[petsc-users] Interaction between multiple DMDA grid

[Somdeb Bandopadhyay]

Hi Sir,
  Thanks a lot for the clarification.
  I will give it a try, let's see how things go.


Somdeb

On Thu, Dec 29, 2016 at 9:37 AM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
>    Sadly this type of situation is not as easy to handle as one would
> hope. What you suggest is possible, there are basically two different
> approaches
>
> 1) have both DA live on all processes
>
> 2) Create a subcommunicator for DAtop and its complement for DAcavity.
>
>  In either case I would suggest using the "ghost" boundary conditions for
> the top of the DAcavity and the bottom of the DAtop and  use two
> VecScatters to communicate from/to them and the regular parts of the
> domain. Then essentially ghost point updates are done with
> DAGlobalToLocal() on each DA and the VecScatters. For parts of DATop that
> are not above the DACavity you would just ignore the "extra" ghost
> locations.
>
>   I would start by figuring out how to do this and not yet worry about
> Jacobians etc. Just be able to go from global to local on the composite
> grid vector to the local vectors. Use a very small number of points and run
> starting on one process. I would use 1) not 2) since it is simpler to
> understand.
>
>    Good luck,
>
>     Barry
>
>
> > On Dec 28, 2016, at 3:49 PM, Somdeb Bandopadhyay <sb020287 at gmail.com>
> wrote:
> >
> > Hi all,
> >   I am trying to modify a single block incompressible solver for flow
> over open cavity. One way I could do it, is to set part of the domain as
> flagged and apply velocity field=0 all over it. But it does not seem to be
> appropriate way (I am wasting alot of grid, just to have a small cavity).
> So I was wondering, is there any example to interact between two DMDA
> grids? I am using petsc to solve the poisson equation so if I can just
> create two set of grid (say DA_grid1 and DA_grid2) and have a interface
> between them, my problem would be alot more easier.
> >
> > Thanks a lot in advance.
> >
> > Somdeb
>
>
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