bugGNU Octave - Bugs: bug #40057, exit criterion in pcg


bug #40057: exit criterion in pcg

Submitted by:  Marco Caliari <caliari>
Submitted on:  Wed 18 Sep 2013 09:40:46 AM UTC  
Category:  Octave Function Severity:  2 - Minor
Priority:  5 - Normal Item Group:  Matlab Compatibility
Status:  Fixed Assigned to:  None
Originator Name:  Open/Closed:  Closed
Release:  3.6.2 Operating System:  GNU/Linux

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Thu 17 Oct 2013 11:05:42 PM UTC, comment #1:

I changed the criterion in this changeset (http://hg.savannah.gnu.org/hgweb/octave/rev/f6fded839513). Closing report.

Rik <rik5>
Project Administrator
Wed 18 Sep 2013 09:40:46 AM UTC, original submission:

Dear all,

the exit criterion in pcg is

On the other hand, in C.T. Kelley (quoted as reference book), p.23, it is used

and the same in matlab (as I understand from the description of [X,FLAG,RELRES] output). Of course, Octave criterion is a valid one and they coincide for X0 = zeros (the default value). I think it should be changed for compatibility. If one really needs the current behavior, he can give TOL * norm (B - A * X0) / norm (B) as input tolerance.



Marco Caliari <caliari>
Project Member


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    Follow 2 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2013-10-17 rik5 StatusNone => Fixed
        Open/ClosedOpen => Closed

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