[Octave-bug-tracker] [bug #36568] wrong flag returned by gmres

[Gerard BURNSIDE]

URL:
  <http://savannah.gnu.org/bugs/?36568>

                 Summary: wrong flag returned by gmres
                 Project: GNU Octave
            Submitted by: gerardburnside
            Submitted on: jeu. 31 mai 2012 15:20:47 GMT
                Category: None
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Inaccurate Result
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 3.6.1
        Operating System: Any

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Details:

While checking out the samples for gmres and bicgstab, I noticed that gmres
returned a flag 1 (max num iterations reached) where I expected it to return a
flag 0 (converged).

Looking at gmres.m it seems that you just need to change the inequality after
the while loop from:

 if (presn > rtol * prec_b_norm)
   flag = 0;

to:

 if (presn <= rtol * prec_b_norm)
   flag = 0;

(by default the flag is initializd to 1).




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