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

[Jed B. <je...@je...>]

"Salazar De Troya, Miguel" <sal...@ll...> writes:

> No. There does not seem to be more output. The program keeps running, but after the first time I see this error, all subsequent solves return a "nan" residual norm and the same preconditioner error pops up. Is there any way to obtain more output? This is the output in the context of the KSPSolve:
>
>
> First solve where the preconditioner fails:
>
>
> Residual norms for Elasticity_ solve.
> 0 KSP unpreconditioned resid norm 1.421591570438e+02 true resid norm 1.421591570438e+02 ||r(i)||/||b|| 1.000000000000e+00
> Linear Elasticity_ solve did not converge due to DIVERGED_PCSETUP_FAILED iterations 0
> PCSETUP_FAILED due to FACTOR_NOERROR

What code is printing this last line?  The PC isn't of type Factor so I
don't see why it would be printed.  You could try running with -info to
get more detailed information from PETSc.  Or run in a debugger.

The Libmesh/user code on the outside probably shouldn't naively continue
after the first error.  It could, for example, recompute the operators
with a smaller time step and retry the solve.

> Following solves (the optimization keeps running) all look like this:
>
> Residual norms for Elasticity_ solve.
> 0 KSP unpreconditioned resid norm 1.450166975748e+02 true resid norm           -nan ||r(i)||/||b||           -nan
> Linear Elasticity_ solve did not converge due to DIVERGED_PCSETUP_FAILED iterations 0
> PCSETUP_FAILED due to FACTOR_NOERROR
>
> Any way I can catch this PCSETUP_FAILED due to FACTOR_NOERROR?
>
>
> Miguel
>
> ________________________________
> From: Jed Brown <je...@je...>
> Sent: Sunday, November 12, 2017 12:11:29 PM
> To: Salazar De Troya, Miguel; lib...@li...
> Subject: Re: [Libmesh-users] try-catch in a PETSc solve()
>
> "Salazar De Troya, Miguel" <sal...@ll...> writes:
>
>> The error is:
>>
>>
>> Linear Elasticity_ solve did not converge due to DIVERGED_PCSETUP_FAILED iterations 0
>
> This is PETSc output due to
>
>   -Elasticity_ksp_converged_reason
>
> It doesn't set an error.
>
>>                                       PCSETUP_FAILED due to FACTOR_NOERROR
>
> Is there really no other output?  Always send all the output.
>
>> The program actually continues, Is there any way I can catch this divergence and do some operation like writing to disk?
>>
>> Thanks
>> Miguel
>>
>>
>>
>> ________________________________
>> From: Jed Brown <je...@je...>
>> Sent: Saturday, November 11, 2017 1:43:32 PM
>> To: Salazar De Troya, Miguel; lib...@li...
>> Subject: Re: [Libmesh-users] try-catch in a PETSc solve()
>>
>> What is your error message?  If the error is raised in PETSc, there is
>> usually a setting to make it return without raising an error (instead
>> setting a "diverged" reason).
>>
>> "Salazar De Troya, Miguel" <sal...@ll...> writes:
>>
>>> 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")
>>>
>>> }
>>>
>>>
>>> Thanks
>>>
>>> Miguel
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