Matrix computations (3rd ed.)
Linking the TPR1, DPR1 and Arrow-Head Matrix Structures
Computers & Mathematics with Applications
Null space and eigenspace computations with additive preprocessing
Proceedings of the 2007 international workshop on Symbolic-numeric computation
Structured matrix methods for polynomial root-finding
Proceedings of the 2007 international symposium on Symbolic and algebraic computation
Additive preconditioning and aggregation in matrix computations
Computers & Mathematics with Applications
Algebraic and numerical algorithms
Algorithms and theory of computation handbook
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Highly effective polynomial root-finders have been recently designed based on eigen-solving for DPR1 (that is diagonal + rank-one) matrices. We extend these algorithms to eigen-solving for the general matrix by reducing the problem to the case of the DPR1 input via intermediate transition to a TPR1 (that is triangular + rank-one) matrix. Our transforms use substantially fewer arithmetic operations than the QR classical algorithms but employ non-unitary similarity transforms of a TPR1 matrix, whose representation tends to be numerically unstable. We, however, operate with TPR1 matrices implicitly, as with the inverses of Hessenberg matrices. In this way our transform of an input matrix into a similar DPR1 matrix partly avoids numerical stability problems and still substantially decreases arithmetic cost versus the QR algorithm.