[petsc-users] Snes behavior

[Barry Smith]

   JUST run with -snes_mf_operator and then with -snes_type test NOT  
together,

    Barry

On Jan 10, 2010, at 4:42 PM, Ryan Yan wrote:

> Hi Barry,
> Please see reply below,
>
> On Sun, Jan 10, 2010 at 4:57 PM, Barry Smith <bsmith at mcs.anl.gov>  
> wrote:
>
> On Jan 10, 2010, at 3:52 PM, Ryan Yan wrote:
>
> Hi Barry,
> Yes, exactly. The original multi-components system scale quite  
> unevenly. I will try to rescale it.
> Could this be helpful to show some promise on quadratic convergence?
>
>   I won't be concerned about "quadratic convergence" I'd only be  
> concerned that it is converging to the correct answer and that you  
> are getting close enough to the correct answer.
>
> Yes, I agree.
>
>    You can run with -snes_mf_operator and -snes_type test to verify  
> if the Jacobian being computed is accurate. Perhaps in your function  
> evaluation you are not using the stencil that you set with the DA,  
> this would cause the wrong Jacobian to be computed.
>
>
> After passing in -snes_mf_operator and -snes_type test as follows:
> vyan2000 at vyan2000-linux ~/NCproject/general : mpirun -np 2 ./ 
> HeatProfile1D -snes_mf_operator -snes_type test
> I got errors, as expected:
>
> [0]PETSC ERROR: --------------------- Error Message  
> ------------------------------------
> [0]PETSC ERROR: Invalid argument!
> [0]PETSC ERROR: Cannot test with alternative preconditioner!
> [0]PETSC ERROR:  
> ------------------------------------------------------------------------
> [0]PETSC ERROR: Petsc Release Version 3.0.0, Patch 5, Mon Apr 13  
> 09:15:37 CDT 2009
> [0]PETSC ERROR: See docs/changes/index.html for recent updates.
> [0]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
> [0]PETSC ERROR: See docs/index.html for manual pages.
> [0]PETSC ERROR:  
> ------------------------------------------------------------------------
> [0]PETSC ERROR: ./HeatProfile1D on a O-hypre-p named vyan2000-linux  
> by vyan2000 Sun Jan 10 17:16:00 2010
> [0]PETSC ERROR: Libraries linked from /home/vyan2000/local/PPETSc/ 
> petsc-3.0.0-p5/O-hypre-prometheus/lib
> [0]PETSC ERROR: Configure run at Thu Jun 25 13:49:36 2009
> [0]PETSC ERROR: Configure options --download-mpich=1 --with- 
> debugger=gdb --download-hypre=1 --download-parmetis=1 --download- 
> prometheus=1 --with-shared=0
> [0]PETSC ERROR:  
> ------------------------------------------------------------------------
> [0]PETSC ERROR: SNESSolve_Test() line 28 in src/snes/impls/test/ 
> snestest.c
> [0]PETSC ERROR: SNESSolve() line 2221 in src/snes/interface/snes.c
> [0]PETSC ERROR: DMMGSolveSNES() line 510 in src/snes/utils/damgsnes.c
> [0]PETSC ERROR: DMMGSolve() line 372 in src/snes/utils/damg.c
> [0]PETSC ERROR: main() line 270 in /home/vyan2000/local/PPETSc/ 
> petsc-2.3.3-p15/src/ksp/ksp/examples/tutorials/ 
> NCprojectHeatProfile1D.c
> application called MPI_Abort(MPI_COMM_WORLD, 62) - process 0[cli_0]:  
> aborting job:
> application called MPI_Abort(MPI_COMM_WORLD, 62) - process 0
>
> The error makes sense, since I did not pass in the analytical  
> Jacobian for the preconditioner matrix. In stead, I was using  
> DMMGSetSNESLocal(dmmg,FormFunctionLocal, 
> 0,ad_FormFunctionLocal,admf_FormFunctionLocal). I am going to change  
> the code a bit, pass in the analytical Jacobian and do the - 
> snes_type test.
>
> I will bear your suggestion in mind during the test.
>
> Thanks a lot,
>
> Yan
>
>
>
>   Barry
>
>
>
> Thanks a lot,
>
> Yan
>
> On Sun, Jan 10, 2010 at 4:35 PM, Barry Smith <bsmith at mcs.anl.gov>  
> wrote:
>
>  You already got a 10^16 drop in the residual norm. It is not  
> realistic to expect to get much more than that for double precision  
> calculations. Perhaps your original F() has some funky scaling of  
> different components that you can fix.
>
>
>
>  Barry
>
>
> On Jan 10, 2010, at 2:55 PM, Ryan Yan wrote:
>
> Hi All,
> I am solving a nonlinear system using snes. The -snes_monitor option  
> has the following output:
>
>  0 SNES Function norm 2.640163923729e+09
>  1 SNES Function norm 1.047643565314e+08
>  2 SNES Function norm 1.712732074788e+06
>  3 SNES Function norm 1.002169173269e+04
>  4 SNES Function norm 1.655878303433e+03
>  5 SNES Function norm 3.746498305706e+02
>  6 SNES Function norm 8.317435704773e+01
>  7 SNES Function norm 1.857639969641e+01
>  8 SNES Function norm 4.149691057773e+00
>  9 SNES Function norm 9.265604042412e-01
>  10 SNES Function norm 2.069527103214e-01
>  11 SNES Function norm 4.624186491082e-02
>  12 SNES Function norm 1.035558432688e-02
>  13 SNES Function norm 2.341362958811e-03
>  14 SNES Function norm 5.507445427277e-04
>  15 SNES Function norm 1.485123568354e-04
>  16 SNES Function norm 5.180043781814e-05
>  17 SNES Function norm 2.341966514486e-05
>  18 SNES Function norm 1.344936158651e-05
>  19 SNES Function norm 1.054812641176e-05
> Number of Newton iterations = 19
> Converged reason is 4
>
> It looks like the iterate never falls into a quadratic convergence  
> region before it converges. Is there any hint to understand this  
> behavior?
>
> Thanks a lot,
>
> Yan
>
>
>
>
>
>