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authorGravatar Gael Guennebaud <g.gael@free.fr>2019-02-18 14:43:07 +0100
committerGravatar Gael Guennebaud <g.gael@free.fr>2019-02-18 14:43:07 +0100
commitc69d0d08d0d71c779a245babe80342f0cf1ea985 (patch)
treee31690b52ed0cb75e59fdb17a649abd0e45e9157
parent512b74aaa19fa12a05774dd30205d2c97e8bdef9 (diff)
Set cost of conjugate to 0 (in practice it boils down to a no-op).
This is also important to make sure that A.conjugate() * B.conjugate() does not evaluate its arguments into temporaries (e.g., if A and B are fixed and small, or * fall back to lazyProduct)
-rw-r--r--Eigen/src/Core/functors/UnaryFunctors.h10
-rw-r--r--test/product_notemporary.cpp2
2 files changed, 11 insertions, 1 deletions
diff --git a/Eigen/src/Core/functors/UnaryFunctors.h b/Eigen/src/Core/functors/UnaryFunctors.h
index 55994047e..1d5eb3678 100644
--- a/Eigen/src/Core/functors/UnaryFunctors.h
+++ b/Eigen/src/Core/functors/UnaryFunctors.h
@@ -117,7 +117,15 @@ template<typename Scalar>
struct functor_traits<scalar_conjugate_op<Scalar> >
{
enum {
- Cost = NumTraits<Scalar>::IsComplex ? NumTraits<Scalar>::AddCost : 0,
+ Cost = 0,
+ // Yes the cost is zero even for complexes because in most cases for which
+ // the cost is used, conjugation turns to be a no-op. Some examples:
+ // cost(a*conj(b)) == cost(a*b)
+ // cost(a+conj(b)) == cost(a+b)
+ // <etc.
+ // If we don't set it to zero, then:
+ // A.conjugate().lazyProduct(B.conjugate())
+ // will bake its operands. We definitely don't want that!
PacketAccess = packet_traits<Scalar>::HasConj
};
};
diff --git a/test/product_notemporary.cpp b/test/product_notemporary.cpp
index 7f169e6ae..8b6419d0c 100644
--- a/test/product_notemporary.cpp
+++ b/test/product_notemporary.cpp
@@ -134,7 +134,9 @@ template<typename MatrixType> void product_notemporary(const MatrixType& m)
VERIFY_EVALUATION_COUNT( m3.noalias() = m1.block(r0,r0,r1,r1).template triangularView<UnitUpper>() * m2.block(r0,c0,r1,c1), 1);
// Zero temporaries for lazy products ...
+ m3.setRandom(rows,cols);
VERIFY_EVALUATION_COUNT( Scalar tmp = 0; tmp += Scalar(RealScalar(1)) / (m3.transpose().lazyProduct(m3)).diagonal().sum(), 0 );
+ VERIFY_EVALUATION_COUNT( m3.noalias() = m1.conjugate().lazyProduct(m2.conjugate()), 0);
// ... and even no temporary for even deeply (>=2) nested products
VERIFY_EVALUATION_COUNT( Scalar tmp = 0; tmp += Scalar(RealScalar(1)) / (m3.transpose() * m3).diagonal().sum(), 0 );