[petsc-dev] Using PCFieldSplitSetIS
Barry Smith
bsmith at mcs.anl.gov
Thu Mar 17 16:06:44 CDT 2011
Did you get a chance to run as I requested with "Please run with -ksp_view and send the output."
We are eager to determine the problem.
Barry
On Mar 16, 2011, at 11:03 AM, Barry Smith wrote:
>
> On Mar 16, 2011, at 8:57 AM, Thomas Witkowski wrote:
>
> -pc_fieldsplit_type schur -fieldsplit_interior_ksp_type preonly -fieldsplit_interior_pc_type bjacobi -fieldsplit_interior_sub_pc_type lu -fieldsplit_boundary_ksp_monitor -ksp_monitor_true_residual
>
>
>> Residual norms for fieldsplit_boundary_ solve.
>> 0 KSP Residual norm 1.790059331071e-04
>> .....
>> 18 KSP Residual norm 1.593454221996e-09
>> 0 KSP preconditioned resid norm 5.745043818120e-01 true resid norm 1.584249437360e-01 ||r(i)||/||b|| 1.000000000000e+00
> This is the norms on the outer iteration variables
>> Residual norms for fieldsplit_boundary_ solve.
>> 0 KSP Residual norm 1.790059331000e-04
> This is the norms on the Schur complement iteration
>> ....
>> 18 KSP Residual norm 1.593449602302e-09
>
> It is unclear to me why it starts up another solve here, starting basically where it left off. I think it should just kick out to print the norm of the residual of the outer iteration.
>
>> Residual norms for fieldsplit_boundary_ solve.
>> 0 KSP Residual norm 1.593449603155e-09
>> ...
>> 18 KSP Residual norm 1.335744434252e-14
>> 1 KSP preconditioned resid norm 2.608069232839e-13 true resid norm 1.449869994655e-13 ||r(i)||/||b|| 9.151778504469e-13
>>
>
> Are you running with petsc-dev?
>
> Please run with -ksp_view and send the output.
>
> When I run tutorials/multiphysics/mp.c with the options ./mp -couple -snes_monitor_short -pc_type fieldsplit -ksp_monitor -pc_fieldsplit_type schur -fieldsplit_ksp_monitor -fieldsplit_1_ksp_type fgmres -fieldsplit_0_ksp_type gmres -snes_view I do not see the "double" iteration business.
>
> Barry
>
>
>
>>
>> So, are there now two or one outer iterations?
>>
>> Thomas
>>
>>
>>
>>
>> Matthew Knepley wrote:
>>> On Wed, Mar 16, 2011 at 8:27 AM, Thomas Witkowski <thomas.witkowski at tu-dresden.de <mailto:thomas.witkowski at tu-dresden.de>> wrote:
>>>
>>> Jed Brown wrote:
>>>
>>> On Wed, Mar 16, 2011 at 07:37, Thomas Witkowski
>>> <thomas.witkowski at tu-dresden.de
>>> <mailto:thomas.witkowski at tu-dresden.de>
>>> <mailto:thomas.witkowski at tu-dresden.de
>>> <mailto:thomas.witkowski at tu-dresden.de>>> wrote:
>>>
>>> Thanks for explanations! It works fine in my code. But I
>>> have two
>>> questions about it, maybe you can help me with them:
>>> - To the first, is the LU factorization on block A_00 done
>>> only once?
>>>
>>>
>>> Yes, one way to confirm this is to run with -log_summary and
>>> check MatLUFactor{Sym,Num}.
>>> - I have run the code with -fieldsplit_1_ksp_monitor to get
>>> some
>>> more information about the internal solves. I expected to get
>>> information about one iterative solver (for solving the Schur
>>> complement system), but I got three, all of them need around 20
>>> iterations for my example. Could you explain to me what is
>>> actually solved there?
>>>
>>>
>>> I'm going to guess that you still have an outer KSP that (in
>>> the global norm, rather than the partitioned norm used inside
>>> of splits) has a tighter tolerance, therefore it takes a few
>>> outer iterations. If you use loose inner tolerances then the
>>> preconditioner becomes nonlinear and you'll need to use FGMRES
>>> for the outer. When in doubt, run with -ksp_view and show us
>>> the results if you don't understand. Additionally, monitoring
>>> inner solves separately can be useful, e.g.
>>> -fieldsplit_0_ksp_converged_reason -fieldsplit_1_ksp_monitor
>>> -ksp_monitor_true_residual.
>>>
>>> Okay, I run my code with the options "-pc_fieldsplit_type schur
>>> -fieldsplit_interior_ksp_type preonly -fieldsplit_interior_pc_type
>>> bjacobi -fieldsplit_interior_sub_pc_type lu
>>> -fieldsplit_boundary_ksp_monitor -ksp_monitor_true_residual
>>> -fieldsplit_interior_ksp_converged_reason". The splits are named
>>> "interior" and "boundary". The ksp output is as follows:
>>>
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> Residual norms for fieldsplit_boundary_ solve.
>>> 0 KSP Residual norm 1.790059331071e-04
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 1 KSP Residual norm 1.237356212928e-04
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 2 KSP Residual norm 7.952220245101e-05
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 3 KSP Residual norm 3.502858665398e-05
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 4 KSP Residual norm 1.601085190129e-05
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 5 KSP Residual norm 8.491161243057e-06
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 6 KSP Residual norm 4.778227395989e-06
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 7 KSP Residual norm 2.571919352633e-06
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 8 KSP Residual norm 1.353979940120e-06
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 9 KSP Residual norm 7.408377337496e-07
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 10 KSP Residual norm 3.810694345834e-07
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 11 KSP Residual norm 1.955889542056e-07
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 12 KSP Residual norm 9.938906113920e-08
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 13 KSP Residual norm 4.893445675773e-08
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 14 KSP Residual norm 2.395128458062e-08
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 15 KSP Residual norm 1.2464425896 <tel:1.2464425896>57e-08
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 16 KSP Residual norm 6.316454504022e-09
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 17 KSP Residual norm 3.088668836241e-09
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 18 KSP Residual norm 1.593454221996e-09
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> [0] Petsc-Iteration 0: 0.574504
>>> 0 KSP preconditioned resid norm 5.745043818120e-01 true resid
>>> norm 1.584249437360e-01 ||r(i)||/||b|| 1.000000000000e+00
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> Residual norms for fieldsplit_boundary_ solve.
>>> 0 KSP Residual norm 1.790059331000e-04
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 1 KSP Residual norm 1.237356237744e-04
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 2 KSP Residual norm 7.952220078415e-05
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 3 KSP Residual norm 3.502859285561e-05
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 4 KSP Residual norm 1.601086485810e-05
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 5 KSP Residual norm 8.491169384185e-06
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 6 KSP Residual norm 4.778229157872e-06
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 7 KSP Residual norm 2.571917112191e-06
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 8 KSP Residual norm 1.353977280183e-06
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 9 KSP Residual norm 7.408352317360e-07
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 10 KSP Residual norm 3.810710583336e-07
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 11 KSP Residual norm 1.955898169394e-07
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 12 KSP Residual norm 9.938892788465e-08
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 13 KSP Residual norm 4.893428546840e-08
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 14 KSP Residual norm 2.395120857135e-08
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 15 KSP Residual norm 1.2464367927 <tel:1.2464367927>84e-08
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 16 KSP Residual norm 6.316409779118e-09
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 17 KSP Residual norm 3.088649355374e-09
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 18 KSP Residual norm 1.593449602302e-09
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> Residual norms for fieldsplit_boundary_ solve.
>>> 0 KSP Residual norm 1.593449603155e-09
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 1 KSP Residual norm 1.011857676662e-09
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 2 KSP Residual norm 5.660892669788e-10
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 3 KSP Residual norm 3.046799343903e-10
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 4 KSP Residual norm 1.6004713993 <tel:1.6004713993>29e-10
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 5 KSP Residual norm 8.083216601016e-11
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 6 KSP Residual norm 4.308671648345e-11
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 7 KSP Residual norm 2.381959817139e-11
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 8 KSP Residual norm 1.264839790114e-11
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 9 KSP Residual norm 6.435098853282e-12
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 10 KSP Residual norm 3.184769579797e-12
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 11 KSP Residual norm 1.5022019430 <tel:1.5022019430>16e-12
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 12 KSP Residual norm 7.099486208425e-13
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 13 KSP Residual norm 3.443222176388e-13
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 14 KSP Residual norm 1.6478434989 <tel:1.6478434989>12e-13
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 15 KSP Residual norm 8.208508173926e-14
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 16 KSP Residual norm 4.376604355287e-14
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 17 KSP Residual norm 2.596069152755e-14
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 18 KSP Residual norm 1.335744434252e-14
>>> Linear solve converged due to CONVERGED_ITS iterations 1
>>> 1 KSP preconditioned resid norm 2.608069232839e-13 true resid
>>> norm 1.449869994655e-13 ||r(i)||/||b|| 9.151778504469e-13
>>>
>>> I have no idea how to interpret this output! Could you help me
>>> with it?
>>>
>>>
>>> Get rid of -fieldsplit_interior_ksp_converged_reason. It is confusing things. Then you will see
>>> the outer iteration and the inner boundary iteration which is indented.
>>>
>>> Matt
>>>
>>>
>>> Thomas
>>>
>>>
>>>
>>>
>>> --
>>> 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
>>
>
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