[petsc-dev] Using PCFieldSplitSetIS
Thomas Witkowski
thomas.witkowski at tu-dresden.de
Wed Mar 16 08:57:27 CDT 2011
Matt, it makes the output nicer, but does not help me to understand
what's going on inside of PETSc:
Residual norms for fieldsplit_boundary_ solve.
0 KSP Residual norm 1.790059331071e-04
1 KSP Residual norm 1.237356212928e-04
2 KSP Residual norm 7.952220245101e-05
3 KSP Residual norm 3.502858665398e-05
4 KSP Residual norm 1.601085190129e-05
5 KSP Residual norm 8.491161243057e-06
6 KSP Residual norm 4.778227395989e-06
7 KSP Residual norm 2.571919352633e-06
8 KSP Residual norm 1.353979940120e-06
9 KSP Residual norm 7.408377337496e-07
10 KSP Residual norm 3.810694345834e-07
11 KSP Residual norm 1.955889542056e-07
12 KSP Residual norm 9.938906113920e-08
13 KSP Residual norm 4.893445675773e-08
14 KSP Residual norm 2.395128458062e-08
15 KSP Residual norm 1.246442589657e-08
16 KSP Residual norm 6.316454504022e-09
17 KSP Residual norm 3.088668836241e-09
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
Residual norms for fieldsplit_boundary_ solve.
0 KSP Residual norm 1.790059331000e-04
1 KSP Residual norm 1.237356237744e-04
2 KSP Residual norm 7.952220078415e-05
3 KSP Residual norm 3.502859285561e-05
4 KSP Residual norm 1.601086485810e-05
5 KSP Residual norm 8.491169384185e-06
6 KSP Residual norm 4.778229157872e-06
7 KSP Residual norm 2.571917112191e-06
8 KSP Residual norm 1.353977280183e-06
9 KSP Residual norm 7.408352317360e-07
10 KSP Residual norm 3.810710583336e-07
11 KSP Residual norm 1.955898169394e-07
12 KSP Residual norm 9.938892788465e-08
13 KSP Residual norm 4.893428546840e-08
14 KSP Residual norm 2.395120857135e-08
15 KSP Residual norm 1.246436792784e-08
16 KSP Residual norm 6.316409779118e-09
17 KSP Residual norm 3.088649355374e-09
18 KSP Residual norm 1.593449602302e-09
Residual norms for fieldsplit_boundary_ solve.
0 KSP Residual norm 1.593449603155e-09
1 KSP Residual norm 1.011857676662e-09
2 KSP Residual norm 5.660892669788e-10
3 KSP Residual norm 3.046799343903e-10
4 KSP Residual norm 1.600471399329e-10
5 KSP Residual norm 8.083216601016e-11
6 KSP Residual norm 4.308671648345e-11
7 KSP Residual norm 2.381959817139e-11
8 KSP Residual norm 1.264839790114e-11
9 KSP Residual norm 6.435098853282e-12
10 KSP Residual norm 3.184769579797e-12
11 KSP Residual norm 1.502201943016e-12
12 KSP Residual norm 7.099486208425e-13
13 KSP Residual norm 3.443222176388e-13
14 KSP Residual norm 1.647843498912e-13
15 KSP Residual norm 8.208508173926e-14
16 KSP Residual norm 4.376604355287e-14
17 KSP Residual norm 2.596069152755e-14
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
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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