[petsc-users] "-ts_exact_final_time matchstep" leads to DIVERGED_STEP_REJECTED

[Barry Smith]

> On Dec 9, 2024, at 2:56 PM, Blondel, Sophie via petsc-users <petsc-users at mcs.anl.gov> wrote:
> 
> Hi,
> 
> I am trying to understand a strange behavior I'm encountering: when running my application with "-ts_exact_final_time stepover" everything goes well, but when I switch to "matchstep" I get DIVERGED_STEP_REJECTED before the first time step is finished.

   This is in the very first time-step in TSSolve? 

    Please run with -ts_monitor and send all the output (best for a short time interval and do it twice once with -ts_exact_final_time stepover and once with exact.

   Barry


> I tried increasing the maximum number of rejections and it just takes longer to diverge, and if I set the value to "unlimited" it is basically an infinite loop.
> 
> Is there a way to check why is the step rejected? Could the "matchstep" option change tolerances somewhere that would cause that behavior?
> 
> Let me know if I should provide more information.
> 
> Best,
> 
> Sophie Blondel

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