Dear Simon, Thank you very much for your reply. The wrapper code looks embarrassingly simple!
> If you are working with a perfectly Cartesian background I would expect that > it would actually be faster to generate the quadrature in real space and then > transform the quadrature to reference space before passing it to FEValues. If > you want to do this the functions cell->bounding_box() and > BoundingBox::real_to_unit(..) are useful. That I did not think about for some reason :) If my element is not aligned with the axes, won't I risk getting quadrature points outside of the element though? Or is this what you meant by the "perfect Cartesian" situation? Also I am not 100% clear at the moment about how to change the quadrature weights after the physical->unit transformation, as I would need access to Jacobian determinants. Another option I was contemplating is to apply the NonMatching::DiscreteQuadratureGenerator<dim> on a fake triangulation with just one element. Then I simply would need to interpolate (evaluate) my real-space function at this one element and let the class' implementation do the magic for me. This is probably cheaper and about equally accurate? /Anton On Fri, Aug 4, 2023 at 12:07 PM Simon Sticko <simonsti...@gmail.com> wrote: > > Hi. > > I have done this in the past. I dug up the wrapper function I had for it, in > case we decide that we should add it to the library: > > https://github.com/dealii/dealii/pull/15838 > > The problem with this approach is that evaluating the reference space level > set function gets very expensive. QuadratureGenerator uses many function > calls and we have to use the Jacobian and its derivative in the > transformation. This makes this approach significantly slower than using an > interpolated level set function. > > If you are working with a perfectly Cartesian background I would expect that > it would actually be faster to generate the quadrature in real space and then > transform the quadrature to reference space before passing it to FEValues. If > you want to do this the functions cell->bounding_box() and > BoundingBox::real_to_unit(..) are useful. > > Best, > Simon > > On 03/08/2023 23:11, Anton wrote: > > Hello, > > > > I would like to use the NonMatching::QuadratureGenerator<dim> class > > directly, as I need to generate multiple (as in many!, unfortunately) > > nonmatching quadratures for the same cell. Therefore I would like to avoid > > the route of interpolating the level set function onto the whole mesh etc, > > as described in CutFEM tutorial. > > > > Therefore I am thinking about calling the "generate" function, which only > > needs a level set function and a bounding box as inputs. According to the > > documentation the level set function should provide the gradient and the > > Hessian. I would like to do this in the reference cell coordinates, so > > that I can simply use this quadrature later via FEView as one normally does. > > * The bounding box I presume is the hypercube [0,1]^{dim} for the meshes > > I am interested in. (Can one request them for the reference cell and not > > the triangulation cell?) > > > > * The level set function should also be reasonably straightforward. I > > know the function in the physical coordinates (say, f(x)) and all its > > derivatives. I can also get the map from reference to physical coordinates > > via FEView, let us call this map x=M(y). The issue is how to extract the > > derivatives of this map so that the chain rule can be applied? I am mostly > > working with Q1 maps, so of course I could figure out the derivatives "by > > hand". I am just wondering if there is a more intelligent (code-wise) way > > of doing this? > > > > -- > > The deal.II project is located at http://www.dealii.org/ > > <http://www.dealii.org/> > > For mailing list/forum options, see > > https://groups.google.com/d/forum/dealii?hl=en > > <https://groups.google.com/d/forum/dealii?hl=en> > > --- > > You received this message because you are subscribed to the Google Groups > > "deal.II User Group" group. > > To unsubscribe from this group and stop receiving emails from it, send an > > email to dealii+unsubscr...@googlegroups.com > > <mailto:dealii+unsubscr...@googlegroups.com>. > > To view this discussion on the web visit > > https://groups.google.com/d/msgid/dealii/4ac38563-e467-4f1d-8cb4-ee35379515a6n%40googlegroups.com > > > > <https://groups.google.com/d/msgid/dealii/4ac38563-e467-4f1d-8cb4-ee35379515a6n%40googlegroups.com?utm_medium=email&utm_source=footer>. > > -- > The deal.II project is located at http://www.dealii.org/ > For mailing list/forum options, see > https://groups.google.com/d/forum/dealii?hl=en > --- > You received this message because you are subscribed to a topic in the Google > Groups "deal.II User Group" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/dealii/FONV6StZZus/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > dealii+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/dealii/f1642630-6453-2028-1345-3db743d814f2%40gmail.com. -- Anton Evgrafov -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. 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