> On Oct 15, 2017, at 10:14 AM, Matthew Knepley <[email protected]> wrote:
>
> Someone had to do it.
>
> I will not try to frame the entire discussion. Barry has already thrown down
> the "show me your interface" gauntlet. However, I want to emphasize one point
> that may have been lost in the prior discussion. Every example I have looked
> at so far is focused on the reduced space formulation of the optimization
> problem. However, I am interested in the full space formulation so that I can
> do multigrid on the entire optimal control problem. This is not a new idea,
> in particular Borzi does this in SIAM Review in 2009. I think we have a
> tremendous opportunity here since other codes cannot do this, it has the
> potential (I think) for much better globalization, and perhaps can be faster.
>
> So, when we come up with interface proposals, I think we should keep a full
> space solution method in mind.
Matt,
Thanks for bringing this topic up.
Yes, if it could be a command line option to get it that would be optimal.
If not how close can we get to that? I still don't understand all the
relationships between the
reduced space formulation (adjoints)
full space (parallel in time)
approaches. Do they sometimes?/always?/rarely? represent the exact same model
and discretization? Seemingly not, as how can the "full space" support adaptive
time-stepping and mesh refinement/unrefinement (while that is easy with
continuous adjoints and doable on the forward ODE solve for discrete (though
solving the adjoint in the discrete case means using the same meshes and time
steps as the forward ODE solve)).
Barry
>
> Thanks,
>
> Matt
>
> --
> 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/
