From 87963f441c9abd8514b94b6b2c712652d646ed64 Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Tue, 10 Jan 2017 14:25:30 +0100
Subject: Fallback to Block<> when possible (Index, all, seq with > increment).
 This is important to take advantage of the optimized implementations
 (evaluator, products, etc.), and to support sparse matrices.

---
 Eigen/src/Core/DenseBase.h | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

(limited to 'Eigen/src/Core/DenseBase.h')

diff --git a/Eigen/src/Core/DenseBase.h b/Eigen/src/Core/DenseBase.h
index 07057ce69..7c01e9328 100644
--- a/Eigen/src/Core/DenseBase.h
+++ b/Eigen/src/Core/DenseBase.h
@@ -557,15 +557,36 @@ template<typename Derived> class DenseBase
     }
     EIGEN_DEVICE_FUNC void reverseInPlace();
 
+    template<typename RowIndices, typename ColIndices>
+    struct IndexedViewType {
+      typedef IndexedView<const Derived,typename internal::MakeIndexing<RowIndices>::type,typename internal::MakeIndexing<ColIndices>::type> type;
+    };
+
     template<typename RowIndices, typename ColIndices>
     typename internal::enable_if<
-      !(internal::is_integral<RowIndices>::value && internal::is_integral<ColIndices>::value),
-      IndexedView<const Derived,typename internal::MakeIndexing<RowIndices>::type,typename internal::MakeIndexing<ColIndices>::type> >::type
+      !  (internal::traits<typename IndexedViewType<RowIndices,ColIndices>::type>::IsBlockAlike
+      || (internal::is_integral<RowIndices>::value && internal::is_integral<ColIndices>::value)),
+      typename IndexedViewType<RowIndices,ColIndices>::type >::type
     operator()(const RowIndices& rowIndices, const ColIndices& colIndices) const {
-      return IndexedView<const Derived,typename internal::MakeIndexing<RowIndices>::type,typename internal::MakeIndexing<ColIndices>::type>(
+      return typename IndexedViewType<RowIndices,ColIndices>::type(
                 derived(), internal::make_indexing(rowIndices,derived().rows()), internal::make_indexing(colIndices,derived().cols()));
     }
 
+    template<typename RowIndices, typename ColIndices>
+    typename internal::enable_if<
+      internal::traits<typename IndexedViewType<RowIndices,ColIndices>::type>::IsBlockAlike,
+      typename internal::traits<typename IndexedViewType<RowIndices,ColIndices>::type>::BlockType>::type
+    operator()(const RowIndices& rowIndices, const ColIndices& colIndices) const {
+      typedef typename internal::traits<typename IndexedViewType<RowIndices,ColIndices>::type>::BlockType BlockType;
+      typename internal::MakeIndexing<RowIndices>::type actualRowIndices = internal::make_indexing(rowIndices,derived().rows());
+      typename internal::MakeIndexing<ColIndices>::type actualColIndices = internal::make_indexing(colIndices,derived().cols());
+      return BlockType(derived(),
+                       internal::first(actualRowIndices),
+                       internal::first(actualColIndices),
+                       internal::size(actualRowIndices),
+                       internal::size(actualColIndices));
+    }
+
     template<typename RowIndicesT, std::size_t RowIndicesN, typename ColIndices>
     IndexedView<const Derived,const RowIndicesT (&)[RowIndicesN],typename internal::MakeIndexing<ColIndices>::type>
     operator()(const RowIndicesT (&rowIndices)[RowIndicesN], const ColIndices& colIndices) const {
-- 
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