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      1 // This file is part of Eigen, a lightweight C++ template library
      2 // for linear algebra.
      3 //
      4 // Copyright (C) 2014 Gael Guennebaud <gael.guennebaud (at) inria.fr>
      5 //
      6 // This Source Code Form is subject to the terms of the Mozilla
      7 // Public License v. 2.0. If a copy of the MPL was not distributed
      8 // with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
      9 
     10 #ifndef EIGEN_SOLVEWITHGUESS_H
     11 #define EIGEN_SOLVEWITHGUESS_H
     12 
     13 namespace Eigen {
     14 
     15 template<typename Decomposition, typename RhsType, typename GuessType> class SolveWithGuess;
     16 
     17 /** \class SolveWithGuess
     18   * \ingroup IterativeLinearSolvers_Module
     19   *
     20   * \brief Pseudo expression representing a solving operation
     21   *
     22   * \tparam Decomposition the type of the matrix or decomposion object
     23   * \tparam Rhstype the type of the right-hand side
     24   *
     25   * This class represents an expression of A.solve(B)
     26   * and most of the time this is the only way it is used.
     27   *
     28   */
     29 namespace internal {
     30 
     31 
     32 template<typename Decomposition, typename RhsType, typename GuessType>
     33 struct traits<SolveWithGuess<Decomposition, RhsType, GuessType> >
     34   : traits<Solve<Decomposition,RhsType> >
     35 {};
     36 
     37 }
     38 
     39 
     40 template<typename Decomposition, typename RhsType, typename GuessType>
     41 class SolveWithGuess : public internal::generic_xpr_base<SolveWithGuess<Decomposition,RhsType,GuessType>, MatrixXpr, typename internal::traits<RhsType>::StorageKind>::type
     42 {
     43 public:
     44   typedef typename internal::traits<SolveWithGuess>::Scalar Scalar;
     45   typedef typename internal::traits<SolveWithGuess>::PlainObject PlainObject;
     46   typedef typename internal::generic_xpr_base<SolveWithGuess<Decomposition,RhsType,GuessType>, MatrixXpr, typename internal::traits<RhsType>::StorageKind>::type Base;
     47   typedef typename internal::ref_selector<SolveWithGuess>::type Nested;
     48 
     49   SolveWithGuess(const Decomposition &dec, const RhsType &rhs, const GuessType &guess)
     50     : m_dec(dec), m_rhs(rhs), m_guess(guess)
     51   {}
     52 
     53   EIGEN_DEVICE_FUNC Index rows() const { return m_dec.cols(); }
     54   EIGEN_DEVICE_FUNC Index cols() const { return m_rhs.cols(); }
     55 
     56   EIGEN_DEVICE_FUNC const Decomposition& dec()   const { return m_dec; }
     57   EIGEN_DEVICE_FUNC const RhsType&       rhs()   const { return m_rhs; }
     58   EIGEN_DEVICE_FUNC const GuessType&     guess() const { return m_guess; }
     59 
     60 protected:
     61   const Decomposition &m_dec;
     62   const RhsType       &m_rhs;
     63   const GuessType     &m_guess;
     64 
     65 private:
     66   Scalar coeff(Index row, Index col) const;
     67   Scalar coeff(Index i) const;
     68 };
     69 
     70 namespace internal {
     71 
     72 // Evaluator of SolveWithGuess -> eval into a temporary
     73 template<typename Decomposition, typename RhsType, typename GuessType>
     74 struct evaluator<SolveWithGuess<Decomposition,RhsType, GuessType> >
     75   : public evaluator<typename SolveWithGuess<Decomposition,RhsType,GuessType>::PlainObject>
     76 {
     77   typedef SolveWithGuess<Decomposition,RhsType,GuessType> SolveType;
     78   typedef typename SolveType::PlainObject PlainObject;
     79   typedef evaluator<PlainObject> Base;
     80 
     81   evaluator(const SolveType& solve)
     82     : m_result(solve.rows(), solve.cols())
     83   {
     84     ::new (static_cast<Base*>(this)) Base(m_result);
     85     m_result = solve.guess();
     86     solve.dec()._solve_with_guess_impl(solve.rhs(), m_result);
     87   }
     88 
     89 protected:
     90   PlainObject m_result;
     91 };
     92 
     93 // Specialization for "dst = dec.solveWithGuess(rhs)"
     94 // NOTE we need to specialize it for Dense2Dense to avoid ambiguous specialization error and a Sparse2Sparse specialization must exist somewhere
     95 template<typename DstXprType, typename DecType, typename RhsType, typename GuessType, typename Scalar>
     96 struct Assignment<DstXprType, SolveWithGuess<DecType,RhsType,GuessType>, internal::assign_op<Scalar,Scalar>, Dense2Dense>
     97 {
     98   typedef SolveWithGuess<DecType,RhsType,GuessType> SrcXprType;
     99   static void run(DstXprType &dst, const SrcXprType &src, const internal::assign_op<Scalar,Scalar> &)
    100   {
    101     Index dstRows = src.rows();
    102     Index dstCols = src.cols();
    103     if((dst.rows()!=dstRows) || (dst.cols()!=dstCols))
    104       dst.resize(dstRows, dstCols);
    105 
    106     dst = src.guess();
    107     src.dec()._solve_with_guess_impl(src.rhs(), dst/*, src.guess()*/);
    108   }
    109 };
    110 
    111 } // end namepsace internal
    112 
    113 } // end namespace Eigen
    114 
    115 #endif // EIGEN_SOLVEWITHGUESS_H
    116