Now it is clear. Thank you for your help.
- Jibum ----- Original Message ----- From: "jibum kim" <[email protected]> To: "PETSc users list" <petsc-users at mcs.anl.gov> Sent: Monday, November 01, 2010 3:46 PM Subject: Re: [petsc-users] Boomeramg as a solver > Are you saying that boomeramg with richardson iterations is same as the > multigrid without a preconditioner? and if it the case, how can I set an > extra preconditioner like ILU ? > > Thanks, > > - Jibum > > ----- Original Message ----- > From: "Barry Smith" <bsmith at mcs.anl.gov> > To: "PETSc users list" <petsc-users at mcs.anl.gov> > Sent: Monday, November 01, 2010 2:25 PM > Subject: Re: [petsc-users] Boomeramg as a solver > > > > On Nov 1, 2010, at 12:35 PM, jibum kim wrote: > >> Hello, >> >> I've used Boomeramg as a preconditioner. >> >> Now, I am wondering whether I can use Boomeramg as a solver ? and is it >> possible that I use Boomeramg as both a preconditioner and a solver? >> >> I saw one slide saying that I can use KSPSetType(ksp, KSPRICHARDSON); >> >> But when I try it and use -ksp_view, it shows that my solver is >> Richardson not Boomeramg. >> >> Could u clarify this issue ? > > Richardson is our name for the iterative process u^{n+1} = u^n + B(b - > A u^n) for n=1,...max_it where B is the application of the preconditioner > (in other words running a linear iterative method without any Krylov > acceleration). In BoomerAMG's case B is one application of the V or W > cycle (depending on your choice of BoomerAMG options). So even though it > says the "solver" is Richardson it is using BoomerAMG for the entire > solution process, that is algebraic multigrid with multiple V (or W > cycles). > > Barry > > > > >> >> Thank you. >> >> - Jibum > >
