[petsc-users] Error occurred when version change

[Barry Smith]

  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.

  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 <mailto: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>

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