Oh yes, it could happen with Nan.
KSPGMRESClassicalGramSchmidtOrthogonalization() calls
KSPCheckDot(ksp,lhh[j]); so should detect any NAN that appear and set
ksp->convergedreason but the call to MAXPY() is still made before returning
and hence producing the error message.
We should circuit the orthogonalization as soon as it sees a Nan/Inf and
return immediately for GMRES to cleanup and produce a very useful error
message.
Alfredo,
It is also possible that the hypre preconditioners are producing a Nan
because your matrix is too difficult for them to handle, but it would be odd to
happen after many iterations.
As I suggested before run with -pc_type bjacobi to see if you get the same
problem.
Barry
> On Aug 24, 2020, at 6:38 PM, Matthew Knepley <[email protected]> wrote:
>
> On Mon, Aug 24, 2020 at 6:27 PM Barry Smith <[email protected]
> <mailto:[email protected]>> wrote:
>
> Alfredo,
>
> This should never happen. The input to the VecMAXPY in gmres is
> computed via VMDot which produces the same result on all processes.
>
> If you run with -pc_type bjacobi does it also happen?
>
> Is this your custom code or does it happen in PETSc examples also?
> Like src/snes/tutorials/ex19 -da_refine 5
>
> Could be memory corruption, can you run under valgrind?
>
> Couldn't it happen if something generates a NaN? That also should not happen,
> but I was allowing that pilut might do it.
>
> Thanks,
>
> Matt
>
> Barry
>
>
> > On Aug 24, 2020, at 4:05 PM, Alfredo Jaramillo <[email protected]
> > <mailto:[email protected]>> wrote:
> >
> > Dear PETSc developers,
> >
> > I'm trying to solve a linear problem with GMRES preconditioned with pilut
> > from HYPRE. For this I'm using the options:
> >
> > -ksp_type gmres -pc_type hypre -pc_hypre_type pilut -ksp_monitor
> >
> > If I use a single core, GMRES (+ pilut or euclid) converges. However, when
> > using multiple cores the next error appears after some number of iterations:
> >
> > [0]PETSC ERROR: Scalar value must be same on all processes, argument # 3
> >
> > relative to the function VecMAXPY. I attached a screenshot with more
> > detailed output. The same happens when using euclid. Can you please give me
> > some insight on this?
> >
> > best regards
> > Alfredo
> > <Screenshot from 2020-08-24 17-57-52.png>
>
>
>
> --
> What most experimenters take for granted before they begin their experiments
> is infinitely more interesting than any results to which their experiments
> lead.
> -- Norbert Wiener
>
> https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
