From eeabf7975e59b47f4e3677c340013ebbfcfbc2bd Mon Sep 17 00:00:00 2001
From: Benoit Steiner <benoit.steiner.goog@gmail.com>
Date: Wed, 12 Nov 2014 22:35:44 -0800
Subject: Optimized broadcasting

---
 .../Eigen/CXX11/src/Tensor/TensorBroadcasting.h    | 36 +++++++++++++++++-----
 1 file changed, 29 insertions(+), 7 deletions(-)

(limited to 'unsupported/Eigen/CXX11/src/Tensor/TensorBroadcasting.h')

diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorBroadcasting.h b/unsupported/Eigen/CXX11/src/Tensor/TensorBroadcasting.h
index 2bd158dac..a77903dca 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorBroadcasting.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorBroadcasting.h
@@ -24,11 +24,13 @@ template<typename Broadcast, typename XprType>
 struct traits<TensorBroadcastingOp<Broadcast, XprType> > : public traits<XprType>
 {
   typedef typename XprType::Scalar Scalar;
-  typedef typename internal::packet_traits<Scalar>::type Packet;
-  typedef typename traits<XprType>::StorageKind StorageKind;
-  typedef typename traits<XprType>::Index Index;
+  typedef traits<XprType> XprTraits;
+  typedef typename packet_traits<Scalar>::type Packet;
+  typedef typename XprTraits::StorageKind StorageKind;
+  typedef typename XprTraits::Index Index;
   typedef typename XprType::Nested Nested;
   typedef typename remove_reference<Nested>::type _Nested;
+  static const int NumDimensions = XprTraits::NumDimensions;
 };
 
 template<typename Broadcast, typename XprType>
@@ -85,6 +87,7 @@ struct TensorEvaluator<const TensorBroadcastingOp<Broadcast, ArgType>, Device>
   static const int NumDims = internal::array_size<typename TensorEvaluator<ArgType, Device>::Dimensions>::value;
   typedef DSizes<Index, NumDims> Dimensions;
   typedef typename XprType::Scalar Scalar;
+  typedef typename TensorEvaluator<ArgType, Device>::Dimensions InputDimensions;
 
   enum {
     IsAligned = false,
@@ -129,10 +132,19 @@ struct TensorEvaluator<const TensorBroadcastingOp<Broadcast, ArgType>, Device>
     Index inputIndex = 0;
     for (int i = NumDims - 1; i > 0; --i) {
       const Index idx = index / m_outputStrides[i];
-      inputIndex += (idx % m_impl.dimensions()[i]) * m_inputStrides[i];
+      if (internal::index_statically_eq<InputDimensions>()(i, 1)) {
+        eigen_assert(idx % m_impl.dimensions()[i] == 0);
+      } else {
+        inputIndex += (idx % m_impl.dimensions()[i]) * m_inputStrides[i];
+      }
       index -= idx * m_outputStrides[i];
     }
-    inputIndex += (index % m_impl.dimensions()[0]);
+    if (internal::index_statically_eq<Broadcast>()(0, 1)) {
+      eigen_assert(index < m_impl.dimensions()[0]);
+      inputIndex += index;
+    } else {
+      inputIndex += (index % m_impl.dimensions()[0]);
+    }
     return m_impl.coeff(inputIndex);
   }
 
@@ -150,10 +162,20 @@ struct TensorEvaluator<const TensorBroadcastingOp<Broadcast, ArgType>, Device>
     Index inputIndex = 0;
     for (int i = NumDims - 1; i > 0; --i) {
       const Index idx = index / m_outputStrides[i];
-      inputIndex += (idx % m_impl.dimensions()[i]) * m_inputStrides[i];
+      if (internal::index_statically_eq<InputDimensions>()(i, 1)) {
+         eigen_assert(idx % m_impl.dimensions()[i] == 0);
+      } else {
+        inputIndex += (idx % m_impl.dimensions()[i]) * m_inputStrides[i];
+      }
       index -= idx * m_outputStrides[i];
     }
-    const Index innermostLoc = index % m_impl.dimensions()[0];
+    Index innermostLoc;
+    if (internal::index_statically_eq<Broadcast>()(0, 1)) {
+      eigen_assert(index < m_impl.dimensions()[0]);
+      innermostLoc = index;
+    } else {
+      innermostLoc = index % m_impl.dimensions()[0];
+    }
     inputIndex += innermostLoc;
 
     // Todo: this could be extended to the second dimension if we're not
-- 
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