1// This file is part of Eigen, a lightweight C++ template library
2// for linear algebra.
3//
4// Copyright (C) 2012 Gael Guennebaud <gael.guennebaud@inria.fr>
5//
6// This Source Code Form is subject to the terms of the Mozilla
7// Public License v. 2.0. If a copy of the MPL was not distributed
8// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
9
10#ifndef EIGEN_REF_H
11#define EIGEN_REF_H
12
13namespace Eigen {
14
15namespace internal {
16
17template<typename _PlainObjectType, int _Options, typename _StrideType>
18struct traits<Ref<_PlainObjectType, _Options, _StrideType> >
19 : public traits<Map<_PlainObjectType, _Options, _StrideType> >
20{
21 typedef _PlainObjectType PlainObjectType;
22 typedef _StrideType StrideType;
23 enum {
24 Options = _Options,
25 Flags = traits<Map<_PlainObjectType, _Options, _StrideType> >::Flags | NestByRefBit,
26 Alignment = traits<Map<_PlainObjectType, _Options, _StrideType> >::Alignment
27 };
28
29 template<typename Derived> struct match {
30 enum {
31 HasDirectAccess = internal::has_direct_access<Derived>::ret,
32 StorageOrderMatch = PlainObjectType::IsVectorAtCompileTime || Derived::IsVectorAtCompileTime || ((PlainObjectType::Flags&RowMajorBit)==(Derived::Flags&RowMajorBit)),
33 InnerStrideMatch = int(StrideType::InnerStrideAtCompileTime)==int(Dynamic)
34 || int(StrideType::InnerStrideAtCompileTime)==int(Derived::InnerStrideAtCompileTime)
35 || (int(StrideType::InnerStrideAtCompileTime)==0 && int(Derived::InnerStrideAtCompileTime)==1),
36 OuterStrideMatch = Derived::IsVectorAtCompileTime
37 || int(StrideType::OuterStrideAtCompileTime)==int(Dynamic) || int(StrideType::OuterStrideAtCompileTime)==int(Derived::OuterStrideAtCompileTime),
38 // NOTE, this indirection of evaluator<Derived>::Alignment is needed
39 // to workaround a very strange bug in MSVC related to the instantiation
40 // of has_*ary_operator in evaluator<CwiseNullaryOp>.
41 // This line is surprisingly very sensitive. For instance, simply adding parenthesis
42 // as "DerivedAlignment = (int(evaluator<Derived>::Alignment))," will make MSVC fail...
43 DerivedAlignment = int(evaluator<Derived>::Alignment),
44 AlignmentMatch = (int(traits<PlainObjectType>::Alignment)==int(Unaligned)) || (DerivedAlignment >= int(Alignment)), // FIXME the first condition is not very clear, it should be replaced by the required alignment
45 ScalarTypeMatch = internal::is_same<typename PlainObjectType::Scalar, typename Derived::Scalar>::value,
46 MatchAtCompileTime = HasDirectAccess && StorageOrderMatch && InnerStrideMatch && OuterStrideMatch && AlignmentMatch && ScalarTypeMatch
47 };
48 typedef typename internal::conditional<MatchAtCompileTime,internal::true_type,internal::false_type>::type type;
49 };
50
51};
52
53template<typename Derived>
54struct traits<RefBase<Derived> > : public traits<Derived> {};
55
56}
57
58template<typename Derived> class RefBase
59 : public MapBase<Derived>
60{
61 typedef typename internal::traits<Derived>::PlainObjectType PlainObjectType;
62 typedef typename internal::traits<Derived>::StrideType StrideType;
63
64public:
65
66 typedef MapBase<Derived> Base;
67 EIGEN_DENSE_PUBLIC_INTERFACE(RefBase)
68
69 EIGEN_DEVICE_FUNC inline Index innerStride() const
70 {
71 return StrideType::InnerStrideAtCompileTime != 0 ? m_stride.inner() : 1;
72 }
73
74 EIGEN_DEVICE_FUNC inline Index outerStride() const
75 {
76 return StrideType::OuterStrideAtCompileTime != 0 ? m_stride.outer()
77 : IsVectorAtCompileTime ? this->size()
78 : int(Flags)&RowMajorBit ? this->cols()
79 : this->rows();
80 }
81
82 EIGEN_DEVICE_FUNC RefBase()
83 : Base(0,RowsAtCompileTime==Dynamic?0:RowsAtCompileTime,ColsAtCompileTime==Dynamic?0:ColsAtCompileTime),
84 // Stride<> does not allow default ctor for Dynamic strides, so let' initialize it with dummy values:
85 m_stride(StrideType::OuterStrideAtCompileTime==Dynamic?0:StrideType::OuterStrideAtCompileTime,
86 StrideType::InnerStrideAtCompileTime==Dynamic?0:StrideType::InnerStrideAtCompileTime)
87 {}
88
89 EIGEN_INHERIT_ASSIGNMENT_OPERATORS(RefBase)
90
91protected:
92
93 typedef Stride<StrideType::OuterStrideAtCompileTime,StrideType::InnerStrideAtCompileTime> StrideBase;
94
95 template<typename Expression>
96 EIGEN_DEVICE_FUNC void construct(Expression& expr)
97 {
98 EIGEN_STATIC_ASSERT_SAME_MATRIX_SIZE(PlainObjectType,Expression);
99
100 if(PlainObjectType::RowsAtCompileTime==1)
101 {
102 eigen_assert(expr.rows()==1 || expr.cols()==1);
103 ::new (static_cast<Base*>(this)) Base(expr.data(), 1, expr.size());
104 }
105 else if(PlainObjectType::ColsAtCompileTime==1)
106 {
107 eigen_assert(expr.rows()==1 || expr.cols()==1);
108 ::new (static_cast<Base*>(this)) Base(expr.data(), expr.size(), 1);
109 }
110 else
111 ::new (static_cast<Base*>(this)) Base(expr.data(), expr.rows(), expr.cols());
112
113 if(Expression::IsVectorAtCompileTime && (!PlainObjectType::IsVectorAtCompileTime) && ((Expression::Flags&RowMajorBit)!=(PlainObjectType::Flags&RowMajorBit)))
114 ::new (&m_stride) StrideBase(expr.innerStride(), StrideType::InnerStrideAtCompileTime==0?0:1);
115 else
116 ::new (&m_stride) StrideBase(StrideType::OuterStrideAtCompileTime==0?0:expr.outerStride(),
117 StrideType::InnerStrideAtCompileTime==0?0:expr.innerStride());
118 }
119
120 StrideBase m_stride;
121};
122
123/** \class Ref
124 * \ingroup Core_Module
125 *
126 * \brief A matrix or vector expression mapping an existing expression
127 *
128 * \tparam PlainObjectType the equivalent matrix type of the mapped data
129 * \tparam Options specifies the pointer alignment in bytes. It can be: \c #Aligned128, , \c #Aligned64, \c #Aligned32, \c #Aligned16, \c #Aligned8 or \c #Unaligned.
130 * The default is \c #Unaligned.
131 * \tparam StrideType optionally specifies strides. By default, Ref implies a contiguous storage along the inner dimension (inner stride==1),
132 * but accepts a variable outer stride (leading dimension).
133 * This can be overridden by specifying strides.
134 * The type passed here must be a specialization of the Stride template, see examples below.
135 *
136 * This class provides a way to write non-template functions taking Eigen objects as parameters while limiting the number of copies.
137 * A Ref<> object can represent either a const expression or a l-value:
138 * \code
139 * // in-out argument:
140 * void foo1(Ref<VectorXf> x);
141 *
142 * // read-only const argument:
143 * void foo2(const Ref<const VectorXf>& x);
144 * \endcode
145 *
146 * In the in-out case, the input argument must satisfy the constraints of the actual Ref<> type, otherwise a compilation issue will be triggered.
147 * By default, a Ref<VectorXf> can reference any dense vector expression of float having a contiguous memory layout.
148 * Likewise, a Ref<MatrixXf> can reference any column-major dense matrix expression of float whose column's elements are contiguously stored with
149 * the possibility to have a constant space in-between each column, i.e. the inner stride must be equal to 1, but the outer stride (or leading dimension)
150 * can be greater than the number of rows.
151 *
152 * In the const case, if the input expression does not match the above requirement, then it is evaluated into a temporary before being passed to the function.
153 * Here are some examples:
154 * \code
155 * MatrixXf A;
156 * VectorXf a;
157 * foo1(a.head()); // OK
158 * foo1(A.col()); // OK
159 * foo1(A.row()); // Compilation error because here innerstride!=1
160 * foo2(A.row()); // Compilation error because A.row() is a 1xN object while foo2 is expecting a Nx1 object
161 * foo2(A.row().transpose()); // The row is copied into a contiguous temporary
162 * foo2(2*a); // The expression is evaluated into a temporary
163 * foo2(A.col().segment(2,4)); // No temporary
164 * \endcode
165 *
166 * The range of inputs that can be referenced without temporary can be enlarged using the last two template parameters.
167 * Here is an example accepting an innerstride!=1:
168 * \code
169 * // in-out argument:
170 * void foo3(Ref<VectorXf,0,InnerStride<> > x);
171 * foo3(A.row()); // OK
172 * \endcode
173 * The downside here is that the function foo3 might be significantly slower than foo1 because it won't be able to exploit vectorization, and will involve more
174 * expensive address computations even if the input is contiguously stored in memory. To overcome this issue, one might propose to overload internally calling a
175 * template function, e.g.:
176 * \code
177 * // in the .h:
178 * void foo(const Ref<MatrixXf>& A);
179 * void foo(const Ref<MatrixXf,0,Stride<> >& A);
180 *
181 * // in the .cpp:
182 * template<typename TypeOfA> void foo_impl(const TypeOfA& A) {
183 * ... // crazy code goes here
184 * }
185 * void foo(const Ref<MatrixXf>& A) { foo_impl(A); }
186 * void foo(const Ref<MatrixXf,0,Stride<> >& A) { foo_impl(A); }
187 * \endcode
188 *
189 *
190 * \sa PlainObjectBase::Map(), \ref TopicStorageOrders
191 */
192template<typename PlainObjectType, int Options, typename StrideType> class Ref
193 : public RefBase<Ref<PlainObjectType, Options, StrideType> >
194{
195 private:
196 typedef internal::traits<Ref> Traits;
197 template<typename Derived>
198 EIGEN_DEVICE_FUNC inline Ref(const PlainObjectBase<Derived>& expr,
199 typename internal::enable_if<bool(Traits::template match<Derived>::MatchAtCompileTime),Derived>::type* = 0);
200 public:
201
202 typedef RefBase<Ref> Base;
203 EIGEN_DENSE_PUBLIC_INTERFACE(Ref)
204
205
206 #ifndef EIGEN_PARSED_BY_DOXYGEN
207 template<typename Derived>
208 EIGEN_DEVICE_FUNC inline Ref(PlainObjectBase<Derived>& expr,
209 typename internal::enable_if<bool(Traits::template match<Derived>::MatchAtCompileTime),Derived>::type* = 0)
210 {
211 EIGEN_STATIC_ASSERT(bool(Traits::template match<Derived>::MatchAtCompileTime), STORAGE_LAYOUT_DOES_NOT_MATCH);
212 Base::construct(expr.derived());
213 }
214 template<typename Derived>
215 EIGEN_DEVICE_FUNC inline Ref(const DenseBase<Derived>& expr,
216 typename internal::enable_if<bool(Traits::template match<Derived>::MatchAtCompileTime),Derived>::type* = 0)
217 #else
218 /** Implicit constructor from any dense expression */
219 template<typename Derived>
220 inline Ref(DenseBase<Derived>& expr)
221 #endif
222 {
223 EIGEN_STATIC_ASSERT(bool(internal::is_lvalue<Derived>::value), THIS_EXPRESSION_IS_NOT_A_LVALUE__IT_IS_READ_ONLY);
224 EIGEN_STATIC_ASSERT(bool(Traits::template match<Derived>::MatchAtCompileTime), STORAGE_LAYOUT_DOES_NOT_MATCH);
225 EIGEN_STATIC_ASSERT(!Derived::IsPlainObjectBase,THIS_EXPRESSION_IS_NOT_A_LVALUE__IT_IS_READ_ONLY);
226 Base::construct(expr.const_cast_derived());
227 }
228
229 EIGEN_INHERIT_ASSIGNMENT_OPERATORS(Ref)
230
231};
232
233// this is the const ref version
234template<typename TPlainObjectType, int Options, typename StrideType> class Ref<const TPlainObjectType, Options, StrideType>
235 : public RefBase<Ref<const TPlainObjectType, Options, StrideType> >
236{
237 typedef internal::traits<Ref> Traits;
238 public:
239
240 typedef RefBase<Ref> Base;
241 EIGEN_DENSE_PUBLIC_INTERFACE(Ref)
242
243 template<typename Derived>
244 EIGEN_DEVICE_FUNC inline Ref(const DenseBase<Derived>& expr,
245 typename internal::enable_if<bool(Traits::template match<Derived>::ScalarTypeMatch),Derived>::type* = 0)
246 {
247// std::cout << match_helper<Derived>::HasDirectAccess << "," << match_helper<Derived>::OuterStrideMatch << "," << match_helper<Derived>::InnerStrideMatch << "\n";
248// std::cout << int(StrideType::OuterStrideAtCompileTime) << " - " << int(Derived::OuterStrideAtCompileTime) << "\n";
249// std::cout << int(StrideType::InnerStrideAtCompileTime) << " - " << int(Derived::InnerStrideAtCompileTime) << "\n";
250 construct(expr.derived(), typename Traits::template match<Derived>::type());
251 }
252
253 EIGEN_DEVICE_FUNC inline Ref(const Ref& other) : Base(other) {
254 // copy constructor shall not copy the m_object, to avoid unnecessary malloc and copy
255 }
256
257 template<typename OtherRef>
258 EIGEN_DEVICE_FUNC inline Ref(const RefBase<OtherRef>& other) {
259 construct(other.derived(), typename Traits::template match<OtherRef>::type());
260 }
261
262 protected:
263
264 template<typename Expression>
265 EIGEN_DEVICE_FUNC void construct(const Expression& expr,internal::true_type)
266 {
267 Base::construct(expr);
268 }
269
270 template<typename Expression>
271 EIGEN_DEVICE_FUNC void construct(const Expression& expr, internal::false_type)
272 {
273 internal::call_assignment_no_alias(m_object,expr,internal::assign_op<Scalar,Scalar>());
274 Base::construct(m_object);
275 }
276
277 protected:
278 TPlainObjectType m_object;
279};
280
281} // end namespace Eigen
282
283#endif // EIGEN_REF_H
284