[petsc-users] DMDACreateSection

[gouarin]

Le 27/04/2016 17:21, Matthew Knepley a écrit :
> On Wed, Apr 27, 2016 at 10:17 AM, gouarin <loic.gouarin at math.u-psud.fr
> <mailto:loic.gouarin at math.u-psud.fr>> wrote:
>
>     Hi,
>
>     I would like to know if it is possible to use DMDACreateSection to
>     create a grid for Stokes problem for example using Q2-Q1 finite
>     element discretization. I read old threads that tell that the
>     implementation was not yet finished. And there is some comments in
>     the code like "this is wrong" that tell me that it may be not available.
>
>     It could be great to use DMDA like DMPlex.
>
>
> I agree, but it was a lot of work to keep the implementation up, and I
> am way behind.
>
>     I use dmcomposite to do two grids but sections seems to be more easy
>     to use and probably more efficient for the creation of the non zero
>     structure of the matrix that solves the problem.
>
>
> I have switched to just using Plex for these things, since the data in
> the mesh is pretty small compared
> to the solution, even if I represent the entire Cartesian grid.
>
> I will also note that I think this is correct for the future as well
> since the DMForest implementation (the
> wrapper Toby Isaac wrote for p4est) uses PetscSection as well, is memory
> efficient, and does structured
> AMR. I am switching everything I had on DMDA to use this. If you want
> help in this direction, of course
> I am at your service. I am currently getting my magma dynamics code to
> work in this way.
>
Thanks Matt for your answer. I will switch to Plex then.

Loic

>    Thanks,
>
>       Matt
>
>     Best,
>     Loic
>
>
>
>
> --
> 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

-- 
Loic Gouarin
Laboratoire de Mathématiques
Université Paris-Sud
Bâtiment 425
91405 Orsay Cedex
France
Tel: (+33) 1 69 15 60 14
Fax: (+33) 1 69 15 67 18