PreprintarXiv licencearXiv
A Modified Direct Eigenvalue Swapping Algorithm with Guaranteed Stability
Abstract
For a given matrix A in the real Schur form, the eigenvalue swapping algorithm is used to swap two adjacent diagonal blocks. In LAPACK, this operation is performed by the subroutine~\texttt{SLAEXC}/\texttt{DLAEXC}, which is based on a direct swapping algorithm proposed by Bai and Demmel in 1993. In this work, we present a thorough error analysis of a modified direct swapping algorithm. By a carefully designed pivoted Givens QR factorization, this algorithm can achieve an error bound of the form O( u lVert A rVert ) under mild assumptions, where u is the unit roundoff. We present empirical evidence to illustrate the superior stability of our algorithm over existing approaches.
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BibTeX
@misc{shao2026modified,
title = {{A Modified Direct Eigenvalue Swapping Algorithm with Guaranteed Stability}},
author = {Meiyue Shao and Rentao Xu},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.30795},
eprint = {2610.30795},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.30795},
}
RIS
TY - UNPB
TI - A Modified Direct Eigenvalue Swapping Algorithm with Guaranteed Stability
AU - Meiyue Shao
AU - Rentao Xu
PY - 2026
DA - 2026/10/22
PB - arXiv
DO - 10.48550/arxiv.2610.30795
UR - https://arxiv.org/abs/2610.30795
AB - For a given matrix A in the real Schur form, the eigenvalue swapping algorithm is used to swap two adjacent diagonal blocks. In LAPACK, this operation is performed by the subroutine~\texttt{SLAEXC}/\texttt{DLAEXC}, which is based on a direct swapping algorithm proposed by Bai and Demmel in 1993. In this work, we present a thorough error analysis of a modified direct swapping algorithm. By a carefully designed pivoted Givens QR factorization, this algorithm can achieve an error bound of the form O( u lVert A rVert ) under mild assumptions, where u is the unit roundoff. We present empirical evidence to illustrate the superior stability of our algorithm over existing approaches.
ER -