On Tue, Oct 17, 2017 at 03:40:10PM -0400, Mark Adams wrote: > Let me just add that we (me and Toby (p4est)) think of tensor grids for > kinetic problems. A (phase space) grid at every spatial grid point. THis > allows us to compose our existing 3D grids to get 6D, for instance. This > work well/easily for Valsov-Maxwell because there are only grad_x and > grad_v terms. > > I have explored this with a Vlasov code and worked some of it out. We have > a pretty good idea of what to do but it needs work. > > So we are moving with the new Plex abstraction and DMDA not in our plans. I > like Plex, it abstracts the grid from the numerics nicely. The only bad > thing about it is that stencil methods are not natural (at all). So you, > for instance, compute fluxes and then divergences, instead of composing > them on paper to create a stencil.
Which is something so rote that creating DTFD to convert the pointwise residuals/jacobians into stencils would go along way towards unifying DMDA and DMPlex in a single useful interface. </sidebar> Cheers, Toby > > Mark > > On Tue, Oct 17, 2017 at 2:54 PM, Matthew Knepley <[email protected]> wrote: > > > On Tue, Oct 17, 2017 at 2:51 PM, Hittinger, Jeffrey A. F. < > > [email protected]> wrote: > > > >> Bummer. > >> > >> > >> > >> Matt - Never is a very strong word. Don’t underestimate the power of > >> mappings and/or AMR. Also, sparse grid techniques haven’t (yet) proven to > >> be particularly useful for kinetic problems. > >> > > > > None of the above is wrong, but I really meant "regular grids in high > > dimension". DMDA will never do AMR or sparse grids since its designed > > to be the simplest thing possible. For AMR we are using p4est, and that > > could definitely work in higher dimensions. I have read the Irene Gamba > > stuff on Boltzmann Transport using higher-D regular grids, but its just > > tremendously expensive, and they really play up spectral convergence, > > which relies on regularity which is often not there in practical problems. > > > > Thanks, > > > > Matt > > > > > >> > >> > >> Thanks for the quick response. > >> > >> > >> > >> j- > >> > >> -.-- -.-- --.. > >> > >> Jeffrey A. F. Hittinger > >> > >> Center for Applied Scientific Computing > >> > >> Lawrence Livermore National Laboratory > >> > >> Office: (925) 422-0993 > >> > >> FAX: (925) 423-2993 > >> > >> > >> > >> *From: *Matthew Knepley <[email protected]> > >> *Date: *Tuesday, October 17, 2017 at 11:42 AM > >> *To: *Barry Smith <[email protected]> > >> *Cc: *Undisclosed recipients <[email protected]>, " > >> [email protected]" <[email protected]> > >> *Subject: *Re: [petsc-users] High-dimensional DMDA > >> > >> > >> > >> On Tue, Oct 17, 2017 at 2:32 PM, Barry Smith <[email protected]> wrote: > >> > >> > >> No and it is highly unlikely to appear (the 3d code is already too > >> complicated and we tried to write a dimension independent version but that > >> failed) > >> > >> But note that by using a dof argument > 1 one can handle some "4d" > >> problems so long as one does no parallelize in the 4th dimension. > >> > >> > >> > >> History: We did have a version for arbitrary dimension called ADDA > >> written by a student of David Keyes, that exists > >> > >> in the bowels of Git. We are unlikely to replicate it because regular > >> grids in high dimension never seem like the right > >> > >> thing to do. > >> > >> > >> > >> Thanks, > >> > >> > >> > >> Matt > >> > >> > >> > >> > >> Barry > >> > >> > >> > On Oct 17, 2017, at 1:15 PM, Hittinger, Jeffrey A. F. < > >> [email protected]> wrote: > >> > > >> > Quick question: is there a version of the DMDA structured grid > >> interface that supports dimensions higher than 3? > >> > > >> > j- > >> > -.-- -.-- --.. > >> > Jeffrey A. F. Hittinger > >> > Center for Applied Scientific Computing > >> > Lawrence Livermore National Laboratory > >> > Office: (925) 422-0993 > >> > FAX: (925) 423-2993 > >> > >> > >> > >> > >> > >> -- > >> > >> 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/> > >> > > > > > > > > -- > > 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/> > >
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