> Berk: Do you have the ability to mark a node as "owned" by one partition and as "ghost" on > other partitions?
Yes! We classify processes as master and slaves according to their ranking numbers. After this we can assign the shared node to a master (which will take care of shared computations) and tell the slave process that this node is being shared with a master (and the slave process will consider it as a "ghost" for computations). The ideas we used in our parallel solver were taken from the following article: Karanam, A. K., Jansen, K. E. and Whitinig, C. H., "Geometry Based Pre-processor for Parallel Fluid Dynamic Simulations Using a Hierarchical Basis", Engineering with Computers (24):17-26, 2008. This article was made available from the author in http://www.scorec.rpi.edu/REPORTS/2007-3.pdf (Figures 7 to 9 explain the communication method between processes), Regards Renato. On Tue, Mar 1, 2011 at 12:24 PM, Berk Geveci <[email protected]>wrote: > Hi Renato, > > > I think I'm missing something.... you said cells only?! > > If I understood this subject correctly, a cell should be considered ghost > if > > it's held by more than one partition/process, isn't it?! In this case, > > there'll be an overlapped layer of elements. The problem is that my MPI > > solver does not make use of this overlapped layer of cells/elements. > > Yep. You understood correctly. Ghost cells are very common for finite > difference calculations but not as common for finite elements. > > > It only > > has nodes/points that are shared by processes. This explains why I asked > by > > a ghost node (shared node would be more appropriated to define such kind > of > > node). > > Can I consider a cell as ghost if it touches the parallel interface > (without > > overlapping)? Would it work? > > Nope. Then you'd start seeing gaps. The right thing to do is for > ParaView to support ghost points (nodes) better. However, this is > non-trivial in some cases. For removing internal interfaces, it is > sufficient to mark points as ghosts. However, for accurately > performing statistics, you need to make sure that you count all points > only once, which requires assigning ghost nodes to processes. So a > replicated node would be marked as ghost (a better word is shared) and > also owned by a particular process. We are going to improve VTK's > ghost level support. This is something we'll support. However, it will > be up to the simulation to produce the write output. Do you have the > ability to mark a node as "owned" by one partition and as "ghost" on > other partitions? > > Best, > -berk > -- Renato N. Elias ============================================= Professor at Technology and Multilanguage Department (DTL) Federal Rural University of Rio de Janeiro (UFRRJ) Nova Iguaçu, RJ - Brazil ============================================= Researcher at High Performance Computing Center (NACAD) Federal University of Rio de Janeiro (UFRJ) Rio de Janeiro, Brazil
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