src/Core/Ref.h

0001 // This file is part of Eigen, a lightweight C++ template library
0002 // for linear algebra.
0003 //
0004 // Copyright (C) 2012 Gael Guennebaud <gael.guennebaud@inria.fr>
0005 //
0006 // This Source Code Form is subject to the terms of the Mozilla
0007 // Public License v. 2.0. If a copy of the MPL was not distributed
0008 // with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
0009
0010 #ifndef EIGEN_REF_H
0011 #define EIGEN_REF_H
0012
0013 namespace Eigen {
0014
0015 namespace internal {
0016
0017 template<typename _PlainObjectType, int _Options, typename _StrideType>
0018 struct traits<Ref<_PlainObjectType, _Options, _StrideType> >
0019   : public traits<Map<_PlainObjectType, _Options, _StrideType> >
0020 {
0021   typedef _PlainObjectType PlainObjectType;
0022   typedef _StrideType StrideType;
0023   enum {
0024     Options = _Options,
0025     Flags = traits<Map<_PlainObjectType, _Options, _StrideType> >::Flags | NestByRefBit,
0026     Alignment = traits<Map<_PlainObjectType, _Options, _StrideType> >::Alignment
0027   };
0028
0029   template<typename Derived> struct match {
0030     enum {
0031       IsVectorAtCompileTime = PlainObjectType::IsVectorAtCompileTime || Derived::IsVectorAtCompileTime,
0032       HasDirectAccess = internal::has_direct_access<Derived>::ret,
0033       StorageOrderMatch = IsVectorAtCompileTime || ((PlainObjectType::Flags&RowMajorBit)==(Derived::Flags&RowMajorBit)),
0034       InnerStrideMatch = int(StrideType::InnerStrideAtCompileTime)==int(Dynamic)
0035                       || int(StrideType::InnerStrideAtCompileTime)==int(Derived::InnerStrideAtCompileTime)
0036                       || (int(StrideType::InnerStrideAtCompileTime)==0 && int(Derived::InnerStrideAtCompileTime)==1),
0037       OuterStrideMatch = IsVectorAtCompileTime
0038                       || int(StrideType::OuterStrideAtCompileTime)==int(Dynamic) || int(StrideType::OuterStrideAtCompileTime)==int(Derived::OuterStrideAtCompileTime),
0039       // NOTE, this indirection of evaluator<Derived>::Alignment is needed
0040       // to workaround a very strange bug in MSVC related to the instantiation
0041       // of has_*ary_operator in evaluator<CwiseNullaryOp>.
0042       // This line is surprisingly very sensitive. For instance, simply adding parenthesis
0043       // as "DerivedAlignment = (int(evaluator<Derived>::Alignment))," will make MSVC fail...
0044       DerivedAlignment = int(evaluator<Derived>::Alignment),
0045       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
0046       ScalarTypeMatch = internal::is_same<typename PlainObjectType::Scalar, typename Derived::Scalar>::value,
0047       MatchAtCompileTime = HasDirectAccess && StorageOrderMatch && InnerStrideMatch && OuterStrideMatch && AlignmentMatch && ScalarTypeMatch
0048     };
0049     typedef typename internal::conditional<MatchAtCompileTime,internal::true_type,internal::false_type>::type type;
0050   };
0051
0052 };
0053
0054 template<typename Derived>
0055 struct traits<RefBase<Derived> > : public traits<Derived> {};
0056
0057 }
0058
0059 template<typename Derived> class RefBase
0060  : public MapBase<Derived>
0061 {
0062   typedef typename internal::traits<Derived>::PlainObjectType PlainObjectType;
0063   typedef typename internal::traits<Derived>::StrideType StrideType;
0064
0065 public:
0066
0067   typedef MapBase<Derived> Base;
0068   EIGEN_DENSE_PUBLIC_INTERFACE(RefBase)
0069
0070   EIGEN_DEVICE_FUNC EIGEN_CONSTEXPR inline Index innerStride() const
0071   {
0072     return StrideType::InnerStrideAtCompileTime != 0 ? m_stride.inner() : 1;
0073   }
0074
0075   EIGEN_DEVICE_FUNC EIGEN_CONSTEXPR inline Index outerStride() const
0076   {
0077     return StrideType::OuterStrideAtCompileTime != 0 ? m_stride.outer()
0078          : IsVectorAtCompileTime ? this->size()
0079          : int(Flags)&RowMajorBit ? this->cols()
0080          : this->rows();
0081   }
0082
0083   EIGEN_DEVICE_FUNC RefBase()
0084     : Base(0,RowsAtCompileTime==Dynamic?0:RowsAtCompileTime,ColsAtCompileTime==Dynamic?0:ColsAtCompileTime),
0085       // Stride<> does not allow default ctor for Dynamic strides, so let' initialize it with dummy values:
0086       m_stride(StrideType::OuterStrideAtCompileTime==Dynamic?0:StrideType::OuterStrideAtCompileTime,
0087                StrideType::InnerStrideAtCompileTime==Dynamic?0:StrideType::InnerStrideAtCompileTime)
0088   {}
0089
0090   EIGEN_INHERIT_ASSIGNMENT_OPERATORS(RefBase)
0091
0092 protected:
0093
0094   typedef Stride<StrideType::OuterStrideAtCompileTime,StrideType::InnerStrideAtCompileTime> StrideBase;
0095
0096   // Resolves inner stride if default 0.
0097   static EIGEN_DEVICE_FUNC EIGEN_CONSTEXPR Index resolveInnerStride(Index inner) {
0098     return inner == 0 ? 1 : inner;
0099   }
0100
0101   // Resolves outer stride if default 0.
0102   static EIGEN_DEVICE_FUNC EIGEN_CONSTEXPR Index resolveOuterStride(Index inner, Index outer, Index rows, Index cols, bool isVectorAtCompileTime, bool isRowMajor) {
0103     return outer == 0 ? isVectorAtCompileTime ? inner * rows * cols : isRowMajor ? inner * cols : inner * rows : outer;
0104   }
0105
0106   // Returns true if construction is valid, false if there is a stride mismatch,
0107   // and fails if there is a size mismatch.
0108   template<typename Expression>
0109   EIGEN_DEVICE_FUNC bool construct(Expression& expr)
0110   {
0111     // Check matrix sizes.  If this is a compile-time vector, we do allow
0112     // implicitly transposing.
0113     EIGEN_STATIC_ASSERT(
0114       EIGEN_PREDICATE_SAME_MATRIX_SIZE(PlainObjectType, Expression)
0115       // If it is a vector, the transpose sizes might match.
0116       || ( PlainObjectType::IsVectorAtCompileTime
0117             && ((int(PlainObjectType::RowsAtCompileTime)==Eigen::Dynamic
0118               || int(Expression::ColsAtCompileTime)==Eigen::Dynamic
0119               || int(PlainObjectType::RowsAtCompileTime)==int(Expression::ColsAtCompileTime))
0120             &&  (int(PlainObjectType::ColsAtCompileTime)==Eigen::Dynamic
0121               || int(Expression::RowsAtCompileTime)==Eigen::Dynamic
0122               || int(PlainObjectType::ColsAtCompileTime)==int(Expression::RowsAtCompileTime)))),
0123       YOU_MIXED_MATRICES_OF_DIFFERENT_SIZES
0124     )
0125
0126     // Determine runtime rows and columns.
0127     Index rows = expr.rows();
0128     Index cols = expr.cols();
0129     if(PlainObjectType::RowsAtCompileTime==1)
0130     {
0131       eigen_assert(expr.rows()==1 || expr.cols()==1);
0132       rows = 1;
0133       cols = expr.size();
0134     }
0135     else if(PlainObjectType::ColsAtCompileTime==1)
0136     {
0137       eigen_assert(expr.rows()==1 || expr.cols()==1);
0138       rows = expr.size();
0139       cols = 1;
0140     }
0141     // Verify that the sizes are valid.
0142     eigen_assert(
0143       (PlainObjectType::RowsAtCompileTime == Dynamic) || (PlainObjectType::RowsAtCompileTime == rows));
0144     eigen_assert(
0145       (PlainObjectType::ColsAtCompileTime == Dynamic) || (PlainObjectType::ColsAtCompileTime == cols));
0146
0147
0148     // If this is a vector, we might be transposing, which means that stride should swap.
0149     const bool transpose = PlainObjectType::IsVectorAtCompileTime && (rows != expr.rows());
0150     // If the storage format differs, we also need to swap the stride.
0151     const bool row_major = ((PlainObjectType::Flags)&RowMajorBit) != 0;
0152     const bool expr_row_major = (Expression::Flags&RowMajorBit) != 0;
0153     const bool storage_differs =  (row_major != expr_row_major);
0154
0155     const bool swap_stride = (transpose != storage_differs);
0156
0157     // Determine expr's actual strides, resolving any defaults if zero.
0158     const Index expr_inner_actual = resolveInnerStride(expr.innerStride());
0159     const Index expr_outer_actual = resolveOuterStride(expr_inner_actual,
0160                                                        expr.outerStride(),
0161                                                        expr.rows(),
0162                                                        expr.cols(),
0163                                                        Expression::IsVectorAtCompileTime != 0,
0164                                                        expr_row_major);
0165
0166     // If this is a column-major row vector or row-major column vector, the inner-stride
0167     // is arbitrary, so set it to either the compile-time inner stride or 1.
0168     const bool row_vector = (rows == 1);
0169     const bool col_vector = (cols == 1);
0170     const Index inner_stride =
0171         ( (!row_major && row_vector) || (row_major && col_vector) ) ?
0172             ( StrideType::InnerStrideAtCompileTime > 0 ? Index(StrideType::InnerStrideAtCompileTime) : 1)
0173             : swap_stride ? expr_outer_actual : expr_inner_actual;
0174
0175     // If this is a column-major column vector or row-major row vector, the outer-stride
0176     // is arbitrary, so set it to either the compile-time outer stride or vector size.
0177     const Index outer_stride =
0178       ( (!row_major && col_vector) || (row_major && row_vector) ) ?
0179           ( StrideType::OuterStrideAtCompileTime > 0 ? Index(StrideType::OuterStrideAtCompileTime) : rows * cols * inner_stride)
0180           : swap_stride ? expr_inner_actual : expr_outer_actual;
0181
0182     // Check if given inner/outer strides are compatible with compile-time strides.
0183     const bool inner_valid = (StrideType::InnerStrideAtCompileTime == Dynamic)
0184         || (resolveInnerStride(Index(StrideType::InnerStrideAtCompileTime)) == inner_stride);
0185     if (!inner_valid) {
0186       return false;
0187     }
0188
0189     const bool outer_valid = (StrideType::OuterStrideAtCompileTime == Dynamic)
0190         || (resolveOuterStride(
0191               inner_stride,
0192               Index(StrideType::OuterStrideAtCompileTime),
0193               rows, cols, PlainObjectType::IsVectorAtCompileTime != 0,
0194               row_major)
0195             == outer_stride);
0196     if (!outer_valid) {
0197       return false;
0198     }
0199
0200     ::new (static_cast<Base*>(this)) Base(expr.data(), rows, cols);
0201     ::new (&m_stride) StrideBase(
0202       (StrideType::OuterStrideAtCompileTime == 0) ? 0 : outer_stride,
0203       (StrideType::InnerStrideAtCompileTime == 0) ? 0 : inner_stride );
0204     return true;
0205   }
0206
0207   StrideBase m_stride;
0208 };
0209
0210 /** \class Ref
0211   * \ingroup Core_Module
0212   *
0213   * \brief A matrix or vector expression mapping an existing expression
0214   *
0215   * \tparam PlainObjectType the equivalent matrix type of the mapped data
0216   * \tparam Options specifies the pointer alignment in bytes. It can be: \c #Aligned128, , \c #Aligned64, \c #Aligned32, \c #Aligned16, \c #Aligned8 or \c #Unaligned.
0217   *                 The default is \c #Unaligned.
0218   * \tparam StrideType optionally specifies strides. By default, Ref implies a contiguous storage along the inner dimension (inner stride==1),
0219   *                   but accepts a variable outer stride (leading dimension).
0220   *                   This can be overridden by specifying strides.
0221   *                   The type passed here must be a specialization of the Stride template, see examples below.
0222   *
0223   * This class provides a way to write non-template functions taking Eigen objects as parameters while limiting the number of copies.
0224   * A Ref<> object can represent either a const expression or a l-value:
0225   * \code
0226   * // in-out argument:
0227   * void foo1(Ref<VectorXf> x);
0228   *
0229   * // read-only const argument:
0230   * void foo2(const Ref<const VectorXf>& x);
0231   * \endcode
0232   *
0233   * In the in-out case, the input argument must satisfy the constraints of the actual Ref<> type, otherwise a compilation issue will be triggered.
0234   * By default, a Ref<VectorXf> can reference any dense vector expression of float having a contiguous memory layout.
0235   * Likewise, a Ref<MatrixXf> can reference any column-major dense matrix expression of float whose column's elements are contiguously stored with
0236   * 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)
0237   * can be greater than the number of rows.
0238   *
0239   * 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.
0240   * Here are some examples:
0241   * \code
0242   * MatrixXf A;
0243   * VectorXf a;
0244   * foo1(a.head());             // OK
0245   * foo1(A.col());              // OK
0246   * foo1(A.row());              // Compilation error because here innerstride!=1
0247   * foo2(A.row());              // Compilation error because A.row() is a 1xN object while foo2 is expecting a Nx1 object
0248   * foo2(A.row().transpose());  // The row is copied into a contiguous temporary
0249   * foo2(2*a);                  // The expression is evaluated into a temporary
0250   * foo2(A.col().segment(2,4)); // No temporary
0251   * \endcode
0252   *
0253   * The range of inputs that can be referenced without temporary can be enlarged using the last two template parameters.
0254   * Here is an example accepting an innerstride!=1:
0255   * \code
0256   * // in-out argument:
0257   * void foo3(Ref<VectorXf,0,InnerStride<> > x);
0258   * foo3(A.row());              // OK
0259   * \endcode
0260   * 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
0261   * expensive address computations even if the input is contiguously stored in memory. To overcome this issue, one might propose to overload internally calling a
0262   * template function, e.g.:
0263   * \code
0264   * // in the .h:
0265   * void foo(const Ref<MatrixXf>& A);
0266   * void foo(const Ref<MatrixXf,0,Stride<> >& A);
0267   *
0268   * // in the .cpp:
0269   * template<typename TypeOfA> void foo_impl(const TypeOfA& A) {
0270   *     ... // crazy code goes here
0271   * }
0272   * void foo(const Ref<MatrixXf>& A) { foo_impl(A); }
0273   * void foo(const Ref<MatrixXf,0,Stride<> >& A) { foo_impl(A); }
0274   * \endcode
0275   *
0276   * See also the following stackoverflow questions for further references:
0277   *  - <a href="http://stackoverflow.com/questions/21132538/correct-usage-of-the-eigenref-class">Correct usage of the Eigen::Ref<> class</a>
0278   *
0279   * \sa PlainObjectBase::Map(), \ref TopicStorageOrders
0280   */
0281 template<typename PlainObjectType, int Options, typename StrideType> class Ref
0282   : public RefBase<Ref<PlainObjectType, Options, StrideType> >
0283 {
0284   private:
0285     typedef internal::traits<Ref> Traits;
0286     template<typename Derived>
0287     EIGEN_DEVICE_FUNC inline Ref(const PlainObjectBase<Derived>& expr,
0288                                  typename internal::enable_if<bool(Traits::template match<Derived>::MatchAtCompileTime),Derived>::type* = 0);
0289   public:
0290
0291     typedef RefBase<Ref> Base;
0292     EIGEN_DENSE_PUBLIC_INTERFACE(Ref)
0293
0294
0295     #ifndef EIGEN_PARSED_BY_DOXYGEN
0296     template<typename Derived>
0297     EIGEN_DEVICE_FUNC inline Ref(PlainObjectBase<Derived>& expr,
0298                                  typename internal::enable_if<bool(Traits::template match<Derived>::MatchAtCompileTime),Derived>::type* = 0)
0299     {
0300       EIGEN_STATIC_ASSERT(bool(Traits::template match<Derived>::MatchAtCompileTime), STORAGE_LAYOUT_DOES_NOT_MATCH);
0301       // Construction must pass since we will not create temprary storage in the non-const case.
0302       const bool success = Base::construct(expr.derived());
0303       EIGEN_UNUSED_VARIABLE(success)
0304       eigen_assert(success);
0305     }
0306     template<typename Derived>
0307     EIGEN_DEVICE_FUNC inline Ref(const DenseBase<Derived>& expr,
0308                                  typename internal::enable_if<bool(Traits::template match<Derived>::MatchAtCompileTime),Derived>::type* = 0)
0309     #else
0310     /** Implicit constructor from any dense expression */
0311     template<typename Derived>
0312     inline Ref(DenseBase<Derived>& expr)
0313     #endif
0314     {
0315       EIGEN_STATIC_ASSERT(bool(internal::is_lvalue<Derived>::value), THIS_EXPRESSION_IS_NOT_A_LVALUE__IT_IS_READ_ONLY);
0316       EIGEN_STATIC_ASSERT(bool(Traits::template match<Derived>::MatchAtCompileTime), STORAGE_LAYOUT_DOES_NOT_MATCH);
0317       EIGEN_STATIC_ASSERT(!Derived::IsPlainObjectBase,THIS_EXPRESSION_IS_NOT_A_LVALUE__IT_IS_READ_ONLY);
0318       // Construction must pass since we will not create temporary storage in the non-const case.
0319       const bool success = Base::construct(expr.const_cast_derived());
0320       EIGEN_UNUSED_VARIABLE(success)
0321       eigen_assert(success);
0322     }
0323
0324     EIGEN_INHERIT_ASSIGNMENT_OPERATORS(Ref)
0325
0326 };
0327
0328 // this is the const ref version
0329 template<typename TPlainObjectType, int Options, typename StrideType> class Ref<const TPlainObjectType, Options, StrideType>
0330   : public RefBase<Ref<const TPlainObjectType, Options, StrideType> >
0331 {
0332     typedef internal::traits<Ref> Traits;
0333   public:
0334
0335     typedef RefBase<Ref> Base;
0336     EIGEN_DENSE_PUBLIC_INTERFACE(Ref)
0337
0338     template<typename Derived>
0339     EIGEN_DEVICE_FUNC inline Ref(const DenseBase<Derived>& expr,
0340                                  typename internal::enable_if<bool(Traits::template match<Derived>::ScalarTypeMatch),Derived>::type* = 0)
0341     {
0342 //      std::cout << match_helper<Derived>::HasDirectAccess << "," << match_helper<Derived>::OuterStrideMatch << "," << match_helper<Derived>::InnerStrideMatch << "\n";
0343 //      std::cout << int(StrideType::OuterStrideAtCompileTime) << " - " << int(Derived::OuterStrideAtCompileTime) << "\n";
0344 //      std::cout << int(StrideType::InnerStrideAtCompileTime) << " - " << int(Derived::InnerStrideAtCompileTime) << "\n";
0345       construct(expr.derived(), typename Traits::template match<Derived>::type());
0346     }
0347
0348     EIGEN_DEVICE_FUNC inline Ref(const Ref& other) : Base(other) {
0349       // copy constructor shall not copy the m_object, to avoid unnecessary malloc and copy
0350     }
0351
0352     template<typename OtherRef>
0353     EIGEN_DEVICE_FUNC inline Ref(const RefBase<OtherRef>& other) {
0354       construct(other.derived(), typename Traits::template match<OtherRef>::type());
0355     }
0356
0357   protected:
0358
0359     template<typename Expression>
0360     EIGEN_DEVICE_FUNC void construct(const Expression& expr,internal::true_type)
0361     {
0362       // Check if we can use the underlying expr's storage directly, otherwise call the copy version.
0363       if (!Base::construct(expr)) {
0364         construct(expr, internal::false_type());
0365       }
0366     }
0367
0368     template<typename Expression>
0369     EIGEN_DEVICE_FUNC void construct(const Expression& expr, internal::false_type)
0370     {
0371       internal::call_assignment_no_alias(m_object,expr,internal::assign_op<Scalar,Scalar>());
0372       Base::construct(m_object);
0373     }
0374
0375   protected:
0376     TPlainObjectType m_object;
0377 };
0378
0379 } // end namespace Eigen
0380
0381 #endif // EIGEN_REF_H