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 |
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84 | template<typename OtherDerived>
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85 | ExpressionType& operator=(const ReturnByValue<OtherDerived>& func)
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86 | { return m_expression = func; }
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87 | #endif
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88 |
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89 | ExpressionType& expression() const
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90 | {
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91 | return m_expression;
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92 | }
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93 |
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94 | protected:
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95 | ExpressionType& m_expression;
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96 | };
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97 |
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98 | /** \returns a pseudo expression of \c *this with an operator= assuming
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99 | * no aliasing between \c *this and the source expression.
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100 | *
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101 | * More precisely, noalias() allows to bypass the EvalBeforeAssignBit flag.
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102 | * Currently, even though several expressions may alias, only product
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103 | * expressions have this flag. Therefore, noalias() is only usefull when
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104 | * the source expression contains a matrix product.
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105 | *
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106 | * Here are some examples where noalias is usefull:
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107 | * \code
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108 | * D.noalias() = A * B;
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109 | * D.noalias() += A.transpose() * B;
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110 | * D.noalias() -= 2 * A * B.adjoint();
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111 | * \endcode
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112 | *
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113 | * On the other hand the following example will lead to a \b wrong result:
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114 | * \code
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115 | * A.noalias() = A * B;
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116 | * \endcode
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117 | * because the result matrix A is also an operand of the matrix product. Therefore,
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118 | * there is no alternative than evaluating A * B in a temporary, that is the default
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119 | * behavior when you write:
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120 | * \code
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121 | * A = A * B;
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122 | * \endcode
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123 | *
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124 | * \sa class NoAlias
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125 | */
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126 | template<typename Derived>
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127 | NoAlias<Derived,MatrixBase> MatrixBase<Derived>::noalias()
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128 | {
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129 | return derived();
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130 | }
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131 |
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132 | } // end namespace Eigen
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133 |
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134 | #endif // EIGEN_NOALIAS_H
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