diff options
author | Gael Guennebaud <g.gael@free.fr> | 2010-06-04 23:17:57 +0200 |
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committer | Gael Guennebaud <g.gael@free.fr> | 2010-06-04 23:17:57 +0200 |
commit | bfeba41174638c1a19df74436a1572b6f8a6da33 (patch) | |
tree | e1e9cc17785da905fe556bacb426a0533ca6e193 /Eigen/src/Core/Transpositions.h | |
parent | 1ff1bd69acc8f2d50348a57855c8ec35521590bd (diff) |
Add a Transpositions class to ease the representation and
manipulation of permutations as a sequence of transpositions.
Make LDLT use it.
Diffstat (limited to 'Eigen/src/Core/Transpositions.h')
-rw-r--r-- | Eigen/src/Core/Transpositions.h | 285 |
1 files changed, 285 insertions, 0 deletions
diff --git a/Eigen/src/Core/Transpositions.h b/Eigen/src/Core/Transpositions.h new file mode 100644 index 000000000..39cb24fd7 --- /dev/null +++ b/Eigen/src/Core/Transpositions.h @@ -0,0 +1,285 @@ +// This file is part of Eigen, a lightweight C++ template library +// for linear algebra. +// +// Copyright (C) 2010 Gael Guennebaud <g.gael@free.fr> +// +// Eigen is free software; you can redistribute it and/or +// modify it under the terms of the GNU Lesser General Public +// License as published by the Free Software Foundation; either +// version 3 of the License, or (at your option) any later version. +// +// Alternatively, you can redistribute it and/or +// modify it under the terms of the GNU General Public License as +// published by the Free Software Foundation; either version 2 of +// the License, or (at your option) any later version. +// +// Eigen is distributed in the hope that it will be useful, but WITHOUT ANY +// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS +// FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License or the +// GNU General Public License for more details. +// +// You should have received a copy of the GNU Lesser General Public +// License and a copy of the GNU General Public License along with +// Eigen. If not, see <http://www.gnu.org/licenses/>. + +#ifndef EIGEN_TRANSPOSITIONS_H +#define EIGEN_TRANSPOSITIONS_H + +/** \class Transpositions + * + * \brief Represents a sequence of transpositions (row/column interchange) + * + * \param SizeAtCompileTime the number of transpositions, or Dynamic + * \param MaxSizeAtCompileTime the maximum number of transpositions, or Dynamic. This optional parameter defaults to SizeAtCompileTime. Most of the time, you should not have to specify it. + * + * This class represents a permutation transformation as a sequence of \em n transpositions + * \f$[T_{n-1} \ldots T_{i} \ldots T_{0}]\f$. It is internally stored as a vector of integers \c indices. + * Each transposition \f$ T_{i} \f$ applied on the left of a matrix (\f$ T_{i} M\f$) interchanges + * the rows \c i and \c indices[i] of the matrix \c M. + * A transposition applied on the right (e.g., \f$ M T_{i}\f$) yields a column interchange. + * + * Compared to the class PermutationMatrix, such a sequence of transpositions is what is + * computed during a decomposition with pivoting, and it is faster when applying the permutation in-place. + * + * To apply a sequence of transpositions to a matrix, simply use the operator * as in the following example: + * \code + * Transpositions tr; + * MatrixXf mat; + * mat = tr * mat; + * \endcode + * In this example, we detect that the matrix appears on both side, and so the transpositions + * are applied in-place without any temporary or extra copy. + * + * \sa class PermutationMatrix + */ +template<int SizeAtCompileTime, int MaxSizeAtCompileTime = SizeAtCompileTime> class Transpositions; +template<typename TranspositionType, typename MatrixType, int Side, bool Transposed=false> struct ei_transposition_matrix_product_retval; + +template<int SizeAtCompileTime, int MaxSizeAtCompileTime> +class Transpositions +{ + public: + + typedef Matrix<DenseIndex, SizeAtCompileTime, 1, 0, MaxSizeAtCompileTime, 1> IndicesType; + typedef typename IndicesType::Index Index; + + inline Transpositions() {} + + /** Copy constructor. */ + template<int OtherSize, int OtherMaxSize> + inline Transpositions(const Transpositions<OtherSize, OtherMaxSize>& other) + : m_indices(other.indices()) {} + + #ifndef EIGEN_PARSED_BY_DOXYGEN + /** Standard copy constructor. Defined only to prevent a default copy constructor + * from hiding the other templated constructor */ + inline Transpositions(const Transpositions& other) : m_indices(other.indices()) {} + #endif + + /** Generic constructor from expression of the transposition indices. */ + template<typename Other> + explicit inline Transpositions(const MatrixBase<Other>& indices) : m_indices(indices) + {} + + /** Copies the \a other transpositions into \c *this */ + template<int OtherSize, int OtherMaxSize> + Transpositions& operator=(const Transpositions<OtherSize, OtherMaxSize>& other) + { + m_indices = other.indices(); + return *this; + } + + #ifndef EIGEN_PARSED_BY_DOXYGEN + /** This is a special case of the templated operator=. Its purpose is to + * prevent a default operator= from hiding the templated operator=. + */ + Transpositions& operator=(const Transpositions& other) + { + m_indices = other.m_indices; + return *this; + } + #endif + + /** Constructs an uninitialized permutation matrix of given size. + */ + inline Transpositions(Index size) : m_indices(size) + {} + + /** \returns the number of transpositions */ + inline Index size() const { return m_indices.size(); } + + inline const Index& coeff(Index i) const { return m_indices.coeff(i); } + inline Index& coeffRef(Index i) { return m_indices.coeffRef(i); } + inline const Index& operator()(Index i) const { return m_indices(i); } + inline Index& operator()(Index i) { return m_indices(i); } + + /** const version of indices(). */ + const IndicesType& indices() const { return m_indices; } + /** \returns a reference to the stored array representing the transpositions. */ + IndicesType& indices() { return m_indices; } + + /** Resizes to given size. */ + inline void resize(int size) + { + m_indices.resize(size); + } + + /** Sets \c *this to represents an identity transformation */ + void setIdentity() + { + for(int i = 0; i < m_indices.size(); ++i) + m_indices.coeffRef(i) = i; + } + + // FIXME: do we want such methods ? + // might be usefull when the target matrix expression is complex, e.g.: + // object.matrix().block(..,..,..,..) = trans * object.matrix().block(..,..,..,..); + /* + template<typename MatrixType> + void applyForwardToRows(MatrixType& mat) const + { + for(Index k=0 ; k<size() ; ++k) + if(m_indices(k)!=k) + mat.row(k).swap(mat.row(m_indices(k))); + } + + template<typename MatrixType> + void applyBackwardToRows(MatrixType& mat) const + { + for(Index k=size()-1 ; k>=0 ; --k) + if(m_indices(k)!=k) + mat.row(k).swap(mat.row(m_indices(k))); + } + */ + + /** \returns the inverse transformation */ + inline Transpose<Transpositions> inverse() const + { return *this; } + + /** \returns the tranpose transformation */ + inline Transpose<Transpositions> transpose() const + { return *this; } + +#ifndef EIGEN_PARSED_BY_DOXYGEN + template<int OtherSize, int OtherMaxSize> + Transpositions(const Transpose<Transpositions<OtherSize,OtherMaxSize> >& other) + : m_indices(other.size()) + { + Index n = size(); + Index j = size-1; + for(Index i=0; i<n;++i,--j) + m_indices.coeffRef(j) = other.nestedTranspositions().indices().coeff(i); + } +#endif + + protected: + + IndicesType m_indices; +}; + +/** \returns the \a matrix with the \a transpositions applied to the columns. + */ +template<typename Derived, int SizeAtCompileTime, int MaxSizeAtCompileTime> +inline const ei_transposition_matrix_product_retval<Transpositions<SizeAtCompileTime, MaxSizeAtCompileTime>, Derived, OnTheRight> +operator*(const MatrixBase<Derived>& matrix, + const Transpositions<SizeAtCompileTime, MaxSizeAtCompileTime> &transpositions) +{ + return ei_transposition_matrix_product_retval + <Transpositions<SizeAtCompileTime, MaxSizeAtCompileTime>, Derived, OnTheRight> + (transpositions, matrix.derived()); +} + +/** \returns the \a matrix with the \a transpositions applied to the rows. + */ +template<typename Derived, int SizeAtCompileTime, int MaxSizeAtCompileTime> +inline const ei_transposition_matrix_product_retval + <Transpositions<SizeAtCompileTime, MaxSizeAtCompileTime>, Derived, OnTheLeft> +operator*(const Transpositions<SizeAtCompileTime, MaxSizeAtCompileTime> &transpositions, + const MatrixBase<Derived>& matrix) +{ + return ei_transposition_matrix_product_retval + <Transpositions<SizeAtCompileTime, MaxSizeAtCompileTime>, Derived, OnTheLeft> + (transpositions, matrix.derived()); +} + +template<typename TranspositionType, typename MatrixType, int Side, bool Transposed> +struct ei_traits<ei_transposition_matrix_product_retval<TranspositionType, MatrixType, Side, Transposed> > +{ + typedef typename MatrixType::PlainObject ReturnType; +}; + +template<typename TranspositionType, typename MatrixType, int Side, bool Transposed> +struct ei_transposition_matrix_product_retval + : public ReturnByValue<ei_transposition_matrix_product_retval<TranspositionType, MatrixType, Side, Transposed> > +{ + typedef typename ei_cleantype<typename MatrixType::Nested>::type MatrixTypeNestedCleaned; + typedef typename TranspositionType::Index Index; + + ei_transposition_matrix_product_retval(const TranspositionType& tr, const MatrixType& matrix) + : m_transpositions(tr), m_matrix(matrix) + {} + + inline int rows() const { return m_matrix.rows(); } + inline int cols() const { return m_matrix.cols(); } + + template<typename Dest> inline void evalTo(Dest& dst) const + { + const int size = m_transpositions.size(); + Index j = 0; + + if(!(ei_is_same_type<MatrixTypeNestedCleaned,Dest>::ret && ei_extract_data(dst) == ei_extract_data(m_matrix))) + dst = m_matrix; + + for(int k=(Transposed?size-1:0) ; Transposed?k>=0:k<size ; Transposed?--k:++k) + if((j=m_transpositions.coeff(k))!=k) + { + if(Side==OnTheLeft) + dst.row(k).swap(dst.row(j)); + else if(Side==OnTheRight) + dst.col(k).swap(dst.col(j)); + } + } + + protected: + const TranspositionType& m_transpositions; + const typename MatrixType::Nested m_matrix; +}; + +/* Template partial specialization for transposed/inverse transpositions */ + +template<int SizeAtCompileTime, int MaxSizeAtCompileTime> +class Transpose<Transpositions<SizeAtCompileTime, MaxSizeAtCompileTime> > +{ + typedef Transpositions<SizeAtCompileTime, MaxSizeAtCompileTime> TranspositionType; + typedef typename TranspositionType::IndicesType IndicesType; + public: + + Transpose(const TranspositionType& t) : m_transpositions(t) {} + + inline int size() const { return m_transpositions.size(); } + + /** \returns the \a matrix with the inverse transpositions applied to the columns. + */ + template<typename Derived> friend + inline const ei_transposition_matrix_product_retval<TranspositionType, Derived, OnTheRight, true> + operator*(const MatrixBase<Derived>& matrix, const Transpose& trt) + { + return ei_transposition_matrix_product_retval<TranspositionType, Derived, OnTheRight, true>(trt.m_transpositions, matrix.derived()); + } + + /** \returns the \a matrix with the inverse transpositions applied to the rows. + */ + template<typename Derived> + inline const ei_transposition_matrix_product_retval<TranspositionType, Derived, OnTheLeft, true> + operator*(const MatrixBase<Derived>& matrix) const + { + return ei_transposition_matrix_product_retval<TranspositionType, Derived, OnTheLeft, true>(m_transpositions, matrix.derived()); + } + + const TranspositionType& nestedTranspositions() const { return m_transpositions; } + + protected: + const TranspositionType& m_transpositions; +}; + +#endif // EIGEN_TRANSPOSITIONS_H |