[petsc-dev] fixing bugs in resolution of TSEvent's

[Stefano Zampini]

Dear Ilya

Thanks for your willing to contribute back to PETSc. Please submit a PR
from the main branch. We do not allow API changes from minor patch
versions.

Thanks
Stefano

On Mon, Jul 17, 2023, 16:55 Ilya Fursov <ilya.foursov.7bd at gmail.com> wrote:

> Dear to whom is may concern,
>
> A while ago I tried to use TS events in my time stepping code, and I found
> erroneous behaviour of the event resolution algorithm. For that particular
> example it resulted in long series of extremely small time steps. After
> examining the TSEvent handler code, I found some places with obvious
> errors, but in general it was difficult to figure out exactly what was
> going on, and whether there were other errors.
>
> I decided to try and fix that stuff myself, and my choice was to refactor
> the code from scratch. I abandoned the current (in my opinion, obscure)
> code design of TSEventHandler, and wrote my own version, however using some
> ideas from the original code. The refactoring mostly affected the
> algorithmic part in tsevent.c source file. The original
> constructors/destructors, setters/getters have almost not changed. Also,
> some tiny changes occurred in ts.c and tsadapt.c, where interaction with
> events took place.
>
> I've made a number of tests, ensuring the new code runs smoothly. These
> tests also revealed the current/old petsc code results in lots of errors. I
> didn't take notes on the exact numbers, but from my impression, the old
> code failed in 70%-90% of my tests.
>
> So, I would like to contribute to the project what I've done. Well, I've
> never done such thing before, I hope the process goes smoothly.
> I've read the instructions on submitting the code, and one thing I wanted
> to ask -
> Do I need to start a feature branch from "release" integration branch?
> On one hand, I only did bug fixing. On the other hand, I've replaced one
> public API function (plus a runtime option), albeit a very small one, which
> didn't work well with the logic of the new code.
>
> Please advise if there might be any other things to consider while
> submitting the code.
>
> Best Regards,
> Ilya
>
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