Should SlicedCreateLocalVector() exist?

[Barry Smith]

    Jed,

      Feel free to make these changes.

      Just curious, are you using the Sliced in some development?

    Barry

On Apr 16, 2009, at 7:15 AM, Jed Brown wrote:

> It throws away the reference to the global vector and there is no  
> way to
> recover it.  Calling VecDestroy() on the local form won't do the right
> thing, it's essentially the same as VecGhostRestoreLocalForm().  Also,
> SlicedGlobalToLocalBegin/End really have different semantics from
> DAGlobalToLocalBegin/End (requiring that it's actually the same  
> vector).
> I don't see how these functions simplify matters for the user.  If you
> had different behavior than what is currently implemented in mind, I
> might be able to implement it, otherwise I'm in favor of removing  
> these
> functions and having the user work with the VecGhost interface.
>
>
> As for SlicedCreateGlobalVector, I think that ideally after
>
>  SlicedCreateGlobalVector(slice,&g0);
>  VecDestroy(g0);
>  SlicedCreateGlobalVector(slice,&g1);
>
> there should only be one vector allocated.  For this, I think that the
> following will work.  Am I missing something subtle?
>
>  if (slice->globalvector) {
>    ierr = PetscObjectGetReference((PetscObject)slice- 
> >globalvector,&cnt);CHKERRQ(ierr);
>    if (cnt == 1) {
>      *gvec = slice->globalvector;
>      ierr = PetscObjectReference((PetscObject)*gvec);CHKERRQ(ierr);
>      ierr = VecZeroEntries(*gvec);CHKERRQ(ierr);
>    } else {
>      ierr = VecDuplicate(slice->globalvector,gvec);CHKERRQ(ierr);
>    }
>  } else {
>    ...
>  }
>
>
> Jed