[petsc-users] TSSetEventHandler and TSSetPostEventIntervalStep

[Matthew Knepley]

On Tue, Oct 27, 2020 at 4:24 PM Barry Smith <bsmith at petsc.dev> wrote:

>
>   I'm sorry the code is still fundamentally broken, I know I promised a
> long time ago to fix it all up but it is actually pretty hard to get right.
>
>   It detects the zero by finding a small value when it should detect it by
> find a small region where it changes sign but surprising it is so hardwired
> to the size test that fixing it and testing the new code has been very
> difficult to me.  My branch is barry/2019-08-18/fix-tsevent-posteventdt
>

Barry, I do not see this branch on gitlab. Can you give a URL?

  Thanks,

     Matt


>   Barry
>
>
>
> On Oct 27, 2020, at 3:02 PM, Blondel, Sophie via petsc-users <
> petsc-users at mcs.anl.gov> wrote:
>
> Hi Matt,
>
> With the ex40 I attached in my previous email here is what I get printed
> on screen when running "./ex40 -ts_monitor -ts_event_monitor":
> 0 TS dt 0.1 time 0.
> 1 TS dt 0.5 time 0.1
> 2 TS dt 0.5 time 0.6
> 3 TS dt 0.5 time 1.1
> 4 TS dt 0.5 time 1.6
> 5 TS dt 0.5 time 2.1
> 6 TS dt 0.5 time 2.6
> 7 TS dt 0.5 time 3.1
> 8 TS dt 0.5 time 3.6
> 9 TS dt 0.5 time 4.1
> 10 TS dt 0.5 time 4.6
> 11 TS dt 0.5 time 5.1
> 12 TS dt 0.5 time 5.6
> 13 TS dt 0.5 time 6.1
> 14 TS dt 0.5 time 6.6
> 15 TS dt 0.5 time 7.1
> TSEvent: Event 0 zero crossing at time 7.6 located in 0 iterations
> Ball hit the ground at t =  7.60 seconds
> 16 TS dt 0.5 time 7.6
> 17 TS dt 0.5 time 8.1
> 18 TS dt 0.5 time 8.6
> 19 TS dt 0.5 time 9.1
> 20 TS dt 0.5 time 9.6
> 21 TS dt 0.5 time 10.1
> 22 TS dt 0.5 time 10.6
> 23 TS dt 0.5 time 11.1
> 24 TS dt 0.5 time 11.6
> 25 TS dt 0.5 time 12.1
> 26 TS dt 0.5 time 12.6
> 27 TS dt 0.5 time 13.1
> 28 TS dt 0.5 time 13.6
> 29 TS dt 0.5 time 14.1
> 30 TS dt 0.5 time 14.6
> 31 TS dt 0.5 time 15.1
> 32 TS dt 0.5 time 15.6
> 33 TS dt 0.5 time 16.1
> 34 TS dt 0.5 time 16.6
> 35 TS dt 0.5 time 17.1
> 36 TS dt 0.5 time 17.6
> 37 TS dt 0.5 time 18.1
> 38 TS dt 0.5 time 18.6
> 39 TS dt 0.5 time 19.1
> 40 TS dt 0.5 time 19.6
> 41 TS dt 0.5 time 20.1
> 42 TS dt 0.5 time 20.6
> 43 TS dt 0.5 time 21.1
> 44 TS dt 0.5 time 21.6
> 45 TS dt 0.5 time 22.1
> 46 TS dt 0.5 time 22.6
> 47 TS dt 0.5 time 23.1
> 48 TS dt 0.5 time 23.6
> 49 TS dt 0.5 time 24.1
> 50 TS dt 0.5 time 24.6
> 51 TS dt 0.5 time 25.1
> TSEvent: Event 0 zero crossing at time 25.6 located in 0 iterations
> Ball hit the ground at t = 25.60 seconds
> 52 TS dt 0.5 time 25.6
> 53 TS dt 0.5 time 26.1
> 54 TS dt 0.5 time 26.6
> 55 TS dt 0.5 time 27.1
> 56 TS dt 0.5 time 27.6
> 57 TS dt 0.5 time 28.1
> 58 TS dt 0.5 time 28.6
> 59 TS dt 0.5 time 29.1
> 60 TS dt 0.5 time 29.6
> 61 TS dt 0.5 time 30.1
> 0 TS dt 0.1 time 0.
> 1 TS dt 0.5 time 0.1
> 2 TS dt 0.5 time 0.6
> 3 TS dt 0.5 time 1.1
> 4 TS dt 0.5 time 1.6
> 5 TS dt 0.5 time 2.1
> 6 TS dt 0.5 time 2.6
> 7 TS dt 0.5 time 3.1
> 8 TS dt 0.5 time 3.6
> 9 TS dt 0.5 time 4.1
> 10 TS dt 0.5 time 4.6
> 11 TS dt 0.5 time 5.1
> 12 TS dt 0.5 time 5.6
> 13 TS dt 0.5 time 6.1
> 14 TS dt 0.5 time 6.6
> 15 TS dt 0.5 time 7.1
> 16 TS dt 0.5 time 7.6
> 17 TS dt 0.5 time 8.1
> 18 TS dt 0.5 time 8.6
> 19 TS dt 0.5 time 9.1
> 20 TS dt 0.5 time 9.6
> 21 TS dt 0.5 time 10.1
> 22 TS dt 0.5 time 10.6
> 23 TS dt 0.5 time 11.1
> 24 TS dt 0.5 time 11.6
> 25 TS dt 0.5 time 12.1
> 26 TS dt 0.5 time 12.6
> TSEvent: Event 0 zero crossing at time 13.1 located in 0 iterations
> Ball hit the ground at t = 13.10 seconds
> 27 TS dt 0.5 time 13.1
> 28 TS dt 0.5 time 13.6
> 29 TS dt 0.5 time 14.1
> 30 TS dt 0.5 time 14.6
> 31 TS dt 0.5 time 15.1
> 32 TS dt 0.5 time 15.6
> 33 TS dt 0.5 time 16.1
> 34 TS dt 0.5 time 16.6
> 35 TS dt 0.5 time 17.1
> 36 TS dt 0.5 time 17.6
> 37 TS dt 0.5 time 18.1
> 38 TS dt 0.5 time 18.6
> 39 TS dt 0.5 time 19.1
> 40 TS dt 0.5 time 19.6
> 41 TS dt 0.5 time 20.1
> 42 TS dt 0.5 time 20.6
> 43 TS dt 0.5 time 21.1
> 44 TS dt 0.5 time 21.6
> 45 TS dt 0.5 time 22.1
> 46 TS dt 0.5 time 22.6
> 47 TS dt 0.5 time 23.1
> TSEvent: Event 0 zero crossing at time 23.6 located in 0 iterations
> Ball hit the ground at t = 23.60 seconds
> 48 TS dt 0.5 time 23.6
> 49 TS dt 0.5 time 24.1
> 50 TS dt 0.5 time 24.6
> 51 TS dt 0.5 time 25.1
> 52 TS dt 0.5 time 25.6
> 53 TS dt 0.5 time 26.1
> TSEvent: Event 0 zero crossing at time 26.6 located in 0 iterations
> Ball hit the ground at t = 26.60 seconds
> 54 TS dt 0.5 time 26.6
> 55 TS dt 0.5 time 27.1
> 56 TS dt 0.5 time 27.6
> 57 TS dt 0.5 time 28.1
> 58 TS dt 0.5 time 28.6
> 59 TS dt 0.5 time 29.1
> 60 TS dt 0.5 time 29.6
> 61 TS dt 0. time 30.1
>
> I don't see the 0.001 timestep here, do you get a different behavior?
>
> Thank you,
>
> Sophie
> ------------------------------
> *From:* Matthew Knepley <knepley at gmail.com>
> *Sent:* Tuesday, October 27, 2020 15:34
> *To:* Blondel, Sophie <sblondel at utk.edu>
> *Cc:* petsc-users at mcs.anl.gov <petsc-users at mcs.anl.gov>;
> xolotl-psi-development at lists.sourceforge.net <
> xolotl-psi-development at lists.sourceforge.net>
> *Subject:* Re: [petsc-users] TSSetEventHandler and
> TSSetPostEventIntervalStep
>
>
> *[External Email]*
> On Tue, Oct 27, 2020 at 3:09 PM Blondel, Sophie via petsc-users <
> petsc-users at mcs.anl.gov> wrote:
>
> Hi,
>
> I am currently using TSSetEventHandler in my code to detect a random event
> where the solution vector gets modified during the event. Ideally, after
> the event happens I want the solver to use a much smaller timestep using
> TSSetPostEventIntervalStep. However, when I use TSSetPostEventIntervalStep
> the solver doesn't use the set value. I managed to reproduce the behavior
> by modifying ex40.c as attached.
>
>
>  I stepped through ex40, and it does indeed change the timestep to 0.001.
> Can you be more specific, perhaps with monitors, about what you think is
> wrong?
>
>   Thanks,
>
>      Matt
>
>
> I think the issue is related to the fact that the fvalue is not
> technically "approaching" 0 with a random event, it is more of a step
> function instead. Do you have any recommendation on how to implement the
> behavior I'm looking for? Let me know if I can provide additional
> information.
>
> Best,
>
> Sophie
>
>
>
> --
> 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/>
>
>
>

-- 
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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