If there are state changes in the post event callback, then multistep methods would not be a good choice for the application. I would use multistage methods such as RK type instead.
However, restarting the time stepper may still be necessary for other types of discontinuities, e.g. changes in the RHS function. So I would suggest to do unconditional restart at discontinuity points for safety. Hong > On Mar 30, 2016, at 2:49 AM, Lisandro Dalcin <[email protected]> wrote: > > On 30 March 2016 at 02:15, Jed Brown <[email protected]> wrote: >> Emil Constantinescu <[email protected]> writes: >> >>> Jed had something a while back but it may have become stale. Otherwise, >>> we had been relying on Sundials but would gladly support something native. >> >> Yeah, I started a branch for LMS a few years back, but there was a lot >> of work left before it would have been ready for general use. I haven't >> reviewed Lisandro's code, but it sounds like it's further along than >> mine (and not bitrotted). > > My current implementation in PetIGA was written with the limitations > of petsc-3.6 and does not handle events. > > To properly support multistep methods (and particularly BDF), I think > we need an important additional feature in TSEvent: If the post event > callback do change the state (i.e, there is a discontinuity in the > solution), the timestepper has to be "restarted" (BDF implementations > usually discard previous history and go back to order one, i.e. > backward Euler). Would it make sense to extend the TSEvent API in such > a way that the user can flag the timesteper about state changes? > Otherwise, the timestepper has no other choice than unconditionally > restart. > > -- > Lisandro Dalcin > ============ > Research Scientist > Computer, Electrical and Mathematical Sciences & Engineering (CEMSE) > Extreme Computing Research Center (ECRC) > King Abdullah University of Science and Technology (KAUST) > http://ecrc.kaust.edu.sa/ > > 4700 King Abdullah University of Science and Technology > al-Khawarizmi Bldg (Bldg 1), Office # 4332 > Thuwal 23955-6900, Kingdom of Saudi Arabia > http://www.kaust.edu.sa > > Office Phone: +966 12 808-0459
