[petsc-dev] is there a bug in private_DMDALocatePointsIS_3D_Regular?

[Matthew Knepley]

On Wed, Dec 21, 2022 at 1:34 PM Matteo Semplice <
matteo.semplice at uninsubria.it> wrote:

> Dear Matt,
>
>      I am trying to translate the local nCell numbers returned by swarm
> particle location routines into the global (i,j,k) indices in the dmda
> and I have run into some oddities in the 3d case. I have dug into the
> private_DMDALocatePointsIS_2D_Regular and
> private_DMDALocatePointsIS_3D_Regular routines and, using 14 points per
> direction and 1 ghost for the DMDA, on 2 cpus:
>
> - the 2d routine thinks to have 13x6 Q1 elements on cpu0 and 13x7 on cpu
> 1 (which looks correct to me as 6+7 makes 13 elements in the y direction)
>
> - the 2d routine thinks to have 13x13x6 elements on cpu0 and 13x13x8 on
> cpu1 (which looks one too many)
>
> Removing lines 155-157 from src/dm/impls/da/dageometry.c (patch
> attached) seems to fix some things in my code. I have not studied in
> depth the code of private_DMDALocatePointsIS_3D_Regular, but I have seen
> that the left shift of xs,ys,zs are already performed at lines 137-139.
>
> Could you have a look, please?
>
> (This looked more appropriate for petsc-dev than petsc-users, but I am
> not a subscriber, so could you please reply to me directly as well?)
>

Dang! You can see it was fixed in 2D but not in 3D. Thanks for finding
this. I put it in this branch

  knepley/fix-da-point-location

which is the last one I mailed you.

   Matt


> Thanks
>
>      Matteo
>


-- 
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/>
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