On Sun, Oct 15, 2017 at 2:03 PM, Jed Brown <[email protected]> wrote:
> Barry Smith <[email protected]> writes: > > >> I don't see how any of the present interfaces work for waveform > >> relaxation. I also think that is rarely a desirable technique -- too > >> many awkward limitations. My recollection is that Borzi only uses it > >> for parabolic problems, for which adaptivity would have given much > >> faster/cheaper solutions of equivalent accuracy. The techniques are > >> theoretically interesting, but have not demonstrated sufficient > >> practicality to worry about. Someone doing research on these full-space > >> methods can just discretize space-time using SNES. > > > > Yes, but since that is a huge involved process (they need to manage > > time discretization etc themselves) they will NEVER compare with > > reduced methods and that is a huge part of the problem. > > Waveform relaxation and related methods intimately couples the temporal > discretization with the spatial discretization. It's a "transposed" > interface. > > > People do "research" in one or the other approach and never compare > > the two, leading to bad research. If we can combine them then one > > can actually compare the two approaches. > > > > Barry > > > > I'm not saying it is possible to have a nice API that combines them. > > If we don't know how to combine them in a nice API and one is very > important/practical while the other is research of questionable > practicality, I'd rather focus on making the important thing work well > rather than constantly hedging to possibly include the questionable > thing. > I don't think the full space method is of questionable practically in the time-independent case. This is still important in this discussion because the way we talk about the optimization problem, and the specification of adjoint problems will inevitably be shared. 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/ <http://www.caam.rice.edu/~mk51/>
