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      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 (at) 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 
     13 namespace Eigen {
     14 
     15 namespace internal {
     16 
     17 template<typename _PlainObjectType, int _Options, typename _StrideType>
     18 struct 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 
     53 template<typename Derived>
     54 struct traits<RefBase<Derived> > : public traits<Derived> {};
     55 
     56 }
     57 
     58 template<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 
     64 public:
     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 
     91 protected:
     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   */
    190 template<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
    232 template<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