+  };
+
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE TensorEvaluator(TensorRef<Derived>& m, const Device& d) : Base(m, d)
+  { }
+
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Scalar& coeffRef(Index index) {
+    return this->m_ref.coeffRef(index);
+  }
+};
+
+
+
+} // end namespace Eigen
+
+#endif // EIGEN_CXX11_TENSOR_TENSOR_REF_H

unsupported/Eigen/CXX11/src/Tensor/TensorTraits.h

@@ -84,6 +84,20 @@ struct traits<TensorMap<PlainObjectType, Options_> >
   };
 };
 
+template<typename PlainObjectType>
+struct traits<TensorRef<PlainObjectType> >
+  : public traits<PlainObjectType>
+{
+  typedef traits<PlainObjectType> BaseTraits;
+  typedef typename BaseTraits::Scalar Scalar;
+  typedef typename BaseTraits::StorageKind StorageKind;
+  typedef typename BaseTraits::Index Index;
+  enum {
+    Options = BaseTraits::Options,
+    Flags = ((BaseTraits::Flags | LvalueBit) & ~AlignedBit) | (Options&Aligned ? AlignedBit : 0),
+  };
+};
+
 
 template<typename _Scalar, std::size_t NumIndices_, int Options>
 struct eval<Tensor<_Scalar, NumIndices_, Options>, Eigen::Dense>
@@ -121,6 +135,19 @@ struct eval<const TensorMap<PlainObjectType, Options>, Eigen::Dense>
   typedef const TensorMap<PlainObjectType, Options>& type;
 };
 
+template<typename PlainObjectType>
+struct eval<TensorRef<PlainObjectType>, Eigen::Dense>
+{
+  typedef const TensorRef<PlainObjectType>& type;
+};
+
+template<typename PlainObjectType>
+struct eval<const TensorRef<PlainObjectType>, Eigen::Dense>
+{
+  typedef const TensorRef<PlainObjectType>& type;
+};
+
+
 template <typename Scalar_, std::size_t NumIndices_, int Options_>
 struct nested<Tensor<Scalar_, NumIndices_, Options_>, 1, typename eval<Tensor<Scalar_, NumIndices_, Options_> >::type>
 {
@@ -145,6 +172,7 @@ struct nested<const TensorFixedSize<Scalar_, Dimensions, Options>, 1, typename e
   typedef const TensorFixedSize<Scalar_, Dimensions, Options>& type;
 };
 
+
 template <typename PlainObjectType, int Options>
 struct nested<TensorMap<PlainObjectType, Options>, 1, typename eval<TensorMap<PlainObjectType, Options> >::type>
 {
@@ -157,6 +185,18 @@ struct nested<const TensorMap<PlainObjectType, Options>, 1, typename eval<Tensor
   typedef const TensorMap<PlainObjectType, Options>& type;
 };
 
+template <typename PlainObjectType>
+struct nested<TensorRef<PlainObjectType>, 1, typename eval<TensorRef<PlainObjectType> >::type>
+{
+  typedef const TensorRef<PlainObjectType>& type;
+};
+
+template <typename PlainObjectType>
+struct nested<const TensorRef<PlainObjectType>, 1, typename eval<TensorRef<PlainObjectType> >::type>
+{
+  typedef const TensorRef<PlainObjectType>& type;
+};
+
 }  // end namespace internal
 }  // end namespace Eigen
 

unsupported/test/CMakeLists.txt

@@ -126,5 +126,6 @@ if(EIGEN_TEST_CXX11)
   ei_add_test(cxx11_tensor_striding "-std=c++0x")
 #  ei_add_test(cxx11_tensor_device  "-std=c++0x")
   ei_add_test(cxx11_tensor_thread_pool "-std=c++0x")
+  ei_add_test(cxx11_tensor_ref "-std=c++0x")
   ei_add_test(cxx11_tensor_io "-std=c++0x")
 endif()

unsupported/test/cxx11_tensor_ref.cpp

@@ -0,0 +1,192 @@
+// 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/.
+
+#include "main.h"
+
+#include <Eigen/CXX11/Tensor>
+
+using Eigen::Tensor;
+using Eigen::RowMajor;
+
+static void test_simple_lvalue_ref()
+{
+  Tensor<int, 1> input(6);
+  input.setRandom();
+
+  TensorRef<Tensor<int, 1>> ref3(input);
+  TensorRef<Tensor<int, 1>> ref4 = input;
+
+  VERIFY_IS_EQUAL(ref3.data(), input.data());
+  VERIFY_IS_EQUAL(ref4.data(), input.data());
+
+  for (int i = 0; i < 6; ++i) {
+    VERIFY_IS_EQUAL(ref3(i), input(i));
+    VERIFY_IS_EQUAL(ref4(i), input(i));
+  }
+
+  for (int i = 0; i < 6; ++i) {
+    ref3.coeffRef(i) = i;
+  }
+  for (int i = 0; i < 6; ++i) {
+    VERIFY_IS_EQUAL(input(i), i);
+  }
+  for (int i = 0; i < 6; ++i) {
+    ref4.coeffRef(i) = -i * 2;
+  }
+  for (int i = 0; i < 6; ++i) {
+    VERIFY_IS_EQUAL(input(i), -i*2);
+  }
+}
+
+
+static void test_simple_rvalue_ref()
+{
+  Tensor<int, 1> input1(6);
+  input1.setRandom();
+  Tensor<int, 1> input2(6);
+  input2.setRandom();
+
+  TensorRef<Tensor<int, 1>> ref3(input1 + input2);
+  TensorRef<Tensor<int, 1>> ref4 = input1 + input2;
+
+  VERIFY_IS_NOT_EQUAL(ref3.data(), input1.data());
+  VERIFY_IS_NOT_EQUAL(ref4.data(), input1.data());
+  VERIFY_IS_NOT_EQUAL(ref3.data(), input2.data());
+  VERIFY_IS_NOT_EQUAL(ref4.data(), input2.data());
+
+  for (int i = 0; i < 6; ++i) {
+    VERIFY_IS_EQUAL(ref3(i), input1(i) + input2(i));
+    VERIFY_IS_EQUAL(ref4(i), input1(i) + input2(i));
+  }
+}
+
+
+static void test_multiple_dims()
+{
+  Tensor<float, 3> input(3,5,7);
+  input.setRandom();
+
+  TensorRef<Tensor<float, 3>> ref(input);
+  VERIFY_IS_EQUAL(ref.data(), input.data());
+  VERIFY_IS_EQUAL(ref.dimension(0), 3);
+  VERIFY_IS_EQUAL(ref.dimension(1), 5);
+  VERIFY_IS_EQUAL(ref.dimension(2), 7);
+
+  for (int i = 0; i < 3; ++i) {
+    for (int j = 0; j < 5; ++j) {
+      for (int k = 0; k < 7; ++k) {
+        VERIFY_IS_EQUAL(ref(i,j,k), input(i,j,k));
+      }
+    }
+  }
+}
+
+
+static void test_slice()
+{
+  Tensor<float, 5> tensor(2,3,5,7,11);
+  tensor.setRandom();
+
+  Eigen::DSizes<ptrdiff_t, 5> indices(1,2,3,4,5);
+  Eigen::DSizes<ptrdiff_t, 5> sizes(1,1,1,1,1);
+  TensorRef<Tensor<float, 5>> slice = tensor.slice(indices, sizes);
+  VERIFY_IS_EQUAL(slice(0,0,0,0,0), tensor(1,2,3,4,5));
+
+  Eigen::DSizes<ptrdiff_t, 5> indices2(1,1,3,4,5);
+  Eigen::DSizes<ptrdiff_t, 5> sizes2(1,1,2,2,3);
+  slice = tensor.slice(indices2, sizes2);
+  for (int i = 0; i < 2; ++i) {
+    for (int j = 0; j < 2; ++j) {
+      for (int k = 0; k < 3; ++k) {
+        VERIFY_IS_EQUAL(slice(0,0,i,j,k), tensor(1,1,3+i,4+j,5+k));
+      }
+    }
+  }
+
+  Eigen::DSizes<ptrdiff_t, 5> indices3(0,0,0,0,0);
+  Eigen::DSizes<ptrdiff_t, 5> sizes3(2,3,1,1,1);
+  slice = tensor.slice(indices3, sizes3);
+  VERIFY_IS_EQUAL(slice.data(), tensor.data());
+}
+
+
+static void test_ref_of_ref()
+{
+  Tensor<float, 3> input(3,5,7);
+  input.setRandom();
+
+  TensorRef<Tensor<float, 3>> ref(input);
+  TensorRef<Tensor<float, 3>> ref_of_ref(ref);
+  TensorRef<Tensor<float, 3>> ref_of_ref2;
+  ref_of_ref2 = ref;
+
+  VERIFY_IS_EQUAL(ref_of_ref.data(), input.data());
+  VERIFY_IS_EQUAL(ref_of_ref.dimension(0), 3);
+  VERIFY_IS_EQUAL(ref_of_ref.dimension(1), 5);
+  VERIFY_IS_EQUAL(ref_of_ref.dimension(2), 7);
+
+  VERIFY_IS_EQUAL(ref_of_ref2.data(), input.data());
+  VERIFY_IS_EQUAL(ref_of_ref2.dimension(0), 3);
+  VERIFY_IS_EQUAL(ref_of_ref2.dimension(1), 5);
+  VERIFY_IS_EQUAL(ref_of_ref2.dimension(2), 7);
+
+  for (int i = 0; i < 3; ++i) {
+    for (int j = 0; j < 5; ++j) {
+      for (int k = 0; k < 7; ++k) {
+        VERIFY_IS_EQUAL(ref_of_ref(i,j,k), input(i,j,k));
+        VERIFY_IS_EQUAL(ref_of_ref2(i,j,k), input(i,j,k));
+     }
+    }
+  }
+}
+
+
+static void test_ref_in_expr()
+{
+  Tensor<float, 3> input(3,5,7);
+  input.setRandom();
+  TensorRef<Tensor<float, 3>> input_ref(input);
+
+  Tensor<float, 3> result(3,5,7);
+  result.setRandom();
+  TensorRef<Tensor<float, 3>> result_ref(result);
+
+  Tensor<float, 3> bias(3,5,7);
+  bias.setRandom();
+
+  result_ref = input_ref + bias;
+  for (int i = 0; i < 3; ++i) {
+    for (int j = 0; j < 5; ++j) {
+      for (int k = 0; k < 7; ++k) {
+        VERIFY_IS_EQUAL(result_ref(i,j,k), input(i,j,k) + bias(i,j,k));
+        VERIFY_IS_NOT_EQUAL(result(i,j,k), input(i,j,k) + bias(i,j,k));
+      }
+    }
+  }
+
+  result = result_ref;
+  for (int i = 0; i < 3; ++i) {
+    for (int j = 0; j < 5; ++j) {
+      for (int k = 0; k < 7; ++k) {
+        VERIFY_IS_EQUAL(result(i,j,k), input(i,j,k) + bias(i,j,k));
+      }
+    }
+  }
+}
+
+
+void test_cxx11_tensor_ref()
+{
+  CALL_SUBTEST(test_simple_lvalue_ref());
+  CALL_SUBTEST(test_simple_rvalue_ref());
+  CALL_SUBTEST(test_multiple_dims());
+  CALL_SUBTEST(test_slice());
+  CALL_SUBTEST(test_ref_of_ref());
+  CALL_SUBTEST(test_ref_in_expr());
+}