[petsc-users] SNES-norm is zero all the time

[Matthew Knepley]

On Wed, Feb 3, 2021 at 12:39 PM Sepideh Kavousi <skavou1 at lsu.edu> wrote:

> I am not running an specific example. Attached is  my code. and when I wun
> with
> ./step5.out -snes_monitor -snes_fd_color -ts_monitor
> -snes_converged_reason -pc_type lu
>

Did you mean [i][j] here?

    aF[j][j].vx=((vx_x+vx_y)-1*aYdot[j][i].vx*(1));

    Matt


> it seems it does not solve anything because the output is like:
>
>     0 SNES Function norm 0.000000000000e+00
>   Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 0
> 1 TS dt 0.005 time 0.005
> copy!
>     0 SNES Function norm 0.000000000000e+00
>   Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 0
> 2 TS dt 0.005 time 0.01
> copy!
>     0 SNES Function norm 0.000000000000e+00
>   Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 0
> 3 TS dt 0.005 time 0.015
> copy!
>     0 SNES Function norm 0.000000000000e+00
>   Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 0
> 4 TS dt 0.005 time 0.02
> copy!
>     0 SNES Function norm 0.000000000000e+00
>   Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 0
> 5 TS dt 0.005 time 0.025
> copy!
>     0 SNES Function norm 0.000000000000e+00
>   Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 0
> 6 TS dt 0.005 time 0.03
> copy!
>     0 SNES Function norm 0.000000000000e+00
>   Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 0
> 7 TS dt 0.005 time 0.035
> copy!
>     0 SNES Function norm 0.000000000000e+00
>   Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 0
> 8 TS dt 0.005 time 0.04
> copy!
>     0 SNES Function norm 0.000000000000e+00
>   Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 0
> 9 TS dt 0.005 time 0.045
> copy!
>     0 SNES Function norm 0.000000000000e+00
>   Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 0
> 10 TS dt 0.005 time 0.05
> copy!
>     0 SNES Function norm 0.000000000000e+00
>   Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 0
> 11 TS dt 0.005 time 0.055
> copy!
>     0 SNES Function norm 0.000000000000e+00
>   Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 0
> .......
> ------------------------------
> *From:* Jed Brown <jed at jedbrown.org>
> *Sent:* Wednesday, February 3, 2021 11:19 AM
> *To:* Sepideh Kavousi <skavou1 at lsu.edu>; petsc-users at mcs.anl.gov <
> petsc-users at mcs.anl.gov>
> *Subject:* Re: [petsc-users] SNES-norm is zero all the time
>
> Sepideh Kavousi <skavou1 at lsu.edu> writes:
>
> > Hello,
> > I have a very stupid problem that I am really ashamed of asking but it
> has been with me for days and I do not know what to do. I want to solve the
> Javier stokes equation with finite difference method.
>
> Could you run with -snes_monitor -snes_converged_reason -pc_type lu?
>
> > When I wanted to run the code, the snes norm value does not change and i
> get an error for timestep convergence. I thought I might do something wrong
> so, I tried to simplify the equation I want to solve to an easy form, given
> as: u_t=u_x +u_y Where _t is the time derivative and _x and _y are the
> derivative in x and y direction. When I want to solve this problem, it
> still does not do anything at all and the snes function norm is zero all
> the time. I know I am missing something but does anyone have any idea what
> should I check in my code. The answers does not change with time. Best,
> Sepideh
> >
> >
> > Get Outlook for iOS<
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> >
>


-- 
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

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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