[petsc-users] DMGetCoordinatesLocal and DMPlexGetCellCoordinates in PETSc > 3.18
Matthew Knepley
knepley at gmail.com
Wed May 17 16:04:24 CDT 2023
On Wed, May 17, 2023 at 2:01 PM Berend van Wachem <berend.vanwachem at ovgu.de>
wrote:
> Dear Matt,
>
> I tried it, but it doesn't seem to work.
> Attached is a very small working example illustrating the problem.
> I create a DMPlexBox Mesh, periodic in the Y direction. I then scale the Y
> coordinates with a factor 10, and add 1.0 to it. Both
> DMGetCoordinatesLocal and DMGetCellCoordinatesLocal.
> Then I evaluate the coordinates with DMPlexGetCellCoordinates. Most of the
> Y coordinates are correct, but not all of them - for
> instance, the minimum Y coordinate is 0.0, and this should be 1.0.
>
> Am I doing something wrong?
>
Quickly, I see that
a *= 10.0 + 1.0;
is the same as
a *= 11.0;
not multiply by 10 and add 1. I will send it back when I get everything the
way I want.
Thanks,
Matt
> Thanks and best regards,
>
> Berend.
>
> On 5/17/23 17:58, Matthew Knepley wrote:
> > On Wed, May 17, 2023 at 11:20 AM Berend van Wachem <
> berend.vanwachem at ovgu.de <mailto:berend.vanwachem at ovgu.de>> wrote:
> >
> > Dear Matt,
> >
> > Is there a way to 'redo' the DMLocalizeCoordinates() ? Or to undo it?
> > Alternatively, can we make the calling of DMLocalizeCoordinates() in
> the DMPlexCreate...() routines optional?
> >
> > Otherwise, we would have to copy all arrays of coordinates from
> DMGetCoordinatesLocal() and DMGetCellCoordinatesLocal() before
> > scaling them.
> >
> >
> > I am likely not being clear. I think all you have to do is the following:
> >
> > DMGetCoordinatesLocal(dm, &xl);
> > VecScale(xl, scale);
> > DMSetCoordinatesLocal(dm, xl);
> > DMGetCellCoordinatesLocal(dm, &xl);
> > VecScale(xl, scale);
> > DMSetCellCoordinatesLocal(dm, xl);
> >
> > Does this not work?
> >
> > Thanks,
> >
> > Matt
> >
> > Best regards, Berend.
> >
> > On 5/17/23 16:35, Matthew Knepley wrote:
> > > On Wed, May 17, 2023 at 10:21 AM Berend van Wachem <
> berend.vanwachem at ovgu.de <mailto:berend.vanwachem at ovgu.de>
> > <mailto:berend.vanwachem at ovgu.de <mailto:berend.vanwachem at ovgu.de>>>
> wrote:
> > >
> > > Dear Matt,
> > >
> > > Thanks for getting back to me so quickly.
> > >
> > > If I scale each of the coordinates of the mesh (say, I want
> to cube each
> > > co-ordinate), and I do this for both:
> > >
> > > DMGetCoordinatesLocal();
> > > DMGetCellCoordinatesLocal();
> > >
> > > How do I know I am not cubing one coordinate multiple times?
> > >
> > >
> > > Good question. Right now, the only connection between the two
> sets of coordinates is DMLocalizeCoordinates(). Since
> > sometimes
> > > people want to do non-trivial things to
> > > coordinates, I prefer not to push in an API for "just" scaling,
> but I could be convinced
> > > the other way.
> > >
> > > Thanks,
> > >
> > > Matt
> > >
> > > Thanks, Berend.
> > >
> > > On 5/17/23 16:10, Matthew Knepley wrote:
> > > > On Wed, May 17, 2023 at 10:02 AM Berend van Wachem
> > > > <berend.vanwachem at ovgu.de <mailto:berend.vanwachem at ovgu.de>
> <mailto:berend.vanwachem at ovgu.de
> > <mailto:berend.vanwachem at ovgu.de>> <mailto:berend.vanwachem at ovgu.de
> <mailto:berend.vanwachem at ovgu.de>
> > > <mailto:berend.vanwachem at ovgu.de <mailto:
> berend.vanwachem at ovgu.de>>>> wrote:
> > > >
> > > > Dear PETSc Team,
> > > >
> > > > We are using DMPlex, and we create a mesh using
> > > >
> > > > DMPlexCreateBoxMesh (.... );
> > > >
> > > > and get a uniform mesh. The mesh is periodic.
> > > >
> > > > We typically want to "scale" the coordinates
> (vertices) of the mesh,
> > > > and
> > > > to achieve this, we call
> > > >
> > > > DMGetCoordinatesLocal(dm, &coordinates);
> > > >
> > > > and scale the entries in the Vector coordinates
> appropriately.
> > > >
> > > > and then
> > > >
> > > > DMSetCoordinatesLocal(dm, coordinates);
> > > >
> > > >
> > > > After this, we localise the coordinates by calling
> > > >
> > > > DMLocalizeCoordinates(dm);
> > > >
> > > > This worked fine up to PETSc 3.18, but with versions
> after this, the
> > > > coordinates we get from the call
> > > >
> > > > DMPlexGetCellCoordinates(dm, CellID, &isDG, &CoordSize,
> > > > &ArrayCoordinates, &Coordinates);
> > > >
> > > > are no longer correct if the mesh is periodic. A
> number of the
> > > > coordinates returned from calling
> DMPlexGetCellCoordinates are wrong.
> > > >
> > > > I think, this is because DMLocalizeCoordinates is now
> automatically
> > > > called within the routine DMPlexCreateBoxMesh.
> > > >
> > > > So, my question is: How should we scale the
> coordinates from a periodic
> > > > DMPlex mesh so that they are reflected correctly when
> calling both
> > > > DMGetCoordinatesLocal and DMPlexGetCellCoordinates,
> with PETSc versions
> > > > >= 3.18?
> > > >
> > > >
> > > > I think we might have to add an API function. For now,
> when you scale
> > > > the coordinates,
> > > > can you scale both copies?
> > > >
> > > > DMGetCoordinatesLocal()
> > > > DMGetCellCoordinatesLocal();
> > > >
> > > > and then set them back.
> > > >
> > > > Thanks,
> > > >
> > > > Matt
> > > >
> > > > Many thanks, Berend.
> > > >
> > > > --
> > > > 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/ <
> https://www.cse.buffalo.edu/~knepley/>
> > <https://www.cse.buffalo.edu/~knepley/ <
> https://www.cse.buffalo.edu/~knepley/>> <
> http://www.cse.buffalo.edu/~knepley/
> > <http://www.cse.buffalo.edu/~knepley/>
> > > <http://www.cse.buffalo.edu/~knepley/ <
> http://www.cse.buffalo.edu/~knepley/>>>
> > >
> > >
> > >
> > > --
> > > 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/ <
> https://www.cse.buffalo.edu/~knepley/> <
> http://www.cse.buffalo.edu/~knepley/
> > <http://www.cse.buffalo.edu/~knepley/>>
> >
> >
> >
> > --
> > 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/>
--
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/>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20230517/7c8eec38/attachment.html>
More information about the petsc-users
mailing list