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// This file is part of Eigen, a lightweight C++ template library
// for linear algebra. Eigen itself is part of the KDE project.
//
// Copyright (C) 2006-2008 Benoit Jacob <jacob@math.jussieu.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_DIAGONALMATRIX_H
#define EIGEN_DIAGONALMATRIX_H
/** \class DiagonalMatrix
*
* \brief Expression of a diagonal matrix
*
* \param CoeffsVectorType the type of the vector of diagonal coefficients
*
* This class is an expression of a diagonal matrix with given vector of diagonal
* coefficients. It is the return
* type of MatrixBase::diagonal(const OtherDerived&) and most of the time this is
* the only way it is used.
*
* \sa MatrixBase::diagonal(const OtherDerived&)
*/
template<typename CoeffsVectorType>
struct ei_traits<DiagonalMatrix<CoeffsVectorType> >
{
typedef typename CoeffsVectorType::Scalar Scalar;
enum {
RowsAtCompileTime = CoeffsVectorType::SizeAtCompileTime,
ColsAtCompileTime = CoeffsVectorType::SizeAtCompileTime,
MaxRowsAtCompileTime = CoeffsVectorType::MaxSizeAtCompileTime,
MaxColsAtCompileTime = CoeffsVectorType::MaxSizeAtCompileTime,
Flags = CoeffsVectorType::Flags,
CoeffReadCost = CoeffsVectorType::CoeffReadCost
};
};
template<typename CoeffsVectorType>
class DiagonalMatrix : ei_no_assignment_operator,
public MatrixBase<DiagonalMatrix<CoeffsVectorType> >
{
public:
EIGEN_GENERIC_PUBLIC_INTERFACE(DiagonalMatrix)
DiagonalMatrix(const CoeffsVectorType& coeffs) : m_coeffs(coeffs)
{
ei_assert(CoeffsVectorType::IsVectorAtCompileTime
&& coeffs.size() > 0);
}
private:
int _rows() const { return m_coeffs.size(); }
int _cols() const { return m_coeffs.size(); }
const Scalar _coeff(int row, int col) const
{
return row == col ? m_coeffs.coeff(row) : static_cast<Scalar>(0);
}
protected:
const typename CoeffsVectorType::XprCopy m_coeffs;
};
/** \returns an expression of a diagonal matrix with *this as vector of diagonal coefficients
*
* \only_for_vectors
*
* Example: \include MatrixBase_asDiagonal.cpp
* Output: \verbinclude MatrixBase_asDiagonal.out
*
* \sa class DiagonalMatrix, isDiagonal()
**/
template<typename Derived>
const DiagonalMatrix<Derived>
MatrixBase<Derived>::asDiagonal() const
{
return DiagonalMatrix<Derived>(derived());
}
/** \returns true if *this is approximately equal to a diagonal matrix,
* within the precision given by \a prec.
*
* Example: \include MatrixBase_isDiagonal.cpp
* Output: \verbinclude MatrixBase_isDiagonal.out
*
* \sa asDiagonal()
*/
template<typename Derived>
bool MatrixBase<Derived>::isDiagonal
(typename NumTraits<Scalar>::Real prec) const
{
if(cols() != rows()) return false;
RealScalar maxAbsOnDiagonal = static_cast<RealScalar>(-1);
for(int j = 0; j < cols(); j++)
{
RealScalar absOnDiagonal = ei_abs(coeff(j,j));
if(absOnDiagonal > maxAbsOnDiagonal) maxAbsOnDiagonal = absOnDiagonal;
}
for(int j = 0; j < cols(); j++)
for(int i = 0; i < j; i++)
{
if(!ei_isMuchSmallerThan(coeff(i, j), maxAbsOnDiagonal, prec)) return false;
if(!ei_isMuchSmallerThan(coeff(j, i), maxAbsOnDiagonal, prec)) return false;
}
return true;
}
#endif // EIGEN_DIAGONALMATRIX_H
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