Michael Ernst Peter / Eigen

src/Core/NoAlias.h@1:3b8049da21b8, 2019-09-24 (annotated)

Committer:
jsoh91
Date:
Tue Sep 24 00:18:23 2019 +0000
Revision:
1:3b8049da21b8
Parent:
0:13a5d365ba16 
ignore and revise some of error parts

Who changed what in which revision?

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ykuroda 0:13a5d365ba16 1 // This file is part of Eigen, a lightweight C++ template library
ykuroda 0:13a5d365ba16 2 // for linear algebra.
ykuroda 0:13a5d365ba16 3 //
ykuroda 0:13a5d365ba16 4 // Copyright (C) 2009 Gael Guennebaud <gael.guennebaud@inria.fr>
ykuroda 0:13a5d365ba16 5 //
ykuroda 0:13a5d365ba16 6 // This Source Code Form is subject to the terms of the Mozilla
ykuroda 0:13a5d365ba16 7 // Public License v. 2.0. If a copy of the MPL was not distributed
ykuroda 0:13a5d365ba16 8 // with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
ykuroda 0:13a5d365ba16 9
ykuroda 0:13a5d365ba16 10 #ifndef EIGEN_NOALIAS_H
ykuroda 0:13a5d365ba16 11 #define EIGEN_NOALIAS_H
ykuroda 0:13a5d365ba16 12
ykuroda 0:13a5d365ba16 13 namespace Eigen {
ykuroda 0:13a5d365ba16 14
ykuroda 0:13a5d365ba16 15 /** \class NoAlias
ykuroda 0:13a5d365ba16 16 * \ingroup Core_Module
ykuroda 0:13a5d365ba16 17 *
ykuroda 0:13a5d365ba16 18 * \brief Pseudo expression providing an operator = assuming no aliasing
ykuroda 0:13a5d365ba16 19 *
ykuroda 0:13a5d365ba16 20 * \param ExpressionType the type of the object on which to do the lazy assignment
ykuroda 0:13a5d365ba16 21 *
ykuroda 0:13a5d365ba16 22 * This class represents an expression with special assignment operators
ykuroda 0:13a5d365ba16 23 * assuming no aliasing between the target expression and the source expression.
ykuroda 0:13a5d365ba16 24 * More precisely it alloas to bypass the EvalBeforeAssignBit flag of the source expression.
ykuroda 0:13a5d365ba16 25 * It is the return type of MatrixBase::noalias()
ykuroda 0:13a5d365ba16 26 * and most of the time this is the only way it is used.
ykuroda 0:13a5d365ba16 27 *
ykuroda 0:13a5d365ba16 28 * \sa MatrixBase::noalias()
ykuroda 0:13a5d365ba16 29 */
ykuroda 0:13a5d365ba16 30 template<typename ExpressionType, template <typename> class StorageBase>
ykuroda 0:13a5d365ba16 31 class NoAlias
ykuroda 0:13a5d365ba16 32 {
ykuroda 0:13a5d365ba16 33 typedef typename ExpressionType::Scalar Scalar;
ykuroda 0:13a5d365ba16 34 public:
ykuroda 0:13a5d365ba16 35 NoAlias(ExpressionType& expression) : m_expression(expression) {}
ykuroda 0:13a5d365ba16 36
ykuroda 0:13a5d365ba16 37 /** Behaves like MatrixBase::lazyAssign(other)
ykuroda 0:13a5d365ba16 38 * \sa MatrixBase::lazyAssign() */
ykuroda 0:13a5d365ba16 39 template<typename OtherDerived>
ykuroda 0:13a5d365ba16 40 EIGEN_STRONG_INLINE ExpressionType& operator=(const StorageBase<OtherDerived>& other)
ykuroda 0:13a5d365ba16 41 { return internal::assign_selector<ExpressionType,OtherDerived,false>::run(m_expression,other.derived()); }
ykuroda 0:13a5d365ba16 42
ykuroda 0:13a5d365ba16 43 /** \sa MatrixBase::operator+= */
ykuroda 0:13a5d365ba16 44 template<typename OtherDerived>
ykuroda 0:13a5d365ba16 45 EIGEN_STRONG_INLINE ExpressionType& operator+=(const StorageBase<OtherDerived>& other)
ykuroda 0:13a5d365ba16 46 {
ykuroda 0:13a5d365ba16 47 typedef SelfCwiseBinaryOp<internal::scalar_sum_op<Scalar>, ExpressionType, OtherDerived> SelfAdder;
ykuroda 0:13a5d365ba16 48 SelfAdder tmp(m_expression);
ykuroda 0:13a5d365ba16 49 typedef typename internal::nested<OtherDerived>::type OtherDerivedNested;
ykuroda 0:13a5d365ba16 50 typedef typename internal::remove_all<OtherDerivedNested>::type _OtherDerivedNested;
ykuroda 0:13a5d365ba16 51 internal::assign_selector<SelfAdder,_OtherDerivedNested,false>::run(tmp,OtherDerivedNested(other.derived()));
ykuroda 0:13a5d365ba16 52 return m_expression;
ykuroda 0:13a5d365ba16 53 }
ykuroda 0:13a5d365ba16 54
ykuroda 0:13a5d365ba16 55 /** \sa MatrixBase::operator-= */
ykuroda 0:13a5d365ba16 56 template<typename OtherDerived>
ykuroda 0:13a5d365ba16 57 EIGEN_STRONG_INLINE ExpressionType& operator-=(const StorageBase<OtherDerived>& other)
ykuroda 0:13a5d365ba16 58 {
ykuroda 0:13a5d365ba16 59 typedef SelfCwiseBinaryOp<internal::scalar_difference_op<Scalar>, ExpressionType, OtherDerived> SelfAdder;
ykuroda 0:13a5d365ba16 60 SelfAdder tmp(m_expression);
ykuroda 0:13a5d365ba16 61 typedef typename internal::nested<OtherDerived>::type OtherDerivedNested;
ykuroda 0:13a5d365ba16 62 typedef typename internal::remove_all<OtherDerivedNested>::type _OtherDerivedNested;
ykuroda 0:13a5d365ba16 63 internal::assign_selector<SelfAdder,_OtherDerivedNested,false>::run(tmp,OtherDerivedNested(other.derived()));
ykuroda 0:13a5d365ba16 64 return m_expression;
ykuroda 0:13a5d365ba16 65 }
ykuroda 0:13a5d365ba16 66
ykuroda 0:13a5d365ba16 67 #ifndef EIGEN_PARSED_BY_DOXYGEN
ykuroda 0:13a5d365ba16 68 template<typename ProductDerived, typename Lhs, typename Rhs>
ykuroda 0:13a5d365ba16 69 EIGEN_STRONG_INLINE ExpressionType& operator+=(const ProductBase<ProductDerived, Lhs,Rhs>& other)
ykuroda 0:13a5d365ba16 70 { other.derived().addTo(m_expression); return m_expression; }
ykuroda 0:13a5d365ba16 71
ykuroda 0:13a5d365ba16 72 template<typename ProductDerived, typename Lhs, typename Rhs>
ykuroda 0:13a5d365ba16 73 EIGEN_STRONG_INLINE ExpressionType& operator-=(const ProductBase<ProductDerived, Lhs,Rhs>& other)
ykuroda 0:13a5d365ba16 74 { other.derived().subTo(m_expression); return m_expression; }
ykuroda 0:13a5d365ba16 75
ykuroda 0:13a5d365ba16 76 template<typename Lhs, typename Rhs, int NestingFlags>
ykuroda 0:13a5d365ba16 77 EIGEN_STRONG_INLINE ExpressionType& operator+=(const CoeffBasedProduct<Lhs,Rhs,NestingFlags>& other)
ykuroda 0:13a5d365ba16 78 { return m_expression.derived() += CoeffBasedProduct<Lhs,Rhs,NestByRefBit>(other.lhs(), other.rhs()); }
ykuroda 0:13a5d365ba16 79
ykuroda 0:13a5d365ba16 80 template<typename Lhs, typename Rhs, int NestingFlags>
ykuroda 0:13a5d365ba16 81 EIGEN_STRONG_INLINE ExpressionType& operator-=(const CoeffBasedProduct<Lhs,Rhs,NestingFlags>& other)
ykuroda 0:13a5d365ba16 82 { return m_expression.derived() -= CoeffBasedProduct<Lhs,Rhs,NestByRefBit>(other.lhs(), other.rhs()); }
ykuroda 0:13a5d365ba16 83
ykuroda 0:13a5d365ba16 84 template<typename OtherDerived>
ykuroda 0:13a5d365ba16 85 ExpressionType& operator=(const ReturnByValue<OtherDerived>& func)
ykuroda 0:13a5d365ba16 86 { return m_expression = func; }
ykuroda 0:13a5d365ba16 87 #endif
ykuroda 0:13a5d365ba16 88
ykuroda 0:13a5d365ba16 89 ExpressionType& expression() const
ykuroda 0:13a5d365ba16 90 {
ykuroda 0:13a5d365ba16 91 return m_expression;
ykuroda 0:13a5d365ba16 92 }
ykuroda 0:13a5d365ba16 93
ykuroda 0:13a5d365ba16 94 protected:
ykuroda 0:13a5d365ba16 95 ExpressionType& m_expression;
ykuroda 0:13a5d365ba16 96 };
ykuroda 0:13a5d365ba16 97
ykuroda 0:13a5d365ba16 98 /** \returns a pseudo expression of \c *this with an operator= assuming
ykuroda 0:13a5d365ba16 99 * no aliasing between \c *this and the source expression.
ykuroda 0:13a5d365ba16 100 *
ykuroda 0:13a5d365ba16 101 * More precisely, noalias() allows to bypass the EvalBeforeAssignBit flag.
ykuroda 0:13a5d365ba16 102 * Currently, even though several expressions may alias, only product
ykuroda 0:13a5d365ba16 103 * expressions have this flag. Therefore, noalias() is only usefull when
ykuroda 0:13a5d365ba16 104 * the source expression contains a matrix product.
ykuroda 0:13a5d365ba16 105 *
ykuroda 0:13a5d365ba16 106 * Here are some examples where noalias is usefull:
ykuroda 0:13a5d365ba16 107 * \code
ykuroda 0:13a5d365ba16 108 * D.noalias() = A * B;
ykuroda 0:13a5d365ba16 109 * D.noalias() += A.transpose() * B;
ykuroda 0:13a5d365ba16 110 * D.noalias() -= 2 * A * B.adjoint();
ykuroda 0:13a5d365ba16 111 * \endcode
ykuroda 0:13a5d365ba16 112 *
ykuroda 0:13a5d365ba16 113 * On the other hand the following example will lead to a \b wrong result:
ykuroda 0:13a5d365ba16 114 * \code
ykuroda 0:13a5d365ba16 115 * A.noalias() = A * B;
ykuroda 0:13a5d365ba16 116 * \endcode
ykuroda 0:13a5d365ba16 117 * because the result matrix A is also an operand of the matrix product. Therefore,
ykuroda 0:13a5d365ba16 118 * there is no alternative than evaluating A * B in a temporary, that is the default
ykuroda 0:13a5d365ba16 119 * behavior when you write:
ykuroda 0:13a5d365ba16 120 * \code
ykuroda 0:13a5d365ba16 121 * A = A * B;
ykuroda 0:13a5d365ba16 122 * \endcode
ykuroda 0:13a5d365ba16 123 *
ykuroda 0:13a5d365ba16 124 * \sa class NoAlias
ykuroda 0:13a5d365ba16 125 */
ykuroda 0:13a5d365ba16 126 template<typename Derived>
ykuroda 0:13a5d365ba16 127 NoAlias<Derived,MatrixBase> MatrixBase<Derived>::noalias()
ykuroda 0:13a5d365ba16 128 {
ykuroda 0:13a5d365ba16 129 return derived();
ykuroda 0:13a5d365ba16 130 }
ykuroda 0:13a5d365ba16 131
ykuroda 0:13a5d365ba16 132 } // end namespace Eigen
ykuroda 0:13a5d365ba16 133
ykuroda 0:13a5d365ba16 134 #endif // EIGEN_NOALIAS_H