From 8e6dc2c81d478ae1c1699ec69eb02cc42a84ffbf Mon Sep 17 00:00:00 2001
From: Eugene Zhulenev <ezhulenev@google.com>
Date: Wed, 10 Oct 2018 13:23:52 -0700
Subject: [PATCH] Fix bug in partial reduction of expressions requiring
 evaluation

---
 Eigen/src/Core/PartialReduxEvaluator.h | 3 +--
 test/redux.cpp                         | 9 +++++++--
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/Eigen/src/Core/PartialReduxEvaluator.h b/Eigen/src/Core/PartialReduxEvaluator.h
index 0bf8a50e0..d9c0f1224 100644
--- a/Eigen/src/Core/PartialReduxEvaluator.h
+++ b/Eigen/src/Core/PartialReduxEvaluator.h
@@ -134,7 +134,6 @@ struct evaluator<PartialReduxExpr<ArgType, MemberOp, Direction> >
 {
   typedef PartialReduxExpr<ArgType, MemberOp, Direction> XprType;
   typedef typename internal::nested_eval<ArgType,1>::type ArgTypeNested;
-  typedef typename internal::remove_all<ArgTypeNested>::type ArgTypeNestedCleaned;
   typedef typename ArgType::Scalar InputScalar;
   typedef typename XprType::Scalar Scalar;
   enum {
@@ -194,7 +193,7 @@ struct evaluator<PartialReduxExpr<ArgType, MemberOp, Direction> >
   PacketType packet(Index idx) const
   {
     enum { PacketSize = internal::unpacket_traits<PacketType>::size };
-    typedef Block<const ArgType,
+    typedef Block<typename internal::add_const_on_value_type<ArgTypeNested>::type,
                   Direction==Vertical ? int(ArgType::RowsAtCompileTime) : int(PacketSize),
                   Direction==Vertical ? int(PacketSize) : int(ArgType::ColsAtCompileTime),
                   true /* InnerPanel */> PanelType;
diff --git a/test/redux.cpp b/test/redux.cpp
index 9e3ed4546..fdbab7714 100644
--- a/test/redux.cpp
+++ b/test/redux.cpp
@@ -28,6 +28,9 @@ template<typename MatrixType> void matrixRedux(const MatrixType& m)
   // failures if we underflow into denormals. Thus, we scale so that entries are close to 1.
   MatrixType m1_for_prod = MatrixType::Ones(rows, cols) + RealScalar(0.2) * m1;
 
+  Matrix<Scalar, MatrixType::RowsAtCompileTime, MatrixType::RowsAtCompileTime> m2(rows,rows);
+  m2.setRandom();
+
   VERIFY_IS_MUCH_SMALLER_THAN(MatrixType::Zero(rows, cols).sum(), Scalar(1));
   VERIFY_IS_APPROX(MatrixType::Ones(rows, cols).sum(), Scalar(float(rows*cols))); // the float() here to shut up excessive MSVC warning about int->complex conversion being lossy
   Scalar s(0), p(1), minc(numext::real(m1.coeff(0))), maxc(numext::real(m1.coeff(0)));
@@ -46,6 +49,10 @@ template<typename MatrixType> void matrixRedux(const MatrixType& m)
   VERIFY_IS_APPROX(m1_for_prod.prod(), p);
   VERIFY_IS_APPROX(m1.real().minCoeff(), numext::real(minc));
   VERIFY_IS_APPROX(m1.real().maxCoeff(), numext::real(maxc));
+  
+  // test that partial reduction works if nested expressions is forced to evaluate early
+  VERIFY_IS_APPROX((m1.matrix() * m1.matrix().transpose())       .cwiseProduct(m2.matrix()).rowwise().sum().sum(), 
+                   (m1.matrix() * m1.matrix().transpose()).eval().cwiseProduct(m2.matrix()).rowwise().sum().sum());
 
   // test slice vectorization assuming assign is ok
   Index r0 = internal::random<Index>(0,rows-1);
@@ -72,8 +79,6 @@ template<typename MatrixType> void matrixRedux(const MatrixType& m)
 
   // test nesting complex expression
   VERIFY_EVALUATION_COUNT( (m1.matrix()*m1.matrix().transpose()).sum(), (MatrixType::IsVectorAtCompileTime && MatrixType::SizeAtCompileTime!=1 ? 0 : 1) );
-  Matrix<Scalar, MatrixType::RowsAtCompileTime, MatrixType::RowsAtCompileTime> m2(rows,rows);
-  m2.setRandom();
   VERIFY_EVALUATION_COUNT( ((m1.matrix()*m1.matrix().transpose())+m2).sum(),(MatrixType::IsVectorAtCompileTime && MatrixType::SizeAtCompileTime!=1 ? 0 : 1));
 }