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
15template<typename Derived> class RefBase;
16template<typename PlainObjectType, int Options = 0,
17         typename StrideType = typename internal::conditional<PlainObjectType::IsVectorAtCompileTime,InnerStride<1>,OuterStride<> >::type > class Ref;
18
19/** \class Ref
20  * \ingroup Core_Module
21  *
22  * \brief A matrix or vector expression mapping an existing expressions
23  *
24  * \tparam PlainObjectType the equivalent matrix type of the mapped data
25  * \tparam Options specifies whether the pointer is \c #Aligned, or \c #Unaligned.
26  *                The default is \c #Unaligned.
27  * \tparam StrideType optionally specifies strides. By default, Ref implies a contiguous storage along the inner dimension (inner stride==1),
28  *                   but accept a variable outer stride (leading dimension).
29  *                   This can be overridden by specifying strides.
30  *                   The type passed here must be a specialization of the Stride template, see examples below.
31  *
32  * This class permits to write non template functions taking Eigen's object as parameters while limiting the number of copies.
33  * A Ref<> object can represent either a const expression or a l-value:
34  * \code
35  * // in-out argument:
36  * void foo1(Ref<VectorXf> x);
37  *
38  * // read-only const argument:
39  * void foo2(const Ref<const VectorXf>& x);
40  * \endcode
41  *
42  * In the in-out case, the input argument must satisfies the constraints of the actual Ref<> type, otherwise a compilation issue will be triggered.
43  * By default, a Ref<VectorXf> can reference any dense vector expression of float having a contiguous memory layout.
44  * Likewise, a Ref<MatrixXf> can reference any column major dense matrix expression of float whose column's elements are contiguously stored with
45  * the possibility to have a constant space inbetween each column, i.e.: the inner stride mmust be equal to 1, but the outer-stride (or leading dimension),
46  * can be greater than the number of rows.
47  *
48  * 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.
49  * Here are some examples:
50  * \code
51  * MatrixXf A;
52  * VectorXf a;
53  * foo1(a.head());             // OK
54  * foo1(A.col());              // OK
55  * foo1(A.row());              // compilation error because here innerstride!=1
56  * foo2(A.row());              // The row is copied into a contiguous temporary
57  * foo2(2*a);                  // The expression is evaluated into a temporary
58  * foo2(A.col().segment(2,4)); // No temporary
59  * \endcode
60  *
61  * The range of inputs that can be referenced without temporary can be enlarged using the last two template parameter.
62  * Here is an example accepting an innerstride!=1:
63  * \code
64  * // in-out argument:
65  * void foo3(Ref<VectorXf,0,InnerStride<> > x);
66  * foo3(A.row());              // OK
67  * \endcode
68  * 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 involved more
69  * expensive address computations even if the input is contiguously stored in memory. To overcome this issue, one might propose to overloads internally calling a
70  * template function, e.g.:
71  * \code
72  * // in the .h:
73  * void foo(const Ref<MatrixXf>& A);
74  * void foo(const Ref<MatrixXf,0,Stride<> >& A);
75  *
76  * // in the .cpp:
77  * template<typename TypeOfA> void foo_impl(const TypeOfA& A) {
78  *     ... // crazy code goes here
79  * }
80  * void foo(const Ref<MatrixXf>& A) { foo_impl(A); }
81  * void foo(const Ref<MatrixXf,0,Stride<> >& A) { foo_impl(A); }
82  * \endcode
83  *
84  *
85  * \sa PlainObjectBase::Map(), \ref TopicStorageOrders
86  */
87
88namespace internal {
89
90template<typename _PlainObjectType, int _Options, typename _StrideType>
91struct traits<Ref<_PlainObjectType, _Options, _StrideType> >
92  : public traits<Map<_PlainObjectType, _Options, _StrideType> >
93{
94  typedef _PlainObjectType PlainObjectType;
95  typedef _StrideType StrideType;
96  enum {
97    Options = _Options,
98    Flags = traits<Map<_PlainObjectType, _Options, _StrideType> >::Flags | NestByRefBit
99  };
100
101  template<typename Derived> struct match {
102    enum {
103      HasDirectAccess = internal::has_direct_access<Derived>::ret,
104      StorageOrderMatch = PlainObjectType::IsVectorAtCompileTime || Derived::IsVectorAtCompileTime || ((PlainObjectType::Flags&RowMajorBit)==(Derived::Flags&RowMajorBit)),
105      InnerStrideMatch = int(StrideType::InnerStrideAtCompileTime)==int(Dynamic)
106                      || int(StrideType::InnerStrideAtCompileTime)==int(Derived::InnerStrideAtCompileTime)
107                      || (int(StrideType::InnerStrideAtCompileTime)==0 && int(Derived::InnerStrideAtCompileTime)==1),
108      OuterStrideMatch = Derived::IsVectorAtCompileTime
109                      || int(StrideType::OuterStrideAtCompileTime)==int(Dynamic) || int(StrideType::OuterStrideAtCompileTime)==int(Derived::OuterStrideAtCompileTime),
110      AlignmentMatch = (_Options!=Aligned) || ((PlainObjectType::Flags&AlignedBit)==0) || ((traits<Derived>::Flags&AlignedBit)==AlignedBit),
111      MatchAtCompileTime = HasDirectAccess && StorageOrderMatch && InnerStrideMatch && OuterStrideMatch && AlignmentMatch
112    };
113    typedef typename internal::conditional<MatchAtCompileTime,internal::true_type,internal::false_type>::type type;
114  };
115
116};
117
118template<typename Derived>
119struct traits<RefBase<Derived> > : public traits<Derived> {};
120
121}
122
123template<typename Derived> class RefBase
124 : public MapBase<Derived>
125{
126  typedef typename internal::traits<Derived>::PlainObjectType PlainObjectType;
127  typedef typename internal::traits<Derived>::StrideType StrideType;
128
129public:
130
131  typedef MapBase<Derived> Base;
132  EIGEN_DENSE_PUBLIC_INTERFACE(RefBase)
133
134  inline Index innerStride() const
135  {
136    return StrideType::InnerStrideAtCompileTime != 0 ? m_stride.inner() : 1;
137  }
138
139  inline Index outerStride() const
140  {
141    return StrideType::OuterStrideAtCompileTime != 0 ? m_stride.outer()
142         : IsVectorAtCompileTime ? this->size()
143         : int(Flags)&RowMajorBit ? this->cols()
144         : this->rows();
145  }
146
147  RefBase()
148    : Base(0,RowsAtCompileTime==Dynamic?0:RowsAtCompileTime,ColsAtCompileTime==Dynamic?0:ColsAtCompileTime),
149      // Stride<> does not allow default ctor for Dynamic strides, so let' initialize it with dummy values:
150      m_stride(StrideType::OuterStrideAtCompileTime==Dynamic?0:StrideType::OuterStrideAtCompileTime,
151               StrideType::InnerStrideAtCompileTime==Dynamic?0:StrideType::InnerStrideAtCompileTime)
152  {}
153
154  EIGEN_INHERIT_ASSIGNMENT_OPERATORS(RefBase)
155
156protected:
157
158  typedef Stride<StrideType::OuterStrideAtCompileTime,StrideType::InnerStrideAtCompileTime> StrideBase;
159
160  template<typename Expression>
161  void construct(Expression& expr)
162  {
163    if(PlainObjectType::RowsAtCompileTime==1)
164    {
165      eigen_assert(expr.rows()==1 || expr.cols()==1);
166      ::new (static_cast<Base*>(this)) Base(expr.data(), 1, expr.size());
167    }
168    else if(PlainObjectType::ColsAtCompileTime==1)
169    {
170      eigen_assert(expr.rows()==1 || expr.cols()==1);
171      ::new (static_cast<Base*>(this)) Base(expr.data(), expr.size(), 1);
172    }
173    else
174      ::new (static_cast<Base*>(this)) Base(expr.data(), expr.rows(), expr.cols());
175
176    if(Expression::IsVectorAtCompileTime && (!PlainObjectType::IsVectorAtCompileTime) && ((Expression::Flags&RowMajorBit)!=(PlainObjectType::Flags&RowMajorBit)))
177      ::new (&m_stride) StrideBase(expr.innerStride(), StrideType::InnerStrideAtCompileTime==0?0:1);
178    else
179      ::new (&m_stride) StrideBase(StrideType::OuterStrideAtCompileTime==0?0:expr.outerStride(),
180                                   StrideType::InnerStrideAtCompileTime==0?0:expr.innerStride());
181  }
182
183  StrideBase m_stride;
184};
185
186
187template<typename PlainObjectType, int Options, typename StrideType> class Ref
188  : public RefBase<Ref<PlainObjectType, Options, StrideType> >
189{
190    typedef internal::traits<Ref> Traits;
191  public:
192
193    typedef RefBase<Ref> Base;
194    EIGEN_DENSE_PUBLIC_INTERFACE(Ref)
195
196
197    #ifndef EIGEN_PARSED_BY_DOXYGEN
198    template<typename Derived>
199    inline Ref(PlainObjectBase<Derived>& expr,
200               typename internal::enable_if<bool(Traits::template match<Derived>::MatchAtCompileTime),Derived>::type* = 0)
201    {
202      Base::construct(expr);
203    }
204    template<typename Derived>
205    inline Ref(const DenseBase<Derived>& expr,
206               typename internal::enable_if<bool(internal::is_lvalue<Derived>::value&&bool(Traits::template match<Derived>::MatchAtCompileTime)),Derived>::type* = 0,
207               int = Derived::ThisConstantIsPrivateInPlainObjectBase)
208    #else
209    template<typename Derived>
210    inline Ref(DenseBase<Derived>& expr)
211    #endif
212    {
213      Base::construct(expr.const_cast_derived());
214    }
215
216    EIGEN_INHERIT_ASSIGNMENT_OPERATORS(Ref)
217
218};
219
220// this is the const ref version
221template<typename TPlainObjectType, int Options, typename StrideType> class Ref<const TPlainObjectType, Options, StrideType>
222  : public RefBase<Ref<const TPlainObjectType, Options, StrideType> >
223{
224    typedef internal::traits<Ref> Traits;
225  public:
226
227    typedef RefBase<Ref> Base;
228    EIGEN_DENSE_PUBLIC_INTERFACE(Ref)
229
230    template<typename Derived>
231    inline Ref(const DenseBase<Derived>& expr)
232    {
233//      std::cout << match_helper<Derived>::HasDirectAccess << "," << match_helper<Derived>::OuterStrideMatch << "," << match_helper<Derived>::InnerStrideMatch << "\n";
234//      std::cout << int(StrideType::OuterStrideAtCompileTime) << " - " << int(Derived::OuterStrideAtCompileTime) << "\n";
235//      std::cout << int(StrideType::InnerStrideAtCompileTime) << " - " << int(Derived::InnerStrideAtCompileTime) << "\n";
236      construct(expr.derived(), typename Traits::template match<Derived>::type());
237    }
238
239  protected:
240
241    template<typename Expression>
242    void construct(const Expression& expr,internal::true_type)
243    {
244      Base::construct(expr);
245    }
246
247    template<typename Expression>
248    void construct(const Expression& expr, internal::false_type)
249    {
250      m_object.lazyAssign(expr);
251      Base::construct(m_object);
252    }
253
254  protected:
255    TPlainObjectType m_object;
256};
257
258} // end namespace Eigen
259
260#endif // EIGEN_REF_H
261