STOC '95 Proceedings of the twenty-seventh annual ACM symposium on Theory of computing
Matrix computations (3rd ed.)
Polynomial root finding using iterated Eigenvalue computation
Proceedings of the 2001 international symposium on Symbolic and algebraic computation
Univariate polynomials: nearly optimal algorithms for numerical factorization and root-finding
Journal of Symbolic Computation - Computer algebra: Selected papers from ISSAC 2001
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We modify the customary approach to solving the algebraic eigenproblem. Instead of applying the QR algorithm to a Hessenberg matrix, we begin with the recent unitary similarity transform into a triangular plus rank-one matrix. Then we show nonunitary transforms of this matrix at a low arithmetic cost into similar arrow-head matrices. The resulting eigenproblem can be effectively solved by the known algorithms. Based on some properties of the TPRI matrices, we also show that the similarity transforms into both Hessenberg and TPRI forms tend to decrease the geometric multiplicities of the eigenvalues, and we discuss some relevant research topics.