| // This file is part of Eigen, a lightweight C++ template library | 
 | // for linear algebra. | 
 | // | 
 | // Copyright (C) 2012-2013 Desire Nuentsa <desire.nuentsa_wakam@inria.fr> | 
 | // Copyright (C) 2012-2014 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_SPARSE_QR_H | 
 | #define EIGEN_SPARSE_QR_H | 
 |  | 
 | #include "./InternalHeaderCheck.h" | 
 |  | 
 | namespace Eigen { | 
 |  | 
 | template<typename MatrixType, typename OrderingType> class SparseQR; | 
 | template<typename SparseQRType> struct SparseQRMatrixQReturnType; | 
 | template<typename SparseQRType> struct SparseQRMatrixQTransposeReturnType; | 
 | template<typename SparseQRType, typename Derived> struct SparseQR_QProduct; | 
 | namespace internal { | 
 |   template <typename SparseQRType> struct traits<SparseQRMatrixQReturnType<SparseQRType> > | 
 |   { | 
 |     typedef typename SparseQRType::MatrixType ReturnType; | 
 |     typedef typename ReturnType::StorageIndex StorageIndex; | 
 |     typedef typename ReturnType::StorageKind StorageKind; | 
 |     enum { | 
 |       RowsAtCompileTime = Dynamic, | 
 |       ColsAtCompileTime = Dynamic | 
 |     }; | 
 |   }; | 
 |   template <typename SparseQRType> struct traits<SparseQRMatrixQTransposeReturnType<SparseQRType> > | 
 |   { | 
 |     typedef typename SparseQRType::MatrixType ReturnType; | 
 |   }; | 
 |   template <typename SparseQRType, typename Derived> struct traits<SparseQR_QProduct<SparseQRType, Derived> > | 
 |   { | 
 |     typedef typename Derived::PlainObject ReturnType; | 
 |   }; | 
 | } // End namespace internal | 
 |  | 
 | /** | 
 |   * \ingroup SparseQR_Module | 
 |   * \class SparseQR | 
 |   * \brief Sparse left-looking QR factorization with numerical column pivoting | 
 |   *  | 
 |   * This class implements a left-looking QR decomposition of sparse matrices | 
 |   * with numerical column pivoting. | 
 |   * When a column has a norm less than a given tolerance | 
 |   * it is implicitly permuted to the end. The QR factorization thus obtained is  | 
 |   * given by A*P = Q*R where R is upper triangular or trapezoidal.  | 
 |   *  | 
 |   * P is the column permutation which is the product of the fill-reducing and the | 
 |   * numerical permutations. Use colsPermutation() to get it. | 
 |   *  | 
 |   * Q is the orthogonal matrix represented as products of Householder reflectors.  | 
 |   * Use matrixQ() to get an expression and matrixQ().adjoint() to get the adjoint. | 
 |   * You can then apply it to a vector. | 
 |   *  | 
 |   * R is the sparse triangular or trapezoidal matrix. The later occurs when A is rank-deficient. | 
 |   * matrixR().topLeftCorner(rank(), rank()) always returns a triangular factor of full rank. | 
 |   *  | 
 |   * \tparam MatrixType_ The type of the sparse matrix A, must be a column-major SparseMatrix<> | 
 |   * \tparam OrderingType_ The fill-reducing ordering method. See the \link OrderingMethods_Module | 
 |   *  OrderingMethods \endlink module for the list of built-in and external ordering methods. | 
 |   *  | 
 |   * \implsparsesolverconcept | 
 |   * | 
 |   * The numerical pivoting strategy and default threshold are the same as in SuiteSparse QR, and | 
 |   * detailed in the following paper: | 
 |   * <i> | 
 |   * Tim Davis, "Algorithm 915, SuiteSparseQR: Multifrontal Multithreaded Rank-Revealing | 
 |   * Sparse QR Factorization, ACM Trans. on Math. Soft. 38(1), 2011. | 
 |   * </i> | 
 |   * Even though it is qualified as "rank-revealing", this strategy might fail for some  | 
 |   * rank deficient problems. When this class is used to solve linear or least-square problems | 
 |   * it is thus strongly recommended to check the accuracy of the computed solution. If it | 
 |   * failed, it usually helps to increase the threshold with setPivotThreshold. | 
 |   *  | 
 |   * \warning The input sparse matrix A must be in compressed mode (see SparseMatrix::makeCompressed()). | 
 |   * \warning For complex matrices matrixQ().transpose() will actually return the adjoint matrix. | 
 |   *  | 
 |   */ | 
 | template<typename MatrixType_, typename OrderingType_> | 
 | class SparseQR : public SparseSolverBase<SparseQR<MatrixType_,OrderingType_> > | 
 | { | 
 |   protected: | 
 |     typedef SparseSolverBase<SparseQR<MatrixType_,OrderingType_> > Base; | 
 |     using Base::m_isInitialized; | 
 |   public: | 
 |     using Base::_solve_impl; | 
 |     typedef MatrixType_ MatrixType; | 
 |     typedef OrderingType_ OrderingType; | 
 |     typedef typename MatrixType::Scalar Scalar; | 
 |     typedef typename MatrixType::RealScalar RealScalar; | 
 |     typedef typename MatrixType::StorageIndex StorageIndex; | 
 |     typedef SparseMatrix<Scalar,ColMajor,StorageIndex> QRMatrixType; | 
 |     typedef Matrix<StorageIndex, Dynamic, 1> IndexVector; | 
 |     typedef Matrix<Scalar, Dynamic, 1> ScalarVector; | 
 |     typedef PermutationMatrix<Dynamic, Dynamic, StorageIndex> PermutationType; | 
 |  | 
 |     enum { | 
 |       ColsAtCompileTime = MatrixType::ColsAtCompileTime, | 
 |       MaxColsAtCompileTime = MatrixType::MaxColsAtCompileTime | 
 |     }; | 
 |      | 
 |   public: | 
 |     SparseQR () :  m_analysisIsok(false), m_lastError(""), m_useDefaultThreshold(true),m_isQSorted(false),m_isEtreeOk(false) | 
 |     { } | 
 |      | 
 |     /** Construct a QR factorization of the matrix \a mat. | 
 |       *  | 
 |       * \warning The matrix \a mat must be in compressed mode (see SparseMatrix::makeCompressed()). | 
 |       *  | 
 |       * \sa compute() | 
 |       */ | 
 |     explicit SparseQR(const MatrixType& mat) : m_analysisIsok(false), m_lastError(""), m_useDefaultThreshold(true),m_isQSorted(false),m_isEtreeOk(false) | 
 |     { | 
 |       compute(mat); | 
 |     } | 
 |      | 
 |     /** Computes the QR factorization of the sparse matrix \a mat. | 
 |       *  | 
 |       * \warning The matrix \a mat must be in compressed mode (see SparseMatrix::makeCompressed()). | 
 |       *  | 
 |       * \sa analyzePattern(), factorize() | 
 |       */ | 
 |     void compute(const MatrixType& mat) | 
 |     { | 
 |       analyzePattern(mat); | 
 |       factorize(mat); | 
 |     } | 
 |     void analyzePattern(const MatrixType& mat); | 
 |     void factorize(const MatrixType& mat); | 
 |      | 
 |     /** \returns the number of rows of the represented matrix.  | 
 |       */ | 
 |     inline Index rows() const { return m_pmat.rows(); } | 
 |      | 
 |     /** \returns the number of columns of the represented matrix.  | 
 |       */ | 
 |     inline Index cols() const { return m_pmat.cols();} | 
 |      | 
 |     /** \returns a const reference to the \b sparse upper triangular matrix R of the QR factorization. | 
 |       * \warning The entries of the returned matrix are not sorted. This means that using it in algorithms | 
 |       *          expecting sorted entries will fail. This include random coefficient accesses (SpaseMatrix::coeff()), | 
 |       *          and coefficient-wise operations. Matrix products and triangular solves are fine though. | 
 |       * | 
 |       * To sort the entries, you can assign it to a row-major matrix, and if a column-major matrix | 
 |       * is required, you can copy it again: | 
 |       * \code | 
 |       * SparseMatrix<double>          R  = qr.matrixR();  // column-major, not sorted! | 
 |       * SparseMatrix<double,RowMajor> Rr = qr.matrixR();  // row-major, sorted | 
 |       * SparseMatrix<double>          Rc = Rr;            // column-major, sorted | 
 |       * \endcode | 
 |       */ | 
 |     const QRMatrixType& matrixR() const { return m_R; } | 
 |      | 
 |     /** \returns the number of non linearly dependent columns as determined by the pivoting threshold. | 
 |       * | 
 |       * \sa setPivotThreshold() | 
 |       */ | 
 |     Index rank() const | 
 |     { | 
 |       eigen_assert(m_isInitialized && "The factorization should be called first, use compute()"); | 
 |       return m_nonzeropivots;  | 
 |     } | 
 |      | 
 |     /** \returns an expression of the matrix Q as products of sparse Householder reflectors. | 
 |     * The common usage of this function is to apply it to a dense matrix or vector | 
 |     * \code | 
 |     * VectorXd B1, B2; | 
 |     * // Initialize B1 | 
 |     * B2 = matrixQ() * B1; | 
 |     * \endcode | 
 |     * | 
 |     * To get a plain SparseMatrix representation of Q: | 
 |     * \code | 
 |     * SparseMatrix<double> Q; | 
 |     * Q = SparseQR<SparseMatrix<double> >(A).matrixQ(); | 
 |     * \endcode | 
 |     * Internally, this call simply performs a sparse product between the matrix Q | 
 |     * and a sparse identity matrix. However, due to the fact that the sparse | 
 |     * reflectors are stored unsorted, two transpositions are needed to sort | 
 |     * them before performing the product. | 
 |     */ | 
 |     SparseQRMatrixQReturnType<SparseQR> matrixQ() const  | 
 |     { return SparseQRMatrixQReturnType<SparseQR>(*this); } | 
 |      | 
 |     /** \returns a const reference to the column permutation P that was applied to A such that A*P = Q*R | 
 |       * It is the combination of the fill-in reducing permutation and numerical column pivoting. | 
 |       */ | 
 |     const PermutationType& colsPermutation() const | 
 |     {  | 
 |       eigen_assert(m_isInitialized && "Decomposition is not initialized."); | 
 |       return m_outputPerm_c; | 
 |     } | 
 |      | 
 |     /** \returns A string describing the type of error. | 
 |       * This method is provided to ease debugging, not to handle errors. | 
 |       */ | 
 |     std::string lastErrorMessage() const { return m_lastError; } | 
 |      | 
 |     /** \internal */ | 
 |     template<typename Rhs, typename Dest> | 
 |     bool _solve_impl(const MatrixBase<Rhs> &B, MatrixBase<Dest> &dest) const | 
 |     { | 
 |       eigen_assert(m_isInitialized && "The factorization should be called first, use compute()"); | 
 |       eigen_assert(this->rows() == B.rows() && "SparseQR::solve() : invalid number of rows in the right hand side matrix"); | 
 |  | 
 |       Index rank = this->rank(); | 
 |        | 
 |       // Compute Q^* * b; | 
 |       typename Dest::PlainObject y, b; | 
 |       y = this->matrixQ().adjoint() * B; | 
 |       b = y; | 
 |        | 
 |       // Solve with the triangular matrix R | 
 |       y.resize((std::max<Index>)(cols(),y.rows()),y.cols()); | 
 |       y.topRows(rank) = this->matrixR().topLeftCorner(rank, rank).template triangularView<Upper>().solve(b.topRows(rank)); | 
 |       y.bottomRows(y.rows()-rank).setZero(); | 
 |        | 
 |       // Apply the column permutation | 
 |       if (m_perm_c.size())  dest = colsPermutation() * y.topRows(cols()); | 
 |       else                  dest = y.topRows(cols()); | 
 |        | 
 |       m_info = Success; | 
 |       return true; | 
 |     } | 
 |  | 
 |     /** Sets the threshold that is used to determine linearly dependent columns during the factorization. | 
 |       * | 
 |       * In practice, if during the factorization the norm of the column that has to be eliminated is below | 
 |       * this threshold, then the entire column is treated as zero, and it is moved at the end. | 
 |       */ | 
 |     void setPivotThreshold(const RealScalar& threshold) | 
 |     { | 
 |       m_useDefaultThreshold = false; | 
 |       m_threshold = threshold; | 
 |     } | 
 |      | 
 |     /** \returns the solution X of \f$ A X = B \f$ using the current decomposition of A. | 
 |       * | 
 |       * \sa compute() | 
 |       */ | 
 |     template<typename Rhs> | 
 |     inline const Solve<SparseQR, Rhs> solve(const MatrixBase<Rhs>& B) const  | 
 |     { | 
 |       eigen_assert(m_isInitialized && "The factorization should be called first, use compute()"); | 
 |       eigen_assert(this->rows() == B.rows() && "SparseQR::solve() : invalid number of rows in the right hand side matrix"); | 
 |       return Solve<SparseQR, Rhs>(*this, B.derived()); | 
 |     } | 
 |     template<typename Rhs> | 
 |     inline const Solve<SparseQR, Rhs> solve(const SparseMatrixBase<Rhs>& B) const | 
 |     { | 
 |           eigen_assert(m_isInitialized && "The factorization should be called first, use compute()"); | 
 |           eigen_assert(this->rows() == B.rows() && "SparseQR::solve() : invalid number of rows in the right hand side matrix"); | 
 |           return Solve<SparseQR, Rhs>(*this, B.derived()); | 
 |     } | 
 |      | 
 |     /** \brief Reports whether previous computation was successful. | 
 |       * | 
 |       * \returns \c Success if computation was successful, | 
 |       *          \c NumericalIssue if the QR factorization reports a numerical problem | 
 |       *          \c InvalidInput if the input matrix is invalid | 
 |       * | 
 |       * \sa iparm()           | 
 |       */ | 
 |     ComputationInfo info() const | 
 |     { | 
 |       eigen_assert(m_isInitialized && "Decomposition is not initialized."); | 
 |       return m_info; | 
 |     } | 
 |  | 
 |  | 
 |     /** \internal */ | 
 |     inline void _sort_matrix_Q() | 
 |     { | 
 |       if(this->m_isQSorted) return; | 
 |       // The matrix Q is sorted during the transposition | 
 |       SparseMatrix<Scalar, RowMajor, Index> mQrm(this->m_Q); | 
 |       this->m_Q = mQrm; | 
 |       this->m_isQSorted = true; | 
 |     } | 
 |  | 
 |      | 
 |   protected: | 
 |     bool m_analysisIsok; | 
 |     bool m_factorizationIsok; | 
 |     mutable ComputationInfo m_info; | 
 |     std::string m_lastError; | 
 |     QRMatrixType m_pmat;            // Temporary matrix | 
 |     QRMatrixType m_R;               // The triangular factor matrix | 
 |     QRMatrixType m_Q;               // The orthogonal reflectors | 
 |     ScalarVector m_hcoeffs;         // The Householder coefficients | 
 |     PermutationType m_perm_c;       // Fill-reducing  Column  permutation | 
 |     PermutationType m_pivotperm;    // The permutation for rank revealing | 
 |     PermutationType m_outputPerm_c; // The final column permutation | 
 |     RealScalar m_threshold;         // Threshold to determine null Householder reflections | 
 |     bool m_useDefaultThreshold;     // Use default threshold | 
 |     Index m_nonzeropivots;          // Number of non zero pivots found | 
 |     IndexVector m_etree;            // Column elimination tree | 
 |     IndexVector m_firstRowElt;      // First element in each row | 
 |     bool m_isQSorted;               // whether Q is sorted or not | 
 |     bool m_isEtreeOk;               // whether the elimination tree match the initial input matrix | 
 |      | 
 |     template <typename, typename > friend struct SparseQR_QProduct; | 
 |      | 
 | }; | 
 |  | 
 | /** \brief Preprocessing step of a QR factorization  | 
 |   *  | 
 |   * \warning The matrix \a mat must be in compressed mode (see SparseMatrix::makeCompressed()). | 
 |   *  | 
 |   * In this step, the fill-reducing permutation is computed and applied to the columns of A | 
 |   * and the column elimination tree is computed as well. Only the sparsity pattern of \a mat is exploited. | 
 |   *  | 
 |   * \note In this step it is assumed that there is no empty row in the matrix \a mat. | 
 |   */ | 
 | template <typename MatrixType, typename OrderingType> | 
 | void SparseQR<MatrixType,OrderingType>::analyzePattern(const MatrixType& mat) | 
 | { | 
 |   eigen_assert(mat.isCompressed() && "SparseQR requires a sparse matrix in compressed mode. Call .makeCompressed() before passing it to SparseQR"); | 
 |   // Copy to a column major matrix if the input is rowmajor | 
 |   typename internal::conditional<MatrixType::IsRowMajor,QRMatrixType,const MatrixType&>::type matCpy(mat); | 
 |   // Compute the column fill reducing ordering | 
 |   OrderingType ord;  | 
 |   ord(matCpy, m_perm_c);  | 
 |   Index n = mat.cols(); | 
 |   Index m = mat.rows(); | 
 |   Index diagSize = (std::min)(m,n); | 
 |    | 
 |   if (!m_perm_c.size()) | 
 |   { | 
 |     m_perm_c.resize(n); | 
 |     m_perm_c.indices().setLinSpaced(n, 0,StorageIndex(n-1)); | 
 |   } | 
 |    | 
 |   // Compute the column elimination tree of the permuted matrix | 
 |   m_outputPerm_c = m_perm_c.inverse(); | 
 |   internal::coletree(matCpy, m_etree, m_firstRowElt, m_outputPerm_c.indices().data()); | 
 |   m_isEtreeOk = true; | 
 |    | 
 |   m_R.resize(m, n); | 
 |   m_Q.resize(m, diagSize); | 
 |    | 
 |   // Allocate space for nonzero elements: rough estimation | 
 |   m_R.reserve(2*mat.nonZeros()); //FIXME Get a more accurate estimation through symbolic factorization with the etree | 
 |   m_Q.reserve(2*mat.nonZeros()); | 
 |   m_hcoeffs.resize(diagSize); | 
 |   m_analysisIsok = true; | 
 | } | 
 |  | 
 | /** \brief Performs the numerical QR factorization of the input matrix | 
 |   *  | 
 |   * The function SparseQR::analyzePattern(const MatrixType&) must have been called beforehand with | 
 |   * a matrix having the same sparsity pattern than \a mat. | 
 |   *  | 
 |   * \param mat The sparse column-major matrix | 
 |   */ | 
 | template <typename MatrixType, typename OrderingType> | 
 | void SparseQR<MatrixType,OrderingType>::factorize(const MatrixType& mat) | 
 | { | 
 |   using std::abs; | 
 |    | 
 |   eigen_assert(m_analysisIsok && "analyzePattern() should be called before this step"); | 
 |   StorageIndex m = StorageIndex(mat.rows()); | 
 |   StorageIndex n = StorageIndex(mat.cols()); | 
 |   StorageIndex diagSize = (std::min)(m,n); | 
 |   IndexVector mark((std::max)(m,n)); mark.setConstant(-1);  // Record the visited nodes | 
 |   IndexVector Ridx(n), Qidx(m);                             // Store temporarily the row indexes for the current column of R and Q | 
 |   Index nzcolR, nzcolQ;                                     // Number of nonzero for the current column of R and Q | 
 |   ScalarVector tval(m);                                     // The dense vector used to compute the current column | 
 |   RealScalar pivotThreshold = m_threshold; | 
 |    | 
 |   m_R.setZero(); | 
 |   m_Q.setZero(); | 
 |   m_pmat = mat; | 
 |   if(!m_isEtreeOk) | 
 |   { | 
 |     m_outputPerm_c = m_perm_c.inverse(); | 
 |     internal::coletree(m_pmat, m_etree, m_firstRowElt, m_outputPerm_c.indices().data()); | 
 |     m_isEtreeOk = true; | 
 |   } | 
 |  | 
 |   m_pmat.uncompress(); // To have the innerNonZeroPtr allocated | 
 |    | 
 |   // Apply the fill-in reducing permutation lazily: | 
 |   { | 
 |     // If the input is row major, copy the original column indices, | 
 |     // otherwise directly use the input matrix | 
 |     //  | 
 |     IndexVector originalOuterIndicesCpy; | 
 |     const StorageIndex *originalOuterIndices = mat.outerIndexPtr(); | 
 |     if(MatrixType::IsRowMajor) | 
 |     { | 
 |       originalOuterIndicesCpy = IndexVector::Map(m_pmat.outerIndexPtr(),n+1); | 
 |       originalOuterIndices = originalOuterIndicesCpy.data(); | 
 |     } | 
 |      | 
 |     for (int i = 0; i < n; i++) | 
 |     { | 
 |       Index p = m_perm_c.size() ? m_perm_c.indices()(i) : i; | 
 |       m_pmat.outerIndexPtr()[p] = originalOuterIndices[i];  | 
 |       m_pmat.innerNonZeroPtr()[p] = originalOuterIndices[i+1] - originalOuterIndices[i];  | 
 |     } | 
 |   } | 
 |    | 
 |   /* Compute the default threshold as in MatLab, see: | 
 |    * Tim Davis, "Algorithm 915, SuiteSparseQR: Multifrontal Multithreaded Rank-Revealing | 
 |    * Sparse QR Factorization, ACM Trans. on Math. Soft. 38(1), 2011, Page 8:3  | 
 |    */ | 
 |   if(m_useDefaultThreshold)  | 
 |   { | 
 |     RealScalar max2Norm = 0.0; | 
 |     for (int j = 0; j < n; j++) max2Norm = numext::maxi(max2Norm, m_pmat.col(j).norm()); | 
 |     if(max2Norm==RealScalar(0)) | 
 |       max2Norm = RealScalar(1); | 
 |     pivotThreshold = 20 * (m + n) * max2Norm * NumTraits<RealScalar>::epsilon(); | 
 |   } | 
 |    | 
 |   // Initialize the numerical permutation | 
 |   m_pivotperm.setIdentity(n); | 
 |    | 
 |   StorageIndex nonzeroCol = 0; // Record the number of valid pivots | 
 |   m_Q.startVec(0); | 
 |  | 
 |   // Left looking rank-revealing QR factorization: compute a column of R and Q at a time | 
 |   for (StorageIndex col = 0; col < n; ++col) | 
 |   { | 
 |     mark.setConstant(-1); | 
 |     m_R.startVec(col); | 
 |     mark(nonzeroCol) = col; | 
 |     Qidx(0) = nonzeroCol; | 
 |     nzcolR = 0; nzcolQ = 1; | 
 |     bool found_diag = nonzeroCol>=m; | 
 |     tval.setZero();  | 
 |      | 
 |     // Symbolic factorization: find the nonzero locations of the column k of the factors R and Q, i.e., | 
 |     // all the nodes (with indexes lower than rank) reachable through the column elimination tree (etree) rooted at node k. | 
 |     // Note: if the diagonal entry does not exist, then its contribution must be explicitly added, | 
 |     // thus the trick with found_diag that permits to do one more iteration on the diagonal element if this one has not been found. | 
 |     for (typename QRMatrixType::InnerIterator itp(m_pmat, col); itp || !found_diag; ++itp) | 
 |     { | 
 |       StorageIndex curIdx = nonzeroCol; | 
 |       if(itp) curIdx = StorageIndex(itp.row()); | 
 |       if(curIdx == nonzeroCol) found_diag = true; | 
 |        | 
 |       // Get the nonzeros indexes of the current column of R | 
 |       StorageIndex st = m_firstRowElt(curIdx); // The traversal of the etree starts here | 
 |       if (st < 0 ) | 
 |       { | 
 |         m_lastError = "Empty row found during numerical factorization"; | 
 |         m_info = InvalidInput; | 
 |         return; | 
 |       } | 
 |  | 
 |       // Traverse the etree  | 
 |       Index bi = nzcolR; | 
 |       for (; mark(st) != col; st = m_etree(st)) | 
 |       { | 
 |         Ridx(nzcolR) = st;  // Add this row to the list, | 
 |         mark(st) = col;     // and mark this row as visited | 
 |         nzcolR++; | 
 |       } | 
 |  | 
 |       // Reverse the list to get the topological ordering | 
 |       Index nt = nzcolR-bi; | 
 |       for(Index i = 0; i < nt/2; i++) std::swap(Ridx(bi+i), Ridx(nzcolR-i-1)); | 
 |         | 
 |       // Copy the current (curIdx,pcol) value of the input matrix | 
 |       if(itp) tval(curIdx) = itp.value(); | 
 |       else    tval(curIdx) = Scalar(0); | 
 |        | 
 |       // Compute the pattern of Q(:,k) | 
 |       if(curIdx > nonzeroCol && mark(curIdx) != col )  | 
 |       { | 
 |         Qidx(nzcolQ) = curIdx;  // Add this row to the pattern of Q, | 
 |         mark(curIdx) = col;     // and mark it as visited | 
 |         nzcolQ++; | 
 |       } | 
 |     } | 
 |  | 
 |     // Browse all the indexes of R(:,col) in reverse order | 
 |     for (Index i = nzcolR-1; i >= 0; i--) | 
 |     { | 
 |       Index curIdx = Ridx(i); | 
 |        | 
 |       // Apply the curIdx-th householder vector to the current column (temporarily stored into tval) | 
 |       Scalar tdot(0); | 
 |        | 
 |       // First compute q' * tval | 
 |       tdot = m_Q.col(curIdx).dot(tval); | 
 |  | 
 |       tdot *= m_hcoeffs(curIdx); | 
 |        | 
 |       // Then update tval = tval - q * tau | 
 |       // FIXME: tval -= tdot * m_Q.col(curIdx) should amount to the same (need to check/add support for efficient "dense ?= sparse") | 
 |       for (typename QRMatrixType::InnerIterator itq(m_Q, curIdx); itq; ++itq) | 
 |         tval(itq.row()) -= itq.value() * tdot; | 
 |  | 
 |       // Detect fill-in for the current column of Q | 
 |       if(m_etree(Ridx(i)) == nonzeroCol) | 
 |       { | 
 |         for (typename QRMatrixType::InnerIterator itq(m_Q, curIdx); itq; ++itq) | 
 |         { | 
 |           StorageIndex iQ = StorageIndex(itq.row()); | 
 |           if (mark(iQ) != col) | 
 |           { | 
 |             Qidx(nzcolQ++) = iQ;  // Add this row to the pattern of Q, | 
 |             mark(iQ) = col;       // and mark it as visited | 
 |           } | 
 |         } | 
 |       } | 
 |     } // End update current column | 
 |      | 
 |     Scalar tau = RealScalar(0); | 
 |     RealScalar beta = 0; | 
 |      | 
 |     if(nonzeroCol < diagSize) | 
 |     { | 
 |       // Compute the Householder reflection that eliminate the current column | 
 |       // FIXME this step should call the Householder module. | 
 |       Scalar c0 = nzcolQ ? tval(Qidx(0)) : Scalar(0); | 
 |        | 
 |       // First, the squared norm of Q((col+1):m, col) | 
 |       RealScalar sqrNorm = 0.; | 
 |       for (Index itq = 1; itq < nzcolQ; ++itq) sqrNorm += numext::abs2(tval(Qidx(itq))); | 
 |       if(sqrNorm == RealScalar(0) && numext::imag(c0) == RealScalar(0)) | 
 |       { | 
 |         beta = numext::real(c0); | 
 |         tval(Qidx(0)) = 1; | 
 |       } | 
 |       else | 
 |       { | 
 |         using std::sqrt; | 
 |         beta = sqrt(numext::abs2(c0) + sqrNorm); | 
 |         if(numext::real(c0) >= RealScalar(0)) | 
 |           beta = -beta; | 
 |         tval(Qidx(0)) = 1; | 
 |         for (Index itq = 1; itq < nzcolQ; ++itq) | 
 |           tval(Qidx(itq)) /= (c0 - beta); | 
 |         tau = numext::conj((beta-c0) / beta); | 
 |            | 
 |       } | 
 |     } | 
 |  | 
 |     // Insert values in R | 
 |     for (Index  i = nzcolR-1; i >= 0; i--) | 
 |     { | 
 |       Index curIdx = Ridx(i); | 
 |       if(curIdx < nonzeroCol)  | 
 |       { | 
 |         m_R.insertBackByOuterInnerUnordered(col, curIdx) = tval(curIdx); | 
 |         tval(curIdx) = Scalar(0.); | 
 |       } | 
 |     } | 
 |  | 
 |     if(nonzeroCol < diagSize && abs(beta) >= pivotThreshold) | 
 |     { | 
 |       m_R.insertBackByOuterInner(col, nonzeroCol) = beta; | 
 |       // The householder coefficient | 
 |       m_hcoeffs(nonzeroCol) = tau; | 
 |       // Record the householder reflections | 
 |       for (Index itq = 0; itq < nzcolQ; ++itq) | 
 |       { | 
 |         Index iQ = Qidx(itq); | 
 |         m_Q.insertBackByOuterInnerUnordered(nonzeroCol,iQ) = tval(iQ); | 
 |         tval(iQ) = Scalar(0.); | 
 |       } | 
 |       nonzeroCol++; | 
 |       if(nonzeroCol<diagSize) | 
 |         m_Q.startVec(nonzeroCol); | 
 |     } | 
 |     else | 
 |     { | 
 |       // Zero pivot found: move implicitly this column to the end | 
 |       for (Index j = nonzeroCol; j < n-1; j++)  | 
 |         std::swap(m_pivotperm.indices()(j), m_pivotperm.indices()[j+1]); | 
 |        | 
 |       // Recompute the column elimination tree | 
 |       internal::coletree(m_pmat, m_etree, m_firstRowElt, m_pivotperm.indices().data()); | 
 |       m_isEtreeOk = false; | 
 |     } | 
 |   } | 
 |    | 
 |   m_hcoeffs.tail(diagSize-nonzeroCol).setZero(); | 
 |    | 
 |   // Finalize the column pointers of the sparse matrices R and Q | 
 |   m_Q.finalize(); | 
 |   m_Q.makeCompressed(); | 
 |   m_R.finalize(); | 
 |   m_R.makeCompressed(); | 
 |   m_isQSorted = false; | 
 |  | 
 |   m_nonzeropivots = nonzeroCol; | 
 |    | 
 |   if(nonzeroCol<n) | 
 |   { | 
 |     // Permute the triangular factor to put the 'dead' columns to the end | 
 |     QRMatrixType tempR(m_R); | 
 |     m_R = tempR * m_pivotperm; | 
 |      | 
 |     // Update the column permutation | 
 |     m_outputPerm_c = m_outputPerm_c * m_pivotperm; | 
 |   } | 
 |    | 
 |   m_isInitialized = true;  | 
 |   m_factorizationIsok = true; | 
 |   m_info = Success; | 
 | } | 
 |  | 
 | template <typename SparseQRType, typename Derived> | 
 | struct SparseQR_QProduct : ReturnByValue<SparseQR_QProduct<SparseQRType, Derived> > | 
 | { | 
 |   typedef typename SparseQRType::QRMatrixType MatrixType; | 
 |   typedef typename SparseQRType::Scalar Scalar; | 
 |   // Get the references  | 
 |   SparseQR_QProduct(const SparseQRType& qr, const Derived& other, bool transpose) :  | 
 |   m_qr(qr),m_other(other),m_transpose(transpose) {} | 
 |   inline Index rows() const { return m_qr.matrixQ().rows(); } | 
 |   inline Index cols() const { return m_other.cols(); } | 
 |    | 
 |   // Assign to a vector | 
 |   template<typename DesType> | 
 |   void evalTo(DesType& res) const | 
 |   { | 
 |     Index m = m_qr.rows(); | 
 |     Index n = m_qr.cols(); | 
 |     Index diagSize = (std::min)(m,n); | 
 |     res = m_other; | 
 |     if (m_transpose) | 
 |     { | 
 |       eigen_assert(m_qr.m_Q.rows() == m_other.rows() && "Non conforming object sizes"); | 
 |       //Compute res = Q' * other column by column | 
 |       for(Index j = 0; j < res.cols(); j++){ | 
 |         for (Index k = 0; k < diagSize; k++) | 
 |         { | 
 |           Scalar tau = Scalar(0); | 
 |           tau = m_qr.m_Q.col(k).dot(res.col(j)); | 
 |           if(tau==Scalar(0)) continue; | 
 |           tau = tau * m_qr.m_hcoeffs(k); | 
 |           res.col(j) -= tau * m_qr.m_Q.col(k); | 
 |         } | 
 |       } | 
 |     } | 
 |     else | 
 |     { | 
 |       eigen_assert(m_qr.matrixQ().cols() == m_other.rows() && "Non conforming object sizes"); | 
 |  | 
 |       res.conservativeResize(rows(), cols()); | 
 |  | 
 |       // Compute res = Q * other column by column | 
 |       for(Index j = 0; j < res.cols(); j++) | 
 |       { | 
 |         Index start_k = internal::is_identity<Derived>::value ? numext::mini(j,diagSize-1) : diagSize-1; | 
 |         for (Index k = start_k; k >=0; k--) | 
 |         { | 
 |           Scalar tau = Scalar(0); | 
 |           tau = m_qr.m_Q.col(k).dot(res.col(j)); | 
 |           if(tau==Scalar(0)) continue; | 
 |           tau = tau * numext::conj(m_qr.m_hcoeffs(k)); | 
 |           res.col(j) -= tau * m_qr.m_Q.col(k); | 
 |         } | 
 |       } | 
 |     } | 
 |   } | 
 |    | 
 |   const SparseQRType& m_qr; | 
 |   const Derived& m_other; | 
 |   bool m_transpose; // TODO this actually means adjoint | 
 | }; | 
 |  | 
 | template<typename SparseQRType> | 
 | struct SparseQRMatrixQReturnType : public EigenBase<SparseQRMatrixQReturnType<SparseQRType> > | 
 | {   | 
 |   typedef typename SparseQRType::Scalar Scalar; | 
 |   typedef Matrix<Scalar,Dynamic,Dynamic> DenseMatrix; | 
 |   enum { | 
 |     RowsAtCompileTime = Dynamic, | 
 |     ColsAtCompileTime = Dynamic | 
 |   }; | 
 |   explicit SparseQRMatrixQReturnType(const SparseQRType& qr) : m_qr(qr) {} | 
 |   template<typename Derived> | 
 |   SparseQR_QProduct<SparseQRType, Derived> operator*(const MatrixBase<Derived>& other) | 
 |   { | 
 |     return SparseQR_QProduct<SparseQRType,Derived>(m_qr,other.derived(),false); | 
 |   } | 
 |   // To use for operations with the adjoint of Q | 
 |   SparseQRMatrixQTransposeReturnType<SparseQRType> adjoint() const | 
 |   { | 
 |     return SparseQRMatrixQTransposeReturnType<SparseQRType>(m_qr); | 
 |   } | 
 |   inline Index rows() const { return m_qr.rows(); } | 
 |   inline Index cols() const { return m_qr.rows(); } | 
 |   // To use for operations with the transpose of Q FIXME this is the same as adjoint at the moment | 
 |   SparseQRMatrixQTransposeReturnType<SparseQRType> transpose() const | 
 |   { | 
 |     return SparseQRMatrixQTransposeReturnType<SparseQRType>(m_qr); | 
 |   } | 
 |   const SparseQRType& m_qr; | 
 | }; | 
 |  | 
 | // TODO this actually represents the adjoint of Q | 
 | template<typename SparseQRType> | 
 | struct SparseQRMatrixQTransposeReturnType | 
 | { | 
 |   explicit SparseQRMatrixQTransposeReturnType(const SparseQRType& qr) : m_qr(qr) {} | 
 |   template<typename Derived> | 
 |   SparseQR_QProduct<SparseQRType,Derived> operator*(const MatrixBase<Derived>& other) | 
 |   { | 
 |     return SparseQR_QProduct<SparseQRType,Derived>(m_qr,other.derived(), true); | 
 |   } | 
 |   const SparseQRType& m_qr; | 
 | }; | 
 |  | 
 | namespace internal { | 
 |    | 
 | template<typename SparseQRType> | 
 | struct evaluator_traits<SparseQRMatrixQReturnType<SparseQRType> > | 
 | { | 
 |   typedef typename SparseQRType::MatrixType MatrixType; | 
 |   typedef typename storage_kind_to_evaluator_kind<typename MatrixType::StorageKind>::Kind Kind; | 
 |   typedef SparseShape Shape; | 
 | }; | 
 |  | 
 | template< typename DstXprType, typename SparseQRType> | 
 | struct Assignment<DstXprType, SparseQRMatrixQReturnType<SparseQRType>, internal::assign_op<typename DstXprType::Scalar,typename DstXprType::Scalar>, Sparse2Sparse> | 
 | { | 
 |   typedef SparseQRMatrixQReturnType<SparseQRType> SrcXprType; | 
 |   typedef typename DstXprType::Scalar Scalar; | 
 |   typedef typename DstXprType::StorageIndex StorageIndex; | 
 |   static void run(DstXprType &dst, const SrcXprType &src, const internal::assign_op<Scalar,Scalar> &/*func*/) | 
 |   { | 
 |     typename DstXprType::PlainObject idMat(src.rows(), src.cols()); | 
 |     idMat.setIdentity(); | 
 |     // Sort the sparse householder reflectors if needed | 
 |     const_cast<SparseQRType *>(&src.m_qr)->_sort_matrix_Q(); | 
 |     dst = SparseQR_QProduct<SparseQRType, DstXprType>(src.m_qr, idMat, false); | 
 |   } | 
 | }; | 
 |  | 
 | template< typename DstXprType, typename SparseQRType> | 
 | struct Assignment<DstXprType, SparseQRMatrixQReturnType<SparseQRType>, internal::assign_op<typename DstXprType::Scalar,typename DstXprType::Scalar>, Sparse2Dense> | 
 | { | 
 |   typedef SparseQRMatrixQReturnType<SparseQRType> SrcXprType; | 
 |   typedef typename DstXprType::Scalar Scalar; | 
 |   typedef typename DstXprType::StorageIndex StorageIndex; | 
 |   static void run(DstXprType &dst, const SrcXprType &src, const internal::assign_op<Scalar,Scalar> &/*func*/) | 
 |   { | 
 |     dst = src.m_qr.matrixQ() * DstXprType::Identity(src.m_qr.rows(), src.m_qr.rows()); | 
 |   } | 
 | }; | 
 |  | 
 | } // end namespace internal | 
 |  | 
 | } // end namespace Eigen | 
 |  | 
 | #endif |