Matt, I have used the Hypre AMG option in the past but have not tried ML AMG before. Are there any added advantages in terms of performance/memory footprint and such between the two ?
Vijay On Fri, Dec 3, 2010 at 12:36 PM, Matthew Knepley <knepley at gmail.com> wrote: > On Fri, Dec 3, 2010 at 12:33 PM, Randall Mackie <rlmackie862 at gmail.com> > wrote: >> >> Are there any examples that show how to use the ML PC? > > -pc_type ml > It is Algebraic Multigrid. > ?? Matt > >> >> Randy >> >> On Dec 3, 2010, at 9:02 AM, Matthew Knepley wrote: >> >> I will also note that a good intro for implementing your own might be the >> ML PC >> in Petsc. It puts the ML AMG package into the PCMG framework. >> ?? Matt >> >> On Fri, Dec 3, 2010 at 3:44 AM, Dave May <dave.mayhem23 at gmail.com> wrote: >>> >>> Hey Vijay, >>> ?PCMG is generic. If you provide the operators for each level, along >>> with the restriction and prolongation, >>> you can use PCMG. It doesn't need to know about the mesh. >>> >>> You don't actually need to provide the coarse grid operators. >>> Given the fine grid operator and R and optionally P, you can use >>> Galerkin coarsening by calling >>> PCMGSetGalerkin() or via the command line arg -pc_mg_galerkin >>> Also, if you don't specify the prolongation, petsc will use P = R^T. >>> >>> >>> Cheers, >>> ?Dave >>> >>> >>> On 3 December 2010 06:02, Vijay S. Mahadevan <vijay.m at gmail.com> wrote: >>> > Hi all, >>> > >>> > I was wondering whether the MG preconditioner object is generic enough >>> > to work out of the box like say ILU or SOR. ?To elaborate on this, if >>> > I can provide the number of levels, restriction and prolongation >>> > operators for each level and the system operators along with vectors >>> > allocated for solution and rhs, would it work as a preconditioner for >>> > my given problem and a prescribed rhs at the finest level of PCMG. Or >>> > does it need some knowledge of the fine and coarser meshes to perform >>> > the MG operations correctly ? >>> > >>> > All the examples I've seen using MG in petsc involve the DA and DMMG >>> > objects and since I use my own mesh and corresponding discretization >>> > code for an elliptic system, I'm curious about this usage. It would >>> > not be terribly difficult to write my own framework to do a simple >>> > V-cycle with my existing framework but since petsc already provides >>> > this functionality along with different types of MG solves (with >>> > verified code!), I really want to use it for my system. Any help >>> > and/or pointers are welcome. >>> > >>> > Thanks, >>> > vijay >>> > >> >> >> >> -- >> 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 >> > > > > -- > 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 >
