On Feb 10, 2012, at 5:00 PM, Jed Brown wrote: > On Fri, Feb 10, 2012 at 16:56, Barry Smith <bsmith at mcs.anl.gov> wrote: > I realize that since the DMs may often share "the grid information" and only > be different in the stencil width or box type or something Jed (or maybe it > is Matt) is going to get all upset that their are two DMs with common > information sometimes. My response is "get over it" :-). > > Lots of objects share PetscLayouts, ISLocalToGlobalMappings, etc., without > forcing this sharing on users (or, in most cases, even exposing the existence > of these shared objects to the user). I think DM should work the same way.
I have no objection in principle for there being a way to construct two DMs that share most information, but have only stencil width difference and stuff like that. But I would like the result to be two first class PETSc DM objects that each can be independently passed around and used, I believe this is exactly what you are suggesting so we are in agreement. > > In this case, we are interpreting Vecs as being part of both spaces. I'm less > keen on that, but it's not a deal breaker. > > What about DMDAFormJacobianLocal()? Should it have both matrices? How does > the user manage the two DMs if they want to assemble both matrices in the > same mesh traversal? I guess it can be changed from DMDAFormJacobianLocal(DM da, DMDALocalFunction1 func, Vec X, Mat J, void *ctx) to DMDAFormJacobianLocal(DM da, DM dap, DMDALocalFunction1 func, Vec X, Mat J, Mat B, void *ctx) Barry
