From 25b2f6624d092ed99d0c4936de0c83c9ea4a024d Mon Sep 17 00:00:00 2001
From: Benoit Steiner <benoit.steiner.goog@gmail.com>
Date: Wed, 9 Jul 2014 12:48:34 -0700
Subject: [PATCH] Improved the speed of slicing operations.

---
 unsupported/Eigen/CXX11/src/Tensor/TensorMorphing.h | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorMorphing.h b/unsupported/Eigen/CXX11/src/Tensor/TensorMorphing.h
index 55954a3a7..f6f67afa7 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorMorphing.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorMorphing.h
@@ -320,11 +320,12 @@ struct TensorEvaluator<const TensorSlicingOp<StartIndices, Sizes, ArgType>, Devi
   EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE CoeffReturnType coeff(Index index) const
   {
     Index inputIndex = 0;
-    for (int i = NumDims - 1; i >= 0; --i) {
+    for (int i = NumDims - 1; i > 0; --i) {
       const Index idx = index / m_outputStrides[i];
       inputIndex += (idx + m_offsets[i]) * m_inputStrides[i];
       index -= idx * m_outputStrides[i];
     }
+    inputIndex += (index + m_offsets[0]);
     return m_impl.coeff(inputIndex);
   }
 
@@ -399,11 +400,12 @@ struct TensorEvaluator<TensorSlicingOp<StartIndices, Sizes, ArgType>, Device>
   EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE CoeffReturnType coeff(Index index) const
   {
     Index inputIndex = 0;
-    for (int i = NumDims - 1; i >= 0; --i) {
+    for (int i = NumDims - 1; i > 0; --i) {
       const Index idx = index / m_outputStrides[i];
       inputIndex += (idx + m_offsets[i]) * m_inputStrides[i];
       index -= idx * m_outputStrides[i];
     }
+    inputIndex += (index + m_offsets[0]);
     return m_impl.coeff(inputIndex);
   }
 
@@ -416,11 +418,12 @@ struct TensorEvaluator<TensorSlicingOp<StartIndices, Sizes, ArgType>, Device>
   EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE CoeffReturnType& coeffRef(Index index)
   {
     Index inputIndex = 0;
-    for (int i = NumDims - 1; i >= 0; --i) {
+    for (int i = NumDims - 1; i > 0; --i) {
       const Index idx = index / m_outputStrides[i];
       inputIndex += (idx + m_offsets[i]) * m_inputStrides[i];
       index -= idx * m_outputStrides[i];
     }
+    inputIndex += (index + m_offsets[0]);
     return m_impl.coeffRef(inputIndex);
   }