On Wed, May 9, 2012 at 1:29 PM, Stefano Zampini <stefano.zampini at gmail.com>wrote:
> Finally I have some time to work on BDDC. I'm thinking to restyle some of > my BDDC code. In particular in setting up the coarse environment, I want > to implement a function (mostly reusing some BDDC code I already wrote) > > MatiSSubassemble(A, IS ISSubdomains,*B,*intercomm,*partial_scatter) > > which, given subdomain indices, creates a new MATIS matrix on a subcomm of > the communicator of A by subassembling. In particular, ISSubdomains should > come from a call to MatPartitioningApply on the adjacency matrix of the > subdomains. > > The communicator of B is the subcomm of A of processes which will receive > some of the local matrices > intercomm will be the communicator which can be used between each > receiving process and their sending "friends" > *partial_scatter will be the scatter context associated to the intercomm > > Jed, do you already wrote something similar for your PA? What's the best > logic for you? Should I use MatCoarsen? > MatCoarsen is for graph aggregation/matching, which is different. It seems to me that subassembly doesn't coarsen at all. If MatGetSubMatrices() could extract parallel matrices directly, then it looks more like that's what you're after. I don't think the implementation should use an intercomm (too many implementations are buggy and it requires MPI-2 which PETSc tries to avoid depending on because enough users still have antique systems that don't support it). In any case, I think that creating a partition should be separate from transforming the matrix. For MatIS, I would be fine with creating a new MatIS using the same local matrices on a subcommunicator, then MatConvert'ing it to AIJ (that will do assembly), and discarding the temporary subcomm MatIS. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20120509/4d4a38f1/attachment.html>
