// This file is part of Eigen, a lightweight C++ template library
// for linear algebra. Eigen itself is part of the KDE project.
//
// Copyright (C) 2008 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_CHOLESKY_H
#define EIGEN_CHOLESKY_H

/** \ingroup Cholesky_Module
  *
  * \class Cholesky
  *
  * \deprecated this class has been renamed LLT
  */
template<typename MatrixType> class Cholesky
{
  private:
    typedef typename MatrixType::Scalar Scalar;
    typedef typename NumTraits<typename MatrixType::Scalar>::Real RealScalar;
    typedef Matrix<Scalar, MatrixType::ColsAtCompileTime, 1> VectorType;

    enum {
      PacketSize = ei_packet_traits<Scalar>::size,
      AlignmentMask = int(PacketSize)-1
    };

  public:

    Cholesky(const MatrixType& matrix)
      : m_matrix(matrix.rows(), matrix.cols())
    {
      compute(matrix);
    }

		/** \deprecated */
    inline Part<MatrixType, Lower> matrixL(void) const { return m_matrix; }

    /** \deprecated */
    inline bool isPositiveDefinite(void) const { return m_isPositiveDefinite; }

    template<typename Derived>
    typename Derived::Eval solve(const MatrixBase<Derived> &b) const EIGEN_DEPRECATED;

    template<typename RhsDerived, typename ResDerived>
    bool solve(const MatrixBase<RhsDerived> &b, MatrixBase<ResDerived> *result) const;

    template<typename Derived>
    bool solveInPlace(MatrixBase<Derived> &bAndX) const;

    void compute(const MatrixType& matrix);

  protected:
    /** \internal
      * Used to compute and store L
      * The strict upper part is not used and even not initialized.
      */
    MatrixType m_matrix;
    bool m_isPositiveDefinite;
};

/** \deprecated */
template<typename MatrixType>
void Cholesky<MatrixType>::compute(const MatrixType& a)
{
  assert(a.rows()==a.cols());
  const int size = a.rows();
  m_matrix.resize(size, size);
  const RealScalar eps = ei_sqrt(precision<Scalar>());

  RealScalar x;
  x = ei_real(a.coeff(0,0));
  m_isPositiveDefinite = x > eps && ei_isMuchSmallerThan(ei_imag(a.coeff(0,0)), RealScalar(1));
  m_matrix.coeffRef(0,0) = ei_sqrt(x);
  m_matrix.col(0).end(size-1) = a.row(0).end(size-1).adjoint() / ei_real(m_matrix.coeff(0,0));
  for (int j = 1; j < size; ++j)
  {
    Scalar tmp = ei_real(a.coeff(j,j)) - m_matrix.row(j).start(j).squaredNorm();
    x = ei_real(tmp);
    if (x < eps || (!ei_isMuchSmallerThan(ei_imag(tmp), RealScalar(1))))
    {
      m_isPositiveDefinite = false;
      return;
    }
    m_matrix.coeffRef(j,j) = x = ei_sqrt(x);

    int endSize = size-j-1;
    if (endSize>0) {
      // Note that when all matrix columns have good alignment, then the following
      // product is guaranteed to be optimal with respect to alignment.
      m_matrix.col(j).end(endSize) =
        (m_matrix.block(j+1, 0, endSize, j) * m_matrix.row(j).start(j).adjoint()).lazy();

      // FIXME could use a.col instead of a.row
      m_matrix.col(j).end(endSize) = (a.row(j).end(endSize).adjoint()
        - m_matrix.col(j).end(endSize) ) / x;
    }
  }
}

/** \deprecated */
template<typename MatrixType>
template<typename Derived>
typename Derived::Eval Cholesky<MatrixType>::solve(const MatrixBase<Derived> &b) const
{
  const int size = m_matrix.rows();
  ei_assert(size==b.rows());
  typename ei_eval_to_column_major<Derived>::type x(b);
  solveInPlace(x);
  return x;
}

/** \deprecated */
template<typename MatrixType>
template<typename RhsDerived, typename ResDerived>
bool Cholesky<MatrixType>::solve(const MatrixBase<RhsDerived> &b, MatrixBase<ResDerived> *result) const
{
  const int size = m_matrix.rows();
  ei_assert(size==b.rows() && "Cholesky::solve(): invalid number of rows of the right hand side matrix b");
  return solveInPlace((*result) = b);
}

/** \deprecated */
template<typename MatrixType>
template<typename Derived>
bool Cholesky<MatrixType>::solveInPlace(MatrixBase<Derived> &bAndX) const
{
  const int size = m_matrix.rows();
  ei_assert(size==bAndX.rows());
  if (!m_isPositiveDefinite)
    return false;
  matrixL().solveTriangularInPlace(bAndX);
  m_matrix.adjoint().template part<Upper>().solveTriangularInPlace(bAndX);
  return true;
}

/** \cholesky_module
  * \deprecated has been renamed llt()
  */
template<typename Derived>
inline const Cholesky<typename MatrixBase<Derived>::EvalType>
MatrixBase<Derived>::cholesky() const
{
  return Cholesky<typename ei_eval<Derived>::type>(derived());
}

#endif // EIGEN_CHOLESKY_H