Ref.h revision a829215e078ace896f52702caa0c27608f40e3b0 
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      ScalarTypeMatch = internal::is_same<typename PlainObjectType::Scalar, typename Derived::Scalar>::value,
112      MatchAtCompileTime = HasDirectAccess && StorageOrderMatch && InnerStrideMatch && OuterStrideMatch && AlignmentMatch && ScalarTypeMatch
113    };
114    typedef typename internal::conditional<MatchAtCompileTime,internal::true_type,internal::false_type>::type type;
115  };
116
117};
118
119template<typename Derived>
120struct traits<RefBase<Derived> > : public traits<Derived> {};
121
122}
123
124template<typename Derived> class RefBase
125 : public MapBase<Derived>
126{
127  typedef typename internal::traits<Derived>::PlainObjectType PlainObjectType;
128  typedef typename internal::traits<Derived>::StrideType StrideType;
129
130public:
131
132  typedef MapBase<Derived> Base;
133  EIGEN_DENSE_PUBLIC_INTERFACE(RefBase)
134
135  inline Index innerStride() const
136  {
137    return StrideType::InnerStrideAtCompileTime != 0 ? m_stride.inner() : 1;
138  }
139
140  inline Index outerStride() const
141  {
142    return StrideType::OuterStrideAtCompileTime != 0 ? m_stride.outer()
143         : IsVectorAtCompileTime ? this->size()
144         : int(Flags)&RowMajorBit ? this->cols()
145         : this->rows();
146  }
147
148  RefBase()
149    : Base(0,RowsAtCompileTime==Dynamic?0:RowsAtCompileTime,ColsAtCompileTime==Dynamic?0:ColsAtCompileTime),
150      // Stride<> does not allow default ctor for Dynamic strides, so let' initialize it with dummy values:
151      m_stride(StrideType::OuterStrideAtCompileTime==Dynamic?0:StrideType::OuterStrideAtCompileTime,
152               StrideType::InnerStrideAtCompileTime==Dynamic?0:StrideType::InnerStrideAtCompileTime)
153  {}
154
155  EIGEN_INHERIT_ASSIGNMENT_OPERATORS(RefBase)
156
157protected:
158
159  typedef Stride<StrideType::OuterStrideAtCompileTime,StrideType::InnerStrideAtCompileTime> StrideBase;
160
161  template<typename Expression>
162  void construct(Expression& expr)
163  {
164    if(PlainObjectType::RowsAtCompileTime==1)
165    {
166      eigen_assert(expr.rows()==1 || expr.cols()==1);
167      ::new (static_cast<Base*>(this)) Base(expr.data(), 1, expr.size());
168    }
169    else if(PlainObjectType::ColsAtCompileTime==1)
170    {
171      eigen_assert(expr.rows()==1 || expr.cols()==1);
172      ::new (static_cast<Base*>(this)) Base(expr.data(), expr.size(), 1);
173    }
174    else
175      ::new (static_cast<Base*>(this)) Base(expr.data(), expr.rows(), expr.cols());
176
177    if(Expression::IsVectorAtCompileTime && (!PlainObjectType::IsVectorAtCompileTime) && ((Expression::Flags&RowMajorBit)!=(PlainObjectType::Flags&RowMajorBit)))
178      ::new (&m_stride) StrideBase(expr.innerStride(), StrideType::InnerStrideAtCompileTime==0?0:1);
179    else
180      ::new (&m_stride) StrideBase(StrideType::OuterStrideAtCompileTime==0?0:expr.outerStride(),
181                                   StrideType::InnerStrideAtCompileTime==0?0:expr.innerStride());
182  }
183
184  StrideBase m_stride;
185};
186
187
188template<typename PlainObjectType, int Options, typename StrideType> class Ref
189  : public RefBase<Ref<PlainObjectType, Options, StrideType> >
190{
191  private:
192    typedef internal::traits<Ref> Traits;
193    template<typename Derived>
194    inline Ref(const PlainObjectBase<Derived>& expr,
195               typename internal::enable_if<bool(Traits::template match<Derived>::MatchAtCompileTime),Derived>::type* = 0);
196  public:
197
198    typedef RefBase<Ref> Base;
199    EIGEN_DENSE_PUBLIC_INTERFACE(Ref)
200
201
202    #ifndef EIGEN_PARSED_BY_DOXYGEN
203    template<typename Derived>
204    inline Ref(PlainObjectBase<Derived>& expr,
205               typename internal::enable_if<bool(Traits::template match<Derived>::MatchAtCompileTime),Derived>::type* = 0)
206    {
207      EIGEN_STATIC_ASSERT(static_cast<bool>(Traits::template match<Derived>::MatchAtCompileTime), STORAGE_LAYOUT_DOES_NOT_MATCH);
208      Base::construct(expr.derived());
209    }
210    template<typename Derived>
211    inline Ref(const DenseBase<Derived>& expr,
212               typename internal::enable_if<bool(Traits::template match<Derived>::MatchAtCompileTime),Derived>::type* = 0)
213    #else
214    template<typename Derived>
215    inline Ref(DenseBase<Derived>& expr)
216    #endif
217    {
218      EIGEN_STATIC_ASSERT(static_cast<bool>(internal::is_lvalue<Derived>::value), THIS_EXPRESSION_IS_NOT_A_LVALUE__IT_IS_READ_ONLY);
219      EIGEN_STATIC_ASSERT(static_cast<bool>(Traits::template match<Derived>::MatchAtCompileTime), STORAGE_LAYOUT_DOES_NOT_MATCH);
220      enum { THIS_EXPRESSION_IS_NOT_A_LVALUE__IT_IS_READ_ONLY = Derived::ThisConstantIsPrivateInPlainObjectBase};
221      Base::construct(expr.const_cast_derived());
222    }
223
224    EIGEN_INHERIT_ASSIGNMENT_OPERATORS(Ref)
225
226};
227
228// this is the const ref version
229template<typename TPlainObjectType, int Options, typename StrideType> class Ref<const TPlainObjectType, Options, StrideType>
230  : public RefBase<Ref<const TPlainObjectType, Options, StrideType> >
231{
232    typedef internal::traits<Ref> Traits;
233  public:
234
235    typedef RefBase<Ref> Base;
236    EIGEN_DENSE_PUBLIC_INTERFACE(Ref)
237
238    template<typename Derived>
239    inline Ref(const DenseBase<Derived>& expr,
240               typename internal::enable_if<bool(Traits::template match<Derived>::ScalarTypeMatch),Derived>::type* = 0)
241    {
242//      std::cout << match_helper<Derived>::HasDirectAccess << "," << match_helper<Derived>::OuterStrideMatch << "," << match_helper<Derived>::InnerStrideMatch << "\n";
243//      std::cout << int(StrideType::OuterStrideAtCompileTime) << " - " << int(Derived::OuterStrideAtCompileTime) << "\n";
244//      std::cout << int(StrideType::InnerStrideAtCompileTime) << " - " << int(Derived::InnerStrideAtCompileTime) << "\n";
245      construct(expr.derived(), typename Traits::template match<Derived>::type());
246    }
247
248  protected:
249
250    template<typename Expression>
251    void construct(const Expression& expr,internal::true_type)
252    {
253      Base::construct(expr);
254    }
255
256    template<typename Expression>
257    void construct(const Expression& expr, internal::false_type)
258    {
259      m_object.lazyAssign(expr);
260      Base::construct(m_object);
261    }
262
263  protected:
264    TPlainObjectType m_object;
265};
266
267} // end namespace Eigen
268
269#endif // EIGEN_REF_H
270