On exit: the current estimate of the largest singular value
${\sigma}_{1}\left(\stackrel{-}{A}\right)$ of the preconditioned iteration matrix
$\stackrel{-}{A}={E}^{-1}A{E}^{-\mathrm{H}}$, when either it has been supplied to
F11GRF or it has been estimated by
F11GSF (see also
Sections 3 and
5 in F11GRF). Note that if
${\mathbf{ITS}}<{\mathbf{ITN}}$ then
SIGMAX contains the final estimate. If, on final exit from
F11GSF,
${\mathbf{ITS}}={\mathbf{ITN}}$, then the estimation of
${\sigma}_{1}\left(\stackrel{-}{A}\right)$ may have not converged: in this case you should look at the value returned in
SIGERR. Otherwise,
${\mathbf{SIGMAX}}=0.0$ is returned.