Problem with rectangular matrices

Matthew Knepley knepley at
Tue May 26 12:31:37 CDT 2009

On Tue, May 26, 2009 at 12:29 PM, Jed Brown <jed at> wrote:

> Matthew Knepley wrote:
> > It not computing Ab. Its computing Ab, A^2b, A^3b, etc.
> Of course, but that's all possible if A*b is computable.  Lisandro
> demonstrated that A*x was fine, which it better be because of how x was
> obtained.  Had he tried A*b, which is the first thing the KSP needs, the
> problem would have been obvious.

This is the whole point. b and x cannot have different local sizes in a
method. It makes no sense.


> Jed
What most experimenters take for granted before they begin their experiments
is infinitely more interesting than any results to which their experiments
-- Norbert Wiener
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