On Tue 2009-04-14 22:17, Wee-Beng TAY wrote: > Supposed for my 8x8 grid, there's ghost cells on the edge, hence > changing to 0->9 x 0->9 no. of grids.
It is very important to distinguish between the global vector which the solver sees and local vectors which often have ghost values. The global vector should have exactly one entry per global degree of freedom---no ghost entries. It sounds like you are using a structured grid so you probably want to look at the DA object which manages the global vectors and local vectors with ghosting. If you insist on doing it yourself, you should partition the domain so that each node is owned by exactly one process. Create a global vector based on this decomposition, it is what the solver will see. Then create a (sequential) local vector on each process that includes the ghost points. Now create a global-to-local scatter to update the local vector. Jed -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 197 bytes Desc: not available URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20090414/ddabe4b1/attachment.pgp>
