1 | // This file is part of Eigen, a lightweight C++ template library |
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2 | // for linear algebra. |
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3 | // |
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4 | // Copyright (C) 2009 Gael Guennebaud <gael.guennebaud@inria.fr> |
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5 | // |
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6 | // This Source Code Form is subject to the terms of the Mozilla |
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7 | // Public License v. 2.0. If a copy of the MPL was not distributed |
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8 | // with this file, You can obtain one at http://mozilla.org/MPL/2.0/. |
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9 | |
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10 | #ifndef EIGEN_NOALIAS_H |
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11 | #define EIGEN_NOALIAS_H |
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12 | |
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13 | namespace Eigen { |
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14 | |
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15 | /** \class NoAlias |
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16 | * \ingroup Core_Module |
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17 | * |
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18 | * \brief Pseudo expression providing an operator = assuming no aliasing |
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19 | * |
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20 | * \param ExpressionType the type of the object on which to do the lazy assignment |
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21 | * |
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22 | * This class represents an expression with special assignment operators |
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23 | * assuming no aliasing between the target expression and the source expression. |
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24 | * More precisely it alloas to bypass the EvalBeforeAssignBit flag of the source expression. |
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25 | * It is the return type of MatrixBase::noalias() |
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26 | * and most of the time this is the only way it is used. |
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27 | * |
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28 | * \sa MatrixBase::noalias() |
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29 | */ |
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30 | template<typename ExpressionType, template <typename> class StorageBase> |
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31 | class NoAlias |
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32 | { |
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33 | typedef typename ExpressionType::Scalar Scalar; |
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34 | public: |
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35 | NoAlias(ExpressionType& expression) : m_expression(expression) {} |
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36 | |
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37 | /** Behaves like MatrixBase::lazyAssign(other) |
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38 | * \sa MatrixBase::lazyAssign() */ |
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39 | template<typename OtherDerived> |
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40 | EIGEN_STRONG_INLINE ExpressionType& operator=(const StorageBase<OtherDerived>& other) |
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41 | { return internal::assign_selector<ExpressionType,OtherDerived,false>::run(m_expression,other.derived()); } |
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42 | |
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43 | /** \sa MatrixBase::operator+= */ |
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44 | template<typename OtherDerived> |
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45 | EIGEN_STRONG_INLINE ExpressionType& operator+=(const StorageBase<OtherDerived>& other) |
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46 | { |
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47 | typedef SelfCwiseBinaryOp<internal::scalar_sum_op<Scalar>, ExpressionType, OtherDerived> SelfAdder; |
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48 | SelfAdder tmp(m_expression); |
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49 | typedef typename internal::nested<OtherDerived>::type OtherDerivedNested; |
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50 | typedef typename internal::remove_all<OtherDerivedNested>::type _OtherDerivedNested; |
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51 | internal::assign_selector<SelfAdder,_OtherDerivedNested,false>::run(tmp,OtherDerivedNested(other.derived())); |
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52 | return m_expression; |
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53 | } |
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54 | |
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55 | /** \sa MatrixBase::operator-= */ |
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56 | template<typename OtherDerived> |
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57 | EIGEN_STRONG_INLINE ExpressionType& operator-=(const StorageBase<OtherDerived>& other) |
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58 | { |
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59 | typedef SelfCwiseBinaryOp<internal::scalar_difference_op<Scalar>, ExpressionType, OtherDerived> SelfAdder; |
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60 | SelfAdder tmp(m_expression); |
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61 | typedef typename internal::nested<OtherDerived>::type OtherDerivedNested; |
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62 | typedef typename internal::remove_all<OtherDerivedNested>::type _OtherDerivedNested; |
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63 | internal::assign_selector<SelfAdder,_OtherDerivedNested,false>::run(tmp,OtherDerivedNested(other.derived())); |
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64 | return m_expression; |
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65 | } |
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66 | |
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67 | #ifndef EIGEN_PARSED_BY_DOXYGEN |
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68 | template<typename ProductDerived, typename Lhs, typename Rhs> |
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69 | EIGEN_STRONG_INLINE ExpressionType& operator+=(const ProductBase<ProductDerived, Lhs,Rhs>& other) |
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70 | { other.derived().addTo(m_expression); return m_expression; } |
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71 | |
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72 | template<typename ProductDerived, typename Lhs, typename Rhs> |
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73 | EIGEN_STRONG_INLINE ExpressionType& operator-=(const ProductBase<ProductDerived, Lhs,Rhs>& other) |
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74 | { other.derived().subTo(m_expression); return m_expression; } |
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75 | |
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76 | template<typename Lhs, typename Rhs, int NestingFlags> |
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77 | EIGEN_STRONG_INLINE ExpressionType& operator+=(const CoeffBasedProduct<Lhs,Rhs,NestingFlags>& other) |
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78 | { return m_expression.derived() += CoeffBasedProduct<Lhs,Rhs,NestByRefBit>(other.lhs(), other.rhs()); } |
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79 | |
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80 | template<typename Lhs, typename Rhs, int NestingFlags> |
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81 | EIGEN_STRONG_INLINE ExpressionType& operator-=(const CoeffBasedProduct<Lhs,Rhs,NestingFlags>& other) |
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82 | { return m_expression.derived() -= CoeffBasedProduct<Lhs,Rhs,NestByRefBit>(other.lhs(), other.rhs()); } |
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83 | #endif |
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84 | |
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85 | protected: |
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86 | ExpressionType& m_expression; |
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87 | }; |
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88 | |
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89 | /** \returns a pseudo expression of \c *this with an operator= assuming |
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90 | * no aliasing between \c *this and the source expression. |
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91 | * |
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92 | * More precisely, noalias() allows to bypass the EvalBeforeAssignBit flag. |
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93 | * Currently, even though several expressions may alias, only product |
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94 | * expressions have this flag. Therefore, noalias() is only usefull when |
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95 | * the source expression contains a matrix product. |
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96 | * |
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97 | * Here are some examples where noalias is usefull: |
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98 | * \code |
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99 | * D.noalias() = A * B; |
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100 | * D.noalias() += A.transpose() * B; |
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101 | * D.noalias() -= 2 * A * B.adjoint(); |
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102 | * \endcode |
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103 | * |
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104 | * On the other hand the following example will lead to a \b wrong result: |
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105 | * \code |
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106 | * A.noalias() = A * B; |
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107 | * \endcode |
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108 | * because the result matrix A is also an operand of the matrix product. Therefore, |
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109 | * there is no alternative than evaluating A * B in a temporary, that is the default |
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110 | * behavior when you write: |
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111 | * \code |
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112 | * A = A * B; |
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113 | * \endcode |
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114 | * |
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115 | * \sa class NoAlias |
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116 | */ |
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117 | template<typename Derived> |
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118 | NoAlias<Derived,MatrixBase> MatrixBase<Derived>::noalias() |
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119 | { |
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120 | return derived(); |
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121 | } |
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122 | |
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123 | } // end namespace Eigen |
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124 | |
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125 | #endif // EIGEN_NOALIAS_H |
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