Hi Ravi, I have been using BoomerAMG as a preconditioner joint with an iterative solver, e.g. GMRES of BiCGs for regular 3D CFD problems. On the top of my head, I can not remember if I had the strong scaling tests done (I will look into it and let you know if you found any), but for the weak-scaling case, I definitely saw some scaling issues. As the size of the system increases, the number of iterations does also increase (somewhat significantly for my test problem, i.e. incompressible N-S with complex geometry) which ultimately deteriorates the weak-scaling behaviors.
This is also reported in the reports given by the hypre team, cf. https://computation.llnl.gov/casc/linear_solvers/pubs/pmis_report.pdf (cf. see Table 6.1 for the Stokes flow simulation results and scaling). Also, inherited with the multigrid nature, there are always fine-tuning factors which are, unfortunately, problem dependent. Good luck, Mohamad On Thu, Dec 15, 2011 at 8:23 AM, Ravi Kannan <rxk at cfdrc.com> wrote: > Dear All,**** > > ** ** > > This is Ravi Kannan from CFD Research Corporation. Recently, we are > experimenting with the BoomerAMG preconditioner for some ?stiff? CFD > problems. In that regard, all the other standard solver-preconditioner > combinations failed for the current CFD problem. The boomer is the only one > which is able to provide with ?converged? solutions.**** > > ** ** > > We noticed that the scalability of this boomer preconditioner is really > poor. For instance, even with a cell size of 2 million, we cannot scale to > even 16 partitions (in contrast, the other solver-preconditioner > combinations like the BI-CGS/BJacobi gave good enough scalability).**** > > ** ** > > Are we missing something? Do we need to use a more latest version of > boomer?**** > > ** ** > > Thanks,**** > > Ravi. **** > > ** ** > > ** ** > > ** ** > > ** ** > > ** ** > > *From:* petsc-dev-bounces at mcs.anl.gov [mailto: > petsc-dev-bounces at mcs.anl.gov] *On Behalf Of *Bobby Philip > *Sent:* Thursday, December 15, 2011 9:22 AM > *To:* For users of the development version of PETSc > *Subject:* Re: [petsc-dev] controlling vector values while doing matrix > free operations**** > > ** ** > > Hmmmm..sorry guys - the entire thread got put away in a folder by my mail > reader and I just discovered all your emails :-)**** > > ** ** > > SNESVI looks interesting but as someone pointed out I am using matrix > free. And as I understand from Barry a matrix free version of SNESVI is not > implemented. The idea of flipping the sign seems to be a poor mans approach > that might work for me though I would still need some mechanisms in SNES to > put the hooks in.**** > > ** ** > > Bobby**** > > ** ** > > On Dec 14, 2011, at 10:45 PM, Jed Brown wrote:**** > > > > **** > > On Wed, Dec 14, 2011 at 19:40, Dmitry Karpeev <karpeev at mcs.anl.gov> wrote: > **** > > The trouble is that the constraints can get "eliminated" only when they > become active. **** > > ** ** > > That's not what I meant. I meant to transform the algebraic system so that > those extra variables were eliminated. The point is that we tend to put a > lot of effort into designing effective preconditioners for a standard > formulation (e.g. conservative variables), and that is partly lost of we > have this other system in which the evaluations of constitutive relations > are added explicitly.**** > > ** ** > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20111219/3a5362c1/attachment-0001.htm>
