Sped up the assignment of a tensor to a tensor slice, as well as the assigment of a constant slice to a tensor

1 files changed, 11 insertions, 3 deletions

diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorEvaluator.h b/unsupported/Eigen/CXX11/src/Tensor/TensorEvaluator.h
index 9198c17ef..a38af84d5 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorEvaluator.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorEvaluator.h
@@ -132,13 +132,20 @@ struct TensorEvaluator<const Derived, Device>
     CoordAccess = NumCoords > 0,
   };
 
-  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE TensorEvaluator(const Derived& m, const Device&)
-      : m_data(m.data()), m_dims(m.dimensions())
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE TensorEvaluator(const Derived& m, const Device& device)
+      : m_data(m.data()), m_dims(m.dimensions()), m_device(device)
   { }
 
   EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const Dimensions& dimensions() const { return m_dims; }
 
-  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE bool evalSubExprsIfNeeded(CoeffReturnType*) { return true; }
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE bool evalSubExprsIfNeeded(CoeffReturnType* data) {
+    if (internal::is_arithmetic<typename internal::remove_const<Scalar>::type>::value && data) {
+      m_device.memcpy((void*)data, m_data, m_dims.TotalSize() * sizeof(Scalar));
+      return false;
+    }
+    return true;
+  }
+
   EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void cleanup() { }
 
   EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE CoeffReturnType coeff(Index index) const {
@@ -172,6 +179,7 @@ struct TensorEvaluator<const Derived, Device>
  protected:
   const Scalar* m_data;
   Dimensions m_dims;
+  const Device& m_device;
 };