[petsc-users] Manually setting PetscSF

[Nicholas Arnold-Medabalimi]

Hi Petsc Users,


I am working on setting up the star forest to connect my meshes on
different processors.

For a 2-processor example, I have set up a dmplex object and read in the
coordinates nodes and cell2node charts on each one. But right now they are
independent effectively.

For simplicity lets just say each process has 4 cells.

[image: image.png]

I'm trying to build the star forest that sets the edge between the two
partitions. (see fig)

To my understanding, I do this using PetscSFSetGraph. I choose either 9-10
on rank 0 or 1-2 on rank 1 to be the "roots". For simplicity lets say the
1-2 on rank 1 are roots.

(also for the rest of the discussion I'm switching 1 and 2 to be 0 and 1
and 9 and 10 to be 8 9 ) (the figure is 1 indexed but for the code below it
will be 0)

So on rank 0 I would set

nleaves=2
nroots= 8+c1  (graph is only cells and verts so its 8 verts plus the cell
count(c1)

remote[0].rank=1
remote[0].index=0+(cell count on rank1)
leaf[0]=8+c1

remote[1].rank=1
remote[1].index=0+(cell count on rank1)
leaf[1]=9+c1


and on rank 1 we would set

nroots= ncells+nverts
nleaves=0

Since its all roots I don't think I need to set anything else?



PetscSFSetGraph(sf,nroots,nleaves,leaves,PETSC_COPY_VALUES,remote,PETSC_COPY_VALUES)

I am certain I am making a mistake somewhere since I get an error when I
then call PetscSFSetup. I am working in C++ right now but this is just
testing out before implementation in fortran which is why I am using
PETSC_COPY.

Any help and clarification would be appreciated.


Sincerely
Nicholas



-- 
Nicholas Arnold-Medabalimi

Ph.D. Candidate
Computational Aeroscience Lab
University of Michigan
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20221107/0fb4ad58/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image.png
Type: image/png
Size: 18794 bytes
Desc: not available
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20221107/0fb4ad58/attachment-0001.png>