On Mon, Nov 21, 2011 at 9:39 AM, Hui Zhang <mike.hui.zhang at hotmail.com>wrote:
> > > On Nov 21, 2011, at 8:01 AM, Jed Brown wrote: > > > >> On Mon, Nov 21, 2011 at 04:52, Hui Zhang <buyong.huier at gmail.com> > wrote: > >> When using DMDAGlobaltoLocal, how can I communicate only the boundary > of the > >> ghosted domain (with stecil width larger than one)? > >> > >> Only the ghost values are communicated. The interior is all local. > > > > I think Hui means DMDALocalToLocalBegin() and DMDALocalToLocalEnd() > but normally one doesn't need this with the PETSc solvers, one only needs > the DMGlobalToLocalBegin/End() > > > > Barry > > > > Thank you all! > > I'm actually implementing domain decomposition methods with restricted > communication. > From my understanding, DMDALocalToLocalXX is also communicating all ghost > values of > the second Vec. However, in a restricted way, only the ghost points most > far away from > the interior are communicated. No, the communication pattern in the same. You exchange values which are shared by multiple processes. The difference is that LocalToLocal puts values directly into a ghosted local vector, whereas LoaclToGlobal puts them into a global vector, which is not ghosted. 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20111121/f99fa73e/attachment.htm>
