> 在 2022年6月16日，23:22，Matthew Knepley <knep...@gmail.com> 写道： > > >> On Thu, Jun 16, 2022 at 11:11 AM Zongze Yang <yangzon...@gmail.com> wrote: > >> Hi, if I load a `gmsh` file with second-order elements, the coordinates will >> be stored in a DG-P2 space. After obtaining the coordinates of a cell, how >> can I map the coordinates to vertex and edge? > > By default, they are stored as P2, not DG.
I checked the coordinates vector, and found the dogs only defined on cell other than vertex and edge, so I said they are stored as DG. Then the function DMPlexVecGetClosure seems return the coordinates in lex order. Some code in reading gmsh file reads that 1756: if (isSimplex) continuity = PETSC_FALSE; /* XXX FIXME Requires DMPlexSetClosurePermutationLexicographic() */ 1758: GmshCreateFE(comm, NULL, isSimplex, continuity, nodeType, dim, coordDim, order, &fe) The continuity is set to false for simplex. Thanks, Zongze > > You can ask for the coordinates of a vertex or an edge directly using > > https://petsc.org/main/docs/manualpages/DMPLEX/DMPlexPointLocalRead/ > > by giving the vertex or edge point. You can get all the coordinates on a > cell, in the closure order, using > > https://petsc.org/main/docs/manualpages/DMPLEX/DMPlexVecGetClosure/ > Thanks, > > Matt > >> Below is some code load the gmsh file, I want to know the relation between >> `cl` and `cell_coords`. >> >> ``` >> import firedrake as fd >> import numpy as np >> >> # Load gmsh file (2rd) >> plex = fd.mesh._from_gmsh('test-fd-load-p2-rect.msh') >> >> cs, ce = plex.getHeightStratum(0) >> >> cdm = plex.getCoordinateDM() >> csec = dm.getCoordinateSection() >> coords_gvec = dm.getCoordinates() >> >> for i in range(cs, ce): >> cell_coords = cdm.getVecClosure(csec, coords_gvec, i) >> print(f'coordinates for cell {i} :\n{cell_coords.reshape([-1, 3])}') >> cl = dm.getTransitiveClosure(i) >> print('closure:', cl) >> break >> ``` >> >> Best wishes, >> Zongze > > > -- > 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/
