[petsc-users] monitoring the convergence of fieldsplit 0 and 1

[Barry Smith]

   Yes, I would have expected this to work. Could you send the output from -ksp_view in this case?


> On Jan 13, 2017, at 3:46 AM, Klaij, Christiaan <C.Klaij at marin.nl> wrote:
> 
> Barry,
> 
> It's been a while but I'm finally using this function in
> 3.7.4. Is it supposed to work with fieldsplit? Here's why.
> 
> I'm solving a Navier-Stokes system with fieldsplit (pc has one
> velocity solve and one pressure solve) and trying to retrieve the
> totals like this:
> 
>  CALL KSPSolve(ksp_system,rr_system,xx_system,ierr); CHKERRQ(ierr)
>  CALL PCFieldSplitGetSubKSP(pc_system,numsplit,subksp,ierr); CHKERRQ(ierr)
>  CALL KSPGetTotalIterations(subksp(1),nusediter_vv,ierr); CHKERRQ(ierr)
>  CALL KSPGetTotalIterations(subksp(2),nusediter_pp,ierr); CHKERRQ(ierr)
> print *, 'nusediter_vv', nusediter_vv
> print *, 'nusediter_pp', nusediter_pp
> 
> Running the code shows this surprise:
> 
>  Linear sys_fieldsplit_0_ solve converged due to CONVERGED_RTOL iterations 1
>  Linear sys_fieldsplit_0_ solve converged due to CONVERGED_RTOL iterations 1
>  Linear sys_fieldsplit_0_ solve converged due to CONVERGED_RTOL iterations 2
>  Linear sys_fieldsplit_0_ solve converged due to CONVERGED_RTOL iterations 2
>  Linear sys_fieldsplit_0_ solve converged due to CONVERGED_RTOL iterations 7
>  Linear sys_fieldsplit_0_ solve converged due to CONVERGED_RTOL iterations 7
>  Linear sys_fieldsplit_0_ solve converged due to CONVERGED_RTOL iterations 7
>  Linear sys_fieldsplit_0_ solve converged due to CONVERGED_RTOL iterations 7
>  Linear sys_fieldsplit_0_ solve converged due to CONVERGED_RTOL iterations 8
>  Linear sys_fieldsplit_0_ solve converged due to CONVERGED_RTOL iterations 8
>  Linear sys_fieldsplit_0_ solve converged due to CONVERGED_RTOL iterations 8
>  Linear sys_fieldsplit_0_ solve converged due to CONVERGED_RTOL iterations 8
> 
>  Linear sys_fieldsplit_1_ solve converged due to CONVERGED_RTOL iterations 22
>  Linear sys_fieldsplit_1_ solve converged due to CONVERGED_RTOL iterations 6
>  Linear sys_fieldsplit_1_ solve converged due to CONVERGED_RTOL iterations 3
>  Linear sys_fieldsplit_1_ solve converged due to CONVERGED_RTOL iterations 2
>  Linear sys_fieldsplit_1_ solve converged due to CONVERGED_RTOL iterations 2
>  Linear sys_fieldsplit_1_ solve converged due to CONVERGED_RTOL iterations 2
> 
> nusediter_vv          37
> nusediter_pp          37
> 
> So the value of nusediter_pp is indeed 37, but for nusediter_vv
> it should be 66. Any idea what went wrong?
> 
> Chris
> 
> 
> 
> dr. ir. Christiaan Klaij  | CFD Researcher | Research & Development
> MARIN | T +31 317 49 33 44 | mailto:C.Klaij at marin.nl | http://www.marin.nl
> 
> MARIN news: http://www.marin.nl/web/News/News-items/MARIN-wishes-you-a-challenging-inspiring-2017.htm
> 
> ________________________________________
> From: Barry Smith <bsmith at mcs.anl.gov>
> Sent: Saturday, April 11, 2015 12:27 AM
> To: Klaij, Christiaan
> Cc: petsc-users at mcs.anl.gov
> Subject: Re: [petsc-users] monitoring the convergence of fieldsplit 0 and 1
> 
>  Chris,
> 
>  I have added KSPGetTotalIterations() to the branch barry/add-ksp-total-iterations/master and next. After tests it will go into master
> 
>  Barry
> 
>> On Apr 10, 2015, at 8:07 AM, Klaij, Christiaan <C.Klaij at marin.nl> wrote:
>> 
>> Barry,
>> 
>> Sure, I can call PCFieldSplitGetSubKSP() to get the fieldsplit_0
>> ksp and then KSPGetIterationNumber, but what does this number
>> mean?
>> 
>> It appears to be the number of iterations of the last time that
>> the subsystem was solved, right? If so, this corresponds to the
>> last iteration of the coupled system, how about all the previous
>> iterations?
>> 
>> Chris
>> ________________________________________
>> From: Barry Smith <bsmith at mcs.anl.gov>
>> Sent: Friday, April 10, 2015 2:48 PM
>> To: Klaij, Christiaan
>> Cc: petsc-users at mcs.anl.gov
>> Subject: Re: [petsc-users] monitoring the convergence of fieldsplit 0 and 1
>> 
>>  Chris,
>> 
>>    It appears you should call PCFieldSplitGetSubKSP() and then get the information you want out of the individual KSPs. If this doesn't work please let us know.
>> 
>>  Barry
>> 
>>> On Apr 10, 2015, at 6:48 AM, Klaij, Christiaan <C.Klaij at marin.nl> wrote:
>>> 
>>> A question when using PCFieldSplit: for each linear iteration of
>>> the system, how many iterations for fielsplit 0 and 1?
>>> 
>>> One way to find out is to run with -ksp_monitor,
>>> -fieldsplit_0_ksp_monitor and -fieldsplit_0_ksp_monitor. This
>>> gives the complete convergence history.
>>> 
>>> Another way, suggested by Matt, is to use -ksp_monitor,
>>> -fieldsplit_0_ksp_converged_reason and
>>> -fieldsplit_1_ksp_converged_reason. This gives only the totals
>>> for fieldsplit 0 and 1 (but without saying for which one).
>>> 
>>> Both ways require to somehow process the output, which is a bit
>>> inconvenient. Could KSPGetResidualHistory perhaps return (some)
>>> information on the subsystems' convergence for processing inside
>>> the code?
>>> 
>>> Chris
>>> 
>>> 
>>> dr. ir. Christiaan Klaij
>>> CFD Researcher
>>> Research & Development
>>> E mailto:C.Klaij at marin.nl
>>> T +31 317 49 33 44
>>> 
>>> 
>>> MARIN
>>> 2, Haagsteeg, P.O. Box 28, 6700 AA Wageningen, The Netherlands
>>> T +31 317 49 39 11, F +31 317 49 32 45, I www.marin.nl
>>> 
>> 
>