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// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2011-2018 Gael Guennebaud <gael.guennebaud@inria.fr>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
#ifndef EIGEN_PARTIALREDUX_H
#define EIGEN_PARTIALREDUX_H
namespace Eigen {
namespace internal {
/***************************************************************************
*
* This file provides evaluators for partial reductions.
* There are two modes:
*
* - scalar path: simply calls the respective function on the column or row.
* -> nothing special here, all the tricky part is handled by the return
* types of VectorwiseOp's members. They embed the functor calling the
* respective DenseBase's member function.
*
* - vectorized path: implements a packet-wise reductions followed by
* some (optional) processing of the outcome, e.g., division by n for mean.
*
* For the vectorized path let's observe that the packet-size and outer-unrolling
* are both decided by the assignement logic. So all we have to do is to decide
* on the inner unrolling.
*
* For the unrolling, we can reuse "internal::redux_vec_unroller" from Redux.h,
* but be need to be careful to specify correct increment.
*
***************************************************************************/
/* logic deciding a strategy for unrolling of vectorized paths */
template<typename Func, typename Evaluator>
struct packetwise_redux_traits
{
enum {
OuterSize = int(Evaluator::IsRowMajor) ? Evaluator::RowsAtCompileTime : Evaluator::ColsAtCompileTime,
Cost = OuterSize == Dynamic ? HugeCost
: OuterSize * Evaluator::CoeffReadCost + (OuterSize-1) * functor_traits<Func>::Cost,
Unrolling = Cost <= EIGEN_UNROLLING_LIMIT ? CompleteUnrolling : NoUnrolling
};
};
/* Value to be returned when size==0 , by default let's return 0 */
template<typename PacketType,typename Func>
EIGEN_DEVICE_FUNC
PacketType packetwise_redux_empty_value(const Func& ) { return pset1<PacketType>(0); }
/* For products the default is 1 */
template<typename PacketType,typename Scalar>
EIGEN_DEVICE_FUNC
PacketType packetwise_redux_empty_value(const scalar_product_op<Scalar,Scalar>& ) { return pset1<PacketType>(1); }
/* Perform the actual reduction */
template<typename Func, typename Evaluator,
int Unrolling = packetwise_redux_traits<Func, Evaluator>::Unrolling
>
struct packetwise_redux_impl;
/* Perform the actual reduction with unrolling */
template<typename Func, typename Evaluator>
struct packetwise_redux_impl<Func, Evaluator, CompleteUnrolling>
{
typedef redux_novec_unroller<Func,Evaluator, 0, Evaluator::SizeAtCompileTime> Base;
typedef typename Evaluator::Scalar Scalar;
template<typename PacketType>
EIGEN_DEVICE_FUNC static EIGEN_STRONG_INLINE
PacketType run(const Evaluator &eval, const Func& func, Index /*size*/)
{
return redux_vec_unroller<Func, Evaluator, 0, packetwise_redux_traits<Func, Evaluator>::OuterSize>::template run<PacketType>(eval,func);
}
};
/* Add a specialization of redux_vec_unroller for size==0 at compiletime.
* This specialization is not required for general reductions, which is
* why it is defined here.
*/
template<typename Func, typename Evaluator, int Start>
struct redux_vec_unroller<Func, Evaluator, Start, 0>
{
template<typename PacketType>
EIGEN_DEVICE_FUNC
static EIGEN_STRONG_INLINE PacketType run(const Evaluator &, const Func& f)
{
return packetwise_redux_empty_value<PacketType>(f);
}
};
/* Perform the actual reduction for dynamic sizes */
template<typename Func, typename Evaluator>
struct packetwise_redux_impl<Func, Evaluator, NoUnrolling>
{
typedef typename Evaluator::Scalar Scalar;
typedef typename redux_traits<Func, Evaluator>::PacketType PacketScalar;
template<typename PacketType>
EIGEN_DEVICE_FUNC
static PacketType run(const Evaluator &eval, const Func& func, Index size)
{
if(size==0)
return packetwise_redux_empty_value<PacketType>(func);
const Index size4 = (size-1)&(~3);
PacketType p = eval.template packetByOuterInner<Unaligned,PacketType>(0,0);
Index i = 1;
// This loop is optimized for instruction pipelining:
// - each iteration generates two independent instructions
// - thanks to branch prediction and out-of-order execution we have independent instructions across loops
for(; i<size4; i+=4)
p = func.packetOp(p,
func.packetOp(
func.packetOp(eval.template packetByOuterInner<Unaligned,PacketType>(i+0,0),eval.template packetByOuterInner<Unaligned,PacketType>(i+1,0)),
func.packetOp(eval.template packetByOuterInner<Unaligned,PacketType>(i+2,0),eval.template packetByOuterInner<Unaligned,PacketType>(i+3,0))));
for(; i<size; ++i)
p = func.packetOp(p, eval.template packetByOuterInner<Unaligned,PacketType>(i,0));
return p;
}
};
template< typename ArgType, typename MemberOp, int Direction>
struct evaluator<PartialReduxExpr<ArgType, MemberOp, Direction> >
: evaluator_base<PartialReduxExpr<ArgType, MemberOp, Direction> >
{
typedef PartialReduxExpr<ArgType, MemberOp, Direction> XprType;
typedef typename internal::nested_eval<ArgType,1>::type ArgTypeNested;
typedef typename internal::add_const_on_value_type<ArgTypeNested>::type ConstArgTypeNested;
typedef typename internal::remove_all<ArgTypeNested>::type ArgTypeNestedCleaned;
typedef typename ArgType::Scalar InputScalar;
typedef typename XprType::Scalar Scalar;
enum {
TraversalSize = Direction==int(Vertical) ? int(ArgType::RowsAtCompileTime) : int(ArgType::ColsAtCompileTime)
};
typedef typename MemberOp::template Cost<int(TraversalSize)> CostOpType;
enum {
CoeffReadCost = TraversalSize==Dynamic ? HugeCost
: TraversalSize==0 ? 1
: TraversalSize * evaluator<ArgType>::CoeffReadCost + int(CostOpType::value),
_ArgFlags = evaluator<ArgType>::Flags,
_Vectorizable = bool(int(_ArgFlags)&PacketAccessBit)
&& bool(MemberOp::Vectorizable)
&& (Direction==int(Vertical) ? bool(_ArgFlags&RowMajorBit) : (_ArgFlags&RowMajorBit)==0)
&& (TraversalSize!=0),
Flags = (traits<XprType>::Flags&RowMajorBit)
| (evaluator<ArgType>::Flags&(HereditaryBits&(~RowMajorBit)))
| (_Vectorizable ? PacketAccessBit : 0)
| LinearAccessBit,
Alignment = 0 // FIXME this will need to be improved once PartialReduxExpr is vectorized
};
EIGEN_DEVICE_FUNC explicit evaluator(const XprType xpr)
: m_arg(xpr.nestedExpression()), m_functor(xpr.functor())
{
EIGEN_INTERNAL_CHECK_COST_VALUE(TraversalSize==Dynamic ? HugeCost : (TraversalSize==0 ? 1 : int(CostOpType::value)));
EIGEN_INTERNAL_CHECK_COST_VALUE(CoeffReadCost);
}
typedef typename XprType::CoeffReturnType CoeffReturnType;
EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
const Scalar coeff(Index i, Index j) const
{
return coeff(Direction==Vertical ? j : i);
}
EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
const Scalar coeff(Index index) const
{
return m_functor(m_arg.template subVector<DirectionType(Direction)>(index));
}
template<int LoadMode,typename PacketType>
EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
PacketType packet(Index i, Index j) const
{
return packet<LoadMode,PacketType>(Direction==Vertical ? j : i);
}
template<int LoadMode,typename PacketType>
EIGEN_STRONG_INLINE EIGEN_DEVICE_FUNC
PacketType packet(Index idx) const
{
enum { PacketSize = internal::unpacket_traits<PacketType>::size };
typedef Block<const ArgTypeNestedCleaned,
Direction==Vertical ? int(ArgType::RowsAtCompileTime) : int(PacketSize),
Direction==Vertical ? int(PacketSize) : int(ArgType::ColsAtCompileTime),
true /* InnerPanel */> PanelType;
PanelType panel(m_arg,
Direction==Vertical ? 0 : idx,
Direction==Vertical ? idx : 0,
Direction==Vertical ? m_arg.rows() : Index(PacketSize),
Direction==Vertical ? Index(PacketSize) : m_arg.cols());
// FIXME
// See bug 1612, currently if PacketSize==1 (i.e. complex<double> with 128bits registers) then the storage-order of panel get reversed
// and methods like packetByOuterInner do not make sense anymore in this context.
// So let's just by pass "vectorization" in this case:
if(PacketSize==1)
return internal::pset1<PacketType>(coeff(idx));
typedef typename internal::redux_evaluator<PanelType> PanelEvaluator;
PanelEvaluator panel_eval(panel);
typedef typename MemberOp::BinaryOp BinaryOp;
PacketType p = internal::packetwise_redux_impl<BinaryOp,PanelEvaluator>::template run<PacketType>(panel_eval,m_functor.binaryFunc(),m_arg.outerSize());
return p;
}
protected:
ConstArgTypeNested m_arg;
const MemberOp m_functor;
};
} // end namespace internal
} // end namespace Eigen
#endif // EIGEN_PARTIALREDUX_H
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