> On Jun 26, 2023, at 11:44 AM, Srikanth Sathyanarayana <[email protected]>
> wrote:
>
> Dear PETSc developers,
>
>
> I am currently working on a Gyrokinetic code where I essentially have to
> implement a block structured grid approach in one of the subdomains of the
> phase space coordinates. I have attached one such example in the x -
> v_parallel subdomains where I go from a full grid to a grid based on 4 blocks
> (divided along x direction) which is still Cartesian but misaligned across
> blocks (the grid is a very coarse representation). So the idea is to
> basically create a library for the existing solver and try to implement the
> block structured grid approach which mainly involves some sort of
> interpolation between the blocks to align the points.
>
>
> I came up with an idea to implement this using DMDA. I looked into the old
> threads where you have suggested using DMComposite in order to tackle such
> problems although a clear path for the interpolation between the DM's was not
> clarified. Nonetheless, my main questions were:
>
> 1. Do you still suggest using DMComposite to approach this problem.
Unfortunately, that is all we have for combining DM's. You can use
unstructured, or structured or unstructed with quad-tree-type refinement but we
don't have a "
canned" approach for combining a bunch of structured grids together efficiently
and cleanly (lots of issues come up in trying to design such a thing in a
distributed memory environment since some blocks may need to live on different
number of MPI ranks)
>
> 2. Is there a way to use DMDA where the user provides the allocation? My main
> problem is that I am not allowed to change the solvers data structure
The allocation for what?
>
> 3. I looked into VecCreateMPIWithArray for the user provided allocation,
> however I am not very sure if this Vector can be used with the DMDA
> operations.
Yes, you can use these variants to create vectors that you use with DMDA; so
long as they have the correct dimensions.
>
>
> Overall, I request you to please let me know what you think of this approach
> (using DMDA) and I would be grateful if you could suggest me any alternatives.
>
>
> Thanks and regards,
>
> Srikanth
> <Screenshot from 2023-06-26 17-24-32.png>
