From f5b1c7394537cc74978617383628c3b6b9399e57 Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Tue, 14 Jun 2016 11:29:06 +0200
Subject: [PATCH] Set cost of constant expression to 0 (the cost should be
 amortized through the expression)

---
 Eigen/src/Core/functors/NullaryFunctors.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Eigen/src/Core/functors/NullaryFunctors.h b/Eigen/src/Core/functors/NullaryFunctors.h
index 78cc22277..eaa582f23 100644
--- a/Eigen/src/Core/functors/NullaryFunctors.h
+++ b/Eigen/src/Core/functors/NullaryFunctors.h
@@ -26,7 +26,8 @@ struct scalar_constant_op {
 };
 template<typename Scalar>
 struct functor_traits<scalar_constant_op<Scalar> >
-{ enum { Cost = 1, PacketAccess = packet_traits<Scalar>::Vectorizable, IsRepeatable = true }; };
+{ enum { Cost = 0 /* as the constant value should be loaded in register only once for the whole expression */,
+         PacketAccess = packet_traits<Scalar>::Vectorizable, IsRepeatable = true }; };
 
 template<typename Scalar> struct scalar_identity_op {
   EIGEN_EMPTY_STRUCT_CTOR(scalar_identity_op)