On Sun, Sep 25, 2016 at 4:06 AM, 丁老师 <[email protected]> wrote:
> Dear professor: > In the ksp example ex50.c, i do not understand the meaning of > *KSPSolve* > <http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/KSP/KSPSolve.html#KSPSolve> > *(ksp,NULL,NULL);* > > * n**MatNullSpaceCreate* > <http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatNullSpaceCreate.html#MatNullSpaceCreate>*(**PETSC_COMM_WORLD* > > <http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PETSC_COMM_WORLD.html#PETSC_COMM_WORLD>*,**PETSC_TRUE* > > <http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PETSC_TRUE.html#PETSC_TRUE>*,0,0,&nullspace); > * > > What is the meaning of NULL in the kspsolve. and two "0" in the > MatNullSpaceCrea > <http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatNullSpaceCreate.html#MatNullSpaceCreate> > te. > 1) The NULL for KSPSolve() means that http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/KSP/KSPSetComputeOperators.html http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/KSP/KSPSetComputeRHS.html#KSPSetComputeRHS are used to make the problem. 2) The NullSpace is the space of constant functions with these arguments Matt Regards > > > > > > > At 2016-09-24 00:25:09, "Jed Brown" <[email protected]> wrote: > >"Kong, Fande" <[email protected]> writes: > > > >> Any references on this topic except the users manual? I am interested in > >> mathematics theory on this topic. > > > >These are relevant. I've only skimmed them briefly, but they might > >suggest ways to improve PETSc's handling of singular systems. The > >technique is ancient. > > > >https://doi.org/10.1137/S0895479803437803 > > > >https://doi.org/10.1007/s10543-009-0247-7 > > > > > -- 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
