Abstract:
MINRES-N is a minimal residual algorithm originally developed by the authors for solving systems of linear equations with normal coefficient matrices whose spectra lie on algebraic curves of low degree. In a previous publication, the authors showed that a variant of MINRES-N
called MINRES-N2 is applicable to nonnormal matrices $A$ for which
$$
\mathrm{rank}\,(A-A^*)=1.
$$
This fact is extended to nonnormal matrices $A$ such that
$$
\mathrm{rank}\,(A-A^*)=k, \qquad k\ge1.
$$