On Wed, Mar 23, 2011 at 11:24:37PM +0000, Garth N. Wells wrote: > We've heard about this work, but never seen it ;). > > Can you post it somewhere? It could provide a discussion basis on how to > move this along. > > I think that we should be careful in asking FFC to do too much. It may > better to compute J, det(J), etc, outside tabulate_tensor(...) functions.
Aren't those computed using codesnippets just pasted in by FFC into the code anyway? Perhaps those codesnippets can be expanded with higher order codesnippets? -- Anders > Garth > > On 23/03/11 21:05, Peter Brune wrote: > > I saw this thread and had already started running the tests I had for > > this with the latest FFC to see if anything had changed recently. I > > never made isoparametry through UFL public because I could never get the > > efficiency to be reasonable. The situation appears to have improved a > > little bit from a year ago, but not much. With the latest FFC, it's > > about 10x slower (in 2D) to assemble Poisson with P1 for the test/trial > > space and P2 for the coordinates than the same problem with affine > > coordinates. It's even worse if you include things like > > Piola-transformed surface normals into the mix. When I was working on > > this I only assembled a very small fraction of the elements (around a > > cylinder in a flow) with the parametric Jacobian, so it worked OK for > > small problems. > > > > I believe that it would do much, much better if the optimizing > > quadrature compiler in FFC supported fractions. This is necessary > > because you need to apply the inverse isoparametric Jacobian, which > > includes 1 / |J|, to any basis function derivatives in the form. > > > > For reference, here are the assembly times for the iso(super, I suppose > > is more accurate)-parametric, optimized, and non-optimized Poisson > > problems in 2D on a 256x256 square (with the parametric coordinates just > > being the regular coordinates passed through). > > > > isoparametric assembly | 3.2017 3.2017 1 > > optimized assembly | 0.34515 0.34515 1 > > regular assembly | 0.36524 0.36524 1 > > > > I got really deep in FFC trying to make this work with no success, but > > this was before the rewrite. I'd be willing to declare victory on this > > one and submit my code if someone else were willing to make it fast > > enough to use. There's also the issue of how exactly to extend the > > interface to support this in an elegant fashion. Right now I just call > > a function that takes a form and a parametric Jacobian, runs a > > Transformer on the form, and spits out a new form. > > > > - Peter > > > > > > On Wed, Mar 23, 2011 at 3:30 PM, Anders Logg <[email protected] > > <mailto:[email protected]>> wrote: > > > > Peter Brune claims to have solved this by a small addition to the form > > language that automatically expresses the curved elements as a mapping > > and expands appropriately (and invisible to the user) those mappings > > to yield a form that may then be assembled. The higher order geometry > > is then expressed as a vector-field on the mesh. > > > > Perhaps Peter can be pushed to polish up on his code and submit it. > > > > > > > > On Wed, Mar 23, 2011 at 07:46:57PM +0000, Garth N. Wells wrote: > > > We haven't really looked at this. It was discussed a while back, > > but no > > > one has committed much time to it. We struggled to settle on an > > > appropriate abstraction to push on with. > > > > > > Garth > > > > > > On 23/03/11 18:40, Douglas Arnold wrote: > > > > What is the status of curved (e.g., isoparametric) elements in > > dolfin? > > > > I gather they are not implemented in the main branch. Has anyone > > > > done anything with this can be used? Is there any example code? > > > > (For example, if you want to > > > > solve the Poisson problem in a disc and get better than 2nd order > > > > convergence, you need to do better than polygonal approximation of > > > > the disc.) > > > > > > > > -- Doug > > > > > > > > _______________________________________________ > > > > Mailing list: https://launchpad.net/~dolfin > > <https://launchpad.net/%7Edolfin> > > > > Post to : [email protected] > > <mailto:[email protected]> > > > > Unsubscribe : https://launchpad.net/~dolfin > > <https://launchpad.net/%7Edolfin> > > > > More help : https://help.launchpad.net/ListHelp > > > > > > _______________________________________________ > > > Mailing list: https://launchpad.net/~dolfin > > <https://launchpad.net/%7Edolfin> > > > Post to : [email protected] > > <mailto:[email protected]> > > > Unsubscribe : https://launchpad.net/~dolfin > > <https://launchpad.net/%7Edolfin> > > > More help : https://help.launchpad.net/ListHelp > > > > _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : [email protected] Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
