Re: [Libmesh-users] try-catch in a PETSc solve()

[John P. <jwp...@gm...>]

On Sat, Nov 11, 2017 at 2:14 PM, Salazar De Troya, Miguel <
sal...@ll...> wrote:

> Hello
>
>
> I have an optimization problem for which at a certain iteration, PETSc
> fails to build the preconditioner. I would like to catch that error and
> print my EquationSystem to disk so I can rerun the PETSc solve at that
> optimization iteration from the start. I cannot just rerun my optimization
> and write to disk at the iteration I know it is going to fail. The reason
> is that in parallel the optimization slightly differs every time I run it
> so the iteration it is going to fail at keeps changing. Maybe something
> along this lines:
>
>
> try{
>
>     system.solve()
>
> }
>
> catch(...){
>
>    EquationSystem & es = system.get_equation_systems();
>
>    es.write("eq_output.xdr")
>
> }
>

I'm pretty sure we don't throw an exception when a solve fails, so there's
not going to be anything for you to catch here...

For a LinearImplicitSystem, the usual approach is to inspect the value of

system.get_linear_solver()->get_converged_reason();

and then decide what to do (retry the last time step, etc.) from there.

When you say "optimization problem" are you actually using the TAO-based
OptimizationSystem class that is in libmesh?

-- 
John