[petsc-dev] DMComplex and PCFieldSplit

[Barry Smith]

On Feb 24, 2012, at 2:23 PM, Jed Brown wrote:

> We need a richer field interface. Some way for a client of DM to discover vector and tensor structure.

   No idea what a tensor is, but DMGetSubDMS(dm,PetscInt *cnt,IS *ises,DM *dms);   and DMPushSubDMType(DM,"name of a type of splitting like u,v,p or velocity,p"); DMPopSubDMType(); and DMGetAvailableSubDMTypes(DM,char **);

  Do you need more than that?

    Barry

Note that current DMDA's default subdms served up would be a DM for each field consisting of one of the degrees of freedom per node and it could also serve up  DMs that represent any collections of those for example dof 0 and 1 per node, then dof 2 per node. We'll need to come up with some naming convention for these.


> Possibly also (eventually) a way to solve equations of state so that we can formulate reduced problems in non-conservative variables.
> 
> On Feb 24, 2012 2:19 PM, "Matthew Knepley" <knepley at gmail.com> wrote:
> On Fri, Feb 24, 2012 at 1:58 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
> http://petsc.cs.iit.edu/petsc/petsc-dev/rev/518ff70e8a0a
> 
> Matt, I want to get rid of these conditionals, not add more. We should have a DM base interface for getting fields on which to split, that common interface should _replace_ the DMComposite specialization.
> 
> I agree. However, I won't put anything in until I do it by hand once.
> 
> Also, I was tempted to just promote DMGetGlobalISes(), but its not quite right. I am planning
> to put the IS method in PetscSection. I am hoping eventually DMDA uses PetscSection for
> layout.
> 
>    Matt
> 
> -- 
> 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