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A graph-theoretic model of symmetric givens operations and its implications
Journal article   Open access   Peer reviewed

A graph-theoretic model of symmetric givens operations and its implications

D.E Stewart
Linear algebra and its applications, Vol.257(1-3), pp.311-320
1997
DOI: 10.1016/S0024-3795(96)00157-7
url
https://doi.org/10.1016/S0024-3795(96)00157-7View
Published (Version of record) Open Access

Abstract

Symmetric Givens operations ( A′ ← GAG T , G a Givens rotation matrix) are a basic tool in many matrix computations, especially for eigenvalue-eigenvector computations. A graph-theoretic model of these operations is given for symmetric matrices, analogous to the graph-theoretic model of Cholesky factorization. Using this model, it is shown that unless there is “accidental cancellation,” it is impossible to reduce a range of different matrix classes to tridiagonal form in o( n 2) Givens operations; these classes include arrowhead matrices, pentadiagonal matrices, and cyclic tridiagonal matrices.

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