[petsc-users] KSP changes for successive solver

[Barry Smith]

   Dang, it was in next but never got into master barry/remove-pcsetup-mg-changeofpreonly/master

   I have put the change into master

  Barry

> On Jul 18, 2015, at 10:40 PM, Matthew Knepley <knepley at gmail.com> wrote:
> 
> On Sat, Jul 18, 2015 at 10:31 PM, Michele Rosso <mrosso at uci.edu> wrote:
> Matt,
> 
> please find the log_summary attached.
> 
> Okay, it is running master. Barry, where should he look in the code to see why its still changing,
> meaning what changeset fixed this?
> 
>   Thanks,
> 
>     Matt
>  
> Michele
> 
> On Sat, 2015-07-18 at 21:56 -0500, Matthew Knepley wrote:
>> On Sat, Jul 18, 2015 at 9:53 PM, Michele Rosso <mrosso at uci.edu> wrote:
>> Barry,
>> 
>> I tried the master branch of PETSc as you suggested and unfortunately the problem with KSP being set to GMRES on the coarse level when using "-mg_coarse_ksp_type preonly"  is still there. I attached the output from ksp view and the options stack.
>> Am I missing something?
>> 
>> 
>> 
>> If you show output from -log_summary we can make sure you are running the version we expect.
>> 
>> 
>>   Thanks,
>> 
>> 
>>     Matt
>>  
>> Thanks,
>> Michele
>> 
>> 
>> On Thu, 2015-07-16 at 17:30 -0500, Barry Smith wrote:
>>>    Michel,
>>> 
>>>     This is a very annoying feature that has been fixed in master 
>>> http://www.mcs.anl.gov/petsc/developers/index.html
>>>   I would like to have changed it in maint but Jed would have a shit-fit :-) since it changes behavior.
>>> 
>>>   Barry
>>> 
>>> 
>>> > On Jul 16, 2015, at 4:53 PM, Michele Rosso <mrosso at uci.edu> wrote:
>>> > 
>>> > Hi,
>>> > 
>>> > I am performing a series of solves inside a loop. The matrix for each solve changes but not enough to justify a rebuilt of the PC at each solve.
>>> > Therefore I am using  KSPSetReusePreconditioner to avoid rebuilding unless necessary. The solver is CG + MG with a custom  PC at the coarse level.
>>> > If KSP is not updated each time, everything works as it is supposed to. 
>>> > When instead I allow the default PETSc  behavior, i.e. updating PC every time the matrix changes, the coarse level KSP , initially set to PREONLY, is changed into GMRES 
>>> > after the first solve. I am not sure where the problem lies (my PC or PETSc), so I would like to have your opinion on this.
>>> > I attached the ksp_view for the 2 successive solve and the options stack.
>>> > 
>>> > Thanks for your help,
>>> > Michel
>>> > 
>>> > 
>>> > 
>>> > <ksp_view.txt><petsc_options.txt>
>>> 
>>> 
>>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> --
>> 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
> 
> 
> 
> 
> -- 
> 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