> On Thu, Feb 03, 2011 at 09:03:58PM +0100, Niclas Jansson wrote: >> Anders Logg <l...@simula.no> writes: >> >>> On Tue, Feb 01, 2011 at 11:57:28AM -0000, Anders Logg wrote: >>>> Question #143645 on DOLFIN changed: >>>> https://answers.launchpad.net/dolfin/+question/143645 >>>> >>>> Anders Logg proposed the following answer: >>>> On Tue, Feb 01, 2011 at 11:50:37AM -0000, Garth Wells wrote: >>>>> Question #143645 on DOLFIN changed: >>>>> https://answers.launchpad.net/dolfin/+question/143645 >>>>> >>>>> Status: Open => Answered >>>>> >>>>> Garth Wells proposed the following answer: >>>>> I don't think so. >>>> >>>> I think it should be possible, at least "in principle". I'll comment >>>> more later. I'm in a meeting now. >>> >>> Sorry for my late reply. >>> >>> What you can do is to get the "overlap": >>> >>> std::map<uint, std::vector<uint> >* overlap = >>> mesh.data().vector_mapping("overlap"); >>> >>> This gives you a mapping for each shared vertex to its neighboring >>> processes (the processes it's shared with). >>> >>> You can check if a vertex is shared by >>> >>> overlap->find(i) != overlap->end() >>> >>> There is no functionality for checking edges, cells etc. Such >>> operations must be expressed in terms of their vertices. >>> >>> It would be easy to add some shortcuts like >>> >>> bool Vertex::is_ shared() const; >>> >>> and even >>> >>> bool MeshEntity::is_shared() const; >>> >>> etc if that helps. They could just look at the overlap. >>> >>> If that is costly, we could store another MeshFunction that holds the >>> appropriate data (or add as part of ParallelData). >>> >>> >> >> Perfect! That should be enough to get me started porting some code. > > Great! > >> How about owners of mesh entities? If I remember correctly mesh entities >> were not owned by a specific rank. If one could determine if a vertex >> is owned, ghosted or shared, it would make life much simpler when >> implementing various parallel mesh algorithms. > > Isn't the rule that when a vertex is shared, it's owned by the lowest > rank process? >
We don't need to designate an owner for mesh entities. > I don't know how we handle ghosted entities (or if we even have > ghosted entities). We have ghosted dofs stored in Vectors (handled by > PETSc/Epetra) but I'm not sure how it's handled. Garth knows a great > deal more about that. > Dof ownership is handled via the dof map. When creating a vector, we have a constructor that takes the local size, plus a list of ghost entries. We use built-in PETSc functionality for PETScVector, and home-baked ghosting for EpetraVector. Ownership of mesh entities is not important (at least for the current functionality, integration over interior facets will be different). Garth > -- > Anders > > _______________________________________________ > Mailing list: https://launchpad.net/~dolfin > Post to : dolfin@lists.launchpad.net > Unsubscribe : https://launchpad.net/~dolfin > More help : https://help.launchpad.net/ListHelp _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : dolfin@lists.launchpad.net Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
