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Re: Non repeatability issue


1) Are you sure the -vecscatter_reproduce is working, run with - options_left and see if
says the option was not used.

2) did you do the -ksp_rtol 1.e-12 at the same time as the - vecscatter_reproduce? They
must be done together.

3) what happens on 1 process? Does it behave exactly the same for two identical runs?

4) there is too much going on here to figure out why you get this behavior. Can you please
FIX the continuation parameter and run until Newton converges? Is the convergence in
this case reproduceable? What happens if you only change the continuation parameter
after you have Newton fully converged for the current continuation parameter? is that
reproduceable.

5) in the plots can you indicate when the continuation parameter is changed? You are
merging two algorithms (Newton's method and continuation together) you cannot hope
to understand that merged algorithm until you understand each of them seperately.

   Barry


On Mar 18, 2008, at 5:57 AM, Aldo Bonfiglioli wrote:


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 enclosed
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.

Aldo

--
Dr. Aldo Bonfiglioli
Dip.to 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

<low_ksp_rtol.pdf><vecscatter_reproduce.pdf>