Non repeatability issue

Aldo Bonfiglioli aldo.bonfiglioli at
Tue Mar 18 05:57:59 CDT 2008

> 1)    Have you made runs where you require, say -ksp_rtol 1.e-12 to  
> eliminate the effects of
> not solving the linear systems accurately?

I have performed two runs with ksp_rtol = 1.e-12. The relevant plots are 
where comparisons are made with PETSc's default for ksp_rtol.
In one of these two runs Newton even diverges.
It should however be mentioned that
at least for some Newton steps, the linear solver does not meet the
convergence criterion in 2000 linear iterations (I reduced the default).

> I have added the  argument -vecscatter_reproduce
> that will cause the receives to always be processed in the same order  
> (though order or
> operations in the MPI reductions may still result in slightly  
> different convergence histories.)
>   Hope this helps clear things up,

I am not sure "-vecscatter_reproduce " has changed the situation much.
Out of 4 subsequent runs, 2 converge
while 2 enter a limit cycle I had not seen previously
(I mean without the -vecscatter_reproduce option).
The initial solution is the same as that shown in the other plot.


Dr. Aldo Bonfiglioli di Ingegneria e Fisica dell'Ambiente (DIFA)
Universita' della Basilicata
V.le dell'Ateneo lucano, 10 85100 Potenza ITALY
tel:+39.0971.205203 fax:+39.0971.205160

-------------- next part --------------
A non-text attachment was scrubbed...
Name: low_ksp_rtol.pdf
Type: application/pdf
Size: 10354 bytes
Desc: not available
URL: <>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: vecscatter_reproduce.pdf
Type: application/pdf
Size: 13056 bytes
Desc: not available
URL: <>

More information about the petsc-users mailing list