[petsc-users] Error occurred when version change

Barry Smith bsmith at petsc.dev
Tue Dec 29 13:12:31 CST 2020

  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?


> 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>

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