On Mon, 2020-09-14 at 20:28 -0400, Matthew Knepley wrote: > On Mon, Sep 14, 2020 at 6:15 PM Jeremy Theler <[email protected]> > wrote: > > Hello all > > > > Say I have a fully-interpolated 3D DMPlex and a point with > > arbitrary > > coordinates x,y,z. What's the most efficient way to know which cell > > this point belongs to in parallel? Cells can be either tets or > > hexes. > > I should make a tutorial on this, but have not had time so far.
Thank you very much for this mini-tutorial. > > The intention is that you use > > > https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/DM/DMLocatePoints.html > > This will just brute force search unless you also give > > -dm_plex_hash_location Well, for a 3D DMplex PETSc (and git blame) tells me that you "have only coded this for 2D." :-) > which builds a grid hash to accelerate it. I should probably expose > > DMPlexLocatePoint_Internal() > > which handles the single cell queries. If you just had one point, > that might make it simpler, > although you would still write your own loop. I see that DMLocatePoints() loops over all the cells until it finds the right one. I was thinking about finding first the nearest vertex to the point and then sweeping over all the cells that share this vertex testing for DMPlexLocatePoint_Internal(). The nearest node ought to be found using an octree or similar. Any direction regarding this idea? > If your intention is to interpolate a field at these > locations, I created > > > https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/SNES/DMInterpolationCreate.html > > which no one but me uses so far, but I think it is convenient. Any other example apart from src/snes/tutorials/ex63.c? Thank you. > > Thanks, > > Matt > > > Regards > > -- > > jeremy theler > > www.seamplex.com > > > > > > >
