1// This file is part of Eigen, a lightweight C++ template library
2// for linear algebra.
3//
4// Copyright (C) 2006-2008 Benoit Jacob <jacob.benoit.1@gmail.com>
5// Copyright (C) 2009 Ricard Marxer <email@ricardmarxer.com>
6// Copyright (C) 2009-2010 Gael Guennebaud <gael.guennebaud@inria.fr>
7//
8// This Source Code Form is subject to the terms of the Mozilla
9// Public License v. 2.0. If a copy of the MPL was not distributed
10// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
11
12#ifndef EIGEN_REVERSE_H
13#define EIGEN_REVERSE_H
14
15namespace Eigen {
16
17namespace internal {
18
19template<typename MatrixType, int Direction>
20struct traits<Reverse<MatrixType, Direction> >
21 : traits<MatrixType>
22{
23 typedef typename MatrixType::Scalar Scalar;
24 typedef typename traits<MatrixType>::StorageKind StorageKind;
25 typedef typename traits<MatrixType>::XprKind XprKind;
26 typedef typename ref_selector<MatrixType>::type MatrixTypeNested;
27 typedef typename remove_reference<MatrixTypeNested>::type _MatrixTypeNested;
28 enum {
29 RowsAtCompileTime = MatrixType::RowsAtCompileTime,
30 ColsAtCompileTime = MatrixType::ColsAtCompileTime,
31 MaxRowsAtCompileTime = MatrixType::MaxRowsAtCompileTime,
32 MaxColsAtCompileTime = MatrixType::MaxColsAtCompileTime,
33 Flags = _MatrixTypeNested::Flags & (RowMajorBit | LvalueBit)
34 };
35};
36
37template<typename PacketType, bool ReversePacket> struct reverse_packet_cond
38{
39 static inline PacketType run(const PacketType& x) { return preverse(x); }
40};
41
42template<typename PacketType> struct reverse_packet_cond<PacketType,false>
43{
44 static inline PacketType run(const PacketType& x) { return x; }
45};
46
47} // end namespace internal
48
49/** \class Reverse
50 * \ingroup Core_Module
51 *
52 * \brief Expression of the reverse of a vector or matrix
53 *
54 * \tparam MatrixType the type of the object of which we are taking the reverse
55 * \tparam Direction defines the direction of the reverse operation, can be Vertical, Horizontal, or BothDirections
56 *
57 * This class represents an expression of the reverse of a vector.
58 * It is the return type of MatrixBase::reverse() and VectorwiseOp::reverse()
59 * and most of the time this is the only way it is used.
60 *
61 * \sa MatrixBase::reverse(), VectorwiseOp::reverse()
62 */
63template<typename MatrixType, int Direction> class Reverse
64 : public internal::dense_xpr_base< Reverse<MatrixType, Direction> >::type
65{
66 public:
67
68 typedef typename internal::dense_xpr_base<Reverse>::type Base;
69 EIGEN_DENSE_PUBLIC_INTERFACE(Reverse)
70 typedef typename internal::remove_all<MatrixType>::type NestedExpression;
71 using Base::IsRowMajor;
72
73 protected:
74 enum {
75 PacketSize = internal::packet_traits<Scalar>::size,
76 IsColMajor = !IsRowMajor,
77 ReverseRow = (Direction == Vertical) || (Direction == BothDirections),
78 ReverseCol = (Direction == Horizontal) || (Direction == BothDirections),
79 OffsetRow = ReverseRow && IsColMajor ? PacketSize : 1,
80 OffsetCol = ReverseCol && IsRowMajor ? PacketSize : 1,
81 ReversePacket = (Direction == BothDirections)
82 || ((Direction == Vertical) && IsColMajor)
83 || ((Direction == Horizontal) && IsRowMajor)
84 };
85 typedef internal::reverse_packet_cond<PacketScalar,ReversePacket> reverse_packet;
86 public:
87
88 EIGEN_DEVICE_FUNC explicit inline Reverse(const MatrixType& matrix) : m_matrix(matrix) { }
89
90 EIGEN_INHERIT_ASSIGNMENT_OPERATORS(Reverse)
91
92 EIGEN_DEVICE_FUNC inline Index rows() const { return m_matrix.rows(); }
93 EIGEN_DEVICE_FUNC inline Index cols() const { return m_matrix.cols(); }
94
95 EIGEN_DEVICE_FUNC inline Index innerStride() const
96 {
97 return -m_matrix.innerStride();
98 }
99
100 EIGEN_DEVICE_FUNC const typename internal::remove_all<typename MatrixType::Nested>::type&
101 nestedExpression() const
102 {
103 return m_matrix;
104 }
105
106 protected:
107 typename MatrixType::Nested m_matrix;
108};
109
110/** \returns an expression of the reverse of *this.
111 *
112 * Example: \include MatrixBase_reverse.cpp
113 * Output: \verbinclude MatrixBase_reverse.out
114 *
115 */
116template<typename Derived>
117inline typename DenseBase<Derived>::ReverseReturnType
118DenseBase<Derived>::reverse()
119{
120 return ReverseReturnType(derived());
121}
122
123
124//reverse const overload moved DenseBase.h due to a CUDA compiler bug
125
126/** This is the "in place" version of reverse: it reverses \c *this.
127 *
128 * In most cases it is probably better to simply use the reversed expression
129 * of a matrix. However, when reversing the matrix data itself is really needed,
130 * then this "in-place" version is probably the right choice because it provides
131 * the following additional benefits:
132 * - less error prone: doing the same operation with .reverse() requires special care:
133 * \code m = m.reverse().eval(); \endcode
134 * - this API enables reverse operations without the need for a temporary
135 * - it allows future optimizations (cache friendliness, etc.)
136 *
137 * \sa VectorwiseOp::reverseInPlace(), reverse() */
138template<typename Derived>
139inline void DenseBase<Derived>::reverseInPlace()
140{
141 if(cols()>rows())
142 {
143 Index half = cols()/2;
144 leftCols(half).swap(rightCols(half).reverse());
145 if((cols()%2)==1)
146 {
147 Index half2 = rows()/2;
148 col(half).head(half2).swap(col(half).tail(half2).reverse());
149 }
150 }
151 else
152 {
153 Index half = rows()/2;
154 topRows(half).swap(bottomRows(half).reverse());
155 if((rows()%2)==1)
156 {
157 Index half2 = cols()/2;
158 row(half).head(half2).swap(row(half).tail(half2).reverse());
159 }
160 }
161}
162
163namespace internal {
164
165template<int Direction>
166struct vectorwise_reverse_inplace_impl;
167
168template<>
169struct vectorwise_reverse_inplace_impl<Vertical>
170{
171 template<typename ExpressionType>
172 static void run(ExpressionType &xpr)
173 {
174 Index half = xpr.rows()/2;
175 xpr.topRows(half).swap(xpr.bottomRows(half).colwise().reverse());
176 }
177};
178
179template<>
180struct vectorwise_reverse_inplace_impl<Horizontal>
181{
182 template<typename ExpressionType>
183 static void run(ExpressionType &xpr)
184 {
185 Index half = xpr.cols()/2;
186 xpr.leftCols(half).swap(xpr.rightCols(half).rowwise().reverse());
187 }
188};
189
190} // end namespace internal
191
192/** This is the "in place" version of VectorwiseOp::reverse: it reverses each column or row of \c *this.
193 *
194 * In most cases it is probably better to simply use the reversed expression
195 * of a matrix. However, when reversing the matrix data itself is really needed,
196 * then this "in-place" version is probably the right choice because it provides
197 * the following additional benefits:
198 * - less error prone: doing the same operation with .reverse() requires special care:
199 * \code m = m.reverse().eval(); \endcode
200 * - this API enables reverse operations without the need for a temporary
201 *
202 * \sa DenseBase::reverseInPlace(), reverse() */
203template<typename ExpressionType, int Direction>
204void VectorwiseOp<ExpressionType,Direction>::reverseInPlace()
205{
206 internal::vectorwise_reverse_inplace_impl<Direction>::run(_expression().const_cast_derived());
207}
208
209} // end namespace Eigen
210
211#endif // EIGEN_REVERSE_H
212