It makes sense, thank you. In fact, both ways seems better than my way.
The first one looks the most straightforward. Unfortunately I do not
know how to implement either of them. Could you please direct me to the
corresponding PETSc functions ?
Pierre
On 15/10/21 13:25, Matthew Knepley wrote:
On Fri, Oct 15, 2021 at 7:08 AM Pierre Seize <[email protected]
<mailto:[email protected]>> wrote:
Hi,
I'm writing a code using PETSc to solve NS equations with FV on an
unstructured mesh. Therefore I use DMPlex.
Regarding periodicity, I manage to implement it this way:
- for each couple of boundaries that is linked with periodicity, I
create a buffer vector with an ISLocalToGlobalMapping
- then, when I need to fill the ghost cells corresponding to the
periodicity, the i "true" cell of the local vector fills the buffer
vector on location i with VecSetValuesBlockedLocal, then
VecAssemblyBegin/VecAssemblyEnd ensure each value is send to the
correct
location thanks to the mapping, then the i "ghost" cell of the local
vector reads the vector on location i to get it's value.
It works, but it seems to me there is a better way, with maybe
PetscSF,
VecScatter, or something I don't know yet. Does anyone have any
advice ?
There are at least two other ways to handle this. First, the method
that is advocated in
Plex is to actually make a periodic geometry, meaning connect the
cells that are meant
to be connected. Then, if you partition with overlap = 1,
PetscGlobalToLocal() will fill in
these cell values automatically.
Second, you could use a non-periodic geometry, but alter the
LocalToGlobal map such
that the cells gets filled in anyway. Many codes use this scheme and
it is straightforward
with Plex just by augmenting the map it makes automatically.
Does this make sense?
Thanks,
Matt
Pierre Seize
--
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/%7Eknepley/>
