On Fri, Mar 13, 2020 at 11:20 AM Pierre Jolivet <[email protected]> wrote:
> > > On 13 Mar 2020, at 2:36 PM, Matthew Knepley <[email protected]> wrote: > > On Fri, Mar 13, 2020 at 3:19 AM Pierre Jolivet <[email protected]> > wrote: > >> >> >> On 12 Mar 2020, at 11:40 PM, Matthew Knepley <[email protected]> wrote: >> >> On Thu, Mar 12, 2020 at 5:59 PM Jed Brown <[email protected]> wrote: >> >>> Pierre Jolivet <[email protected]> writes: >>> >>> > Hello, >>> > Has there been any follow-up on this >>> https://lists.mcs.anl.gov/pipermail/petsc-users/2015-January/024020.html >>> < >>> https://lists.mcs.anl.gov/pipermail/petsc-users/2015-January/024020.html >>> >? >>> > Given a 3x3 MatNest A = [A_00,0,0 ; 0,A_11,0 ; 0,0,A_22], I’d like to >>> setup a two-way fieldsplit coupling [A_00,0 ; 0,A_11] and [A_22] but I >>> can’t figure out the proper options. >>> >>> Are you looking for a Schur split or additive/multiplicative? >> >> >> Don’t know yet which will perform best, do you have a specific solution >> in mind for one scenario or the other? >> I was mostly wondering if it was possible in a general context, not >> taking -pc_fieldsplit_type into account. >> >> -pc_fieldsplit_field_0 0,1 -pc_fieldsplit_field_1 2 -pc_fieldsplit_type >> schur >> >> >> These flags, used with my .cpp, yield: >> [0]PETSC ERROR: Arguments are incompatible >> [0]PETSC ERROR: To use Schur complement preconditioner you must have >> exactly 2 fields >> If I use -pc_fieldsplit_%d_fields <a,b,..> as advocated in the manual >> (instead of -pc_fieldsplit_field_%d as you suggested), I get the same error. >> > > Okay it is -pc_fieldsplit_%d_fields. When you use this, how many fields > does it think you have? > > > Three. > In case it’s not clear, the MWE is at the bottom of my first email > (nest.cpp). > $ mpicxx nest.cpp -I$PETSC_DIR/$PETSC_ARCH/include -I$PETSC_DIR/include > -L$PETSC_DIR/$PETSC_ARCH/lib -lpetsc > $ ./a.out -pc_type fieldsplit -pc_fieldsplit_0_fields 0,1 > -pc_fieldsplit_1_fields 2 -pc_fieldsplit_type schur > […] > [0]PETSC ERROR: Arguments are incompatible > [0]PETSC ERROR: To use Schur complement preconditioner you must have > exactly 2 fields > […] > Split info: > Split number 0 Defined by IS > Split number 1 Defined by IS > Split number 2 Defined by IS > […] > Okay, I will run it. Matt > Thanks, > Pierre > > Matt > >> I believe. >> >> Matt >> >> >>> > Jed, in this answer >>> https://lists.mcs.anl.gov/pipermail/petsc-users/2015-January/023993.html >>> < >>> https://lists.mcs.anl.gov/pipermail/petsc-users/2015-January/023993.html>, >>> you recommend not to use MatNest. What would you recommend instead? >>> >>> See src/snes/examples/tutorials/ex28.c for my preferred approach. >> >> >> I’m not using DM, so in terms of Mat, I guess this example shows that I >> pretty much need to reimplement the field splitting myself? >> >> Thanks, >> Pierre >> >> -- >> 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 >> >> https://www.cse.buffalo.edu/~knepley/ >> <http://www.cse.buffalo.edu/~knepley/> >> >> >> > > -- > 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 > > https://www.cse.buffalo.edu/~knepley/ > <http://www.cse.buffalo.edu/~knepley/> > > > -- 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 https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
