On exit: for CG and SYMMLQ methods, the current estimate of the largest singular value
of the preconditioned iteration matrix
, when either it has been supplied to
nag_sparse_sym_basic_setup (f11gdc) or it has been estimated by
nag_sparse_sym_basic_solver (f11gec) (see also
Sections 3 and
5 in
nag_sparse_sym_basic_setup (f11gdc)). Note that if
then
sigmax contains the final estimate. If, on final exit from
nag_sparse_sym_basic_solver (f11gec),
, the estimation of
may have not converged; in this case you should look at the value returned in
sigerr. Otherwise,
is returned.
For MINRES method, an estimate of the final transformed residual.