On Thu, Aug 25, 2011 at 11:24 PM, Alan Wei <zhenglun.wei at gmail.com> wrote:
> Dear all, > I hope you had a nice day. > I have a little bit confusion on src/ksp/ksp/example/tutorial/ex29.c, > which is solving a Poisson equation. The key problem is that I confused > what is the ghosted node, computed nodes and boundary nodes. > 1) For example, if the mesh has 20 * 50 grid on x-, y- direction. For > my understanding, nodes of i = 0, i = 19, j = 0, j = 49 are all boundary > nodes and others are computation nodes. If a Dirichlet boundary condition > is applied in node j = 49, then the value of node j = 49 should be a > constant; while, if a Neumann boundary condition is applied in j = 49, > then change rate from node j = 48 to j = 49 should be a constant. > Fine. > 2) Moreover, If this code is ran with 2 processes, which 2 on > y-direction. This leads a 20 * 25 mesh for each nodes, then the ghost nodes > is created around the local mesh in order to pass data back and forth with > the other node. Is that correct? However, what is the ghost nodes coordinate > value and index? > For proc0, the ghost nodes would be j = 25, and for proc 1 j = 24. However, you should not need to worry about this. Matt > Thanks in advance, > Alan > -- 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/20110826/7e58d3e2/attachment.htm>
