[petsc-users] Error occurred when version change

[Matthew Knepley]

On Tue, Dec 29, 2020 at 10:17 PM Barry Smith <bsmith at petsc.dev> wrote:

>
>   So the really old version fails but a slightly newer but still really
> old version succeeds? I'm sorry but a lot has changed since that time and
> we really have no way of remembering what could have changed around that
> time that might cause this.
>
>   Why can't you use the 3.6.3  version? Whatever code you are using you
> could upgrade to use the 3.6.3 instead of the 3.4.5 I actually urge you
> to upgrade to 3.14 our last release, if it is C code it should relatively straightforward;
> if Fortran code then yes it will be a bit more painful but shouldn't take
> more than a day. And once that painful day is over all the pain of working
> with a really old version of PETSc will be gone for good.
>

I agree with all this. However, we cannot say anything, even about prior
version, without the output of

  -snes_view -snes_monitor -snes_linearsearch_monitor
-ksp_monitor_true_residual

for each run.

  Thanks,

     Matt


>   Barry
>
>
> On Dec 29, 2020, at 8:41 PM, 朱昭霓 <zhuzhaoni2017 at hnu.edu.cn> wrote:
>
>
> Dear Smith,
>
>   Thank you so much for your prompt reply! I have confirmed that the parameters
> of the linear resolver in these two versions are the same and I also run
> the code with -pc_type lu. It disconverges after the first two time steps
> , showing "line search fails" (I have printed the running results using
> 3.6.3 and 3.4.5 versions in the following attachment). I wonder if there
> are some inner functions or parameters which changes with different
> versions leading to the disconvergence in 3.4.5 version ?
>
> Best regards,
> Zhaoni Zhu
>
>
>
> ------------------ Original ------------------
> *From: * "Barry Smith"<bsmith at petsc.dev>;
> *Date: * Wed, Dec 30, 2020 03:12 AM
> *To: * "朱昭霓"<zhuzhaoni2017 at hnu.edu.cn>;
> *Cc: * "petsc-users"<petsc-users at mcs.anl.gov>;
> *Subject: * Re: [petsc-users] Error occurred when version change
>
>
>   It looks like both converged in your image, just at different rates?
> Note the two sides used different number of linear iterations, my guess is
> some default behavior of the linear solvers changed between those two
> ancient releases. First make sure both are using identical linear solvers.
> Then run both with -pc_type lu  do they now have the same SNES convergence?
>
>   Barry
>
>
> On Dec 29, 2020, at 2:51 AM, 朱昭霓 <zhuzhaoni2017 at hnu.edu.cn> wrote:
>
> Dear Sir or Madam:
>
> Hello, I am a new PETSc learner. There are some confusions when I using
> different versions of PETSc. For some reasons, I have to change my codes
> from the version 3.6.3 to 3.4.5. Newton methods in 3.6.3 version converged
> successfully with the time step size dt=100. While with the same dt=100 and
> almost the same codes, Newton methods in version 3.4.5 failed to converge.
> The debug test indicated that there may be something wrong during the line
> search process. I have tried to search the changes in different versions
> but failed. Could you please give me some suggestions? Thank you so much.
>
> Best regards,
>
> Zhaoni Zhu
> <Error_report.jpg>
>
>
> <3.4.5.docx><3.6.3.docx>
>
>
>

-- 
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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