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diff --git a/eigen/Eigen/src/Eigenvalues/SelfAdjointEigenSolver.h b/eigen/Eigen/src/Eigenvalues/SelfAdjointEigenSolver.h new file mode 100644 index 0000000..1131c8a --- /dev/null +++ b/eigen/Eigen/src/Eigenvalues/SelfAdjointEigenSolver.h @@ -0,0 +1,801 @@ +// This file is part of Eigen, a lightweight C++ template library +// for linear algebra. +// +// Copyright (C) 2008-2010 Gael Guennebaud <gael.guennebaud@inria.fr> +// Copyright (C) 2010 Jitse Niesen <jitse@maths.leeds.ac.uk> +// +// 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_SELFADJOINTEIGENSOLVER_H +#define EIGEN_SELFADJOINTEIGENSOLVER_H + +#include "./Tridiagonalization.h" + +namespace Eigen { + +template<typename _MatrixType> +class GeneralizedSelfAdjointEigenSolver; + +namespace internal { +template<typename SolverType,int Size,bool IsComplex> struct direct_selfadjoint_eigenvalues; +} + +/** \eigenvalues_module \ingroup Eigenvalues_Module + * + * + * \class SelfAdjointEigenSolver + * + * \brief Computes eigenvalues and eigenvectors of selfadjoint matrices + * + * \tparam _MatrixType the type of the matrix of which we are computing the + * eigendecomposition; this is expected to be an instantiation of the Matrix + * class template. + * + * A matrix \f$ A \f$ is selfadjoint if it equals its adjoint. For real + * matrices, this means that the matrix is symmetric: it equals its + * transpose. This class computes the eigenvalues and eigenvectors of a + * selfadjoint matrix. These are the scalars \f$ \lambda \f$ and vectors + * \f$ v \f$ such that \f$ Av = \lambda v \f$. The eigenvalues of a + * selfadjoint matrix are always real. If \f$ D \f$ is a diagonal matrix with + * the eigenvalues on the diagonal, and \f$ V \f$ is a matrix with the + * eigenvectors as its columns, then \f$ A = V D V^{-1} \f$ (for selfadjoint + * matrices, the matrix \f$ V \f$ is always invertible). This is called the + * eigendecomposition. + * + * The algorithm exploits the fact that the matrix is selfadjoint, making it + * faster and more accurate than the general purpose eigenvalue algorithms + * implemented in EigenSolver and ComplexEigenSolver. + * + * Only the \b lower \b triangular \b part of the input matrix is referenced. + * + * Call the function compute() to compute the eigenvalues and eigenvectors of + * a given matrix. Alternatively, you can use the + * SelfAdjointEigenSolver(const MatrixType&, int) constructor which computes + * the eigenvalues and eigenvectors at construction time. Once the eigenvalue + * and eigenvectors are computed, they can be retrieved with the eigenvalues() + * and eigenvectors() functions. + * + * The documentation for SelfAdjointEigenSolver(const MatrixType&, int) + * contains an example of the typical use of this class. + * + * To solve the \em generalized eigenvalue problem \f$ Av = \lambda Bv \f$ and + * the likes, see the class GeneralizedSelfAdjointEigenSolver. + * + * \sa MatrixBase::eigenvalues(), class EigenSolver, class ComplexEigenSolver + */ +template<typename _MatrixType> class SelfAdjointEigenSolver +{ + public: + + typedef _MatrixType MatrixType; + enum { + Size = MatrixType::RowsAtCompileTime, + ColsAtCompileTime = MatrixType::ColsAtCompileTime, + Options = MatrixType::Options, + MaxColsAtCompileTime = MatrixType::MaxColsAtCompileTime + }; + + /** \brief Scalar type for matrices of type \p _MatrixType. */ + typedef typename MatrixType::Scalar Scalar; + typedef typename MatrixType::Index Index; + + typedef Matrix<Scalar,Size,Size,ColMajor,MaxColsAtCompileTime,MaxColsAtCompileTime> EigenvectorsType; + + /** \brief Real scalar type for \p _MatrixType. + * + * This is just \c Scalar if #Scalar is real (e.g., \c float or + * \c double), and the type of the real part of \c Scalar if #Scalar is + * complex. + */ + typedef typename NumTraits<Scalar>::Real RealScalar; + + friend struct internal::direct_selfadjoint_eigenvalues<SelfAdjointEigenSolver,Size,NumTraits<Scalar>::IsComplex>; + + /** \brief Type for vector of eigenvalues as returned by eigenvalues(). + * + * This is a column vector with entries of type #RealScalar. + * The length of the vector is the size of \p _MatrixType. + */ + typedef typename internal::plain_col_type<MatrixType, RealScalar>::type RealVectorType; + typedef Tridiagonalization<MatrixType> TridiagonalizationType; + + /** \brief Default constructor for fixed-size matrices. + * + * The default constructor is useful in cases in which the user intends to + * perform decompositions via compute(). This constructor + * can only be used if \p _MatrixType is a fixed-size matrix; use + * SelfAdjointEigenSolver(Index) for dynamic-size matrices. + * + * Example: \include SelfAdjointEigenSolver_SelfAdjointEigenSolver.cpp + * Output: \verbinclude SelfAdjointEigenSolver_SelfAdjointEigenSolver.out + */ + SelfAdjointEigenSolver() + : m_eivec(), + m_eivalues(), + m_subdiag(), + m_isInitialized(false) + { } + + /** \brief Constructor, pre-allocates memory for dynamic-size matrices. + * + * \param [in] size Positive integer, size of the matrix whose + * eigenvalues and eigenvectors will be computed. + * + * This constructor is useful for dynamic-size matrices, when the user + * intends to perform decompositions via compute(). The \p size + * parameter is only used as a hint. It is not an error to give a wrong + * \p size, but it may impair performance. + * + * \sa compute() for an example + */ + SelfAdjointEigenSolver(Index size) + : m_eivec(size, size), + m_eivalues(size), + m_subdiag(size > 1 ? size - 1 : 1), + m_isInitialized(false) + {} + + /** \brief Constructor; computes eigendecomposition of given matrix. + * + * \param[in] matrix Selfadjoint matrix whose eigendecomposition is to + * be computed. Only the lower triangular part of the matrix is referenced. + * \param[in] options Can be #ComputeEigenvectors (default) or #EigenvaluesOnly. + * + * This constructor calls compute(const MatrixType&, int) to compute the + * eigenvalues of the matrix \p matrix. The eigenvectors are computed if + * \p options equals #ComputeEigenvectors. + * + * Example: \include SelfAdjointEigenSolver_SelfAdjointEigenSolver_MatrixType.cpp + * Output: \verbinclude SelfAdjointEigenSolver_SelfAdjointEigenSolver_MatrixType.out + * + * \sa compute(const MatrixType&, int) + */ + SelfAdjointEigenSolver(const MatrixType& matrix, int options = ComputeEigenvectors) + : m_eivec(matrix.rows(), matrix.cols()), + m_eivalues(matrix.cols()), + m_subdiag(matrix.rows() > 1 ? matrix.rows() - 1 : 1), + m_isInitialized(false) + { + compute(matrix, options); + } + + /** \brief Computes eigendecomposition of given matrix. + * + * \param[in] matrix Selfadjoint matrix whose eigendecomposition is to + * be computed. Only the lower triangular part of the matrix is referenced. + * \param[in] options Can be #ComputeEigenvectors (default) or #EigenvaluesOnly. + * \returns Reference to \c *this + * + * This function computes the eigenvalues of \p matrix. The eigenvalues() + * function can be used to retrieve them. If \p options equals #ComputeEigenvectors, + * then the eigenvectors are also computed and can be retrieved by + * calling eigenvectors(). + * + * This implementation uses a symmetric QR algorithm. The matrix is first + * reduced to tridiagonal form using the Tridiagonalization class. The + * tridiagonal matrix is then brought to diagonal form with implicit + * symmetric QR steps with Wilkinson shift. Details can be found in + * Section 8.3 of Golub \& Van Loan, <i>%Matrix Computations</i>. + * + * The cost of the computation is about \f$ 9n^3 \f$ if the eigenvectors + * are required and \f$ 4n^3/3 \f$ if they are not required. + * + * This method reuses the memory in the SelfAdjointEigenSolver object that + * was allocated when the object was constructed, if the size of the + * matrix does not change. + * + * Example: \include SelfAdjointEigenSolver_compute_MatrixType.cpp + * Output: \verbinclude SelfAdjointEigenSolver_compute_MatrixType.out + * + * \sa SelfAdjointEigenSolver(const MatrixType&, int) + */ + SelfAdjointEigenSolver& compute(const MatrixType& matrix, int options = ComputeEigenvectors); + + /** \brief Computes eigendecomposition of given matrix using a direct algorithm + * + * This is a variant of compute(const MatrixType&, int options) which + * directly solves the underlying polynomial equation. + * + * Currently only 3x3 matrices for which the sizes are known at compile time are supported (e.g., Matrix3d). + * + * This method is usually significantly faster than the QR algorithm + * but it might also be less accurate. It is also worth noting that + * for 3x3 matrices it involves trigonometric operations which are + * not necessarily available for all scalar types. + * + * \sa compute(const MatrixType&, int options) + */ + SelfAdjointEigenSolver& computeDirect(const MatrixType& matrix, int options = ComputeEigenvectors); + + /** \brief Returns the eigenvectors of given matrix. + * + * \returns A const reference to the matrix whose columns are the eigenvectors. + * + * \pre The eigenvectors have been computed before. + * + * Column \f$ k \f$ of the returned matrix is an eigenvector corresponding + * to eigenvalue number \f$ k \f$ as returned by eigenvalues(). The + * eigenvectors are normalized to have (Euclidean) norm equal to one. If + * this object was used to solve the eigenproblem for the selfadjoint + * matrix \f$ A \f$, then the matrix returned by this function is the + * matrix \f$ V \f$ in the eigendecomposition \f$ A = V D V^{-1} \f$. + * + * Example: \include SelfAdjointEigenSolver_eigenvectors.cpp + * Output: \verbinclude SelfAdjointEigenSolver_eigenvectors.out + * + * \sa eigenvalues() + */ + const EigenvectorsType& eigenvectors() const + { + eigen_assert(m_isInitialized && "SelfAdjointEigenSolver is not initialized."); + eigen_assert(m_eigenvectorsOk && "The eigenvectors have not been computed together with the eigenvalues."); + return m_eivec; + } + + /** \brief Returns the eigenvalues of given matrix. + * + * \returns A const reference to the column vector containing the eigenvalues. + * + * \pre The eigenvalues have been computed before. + * + * The eigenvalues are repeated according to their algebraic multiplicity, + * so there are as many eigenvalues as rows in the matrix. The eigenvalues + * are sorted in increasing order. + * + * Example: \include SelfAdjointEigenSolver_eigenvalues.cpp + * Output: \verbinclude SelfAdjointEigenSolver_eigenvalues.out + * + * \sa eigenvectors(), MatrixBase::eigenvalues() + */ + const RealVectorType& eigenvalues() const + { + eigen_assert(m_isInitialized && "SelfAdjointEigenSolver is not initialized."); + return m_eivalues; + } + + /** \brief Computes the positive-definite square root of the matrix. + * + * \returns the positive-definite square root of the matrix + * + * \pre The eigenvalues and eigenvectors of a positive-definite matrix + * have been computed before. + * + * The square root of a positive-definite matrix \f$ A \f$ is the + * positive-definite matrix whose square equals \f$ A \f$. This function + * uses the eigendecomposition \f$ A = V D V^{-1} \f$ to compute the + * square root as \f$ A^{1/2} = V D^{1/2} V^{-1} \f$. + * + * Example: \include SelfAdjointEigenSolver_operatorSqrt.cpp + * Output: \verbinclude SelfAdjointEigenSolver_operatorSqrt.out + * + * \sa operatorInverseSqrt(), + * \ref MatrixFunctions_Module "MatrixFunctions Module" + */ + MatrixType operatorSqrt() const + { + eigen_assert(m_isInitialized && "SelfAdjointEigenSolver is not initialized."); + eigen_assert(m_eigenvectorsOk && "The eigenvectors have not been computed together with the eigenvalues."); + return m_eivec * m_eivalues.cwiseSqrt().asDiagonal() * m_eivec.adjoint(); + } + + /** \brief Computes the inverse square root of the matrix. + * + * \returns the inverse positive-definite square root of the matrix + * + * \pre The eigenvalues and eigenvectors of a positive-definite matrix + * have been computed before. + * + * This function uses the eigendecomposition \f$ A = V D V^{-1} \f$ to + * compute the inverse square root as \f$ V D^{-1/2} V^{-1} \f$. This is + * cheaper than first computing the square root with operatorSqrt() and + * then its inverse with MatrixBase::inverse(). + * + * Example: \include SelfAdjointEigenSolver_operatorInverseSqrt.cpp + * Output: \verbinclude SelfAdjointEigenSolver_operatorInverseSqrt.out + * + * \sa operatorSqrt(), MatrixBase::inverse(), + * \ref MatrixFunctions_Module "MatrixFunctions Module" + */ + MatrixType operatorInverseSqrt() const + { + eigen_assert(m_isInitialized && "SelfAdjointEigenSolver is not initialized."); + eigen_assert(m_eigenvectorsOk && "The eigenvectors have not been computed together with the eigenvalues."); + return m_eivec * m_eivalues.cwiseInverse().cwiseSqrt().asDiagonal() * m_eivec.adjoint(); + } + + /** \brief Reports whether previous computation was successful. + * + * \returns \c Success if computation was succesful, \c NoConvergence otherwise. + */ + ComputationInfo info() const + { + eigen_assert(m_isInitialized && "SelfAdjointEigenSolver is not initialized."); + return m_info; + } + + /** \brief Maximum number of iterations. + * + * The algorithm terminates if it does not converge within m_maxIterations * n iterations, where n + * denotes the size of the matrix. This value is currently set to 30 (copied from LAPACK). + */ + static const int m_maxIterations = 30; + + #ifdef EIGEN2_SUPPORT + SelfAdjointEigenSolver(const MatrixType& matrix, bool computeEigenvectors) + : m_eivec(matrix.rows(), matrix.cols()), + m_eivalues(matrix.cols()), + m_subdiag(matrix.rows() > 1 ? matrix.rows() - 1 : 1), + m_isInitialized(false) + { + compute(matrix, computeEigenvectors); + } + + SelfAdjointEigenSolver(const MatrixType& matA, const MatrixType& matB, bool computeEigenvectors = true) + : m_eivec(matA.cols(), matA.cols()), + m_eivalues(matA.cols()), + m_subdiag(matA.cols() > 1 ? matA.cols() - 1 : 1), + m_isInitialized(false) + { + static_cast<GeneralizedSelfAdjointEigenSolver<MatrixType>*>(this)->compute(matA, matB, computeEigenvectors ? ComputeEigenvectors : EigenvaluesOnly); + } + + void compute(const MatrixType& matrix, bool computeEigenvectors) + { + compute(matrix, computeEigenvectors ? ComputeEigenvectors : EigenvaluesOnly); + } + + void compute(const MatrixType& matA, const MatrixType& matB, bool computeEigenvectors = true) + { + compute(matA, matB, computeEigenvectors ? ComputeEigenvectors : EigenvaluesOnly); + } + #endif // EIGEN2_SUPPORT + + protected: + static void check_template_parameters() + { + EIGEN_STATIC_ASSERT_NON_INTEGER(Scalar); + } + + EigenvectorsType m_eivec; + RealVectorType m_eivalues; + typename TridiagonalizationType::SubDiagonalType m_subdiag; + ComputationInfo m_info; + bool m_isInitialized; + bool m_eigenvectorsOk; +}; + +/** \internal + * + * \eigenvalues_module \ingroup Eigenvalues_Module + * + * Performs a QR step on a tridiagonal symmetric matrix represented as a + * pair of two vectors \a diag and \a subdiag. + * + * \param matA the input selfadjoint matrix + * \param hCoeffs returned Householder coefficients + * + * For compilation efficiency reasons, this procedure does not use eigen expression + * for its arguments. + * + * Implemented from Golub's "Matrix Computations", algorithm 8.3.2: + * "implicit symmetric QR step with Wilkinson shift" + */ +namespace internal { +template<typename RealScalar, typename Scalar, typename Index> +static void tridiagonal_qr_step(RealScalar* diag, RealScalar* subdiag, Index start, Index end, Scalar* matrixQ, Index n); +} + +template<typename MatrixType> +SelfAdjointEigenSolver<MatrixType>& SelfAdjointEigenSolver<MatrixType> +::compute(const MatrixType& matrix, int options) +{ + check_template_parameters(); + + using std::abs; + eigen_assert(matrix.cols() == matrix.rows()); + eigen_assert((options&~(EigVecMask|GenEigMask))==0 + && (options&EigVecMask)!=EigVecMask + && "invalid option parameter"); + bool computeEigenvectors = (options&ComputeEigenvectors)==ComputeEigenvectors; + Index n = matrix.cols(); + m_eivalues.resize(n,1); + + if(n==1) + { + m_eivalues.coeffRef(0,0) = numext::real(matrix.coeff(0,0)); + if(computeEigenvectors) + m_eivec.setOnes(n,n); + m_info = Success; + m_isInitialized = true; + m_eigenvectorsOk = computeEigenvectors; + return *this; + } + + // declare some aliases + RealVectorType& diag = m_eivalues; + EigenvectorsType& mat = m_eivec; + + // map the matrix coefficients to [-1:1] to avoid over- and underflow. + mat = matrix.template triangularView<Lower>(); + RealScalar scale = mat.cwiseAbs().maxCoeff(); + if(scale==RealScalar(0)) scale = RealScalar(1); + mat.template triangularView<Lower>() /= scale; + m_subdiag.resize(n-1); + internal::tridiagonalization_inplace(mat, diag, m_subdiag, computeEigenvectors); + + Index end = n-1; + Index start = 0; + Index iter = 0; // total number of iterations + + while (end>0) + { + for (Index i = start; i<end; ++i) + if (internal::isMuchSmallerThan(abs(m_subdiag[i]),(abs(diag[i])+abs(diag[i+1])))) + m_subdiag[i] = 0; + + // find the largest unreduced block + while (end>0 && m_subdiag[end-1]==0) + { + end--; + } + if (end<=0) + break; + + // if we spent too many iterations, we give up + iter++; + if(iter > m_maxIterations * n) break; + + start = end - 1; + while (start>0 && m_subdiag[start-1]!=0) + start--; + + internal::tridiagonal_qr_step(diag.data(), m_subdiag.data(), start, end, computeEigenvectors ? m_eivec.data() : (Scalar*)0, n); + } + + if (iter <= m_maxIterations * n) + m_info = Success; + else + m_info = NoConvergence; + + // Sort eigenvalues and corresponding vectors. + // TODO make the sort optional ? + // TODO use a better sort algorithm !! + if (m_info == Success) + { + for (Index i = 0; i < n-1; ++i) + { + Index k; + m_eivalues.segment(i,n-i).minCoeff(&k); + if (k > 0) + { + std::swap(m_eivalues[i], m_eivalues[k+i]); + if(computeEigenvectors) + m_eivec.col(i).swap(m_eivec.col(k+i)); + } + } + } + + // scale back the eigen values + m_eivalues *= scale; + + m_isInitialized = true; + m_eigenvectorsOk = computeEigenvectors; + return *this; +} + + +namespace internal { + +template<typename SolverType,int Size,bool IsComplex> struct direct_selfadjoint_eigenvalues +{ + static inline void run(SolverType& eig, const typename SolverType::MatrixType& A, int options) + { eig.compute(A,options); } +}; + +template<typename SolverType> struct direct_selfadjoint_eigenvalues<SolverType,3,false> +{ + typedef typename SolverType::MatrixType MatrixType; + typedef typename SolverType::RealVectorType VectorType; + typedef typename SolverType::Scalar Scalar; + typedef typename MatrixType::Index Index; + typedef typename SolverType::EigenvectorsType EigenvectorsType; + + /** \internal + * Computes the roots of the characteristic polynomial of \a m. + * For numerical stability m.trace() should be near zero and to avoid over- or underflow m should be normalized. + */ + static inline void computeRoots(const MatrixType& m, VectorType& roots) + { + using std::sqrt; + using std::atan2; + using std::cos; + using std::sin; + const Scalar s_inv3 = Scalar(1.0)/Scalar(3.0); + const Scalar s_sqrt3 = sqrt(Scalar(3.0)); + + // The characteristic equation is x^3 - c2*x^2 + c1*x - c0 = 0. The + // eigenvalues are the roots to this equation, all guaranteed to be + // real-valued, because the matrix is symmetric. + Scalar c0 = m(0,0)*m(1,1)*m(2,2) + Scalar(2)*m(1,0)*m(2,0)*m(2,1) - m(0,0)*m(2,1)*m(2,1) - m(1,1)*m(2,0)*m(2,0) - m(2,2)*m(1,0)*m(1,0); + Scalar c1 = m(0,0)*m(1,1) - m(1,0)*m(1,0) + m(0,0)*m(2,2) - m(2,0)*m(2,0) + m(1,1)*m(2,2) - m(2,1)*m(2,1); + Scalar c2 = m(0,0) + m(1,1) + m(2,2); + + // Construct the parameters used in classifying the roots of the equation + // and in solving the equation for the roots in closed form. + Scalar c2_over_3 = c2*s_inv3; + Scalar a_over_3 = (c2*c2_over_3 - c1)*s_inv3; + if(a_over_3<Scalar(0)) + a_over_3 = Scalar(0); + + Scalar half_b = Scalar(0.5)*(c0 + c2_over_3*(Scalar(2)*c2_over_3*c2_over_3 - c1)); + + Scalar q = a_over_3*a_over_3*a_over_3 - half_b*half_b; + if(q<Scalar(0)) + q = Scalar(0); + + // Compute the eigenvalues by solving for the roots of the polynomial. + Scalar rho = sqrt(a_over_3); + Scalar theta = atan2(sqrt(q),half_b)*s_inv3; // since sqrt(q) > 0, atan2 is in [0, pi] and theta is in [0, pi/3] + Scalar cos_theta = cos(theta); + Scalar sin_theta = sin(theta); + // roots are already sorted, since cos is monotonically decreasing on [0, pi] + roots(0) = c2_over_3 - rho*(cos_theta + s_sqrt3*sin_theta); // == 2*rho*cos(theta+2pi/3) + roots(1) = c2_over_3 - rho*(cos_theta - s_sqrt3*sin_theta); // == 2*rho*cos(theta+ pi/3) + roots(2) = c2_over_3 + Scalar(2)*rho*cos_theta; + } + + static inline bool extract_kernel(MatrixType& mat, Ref<VectorType> res, Ref<VectorType> representative) + { + using std::abs; + Index i0; + // Find non-zero column i0 (by construction, there must exist a non zero coefficient on the diagonal): + mat.diagonal().cwiseAbs().maxCoeff(&i0); + // mat.col(i0) is a good candidate for an orthogonal vector to the current eigenvector, + // so let's save it: + representative = mat.col(i0); + Scalar n0, n1; + VectorType c0, c1; + n0 = (c0 = representative.cross(mat.col((i0+1)%3))).squaredNorm(); + n1 = (c1 = representative.cross(mat.col((i0+2)%3))).squaredNorm(); + if(n0>n1) res = c0/std::sqrt(n0); + else res = c1/std::sqrt(n1); + + return true; + } + + static inline void run(SolverType& solver, const MatrixType& mat, int options) + { + eigen_assert(mat.cols() == 3 && mat.cols() == mat.rows()); + eigen_assert((options&~(EigVecMask|GenEigMask))==0 + && (options&EigVecMask)!=EigVecMask + && "invalid option parameter"); + bool computeEigenvectors = (options&ComputeEigenvectors)==ComputeEigenvectors; + + EigenvectorsType& eivecs = solver.m_eivec; + VectorType& eivals = solver.m_eivalues; + + // Shift the matrix to the mean eigenvalue and map the matrix coefficients to [-1:1] to avoid over- and underflow. + Scalar shift = mat.trace() / Scalar(3); + // TODO Avoid this copy. Currently it is necessary to suppress bogus values when determining maxCoeff and for computing the eigenvectors later + MatrixType scaledMat = mat.template selfadjointView<Lower>(); + scaledMat.diagonal().array() -= shift; + Scalar scale = scaledMat.cwiseAbs().maxCoeff(); + if(scale > 0) scaledMat /= scale; // TODO for scale==0 we could save the remaining operations + + // compute the eigenvalues + computeRoots(scaledMat,eivals); + + // compute the eigenvectors + if(computeEigenvectors) + { + if((eivals(2)-eivals(0))<=Eigen::NumTraits<Scalar>::epsilon()) + { + // All three eigenvalues are numerically the same + eivecs.setIdentity(); + } + else + { + MatrixType tmp; + tmp = scaledMat; + + // Compute the eigenvector of the most distinct eigenvalue + Scalar d0 = eivals(2) - eivals(1); + Scalar d1 = eivals(1) - eivals(0); + Index k(0), l(2); + if(d0 > d1) + { + std::swap(k,l); + d0 = d1; + } + + // Compute the eigenvector of index k + { + tmp.diagonal().array () -= eivals(k); + // By construction, 'tmp' is of rank 2, and its kernel corresponds to the respective eigenvector. + extract_kernel(tmp, eivecs.col(k), eivecs.col(l)); + } + + // Compute eigenvector of index l + if(d0<=2*Eigen::NumTraits<Scalar>::epsilon()*d1) + { + // If d0 is too small, then the two other eigenvalues are numerically the same, + // and thus we only have to ortho-normalize the near orthogonal vector we saved above. + eivecs.col(l) -= eivecs.col(k).dot(eivecs.col(l))*eivecs.col(l); + eivecs.col(l).normalize(); + } + else + { + tmp = scaledMat; + tmp.diagonal().array () -= eivals(l); + + VectorType dummy; + extract_kernel(tmp, eivecs.col(l), dummy); + } + + // Compute last eigenvector from the other two + eivecs.col(1) = eivecs.col(2).cross(eivecs.col(0)).normalized(); + } + } + + // Rescale back to the original size. + eivals *= scale; + eivals.array() += shift; + + solver.m_info = Success; + solver.m_isInitialized = true; + solver.m_eigenvectorsOk = computeEigenvectors; + } +}; + +// 2x2 direct eigenvalues decomposition, code from Hauke Heibel +template<typename SolverType> struct direct_selfadjoint_eigenvalues<SolverType,2,false> +{ + typedef typename SolverType::MatrixType MatrixType; + typedef typename SolverType::RealVectorType VectorType; + typedef typename SolverType::Scalar Scalar; + typedef typename SolverType::EigenvectorsType EigenvectorsType; + + static inline void computeRoots(const MatrixType& m, VectorType& roots) + { + using std::sqrt; + const Scalar t0 = Scalar(0.5) * sqrt( numext::abs2(m(0,0)-m(1,1)) + Scalar(4)*numext::abs2(m(1,0))); + const Scalar t1 = Scalar(0.5) * (m(0,0) + m(1,1)); + roots(0) = t1 - t0; + roots(1) = t1 + t0; + } + + static inline void run(SolverType& solver, const MatrixType& mat, int options) + { + using std::sqrt; + using std::abs; + + eigen_assert(mat.cols() == 2 && mat.cols() == mat.rows()); + eigen_assert((options&~(EigVecMask|GenEigMask))==0 + && (options&EigVecMask)!=EigVecMask + && "invalid option parameter"); + bool computeEigenvectors = (options&ComputeEigenvectors)==ComputeEigenvectors; + + EigenvectorsType& eivecs = solver.m_eivec; + VectorType& eivals = solver.m_eivalues; + + // map the matrix coefficients to [-1:1] to avoid over- and underflow. + Scalar scale = mat.cwiseAbs().maxCoeff(); + scale = (std::max)(scale,Scalar(1)); + MatrixType scaledMat = mat / scale; + + // Compute the eigenvalues + computeRoots(scaledMat,eivals); + + // compute the eigen vectors + if(computeEigenvectors) + { + if((eivals(1)-eivals(0))<=abs(eivals(1))*Eigen::NumTraits<Scalar>::epsilon()) + { + eivecs.setIdentity(); + } + else + { + scaledMat.diagonal().array () -= eivals(1); + Scalar a2 = numext::abs2(scaledMat(0,0)); + Scalar c2 = numext::abs2(scaledMat(1,1)); + Scalar b2 = numext::abs2(scaledMat(1,0)); + if(a2>c2) + { + eivecs.col(1) << -scaledMat(1,0), scaledMat(0,0); + eivecs.col(1) /= sqrt(a2+b2); + } + else + { + eivecs.col(1) << -scaledMat(1,1), scaledMat(1,0); + eivecs.col(1) /= sqrt(c2+b2); + } + + eivecs.col(0) << eivecs.col(1).unitOrthogonal(); + } + } + + // Rescale back to the original size. + eivals *= scale; + + solver.m_info = Success; + solver.m_isInitialized = true; + solver.m_eigenvectorsOk = computeEigenvectors; + } +}; + +} + +template<typename MatrixType> +SelfAdjointEigenSolver<MatrixType>& SelfAdjointEigenSolver<MatrixType> +::computeDirect(const MatrixType& matrix, int options) +{ + internal::direct_selfadjoint_eigenvalues<SelfAdjointEigenSolver,Size,NumTraits<Scalar>::IsComplex>::run(*this,matrix,options); + return *this; +} + +namespace internal { +template<typename RealScalar, typename Scalar, typename Index> +static void tridiagonal_qr_step(RealScalar* diag, RealScalar* subdiag, Index start, Index end, Scalar* matrixQ, Index n) +{ + using std::abs; + RealScalar td = (diag[end-1] - diag[end])*RealScalar(0.5); + RealScalar e = subdiag[end-1]; + // Note that thanks to scaling, e^2 or td^2 cannot overflow, however they can still + // underflow thus leading to inf/NaN values when using the following commented code: +// RealScalar e2 = numext::abs2(subdiag[end-1]); +// RealScalar mu = diag[end] - e2 / (td + (td>0 ? 1 : -1) * sqrt(td*td + e2)); + // This explain the following, somewhat more complicated, version: + RealScalar mu = diag[end]; + if(td==0) + mu -= abs(e); + else + { + RealScalar e2 = numext::abs2(subdiag[end-1]); + RealScalar h = numext::hypot(td,e); + if(e2==0) mu -= (e / (td + (td>0 ? 1 : -1))) * (e / h); + else mu -= e2 / (td + (td>0 ? h : -h)); + } + + RealScalar x = diag[start] - mu; + RealScalar z = subdiag[start]; + for (Index k = start; k < end; ++k) + { + JacobiRotation<RealScalar> rot; + rot.makeGivens(x, z); + + // do T = G' T G + RealScalar sdk = rot.s() * diag[k] + rot.c() * subdiag[k]; + RealScalar dkp1 = rot.s() * subdiag[k] + rot.c() * diag[k+1]; + + diag[k] = rot.c() * (rot.c() * diag[k] - rot.s() * subdiag[k]) - rot.s() * (rot.c() * subdiag[k] - rot.s() * diag[k+1]); + diag[k+1] = rot.s() * sdk + rot.c() * dkp1; + subdiag[k] = rot.c() * sdk - rot.s() * dkp1; + + + if (k > start) + subdiag[k - 1] = rot.c() * subdiag[k-1] - rot.s() * z; + + x = subdiag[k]; + + if (k < end - 1) + { + z = -rot.s() * subdiag[k+1]; + subdiag[k + 1] = rot.c() * subdiag[k+1]; + } + + // apply the givens rotation to the unit matrix Q = Q * G + if (matrixQ) + { + Map<Matrix<Scalar,Dynamic,Dynamic,ColMajor> > q(matrixQ,n,n); + q.applyOnTheRight(k,k+1,rot); + } + } +} + +} // end namespace internal + +} // end namespace Eigen + +#endif // EIGEN_SELFADJOINTEIGENSOLVER_H |