On the growth factor upper bound for Aasen's algorithm

Abstract

Aasen's algorithm factorizes a symmetric indefinite matrix $A$ as $A=P^{T}LT{L}^{T}P$, where $P$ is a permutation matrix, $L$ is unit lower triangular with its first column being the first column of the identity matrix, and $T$ is tridiagonal. In this note, we provide a growth factor upper bound for Aasen's algorithm which is much smaller than that given by Higham. We also show that the upper bound we have given is not tight when the matrix dimension is greater than or equal to $6$.