Awesome, thanks Barry! On Wed, May 17, 2023 at 11:59 AM Barry Smith <bsm...@petsc.dev> wrote:
> > Absolutely, that is fundamental to the design. > > In the simple case where all the degrees of freedom exist at the same > grid points, hence storage is like u,v,t,p in the vector the nesting is > trivial. You indicate the fields without using IS (don't even need to > change any code) > > -pc_fieldsplit_0_fields 0,1,2 > -fieldsplit_pc_fieldsplit_0_fields 0,1 > > Listing the two complimentary fields > pc_fieldsplit_1_fields 3 > -fieldsplit_pc_fieldsplit_1_fields 2 > should be optional (I can't remember if it is smart enough to allow not > listing them) > > If you have a staggered grid then indicating the fields is trickery (since > you don't have the simple u,v,t,p layout of the degrees of freedom) > > > > > On May 17, 2023, at 12:47 PM, Alexander Lindsay < > alexlindsay...@gmail.com> wrote: > > > > I've seen threads in the archives about nested field split but I'm not > sure they match what I'm asking about. > > > > I'm doing a Schur field split for a porous version of incompressible > Navier-Stokes. In addition to pressure and velocity fields, we have fluid > and solid temperature fields. I plan to put all primal variables in one > split and the pressure obviously in the Schur split. Now within the "primal > variable split" a user is wondering whether we can do a further split, e.g. > perhaps an additive split with the solid temperature split out from the > velocities and fluid temperature (the former is almost pure conduction > whereas the latter may be advection dominated). Is this possible? > > > > Alex > >