________________________________________ From: petsc-users-bounces at mcs.anl.gov [petsc-users-bounces at mcs.anl.gov] On Behalf Of Jed Brown [jedbr...@mcs.anl.gov] Sent: Monday, July 11, 2011 7:38 PM To: PETSc users list Subject: Re: [petsc-users] Field dependent stencil in DAs
On Mon, Jul 11, 2011 at 18:28, Kevin Green <Kevin.Green at uoit.ca<mailto:Kevin.Green at uoit.ca>> wrote: Essentially, I'm (currently) looking to numerically solve a system of 5 time dependent equations, but only 1 of the fields is involved with spatial derivatives. Now, I've found a couple of ways to do this, either by introducing a Field struct cf. ${PETSC_DIR}/src/snes/examples/tutorials/ex19.c, or by changing one of the various ts examples to use DAVecGetArrayDOF(...). Would there be any performance difference between introducing a Field struct compared to DAVecGetArrayDOF(...)? Intuitively, I would think not...but I suppose I should ask since I'm here anyway. I like using field structs because then I get to use names instead of numbers for my fields and because there is one less level of pointer indirection. Now the real reason I came: Is there some sort of mask that can be applied to the DAs that would turn off the communication of ghost points for some degrees of freedom? I assume that the communication structures are set up so that only a single message needs to be passed between communicating processes on update, but this still results in passing 5X the data that I have to. Any comment on this would be much appreciated. DMDASetBlockFills() Thank you Jed, this is exactly what I was looking for. In the most recent version, it appears to be named as just DASetBlockFills().
