You most definitely want to call KSPGetConvergedReason() after every solve
KSPConvergedReason reason
....
call KSPSolve(ksp,b,x,ierr)
call KSPGetConvergedReason(ksp,reason,ierr)
if (reason .lt. 0) then
printf*,'KSPSolve() has not converged'
return
endif
> On May 30, 2019, at 5:13 AM, Edoardo alinovi <edoardo.alin...@gmail.com>
> wrote:
>
> Hello Barry,
>
> I am solving ns eqs using the standard simple algorithm.
>
> As example let's say the the u velocity compoment diverges, the output of ksp
> is a nan as solution vector, but the program keeps going ahead solving also
> for the other components and for the pressure where again I get NaN. The only
> way to stop it is by hand using ctrl+C.
>
> I am not using kspConvergedReason, maybe can you provide me an example in
> fortran?
>
> Many thanks as always!
>
> On Wed, 29 May 2019, 23:54 Smith, Barry F., <bsm...@mcs.anl.gov> wrote:
>
>
> > On May 29, 2019, at 2:54 PM, Edoardo alinovi <edoardo.alin...@gmail.com>
> > wrote:
> >
> > Hello Barry,
> >
> > Using Matt's fix KSP stops exactly at the first NaN. Otherwise the
> > simulation continues
>
> Yes, but what do you mean by the simulation? Are you calling
> KSPGetConvergedReason() after each solve to check if it was valid? Is the
> particular linear solver continuing to run with Nan?
>
>
>
> > even if everything is a NaN. I am using version 3.10.4, is this not enough
> > up to date maybe?
> >
> > Tomorrow, I will run the monitor and get back to you. For today I have got
> > my "safe working limit" :)
> >
> > Thanks a lot guys for the help!
> >
> > ------
> >
> > Edoardo Alinovi, Ph.D.
> >
> > DICCA, Scuola Politecnica,
> > Universita' degli Studi di Genova,
> > 1, via Montallegro,
> > 16145 Genova, Italy
> >
> > Email: edoardo.alin...@dicca.unige.it
> > Tel: +39 010 353 2540
> > Website: https://www.edoardoalinovi.com/
> >
> >
> >
> >
> > Il giorno mer 29 mag 2019 alle ore 20:22 Smith, Barry F.
> > <bsm...@mcs.anl.gov> ha scritto:
> >
> > Hmm, in the lastest couple of releases of PETSc the KSPSolve is suppose
> > to end as soon as it hits a NaN or Infinity. Is that not happening for you?
> > If you run with -ksp_monitor does it print multiple lines with Nan or Inf?
> > If so please send use the -ksp_view output so we can track down which
> > solver is not correctly handling the Nan or Info.
> >
> > That said if you call KSPSolve() multiple times in a loop or from
> > SNESSolve() each new solve may have Nan or Inf (from the previous) but it
> > should only do one iteration before exiting.
> >
> > You should always call KSPGetConvergedReason() after KSPSolve() and
> > confirm that the reason is positive, if it is native it indicates something
> > failed in the solve.
> >
> > Barry
> >
> >
> > > On May 29, 2019, at 2:06 AM, Edoardo alinovi via petsc-users
> > > <petsc-users@mcs.anl.gov> wrote:
> > >
> > > Dear PETSc friends,
> > >
> > > Hope you are doing all well.
> > >
> > > I have a quick question for you that I am not able to solve by my self.
> > > Time to time, while testing new code features, it happens that KSP
> > > diverges but it does not stop automatically and the iterations continue
> > > even after getting a NaN.
> > >
> > > In the KSP setup I use the following instruction to set the divergence
> > > stopping criteria (div = 10000):
> > >
> > > call KSPSetTolerances(myksp, rel_tol, abs_tol, div, itmax, ierr)
> > >
> > > But is does not help. Looking into the documentation I have found also:
> > > KSPConvergedDefault(KSP ksp,PetscInt n,PetscReal rnorm,KSPConvergedReason
> > > *reason,void *ctx)
> > > Which I am not calling in the code. Is this maybe the reason of my
> > > problem? If yes how can I use KSPConvergedDefault in FORTRAN?
> > >
> > > Thanks,
> > >
> > > Edo
> > >
> > > ------
> > >
> > > Edoardo Alinovi, Ph.D.
> > >
> > > DICCA, Scuola Politecnica,
> > > Universita' degli Studi di Genova,
> > > 1, via Montallegro,
> > > 16145 Genova, Italy
> > >
> > > Email: edoardo.alin...@dicca.unige.it
> > > Tel: +39 010 353 2540
> > > Website: https://www.edoardoalinovi.com/
> > >
> > >
> >
>
