diff options
Diffstat (limited to 'unsupported/Eigen/src/Polynomials')
-rw-r--r-- | unsupported/Eigen/src/Polynomials/CMakeLists.txt | 6 | ||||
-rw-r--r-- | unsupported/Eigen/src/Polynomials/Companion.h | 275 | ||||
-rw-r--r-- | unsupported/Eigen/src/Polynomials/PolynomialSolver.h | 386 | ||||
-rw-r--r-- | unsupported/Eigen/src/Polynomials/PolynomialUtils.h | 141 |
4 files changed, 808 insertions, 0 deletions
diff --git a/unsupported/Eigen/src/Polynomials/CMakeLists.txt b/unsupported/Eigen/src/Polynomials/CMakeLists.txt new file mode 100644 index 000000000..51f13f3cb --- /dev/null +++ b/unsupported/Eigen/src/Polynomials/CMakeLists.txt @@ -0,0 +1,6 @@ +FILE(GLOB Eigen_Polynomials_SRCS "*.h") + +INSTALL(FILES + ${Eigen_Polynomials_SRCS} + DESTINATION ${INCLUDE_INSTALL_DIR}/unsupported/Eigen/src/Polynomials COMPONENT Devel + ) 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 diff --git a/unsupported/Eigen/src/Polynomials/PolynomialSolver.h b/unsupported/Eigen/src/Polynomials/PolynomialSolver.h new file mode 100644 index 000000000..70b873dbc --- /dev/null +++ b/unsupported/Eigen/src/Polynomials/PolynomialSolver.h @@ -0,0 +1,386 @@ +// 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_POLYNOMIAL_SOLVER_H +#define EIGEN_POLYNOMIAL_SOLVER_H + +namespace Eigen { + +/** \ingroup Polynomials_Module + * \class PolynomialSolverBase. + * + * \brief Defined to be inherited by polynomial solvers: it provides + * convenient methods such as + * - real roots, + * - greatest, smallest complex roots, + * - real roots with greatest, smallest absolute real value, + * - greatest, smallest real roots. + * + * It stores the set of roots as a vector of complexes. + * + */ +template< typename _Scalar, int _Deg > +class PolynomialSolverBase +{ + public: + EIGEN_MAKE_ALIGNED_OPERATOR_NEW_IF_VECTORIZABLE_FIXED_SIZE(_Scalar,_Deg==Dynamic ? Dynamic : _Deg) + + typedef _Scalar Scalar; + typedef typename NumTraits<Scalar>::Real RealScalar; + typedef std::complex<RealScalar> RootType; + typedef Matrix<RootType,_Deg,1> RootsType; + + typedef DenseIndex Index; + + protected: + template< typename OtherPolynomial > + inline void setPolynomial( const OtherPolynomial& poly ){ + m_roots.resize(poly.size()); } + + public: + template< typename OtherPolynomial > + inline PolynomialSolverBase( const OtherPolynomial& poly ){ + setPolynomial( poly() ); } + + inline PolynomialSolverBase(){} + + public: + /** \returns the complex roots of the polynomial */ + inline const RootsType& roots() const { return m_roots; } + + public: + /** Clear and fills the back insertion sequence with the real roots of the polynomial + * i.e. the real part of the complex roots that have an imaginary part which + * absolute value is smaller than absImaginaryThreshold. + * absImaginaryThreshold takes the dummy_precision associated + * with the _Scalar template parameter of the PolynomialSolver class as the default value. + * + * \param[out] bi_seq : the back insertion sequence (stl concept) + * \param[in] absImaginaryThreshold : the maximum bound of the imaginary part of a complex + * number that is considered as real. + * */ + template<typename Stl_back_insertion_sequence> + inline void realRoots( Stl_back_insertion_sequence& bi_seq, + const RealScalar& absImaginaryThreshold = NumTraits<Scalar>::dummy_precision() ) const + { + bi_seq.clear(); + for(Index i=0; i<m_roots.size(); ++i ) + { + if( internal::abs( m_roots[i].imag() ) < absImaginaryThreshold ){ + bi_seq.push_back( m_roots[i].real() ); } + } + } + + protected: + template<typename squaredNormBinaryPredicate> + inline const RootType& selectComplexRoot_withRespectToNorm( squaredNormBinaryPredicate& pred ) const + { + Index res=0; + RealScalar norm2 = internal::abs2( m_roots[0] ); + for( Index i=1; i<m_roots.size(); ++i ) + { + const RealScalar currNorm2 = internal::abs2( m_roots[i] ); + if( pred( currNorm2, norm2 ) ){ + res=i; norm2=currNorm2; } + } + return m_roots[res]; + } + + public: + /** + * \returns the complex root with greatest norm. + */ + inline const RootType& greatestRoot() const + { + std::greater<Scalar> greater; + return selectComplexRoot_withRespectToNorm( greater ); + } + + /** + * \returns the complex root with smallest norm. + */ + inline const RootType& smallestRoot() const + { + std::less<Scalar> less; + return selectComplexRoot_withRespectToNorm( less ); + } + + protected: + template<typename squaredRealPartBinaryPredicate> + inline const RealScalar& selectRealRoot_withRespectToAbsRealPart( + squaredRealPartBinaryPredicate& pred, + bool& hasArealRoot, + const RealScalar& absImaginaryThreshold = NumTraits<Scalar>::dummy_precision() ) const + { + hasArealRoot = false; + Index res=0; + RealScalar abs2(0); + + for( Index i=0; i<m_roots.size(); ++i ) + { + if( internal::abs( m_roots[i].imag() ) < absImaginaryThreshold ) + { + if( !hasArealRoot ) + { + hasArealRoot = true; + res = i; + abs2 = m_roots[i].real() * m_roots[i].real(); + } + else + { + const RealScalar currAbs2 = m_roots[i].real() * m_roots[i].real(); + if( pred( currAbs2, abs2 ) ) + { + abs2 = currAbs2; + res = i; + } + } + } + else + { + if( internal::abs( m_roots[i].imag() ) < internal::abs( m_roots[res].imag() ) ){ + res = i; } + } + } + return internal::real_ref(m_roots[res]); + } + + + template<typename RealPartBinaryPredicate> + inline const RealScalar& selectRealRoot_withRespectToRealPart( + RealPartBinaryPredicate& pred, + bool& hasArealRoot, + const RealScalar& absImaginaryThreshold = NumTraits<Scalar>::dummy_precision() ) const + { + hasArealRoot = false; + Index res=0; + RealScalar val(0); + + for( Index i=0; i<m_roots.size(); ++i ) + { + if( internal::abs( m_roots[i].imag() ) < absImaginaryThreshold ) + { + if( !hasArealRoot ) + { + hasArealRoot = true; + res = i; + val = m_roots[i].real(); + } + else + { + const RealScalar curr = m_roots[i].real(); + if( pred( curr, val ) ) + { + val = curr; + res = i; + } + } + } + else + { + if( internal::abs( m_roots[i].imag() ) < internal::abs( m_roots[res].imag() ) ){ + res = i; } + } + } + return internal::real_ref(m_roots[res]); + } + + public: + /** + * \returns a real root with greatest absolute magnitude. + * A real root is defined as the real part of a complex root with absolute imaginary + * part smallest than absImaginaryThreshold. + * absImaginaryThreshold takes the dummy_precision associated + * with the _Scalar template parameter of the PolynomialSolver class as the default value. + * If no real root is found the boolean hasArealRoot is set to false and the real part of + * the root with smallest absolute imaginary part is returned instead. + * + * \param[out] hasArealRoot : boolean true if a real root is found according to the + * absImaginaryThreshold criterion, false otherwise. + * \param[in] absImaginaryThreshold : threshold on the absolute imaginary part to decide + * whether or not a root is real. + */ + inline const RealScalar& absGreatestRealRoot( + bool& hasArealRoot, + const RealScalar& absImaginaryThreshold = NumTraits<Scalar>::dummy_precision() ) const + { + std::greater<Scalar> greater; + return selectRealRoot_withRespectToAbsRealPart( greater, hasArealRoot, absImaginaryThreshold ); + } + + + /** + * \returns a real root with smallest absolute magnitude. + * A real root is defined as the real part of a complex root with absolute imaginary + * part smallest than absImaginaryThreshold. + * absImaginaryThreshold takes the dummy_precision associated + * with the _Scalar template parameter of the PolynomialSolver class as the default value. + * If no real root is found the boolean hasArealRoot is set to false and the real part of + * the root with smallest absolute imaginary part is returned instead. + * + * \param[out] hasArealRoot : boolean true if a real root is found according to the + * absImaginaryThreshold criterion, false otherwise. + * \param[in] absImaginaryThreshold : threshold on the absolute imaginary part to decide + * whether or not a root is real. + */ + inline const RealScalar& absSmallestRealRoot( + bool& hasArealRoot, + const RealScalar& absImaginaryThreshold = NumTraits<Scalar>::dummy_precision() ) const + { + std::less<Scalar> less; + return selectRealRoot_withRespectToAbsRealPart( less, hasArealRoot, absImaginaryThreshold ); + } + + + /** + * \returns the real root with greatest value. + * A real root is defined as the real part of a complex root with absolute imaginary + * part smallest than absImaginaryThreshold. + * absImaginaryThreshold takes the dummy_precision associated + * with the _Scalar template parameter of the PolynomialSolver class as the default value. + * If no real root is found the boolean hasArealRoot is set to false and the real part of + * the root with smallest absolute imaginary part is returned instead. + * + * \param[out] hasArealRoot : boolean true if a real root is found according to the + * absImaginaryThreshold criterion, false otherwise. + * \param[in] absImaginaryThreshold : threshold on the absolute imaginary part to decide + * whether or not a root is real. + */ + inline const RealScalar& greatestRealRoot( + bool& hasArealRoot, + const RealScalar& absImaginaryThreshold = NumTraits<Scalar>::dummy_precision() ) const + { + std::greater<Scalar> greater; + return selectRealRoot_withRespectToRealPart( greater, hasArealRoot, absImaginaryThreshold ); + } + + + /** + * \returns the real root with smallest value. + * A real root is defined as the real part of a complex root with absolute imaginary + * part smallest than absImaginaryThreshold. + * absImaginaryThreshold takes the dummy_precision associated + * with the _Scalar template parameter of the PolynomialSolver class as the default value. + * If no real root is found the boolean hasArealRoot is set to false and the real part of + * the root with smallest absolute imaginary part is returned instead. + * + * \param[out] hasArealRoot : boolean true if a real root is found according to the + * absImaginaryThreshold criterion, false otherwise. + * \param[in] absImaginaryThreshold : threshold on the absolute imaginary part to decide + * whether or not a root is real. + */ + inline const RealScalar& smallestRealRoot( + bool& hasArealRoot, + const RealScalar& absImaginaryThreshold = NumTraits<Scalar>::dummy_precision() ) const + { + std::less<Scalar> less; + return selectRealRoot_withRespectToRealPart( less, hasArealRoot, absImaginaryThreshold ); + } + + protected: + RootsType m_roots; +}; + +#define EIGEN_POLYNOMIAL_SOLVER_BASE_INHERITED_TYPES( BASE ) \ + typedef typename BASE::Scalar Scalar; \ + typedef typename BASE::RealScalar RealScalar; \ + typedef typename BASE::RootType RootType; \ + typedef typename BASE::RootsType RootsType; + + + +/** \ingroup Polynomials_Module + * + * \class PolynomialSolver + * + * \brief A polynomial solver + * + * Computes the complex roots of a real polynomial. + * + * \param _Scalar the scalar type, i.e., the type of the polynomial coefficients + * \param _Deg the degree of the polynomial, can be a compile time value or Dynamic. + * Notice that the number of polynomial coefficients is _Deg+1. + * + * This class implements a polynomial solver and provides convenient methods such as + * - real roots, + * - greatest, smallest complex roots, + * - real roots with greatest, smallest absolute real value. + * - greatest, smallest real roots. + * + * WARNING: this polynomial solver is experimental, part of the unsuported Eigen modules. + * + * + * Currently a QR algorithm is used to compute the eigenvalues of the companion matrix of + * the polynomial to compute its roots. + * This supposes that the complex moduli of the roots are all distinct: e.g. there should + * be no multiple roots or conjugate roots for instance. + * With 32bit (float) floating types this problem shows up frequently. + * However, almost always, correct accuracy is reached even in these cases for 64bit + * (double) floating types and small polynomial degree (<20). + */ +template< typename _Scalar, int _Deg > +class PolynomialSolver : public PolynomialSolverBase<_Scalar,_Deg> +{ + public: + EIGEN_MAKE_ALIGNED_OPERATOR_NEW_IF_VECTORIZABLE_FIXED_SIZE(_Scalar,_Deg==Dynamic ? Dynamic : _Deg) + + typedef PolynomialSolverBase<_Scalar,_Deg> PS_Base; + EIGEN_POLYNOMIAL_SOLVER_BASE_INHERITED_TYPES( PS_Base ) + + typedef Matrix<Scalar,_Deg,_Deg> CompanionMatrixType; + typedef EigenSolver<CompanionMatrixType> EigenSolverType; + + public: + /** Computes the complex roots of a new polynomial. */ + template< typename OtherPolynomial > + void compute( const OtherPolynomial& poly ) + { + assert( Scalar(0) != poly[poly.size()-1] ); + internal::companion<Scalar,_Deg> companion( poly ); + companion.balance(); + m_eigenSolver.compute( companion.denseMatrix() ); + m_roots = m_eigenSolver.eigenvalues(); + } + + public: + template< typename OtherPolynomial > + inline PolynomialSolver( const OtherPolynomial& poly ){ + compute( poly ); } + + inline PolynomialSolver(){} + + protected: + using PS_Base::m_roots; + EigenSolverType m_eigenSolver; +}; + + +template< typename _Scalar > +class PolynomialSolver<_Scalar,1> : public PolynomialSolverBase<_Scalar,1> +{ + public: + typedef PolynomialSolverBase<_Scalar,1> PS_Base; + EIGEN_POLYNOMIAL_SOLVER_BASE_INHERITED_TYPES( PS_Base ) + + public: + /** Computes the complex roots of a new polynomial. */ + template< typename OtherPolynomial > + void compute( const OtherPolynomial& poly ) + { + assert( Scalar(0) != poly[poly.size()-1] ); + m_roots[0] = -poly[0]/poly[poly.size()-1]; + } + + protected: + using PS_Base::m_roots; +}; + +} // end namespace Eigen + +#endif // EIGEN_POLYNOMIAL_SOLVER_H diff --git a/unsupported/Eigen/src/Polynomials/PolynomialUtils.h b/unsupported/Eigen/src/Polynomials/PolynomialUtils.h new file mode 100644 index 000000000..c23204c65 --- /dev/null +++ b/unsupported/Eigen/src/Polynomials/PolynomialUtils.h @@ -0,0 +1,141 @@ +// 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_POLYNOMIAL_UTILS_H +#define EIGEN_POLYNOMIAL_UTILS_H + +namespace Eigen { + +/** \ingroup Polynomials_Module + * \returns the evaluation of the polynomial at x using Horner algorithm. + * + * \param[in] poly : the vector of coefficients of the polynomial ordered + * by degrees i.e. poly[i] is the coefficient of degree i of the polynomial + * e.g. \f$ 1 + 3x^2 \f$ is stored as a vector \f$ [ 1, 0, 3 ] \f$. + * \param[in] x : the value to evaluate the polynomial at. + * + * <i><b>Note for stability:</b></i> + * <dd> \f$ |x| \le 1 \f$ </dd> + */ +template <typename Polynomials, typename T> +inline +T poly_eval_horner( const Polynomials& poly, const T& x ) +{ + T val=poly[poly.size()-1]; + for(DenseIndex i=poly.size()-2; i>=0; --i ){ + val = val*x + poly[i]; } + return val; +} + +/** \ingroup Polynomials_Module + * \returns the evaluation of the polynomial at x using stabilized Horner algorithm. + * + * \param[in] poly : the vector of coefficients of the polynomial ordered + * by degrees i.e. poly[i] is the coefficient of degree i of the polynomial + * e.g. \f$ 1 + 3x^2 \f$ is stored as a vector \f$ [ 1, 0, 3 ] \f$. + * \param[in] x : the value to evaluate the polynomial at. + */ +template <typename Polynomials, typename T> +inline +T poly_eval( const Polynomials& poly, const T& x ) +{ + typedef typename NumTraits<T>::Real Real; + + if( internal::abs2( x ) <= Real(1) ){ + return poly_eval_horner( poly, x ); } + else + { + T val=poly[0]; + T inv_x = T(1)/x; + for( DenseIndex i=1; i<poly.size(); ++i ){ + val = val*inv_x + poly[i]; } + + return std::pow(x,(T)(poly.size()-1)) * val; + } +} + +/** \ingroup Polynomials_Module + * \returns a maximum bound for the absolute value of any root of the polynomial. + * + * \param[in] poly : the vector of coefficients of the polynomial ordered + * by degrees i.e. poly[i] is the coefficient of degree i of the polynomial + * e.g. \f$ 1 + 3x^2 \f$ is stored as a vector \f$ [ 1, 0, 3 ] \f$. + * + * <i><b>Precondition:</b></i> + * <dd> the leading coefficient of the input polynomial poly must be non zero </dd> + */ +template <typename Polynomial> +inline +typename NumTraits<typename Polynomial::Scalar>::Real cauchy_max_bound( const Polynomial& poly ) +{ + typedef typename Polynomial::Scalar Scalar; + typedef typename NumTraits<Scalar>::Real Real; + + assert( Scalar(0) != poly[poly.size()-1] ); + const Scalar inv_leading_coeff = Scalar(1)/poly[poly.size()-1]; + Real cb(0); + + for( DenseIndex i=0; i<poly.size()-1; ++i ){ + cb += internal::abs(poly[i]*inv_leading_coeff); } + return cb + Real(1); +} + +/** \ingroup Polynomials_Module + * \returns a minimum bound for the absolute value of any non zero root of the polynomial. + * \param[in] poly : the vector of coefficients of the polynomial ordered + * by degrees i.e. poly[i] is the coefficient of degree i of the polynomial + * e.g. \f$ 1 + 3x^2 \f$ is stored as a vector \f$ [ 1, 0, 3 ] \f$. + */ +template <typename Polynomial> +inline +typename NumTraits<typename Polynomial::Scalar>::Real cauchy_min_bound( const Polynomial& poly ) +{ + typedef typename Polynomial::Scalar Scalar; + typedef typename NumTraits<Scalar>::Real Real; + + DenseIndex i=0; + while( i<poly.size()-1 && Scalar(0) == poly(i) ){ ++i; } + if( poly.size()-1 == i ){ + return Real(1); } + + const Scalar inv_min_coeff = Scalar(1)/poly[i]; + Real cb(1); + for( DenseIndex j=i+1; j<poly.size(); ++j ){ + cb += internal::abs(poly[j]*inv_min_coeff); } + return Real(1)/cb; +} + +/** \ingroup Polynomials_Module + * Given the roots of a polynomial compute the coefficients in the + * monomial basis of the monic polynomial with same roots and minimal degree. + * If RootVector is a vector of complexes, Polynomial should also be a vector + * of complexes. + * \param[in] rv : a vector containing the roots of a polynomial. + * \param[out] poly : the vector of coefficients of the polynomial ordered + * by degrees i.e. poly[i] is the coefficient of degree i of the polynomial + * e.g. \f$ 3 + x^2 \f$ is stored as a vector \f$ [ 3, 0, 1 ] \f$. + */ +template <typename RootVector, typename Polynomial> +void roots_to_monicPolynomial( const RootVector& rv, Polynomial& poly ) +{ + + typedef typename Polynomial::Scalar Scalar; + + poly.setZero( rv.size()+1 ); + poly[0] = -rv[0]; poly[1] = Scalar(1); + for( DenseIndex i=1; i< rv.size(); ++i ) + { + for( DenseIndex j=i+1; j>0; --j ){ poly[j] = poly[j-1] - rv[i]*poly[j]; } + poly[0] = -rv[i]*poly[0]; + } +} + +} // end namespace Eigen + +#endif // EIGEN_POLYNOMIAL_UTILS_H |