On Thu, Oct 27, 2022 at 1:20 PM Yann Jobic <yann.jo...@univ-amu.fr> wrote:
> There is this factor also in front of the rectangle, which should 1/4 > for a unit rectangle of dim 2, but it's also 0.5. > Hi Yann, The reference element in Petsc is [-1, -1] to [1, 1]. This matches FEniCS/Firedrake and also makes it easier to use orthogonal polynomials. Thanks, Matt > Thanks, > Yann > > > Le 10/27/2022 à 6:23 PM, Mark Adams a écrit : > > Area of a unit triangle is (1x1)/2 I would guess. > > > > On Thu, Oct 27, 2022 at 11:32 AM Yann Jobic <yann.jo...@univ-amu.fr > > <mailto:yann.jo...@univ-amu.fr>> wrote: > > > > Hello, > > > > I'm trying to understand how to use the lowlevel Petsc Finit Element > > Framework. I've got few questions about it. > > > > 1) I'm checking the determinant of the Jacobian transformation from > > real > > space to the parametric one. The source code is in : > > > https://petsc.org/main/src/dm/impls/plex/plexgeometry.c.html#DMPlexComputeTriangleGeometry_Internal > < > https://petsc.org/main/src/dm/impls/plex/plexgeometry.c.html#DMPlexComputeTriangleGeometry_Internal > > > > I don't quite understand the 0.5 factor in front of it. > > Geometrically, it should be the ratio of the area/volume of the reel > > element over the referenced one. It's not the case here no ? > > It seems that, for other elements, this factor still applies. > > What this factor represent ? > > > > 2) I only checked triangle elements here. The ordering of the test > > functions and its derivatives is different it seems, with also the > 0.5 > > factor. Am i mistaken ? > > > > I could not find any informations about it in the user-doc. Maybe > it's > > written somewhere else ? > > > > Many Thanks, > > > > Best regards, > > > > Yann > > > -- 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.cse.buffalo.edu/~knepley/>