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    if(PlainObjectType::RowsAtCompileTime==1)
99    {
100      eigen_assert(expr.rows()==1 || expr.cols()==1);
101      ::new (static_cast<Base*>(this)) Base(expr.data(), 1, expr.size());
102    }
103    else if(PlainObjectType::ColsAtCompileTime==1)
104    {
105      eigen_assert(expr.rows()==1 || expr.cols()==1);
106      ::new (static_cast<Base*>(this)) Base(expr.data(), expr.size(), 1);
107    }
108    else
109      ::new (static_cast<Base*>(this)) Base(expr.data(), expr.rows(), expr.cols());
110
111    if(Expression::IsVectorAtCompileTime && (!PlainObjectType::IsVectorAtCompileTime) && ((Expression::Flags&RowMajorBit)!=(PlainObjectType::Flags&RowMajorBit)))
112      ::new (&m_stride) StrideBase(expr.innerStride(), StrideType::InnerStrideAtCompileTime==0?0:1);
113    else
114      ::new (&m_stride) StrideBase(StrideType::OuterStrideAtCompileTime==0?0:expr.outerStride(),
115                                   StrideType::InnerStrideAtCompileTime==0?0:expr.innerStride());
116  }
117
118  StrideBase m_stride;
119};
120
121/** \class Ref
122  * \ingroup Core_Module
123  *
124  * \brief A matrix or vector expression mapping an existing expression
125  *
126  * \tparam PlainObjectType the equivalent matrix type of the mapped data
127  * \tparam Options specifies the pointer alignment in bytes. It can be: \c #Aligned128, , \c #Aligned64, \c #Aligned32, \c #Aligned16, \c #Aligned8 or \c #Unaligned.
128  *                 The default is \c #Unaligned.
129  * \tparam StrideType optionally specifies strides. By default, Ref implies a contiguous storage along the inner dimension (inner stride==1),
130  *                   but accepts a variable outer stride (leading dimension).
131  *                   This can be overridden by specifying strides.
132  *                   The type passed here must be a specialization of the Stride template, see examples below.
133  *
134  * This class provides a way to write non-template functions taking Eigen objects as parameters while limiting the number of copies.
135  * A Ref<> object can represent either a const expression or a l-value:
136  * \code
137  * // in-out argument:
138  * void foo1(Ref<VectorXf> x);
139  *
140  * // read-only const argument:
141  * void foo2(const Ref<const VectorXf>& x);
142  * \endcode
143  *
144  * In the in-out case, the input argument must satisfy the constraints of the actual Ref<> type, otherwise a compilation issue will be triggered.
145  * By default, a Ref<VectorXf> can reference any dense vector expression of float having a contiguous memory layout.
146  * Likewise, a Ref<MatrixXf> can reference any column-major dense matrix expression of float whose column's elements are contiguously stored with
147  * 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)
148  * can be greater than the number of rows.
149  *
150  * 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.
151  * Here are some examples:
152  * \code
153  * MatrixXf A;
154  * VectorXf a;
155  * foo1(a.head());             // OK
156  * foo1(A.col());              // OK
157  * foo1(A.row());              // Compilation error because here innerstride!=1
158  * foo2(A.row());              // Compilation error because A.row() is a 1xN object while foo2 is expecting a Nx1 object
159  * foo2(A.row().transpose());  // The row is copied into a contiguous temporary
160  * foo2(2*a);                  // The expression is evaluated into a temporary
161  * foo2(A.col().segment(2,4)); // No temporary
162  * \endcode
163  *
164  * The range of inputs that can be referenced without temporary can be enlarged using the last two template parameters.
165  * Here is an example accepting an innerstride!=1:
166  * \code
167  * // in-out argument:
168  * void foo3(Ref<VectorXf,0,InnerStride<> > x);
169  * foo3(A.row());              // OK
170  * \endcode
171  * 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
172  * expensive address computations even if the input is contiguously stored in memory. To overcome this issue, one might propose to overload internally calling a
173  * template function, e.g.:
174  * \code
175  * // in the .h:
176  * void foo(const Ref<MatrixXf>& A);
177  * void foo(const Ref<MatrixXf,0,Stride<> >& A);
178  *
179  * // in the .cpp:
180  * template<typename TypeOfA> void foo_impl(const TypeOfA& A) {
181  *     ... // crazy code goes here
182  * }
183  * void foo(const Ref<MatrixXf>& A) { foo_impl(A); }
184  * void foo(const Ref<MatrixXf,0,Stride<> >& A) { foo_impl(A); }
185  * \endcode
186  *
187  *
188  * \sa PlainObjectBase::Map(), \ref TopicStorageOrders
189  */
190template<typename PlainObjectType, int Options, typename StrideType> class Ref
191  : public RefBase<Ref<PlainObjectType, Options, StrideType> >
192{
193  private:
194    typedef internal::traits<Ref> Traits;
195    template<typename Derived>
196    EIGEN_DEVICE_FUNC inline Ref(const PlainObjectBase<Derived>& expr,
197                                 typename internal::enable_if<bool(Traits::template match<Derived>::MatchAtCompileTime),Derived>::type* = 0);
198  public:
199
200    typedef RefBase<Ref> Base;
201    EIGEN_DENSE_PUBLIC_INTERFACE(Ref)
202
203
204    #ifndef EIGEN_PARSED_BY_DOXYGEN
205    template<typename Derived>
206    EIGEN_DEVICE_FUNC inline Ref(PlainObjectBase<Derived>& expr,
207                                 typename internal::enable_if<bool(Traits::template match<Derived>::MatchAtCompileTime),Derived>::type* = 0)
208    {
209      EIGEN_STATIC_ASSERT(bool(Traits::template match<Derived>::MatchAtCompileTime), STORAGE_LAYOUT_DOES_NOT_MATCH);
210      Base::construct(expr.derived());
211    }
212    template<typename Derived>
213    EIGEN_DEVICE_FUNC inline Ref(const DenseBase<Derived>& expr,
214                                 typename internal::enable_if<bool(Traits::template match<Derived>::MatchAtCompileTime),Derived>::type* = 0)
215    #else
216    /** Implicit constructor from any dense expression */
217    template<typename Derived>
218    inline Ref(DenseBase<Derived>& expr)
219    #endif
220    {
221      EIGEN_STATIC_ASSERT(bool(internal::is_lvalue<Derived>::value), THIS_EXPRESSION_IS_NOT_A_LVALUE__IT_IS_READ_ONLY);
222      EIGEN_STATIC_ASSERT(bool(Traits::template match<Derived>::MatchAtCompileTime), STORAGE_LAYOUT_DOES_NOT_MATCH);
223      EIGEN_STATIC_ASSERT(!Derived::IsPlainObjectBase,THIS_EXPRESSION_IS_NOT_A_LVALUE__IT_IS_READ_ONLY);
224      Base::construct(expr.const_cast_derived());
225    }
226
227    EIGEN_INHERIT_ASSIGNMENT_OPERATORS(Ref)
228
229};
230
231// this is the const ref version
232template<typename TPlainObjectType, int Options, typename StrideType> class Ref<const TPlainObjectType, Options, StrideType>
233  : public RefBase<Ref<const TPlainObjectType, Options, StrideType> >
234{
235    typedef internal::traits<Ref> Traits;
236  public:
237
238    typedef RefBase<Ref> Base;
239    EIGEN_DENSE_PUBLIC_INTERFACE(Ref)
240
241    template<typename Derived>
242    EIGEN_DEVICE_FUNC inline Ref(const DenseBase<Derived>& expr,
243                                 typename internal::enable_if<bool(Traits::template match<Derived>::ScalarTypeMatch),Derived>::type* = 0)
244    {
245//      std::cout << match_helper<Derived>::HasDirectAccess << "," << match_helper<Derived>::OuterStrideMatch << "," << match_helper<Derived>::InnerStrideMatch << "\n";
246//      std::cout << int(StrideType::OuterStrideAtCompileTime) << " - " << int(Derived::OuterStrideAtCompileTime) << "\n";
247//      std::cout << int(StrideType::InnerStrideAtCompileTime) << " - " << int(Derived::InnerStrideAtCompileTime) << "\n";
248      construct(expr.derived(), typename Traits::template match<Derived>::type());
249    }
250
251    EIGEN_DEVICE_FUNC inline Ref(const Ref& other) : Base(other) {
252      // copy constructor shall not copy the m_object, to avoid unnecessary malloc and copy
253    }
254
255    template<typename OtherRef>
256    EIGEN_DEVICE_FUNC inline Ref(const RefBase<OtherRef>& other) {
257      construct(other.derived(), typename Traits::template match<OtherRef>::type());
258    }
259
260  protected:
261
262    template<typename Expression>
263    EIGEN_DEVICE_FUNC void construct(const Expression& expr,internal::true_type)
264    {
265      Base::construct(expr);
266    }
267
268    template<typename Expression>
269    EIGEN_DEVICE_FUNC void construct(const Expression& expr, internal::false_type)
270    {
271      internal::call_assignment_no_alias(m_object,expr,internal::assign_op<Scalar,Scalar>());
272      Base::construct(m_object);
273    }
274
275  protected:
276    TPlainObjectType m_object;
277};
278
279} // end namespace Eigen
280
281#endif // EIGEN_REF_H
282