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+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// Copyright (C) 2010-2011 Gael Guennebaud <gael.guennebaud@inria.fr>
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef EIGEN_TRANSPOSITIONS_H
+#define EIGEN_TRANSPOSITIONS_H
+
+namespace Eigen {
+
+/** \class Transpositions
+ * \ingroup Core_Module
+ *
+ * \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
+ */
+
+namespace internal {
+template<typename TranspositionType, typename MatrixType, int Side, bool Transposed=false> struct transposition_matrix_product_retval;
+}
+
+template<typename Derived>
+class TranspositionsBase
+{
+ typedef internal::traits<Derived> Traits;
+
+ public:
+
+ typedef typename Traits::IndicesType IndicesType;
+ typedef typename IndicesType::Scalar Index;
+
+ Derived& derived() { return *static_cast<Derived*>(this); }
+ const Derived& derived() const { return *static_cast<const Derived*>(this); }
+
+ /** Copies the \a other transpositions into \c *this */
+ template<typename OtherDerived>
+ Derived& operator=(const TranspositionsBase<OtherDerived>& other)
+ {
+ indices() = other.indices();
+ return derived();
+ }
+
+ #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=.
+ */
+ Derived& operator=(const TranspositionsBase& other)
+ {
+ indices() = other.indices();
+ return derived();
+ }
+ #endif
+
+ /** \returns the number of transpositions */
+ inline Index size() const { return indices().size(); }
+
+ /** Direct access to the underlying index vector */
+ inline const Index& coeff(Index i) const { return indices().coeff(i); }
+ /** Direct access to the underlying index vector */
+ inline Index& coeffRef(Index i) { return indices().coeffRef(i); }
+ /** Direct access to the underlying index vector */
+ inline const Index& operator()(Index i) const { return indices()(i); }
+ /** Direct access to the underlying index vector */
+ inline Index& operator()(Index i) { return indices()(i); }
+ /** Direct access to the underlying index vector */
+ inline const Index& operator[](Index i) const { return indices()(i); }
+ /** Direct access to the underlying index vector */
+ inline Index& operator[](Index i) { return indices()(i); }
+
+ /** const version of indices(). */
+ const IndicesType& indices() const { return derived().indices(); }
+ /** \returns a reference to the stored array representing the transpositions. */
+ IndicesType& indices() { return derived().indices(); }
+
+ /** Resizes to given size. */
+ inline void resize(Index newSize)
+ {
+ indices().resize(newSize);
+ }
+
+ /** Sets \c *this to represents an identity transformation */
+ void setIdentity()
+ {
+ for(int i = 0; i < indices().size(); ++i)
+ 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<TranspositionsBase> inverse() const
+ { return Transpose<TranspositionsBase>(derived()); }
+
+ /** \returns the tranpose transformation */
+ inline Transpose<TranspositionsBase> transpose() const
+ { return Transpose<TranspositionsBase>(derived()); }
+
+ protected:
+};
+
+namespace internal {
+template<int SizeAtCompileTime, int MaxSizeAtCompileTime, typename IndexType>
+struct traits<Transpositions<SizeAtCompileTime,MaxSizeAtCompileTime,IndexType> >
+{
+ typedef IndexType Index;
+ typedef Matrix<Index, SizeAtCompileTime, 1, 0, MaxSizeAtCompileTime, 1> IndicesType;
+};
+}
+
+template<int SizeAtCompileTime, int MaxSizeAtCompileTime, typename IndexType>
+class Transpositions : public TranspositionsBase<Transpositions<SizeAtCompileTime,MaxSizeAtCompileTime,IndexType> >
+{
+ typedef internal::traits<Transpositions> Traits;
+ public:
+
+ typedef TranspositionsBase<Transpositions> Base;
+ typedef typename Traits::IndicesType IndicesType;
+ typedef typename IndicesType::Scalar Index;
+
+ inline Transpositions() {}
+
+ /** Copy constructor. */
+ template<typename OtherDerived>
+ inline Transpositions(const TranspositionsBase<OtherDerived>& 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>& a_indices) : m_indices(a_indices)
+ {}
+
+ /** Copies the \a other transpositions into \c *this */
+ template<typename OtherDerived>
+ Transpositions& operator=(const TranspositionsBase<OtherDerived>& other)
+ {
+ return Base::operator=(other);
+ }
+
+ #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)
+ {}
+
+ /** 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; }
+
+ protected:
+
+ IndicesType m_indices;
+};
+
+
+namespace internal {
+template<int SizeAtCompileTime, int MaxSizeAtCompileTime, typename IndexType, int _PacketAccess>
+struct traits<Map<Transpositions<SizeAtCompileTime,MaxSizeAtCompileTime,IndexType>,_PacketAccess> >
+{
+ typedef IndexType Index;
+ typedef Map<const Matrix<Index,SizeAtCompileTime,1,0,MaxSizeAtCompileTime,1>, _PacketAccess> IndicesType;
+};
+}
+
+template<int SizeAtCompileTime, int MaxSizeAtCompileTime, typename IndexType, int PacketAccess>
+class Map<Transpositions<SizeAtCompileTime,MaxSizeAtCompileTime,IndexType>,PacketAccess>
+ : public TranspositionsBase<Map<Transpositions<SizeAtCompileTime,MaxSizeAtCompileTime,IndexType>,PacketAccess> >
+{
+ typedef internal::traits<Map> Traits;
+ public:
+
+ typedef TranspositionsBase<Map> Base;
+ typedef typename Traits::IndicesType IndicesType;
+ typedef typename IndicesType::Scalar Index;
+
+ inline Map(const Index* indicesPtr)
+ : m_indices(indicesPtr)
+ {}
+
+ inline Map(const Index* indicesPtr, Index size)
+ : m_indices(indicesPtr,size)
+ {}
+
+ /** Copies the \a other transpositions into \c *this */
+ template<typename OtherDerived>
+ Map& operator=(const TranspositionsBase<OtherDerived>& other)
+ {
+ return Base::operator=(other);
+ }
+
+ #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=.
+ */
+ Map& operator=(const Map& other)
+ {
+ m_indices = other.m_indices;
+ return *this;
+ }
+ #endif
+
+ /** 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; }
+
+ protected:
+
+ IndicesType m_indices;
+};
+
+namespace internal {
+template<typename _IndicesType>
+struct traits<TranspositionsWrapper<_IndicesType> >
+{
+ typedef typename _IndicesType::Scalar Index;
+ typedef _IndicesType IndicesType;
+};
+}
+
+template<typename _IndicesType>
+class TranspositionsWrapper
+ : public TranspositionsBase<TranspositionsWrapper<_IndicesType> >
+{
+ typedef internal::traits<TranspositionsWrapper> Traits;
+ public:
+
+ typedef TranspositionsBase<TranspositionsWrapper> Base;
+ typedef typename Traits::IndicesType IndicesType;
+ typedef typename IndicesType::Scalar Index;
+
+ inline TranspositionsWrapper(IndicesType& a_indices)
+ : m_indices(a_indices)
+ {}
+
+ /** Copies the \a other transpositions into \c *this */
+ template<typename OtherDerived>
+ TranspositionsWrapper& operator=(const TranspositionsBase<OtherDerived>& other)
+ {
+ return Base::operator=(other);
+ }
+
+ #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=.
+ */
+ TranspositionsWrapper& operator=(const TranspositionsWrapper& other)
+ {
+ m_indices = other.m_indices;
+ return *this;
+ }
+ #endif
+
+ /** 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; }
+
+ protected:
+
+ const typename IndicesType::Nested m_indices;
+};
+
+/** \returns the \a matrix with the \a transpositions applied to the columns.
+ */
+template<typename Derived, typename TranspositionsDerived>
+inline const internal::transposition_matrix_product_retval<TranspositionsDerived, Derived, OnTheRight>
+operator*(const MatrixBase<Derived>& matrix,
+ const TranspositionsBase<TranspositionsDerived> &transpositions)
+{
+ return internal::transposition_matrix_product_retval
+ <TranspositionsDerived, Derived, OnTheRight>
+ (transpositions.derived(), matrix.derived());
+}
+
+/** \returns the \a matrix with the \a transpositions applied to the rows.
+ */
+template<typename Derived, typename TranspositionDerived>
+inline const internal::transposition_matrix_product_retval
+ <TranspositionDerived, Derived, OnTheLeft>
+operator*(const TranspositionsBase<TranspositionDerived> &transpositions,
+ const MatrixBase<Derived>& matrix)
+{
+ return internal::transposition_matrix_product_retval
+ <TranspositionDerived, Derived, OnTheLeft>
+ (transpositions.derived(), matrix.derived());
+}
+
+namespace internal {
+
+template<typename TranspositionType, typename MatrixType, int Side, bool Transposed>
+struct traits<transposition_matrix_product_retval<TranspositionType, MatrixType, Side, Transposed> >
+{
+ typedef typename MatrixType::PlainObject ReturnType;
+};
+
+template<typename TranspositionType, typename MatrixType, int Side, bool Transposed>
+struct transposition_matrix_product_retval
+ : public ReturnByValue<transposition_matrix_product_retval<TranspositionType, MatrixType, Side, Transposed> >
+{
+ typedef typename remove_all<typename MatrixType::Nested>::type MatrixTypeNestedCleaned;
+ typedef typename TranspositionType::Index Index;
+
+ transposition_matrix_product_retval(const TranspositionType& tr, const MatrixType& matrix)
+ : m_transpositions(tr), m_matrix(matrix)
+ {}
+
+ inline Index rows() const { return m_matrix.rows(); }
+ inline Index cols() const { return m_matrix.cols(); }
+
+ template<typename Dest> inline void evalTo(Dest& dst) const
+ {
+ const Index size = m_transpositions.size();
+ Index j = 0;
+
+ if(!(is_same<MatrixTypeNestedCleaned,Dest>::value && extract_data(dst) == extract_data(m_matrix)))
+ dst = m_matrix;
+
+ for(Index 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;
+ typename MatrixType::Nested m_matrix;
+};
+
+} // end namespace internal
+
+/* Template partial specialization for transposed/inverse transpositions */
+
+template<typename TranspositionsDerived>
+class Transpose<TranspositionsBase<TranspositionsDerived> >
+{
+ typedef TranspositionsDerived 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 internal::transposition_matrix_product_retval<TranspositionType, Derived, OnTheRight, true>
+ operator*(const MatrixBase<Derived>& matrix, const Transpose& trt)
+ {
+ return internal::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 internal::transposition_matrix_product_retval<TranspositionType, Derived, OnTheLeft, true>
+ operator*(const MatrixBase<Derived>& matrix) const
+ {
+ return internal::transposition_matrix_product_retval<TranspositionType, Derived, OnTheLeft, true>(m_transpositions, matrix.derived());
+ }
+
+ protected:
+ const TranspositionType& m_transpositions;
+};
+
+} // end namespace Eigen
+
+#endif // EIGEN_TRANSPOSITIONS_H