[petsc-users] projection methods in TS

[Matthew Knepley]

That is one answer. Another one is that this particular system is a DAE and
we have methods for that.

   Matt

On Fri, Feb 3, 2017 at 8:40 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> TSSetPostStep(); in your function use TSGetSolution() to get the current
> solution.
>
>   Please let us know how it works out
>
>    Barry
>
>
>
> > On Feb 3, 2017, at 7:14 PM, Gideon Simpson <gideon.simpson at gmail.com>
> wrote:
> >
> > I’m interested in implementing a projection method for an ODE of the
> form:
> >
> > y’ = f(y),
> >
> > such that g(y) = 0 for all time (i.e., g is conserved).  Note that in a
> projection method, a standard time step is made to produce y* from y_{n},
> and then this is corrected to obtain y_{n+1} satisfying g(y) = 0.
> >
> > There were two ways I was thinking of doing this, and I was hoping to
> get some input:
> >
> > Idea 1: Manually loop through using taking a time step and then
> implementing the projection routine.  I see that there is a TSStep command,
> but this doesn’t  seem to be much documentation on how to use it in this
> scenario.  Does anyone have any guidance?
> >
> > Idea 2: Is there some analog to TSMonitor that allows me to modify the
> solution after each time step, instead of just allowing for some
> computation of a statistic?
> >
> >
>
>


-- 
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
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