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Diffstat (limited to 'unsupported/Eigen/src/Polynomials/Companion.h')
| -rw-r--r-- | unsupported/Eigen/src/Polynomials/Companion.h | 275 |
1 files changed, 275 insertions, 0 deletions
diff --git a/unsupported/Eigen/src/Polynomials/Companion.h b/unsupported/Eigen/src/Polynomials/Companion.h new file mode 100644 index 000000000..4badd9d58 --- /dev/null +++ b/unsupported/Eigen/src/Polynomials/Companion.h @@ -0,0 +1,275 @@ +// This file is part of Eigen, a lightweight C++ template library +// for linear algebra. +// +// Copyright (C) 2010 Manuel Yguel <manuel.yguel@gmail.com> +// +// 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_COMPANION_H +#define EIGEN_COMPANION_H + +// This file requires the user to include +// * Eigen/Core +// * Eigen/src/PolynomialSolver.h + +namespace Eigen { + +namespace internal { + +#ifndef EIGEN_PARSED_BY_DOXYGEN + +template <typename T> +T radix(){ return 2; } + +template <typename T> +T radix2(){ return radix<T>()*radix<T>(); } + +template<int Size> +struct decrement_if_fixed_size +{ + enum { + ret = (Size == Dynamic) ? Dynamic : Size-1 }; +}; + +#endif + +template< typename _Scalar, int _Deg > +class companion +{ + public: + EIGEN_MAKE_ALIGNED_OPERATOR_NEW_IF_VECTORIZABLE_FIXED_SIZE(_Scalar,_Deg==Dynamic ? Dynamic : _Deg) + + enum { + Deg = _Deg, + Deg_1=decrement_if_fixed_size<Deg>::ret + }; + + typedef _Scalar Scalar; + typedef typename NumTraits<Scalar>::Real RealScalar; + typedef Matrix<Scalar, Deg, 1> RightColumn; + //typedef DiagonalMatrix< Scalar, Deg_1, Deg_1 > BottomLeftDiagonal; + typedef Matrix<Scalar, Deg_1, 1> BottomLeftDiagonal; + + typedef Matrix<Scalar, Deg, Deg> DenseCompanionMatrixType; + typedef Matrix< Scalar, _Deg, Deg_1 > LeftBlock; + typedef Matrix< Scalar, Deg_1, Deg_1 > BottomLeftBlock; + typedef Matrix< Scalar, 1, Deg_1 > LeftBlockFirstRow; + + typedef DenseIndex Index; + + public: + EIGEN_STRONG_INLINE const _Scalar operator()(Index row, Index col ) const + { + if( m_bl_diag.rows() > col ) + { + if( 0 < row ){ return m_bl_diag[col]; } + else{ return 0; } + } + else{ return m_monic[row]; } + } + + public: + template<typename VectorType> + void setPolynomial( const VectorType& poly ) + { + const Index deg = poly.size()-1; + m_monic = -1/poly[deg] * poly.head(deg); + //m_bl_diag.setIdentity( deg-1 ); + m_bl_diag.setOnes(deg-1); + } + + template<typename VectorType> + companion( const VectorType& poly ){ + setPolynomial( poly ); } + + public: + DenseCompanionMatrixType denseMatrix() const + { + const Index deg = m_monic.size(); + const Index deg_1 = deg-1; + DenseCompanionMatrixType companion(deg,deg); + companion << + ( LeftBlock(deg,deg_1) + << LeftBlockFirstRow::Zero(1,deg_1), + BottomLeftBlock::Identity(deg-1,deg-1)*m_bl_diag.asDiagonal() ).finished() + , m_monic; + return companion; + } + + + + protected: + /** Helper function for the balancing algorithm. + * \returns true if the row and the column, having colNorm and rowNorm + * as norms, are balanced, false otherwise. + * colB and rowB are repectively the multipliers for + * the column and the row in order to balance them. + * */ + bool balanced( Scalar colNorm, Scalar rowNorm, + bool& isBalanced, Scalar& colB, Scalar& rowB ); + + /** Helper function for the balancing algorithm. + * \returns true if the row and the column, having colNorm and rowNorm + * as norms, are balanced, false otherwise. + * colB and rowB are repectively the multipliers for + * the column and the row in order to balance them. + * */ + bool balancedR( Scalar colNorm, Scalar rowNorm, + bool& isBalanced, Scalar& colB, Scalar& rowB ); + + public: + /** + * Balancing algorithm from B. N. PARLETT and C. REINSCH (1969) + * "Balancing a matrix for calculation of eigenvalues and eigenvectors" + * adapted to the case of companion matrices. + * A matrix with non zero row and non zero column is balanced + * for a certain norm if the i-th row and the i-th column + * have same norm for all i. + */ + void balance(); + + protected: + RightColumn m_monic; + BottomLeftDiagonal m_bl_diag; +}; + + + +template< typename _Scalar, int _Deg > +inline +bool companion<_Scalar,_Deg>::balanced( Scalar colNorm, Scalar rowNorm, + bool& isBalanced, Scalar& colB, Scalar& rowB ) +{ + if( Scalar(0) == colNorm || Scalar(0) == rowNorm ){ return true; } + else + { + //To find the balancing coefficients, if the radix is 2, + //one finds \f$ \sigma \f$ such that + // \f$ 2^{2\sigma-1} < rowNorm / colNorm \le 2^{2\sigma+1} \f$ + // then the balancing coefficient for the row is \f$ 1/2^{\sigma} \f$ + // and the balancing coefficient for the column is \f$ 2^{\sigma} \f$ + rowB = rowNorm / radix<Scalar>(); + colB = Scalar(1); + const Scalar s = colNorm + rowNorm; + + while (colNorm < rowB) + { + colB *= radix<Scalar>(); + colNorm *= radix2<Scalar>(); + } + + rowB = rowNorm * radix<Scalar>(); + + while (colNorm >= rowB) + { + colB /= radix<Scalar>(); + colNorm /= radix2<Scalar>(); + } + + //This line is used to avoid insubstantial balancing + if ((rowNorm + colNorm) < Scalar(0.95) * s * colB) + { + isBalanced = false; + rowB = Scalar(1) / colB; + return false; + } + else{ + return true; } + } +} + +template< typename _Scalar, int _Deg > +inline +bool companion<_Scalar,_Deg>::balancedR( Scalar colNorm, Scalar rowNorm, + bool& isBalanced, Scalar& colB, Scalar& rowB ) +{ + if( Scalar(0) == colNorm || Scalar(0) == rowNorm ){ return true; } + else + { + /** + * Set the norm of the column and the row to the geometric mean + * of the row and column norm + */ + const _Scalar q = colNorm/rowNorm; + if( !isApprox( q, _Scalar(1) ) ) + { + rowB = sqrt( colNorm/rowNorm ); + colB = Scalar(1)/rowB; + + isBalanced = false; + return false; + } + else{ + return true; } + } +} + + +template< typename _Scalar, int _Deg > +void companion<_Scalar,_Deg>::balance() +{ + EIGEN_STATIC_ASSERT( Deg == Dynamic || 1 < Deg, YOU_MADE_A_PROGRAMMING_MISTAKE ); + const Index deg = m_monic.size(); + const Index deg_1 = deg-1; + + bool hasConverged=false; + while( !hasConverged ) + { + hasConverged = true; + Scalar colNorm,rowNorm; + Scalar colB,rowB; + + //First row, first column excluding the diagonal + //============================================== + colNorm = abs(m_bl_diag[0]); + rowNorm = abs(m_monic[0]); + + //Compute balancing of the row and the column + if( !balanced( colNorm, rowNorm, hasConverged, colB, rowB ) ) + { + m_bl_diag[0] *= colB; + m_monic[0] *= rowB; + } + + //Middle rows and columns excluding the diagonal + //============================================== + for( Index i=1; i<deg_1; ++i ) + { + // column norm, excluding the diagonal + colNorm = abs(m_bl_diag[i]); + + // row norm, excluding the diagonal + rowNorm = abs(m_bl_diag[i-1]) + abs(m_monic[i]); + + //Compute balancing of the row and the column + if( !balanced( colNorm, rowNorm, hasConverged, colB, rowB ) ) + { + m_bl_diag[i] *= colB; + m_bl_diag[i-1] *= rowB; + m_monic[i] *= rowB; + } + } + + //Last row, last column excluding the diagonal + //============================================ + const Index ebl = m_bl_diag.size()-1; + VectorBlock<RightColumn,Deg_1> headMonic( m_monic, 0, deg_1 ); + colNorm = headMonic.array().abs().sum(); + rowNorm = abs( m_bl_diag[ebl] ); + + //Compute balancing of the row and the column + if( !balanced( colNorm, rowNorm, hasConverged, colB, rowB ) ) + { + headMonic *= colB; + m_bl_diag[ebl] *= rowB; + } + } +} + +} // end namespace internal + +} // end namespace Eigen + +#endif // EIGEN_COMPANION_H |