On Thu, Feb 21, 2013 at 5:46 PM, Boyce Griffith <griffith at cims.nyu.edu>wrote:
> There are no index sets available for the SAMRAI vector data. The > interface only provides access to "capital-V Vector Space" operations > (vector addition, scalar multiplication, dot product, etc.). > > We've discussed this briefly before on some list --- petsc-dev? --- with > Bobby Philip, but the basic story is that SAMRAI does patch-based AMR and > separately allocates data for each patch as simple FORTRAN-style arrays > (e.g. ghost cells are "co-mingled" with patch DOFs). This makes it > cumbersome to generate a Vec representation that plays nice with PETSc. > Surely there is a way to distinguish ghost cells from non-ghost cells. Then you define a contiguous ordering/index set by simply marching through the non-ghost cells labeling them sequentially. > I am working on some code to make it feasible to map SAMRAI data onto a > native PETSc Vec and to generate unique indices for the different data > centerings provided by SAMRAI that we use regularly, but at least for now > Amneet isn't trying to use that stuff. (And by "working on", here I really > mean thinking about working on while I am instead writing grant > applications. ;-) > > It also seems almost feasible to use one of the existing DMs to wrap the > SAMRAI data. I haven't thought about this in a while and don't remember > what I thought sounded like it was feasible. > > > But if you really want to use those other vector space wrappers, you can >> use VecNest. >> > > Great --- this is what I had hoped and what Amneet was trying to figure > out. > If you really don't want to have an IS, you can use VecNestGetSubVec(), just be warned that this makes your code more brittle and harder to interoperate with. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20130221/124b434a/attachment.html>
