[petsc-users] Using petsc with an existing domain decomposition.

[Mark Adams]

On Sun, Oct 13, 2019 at 5:25 AM Pierre Gubernatis via petsc-users <
petsc-users at mcs.anl.gov> wrote:

> Hello all,
>
> It souds that the best way to introduce petsc in a code is not to
> introduce it, but develop the code over the petsc structure.
>

All things being equal, yes, but few users start with PETSc from scratch.
You situation is normal and Matt's suggestion of mirroring your mesh in
PETSc mesh object (DM) is a common approach.


> It is probably true but my problem is that my existing code already is
> equipped with a domain decomposition based on MPI (a typical themal
> hydraulic with cartesian staggered mesh)
>
> The user can slice the domain in sub-domains and construct a linear
> problem by block: each sub-domain assembles its part of the operator and
> its part of the RHS.
>
> I am wondering what is the best way now to introduce petsc (considering
> that I don’t want to assemble a global operator on a given proc). Is there
> an example that would show how to introduce petsc in this situation ?
> Thank you, Pierre
>
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