On Wed, Mar 26, 2014 at 7:54 PM, TAY wee-beng <[email protected]> wrote:
> On 27/3/2014 12:14 AM, Matthew Knepley wrote: > > On Wed, Mar 26, 2014 at 10:42 AM, TAY wee-beng <[email protected]> wrote: > >> On 26/3/2014 11:22 PM, Matthew Knepley wrote: >> >> On Wed, Mar 26, 2014 at 9:59 AM, TAY wee-beng <[email protected]> wrote: >> >>> Hi, >>> >>> I am running a CFD solver. The Poisson eqn was originally solved using >>> HYPRE's geometric multigrid. >>> >> >> Is this on a structured grid? >> >> >> Yes. >> > > Then you can replicate the Hypre structured MG with the PCMG, and it can > be lighter memory than GAMG. You > will need to code the problem in the style of SNES ex5, which is a Poisson > for which geometric MG works from > the command line. > > Thanks, > > Matt > > Hi Matt, > > First of all, is there an easier way out? Is it Boomeramg or GMRES which > has a large memory requirement? Will changing e.g. GMRES to FGMRES or other > ksp solvers solve the problem? > You could perhaps use a low-memory Krylov method, like BiCGStab. How big is your Krylov space? > Also, I switched from geometric multigrid (GMG) to Boomeramg because the > latter is faster. If I use PCMG, am I going back to the GMG path, which was > slower? > If multigrid is working correctly, it should take 10 iterates or so. I am guessing something was wrong with the GMG, like coarse BC. Thanks, Matt > Thanks! > > > >> Matt >> >> >>> Recently, I tested it with Boomeramg as the preconditioner and GMRES as >>> the ksp solver. There's a 20% increase in speed. >>> >>> However, when I increased the grid resolution, I got the out of memory >>> error. Changing the solver back to HYPRE solved the problem. >>> >>> So does GMRES + Boomeramg used more memory than other solvers? Are >>> there alternatives? >>> >>> Thank you. >>> >>> -- >>> Yours sincerely, >>> >>> TAY wee-beng >>> >>> >> >> >> -- >> 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 > > > -- 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
