[petsc-users] TimeStepper norm problems. EMIL Please read this

[Andrew Spott]

Emil:  If I want to fix this myself, do you have any idea where I should start looking?  I assume in the th->endpoint section of TSStep_Theta in http://www.mcs.anl.gov/petsc/petsc-current/src/ts/impls/implicit/theta/theta.c.html?




Thanks,




-Andrew

On Tue, Mar 24, 2015 at 10:52 AM, Lisandro Dalcin <dalcinl at gmail.com>
wrote:

> On 24 March 2015 at 18:40, Emil Constantinescu <emconsta at mcs.anl.gov> wrote:
>>> Of course, though my B-D is order 2, and as you said, it is the just
>>> for the estimator.
>>>
>>>> if the time step varies wildly (can be easily constrained),
>>>> it may create some problems with the estimator.
>>>>
>>>
>>> Indeed, the default clipping 0.1,10 is usually too wide, I usually do
>>> -ts_adapt_basic_clip 0.5,2.0
>>
>>
>> The limits are a bit more strict for BDF2, but that's for the worst case and
>> no filtering. So that looks good too.
> I'm not sure I'm following you 100%. Please note I'm not using BDF2 in
> the usual sense, what I do is to compute an A POSTERIORI error
> estimator using a BD of order 2 to estimate LTE^{n+1} with the
> solution vectors U^{n+1}, U^{n} and U^{n-1}, and this is AFTER
> computing U^{n-1}.
> -- 
> Lisandro Dalcin
> ============
> Research Scientist
> Computer, Electrical and Mathematical Sciences & Engineering (CEMSE)
> Numerical Porous Media Center (NumPor)
> King Abdullah University of Science and Technology (KAUST)
> http://numpor.kaust.edu.sa/
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