[Octave-patch-tracker] [patch #9282] add minres for sparse linear systems

[Marco Caliari]

Follow-up Comment #5, patch #9282 (project octave):

1. Could it be what given in formula (5.17) of Paige&Saunders?
Moreover, it seems that you compute the true residual (b-A*x), which requires
an additional matrix-vector per step. I think you should use formulas
(5.13)--(5.16).

2. If by "ill-conditioned" you mean that octave gives the warning "matrix is
singular...", I think Cristiano did something with try... catch.
You could use issymmetric. Does matlab check it? For instance, there is not
such a check in pcg. 

4. Does matlab accept complex matrices? Does it work with complex matrices?

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