Re: [petsc-users] Near nullspace for preconditioners other than GAMG?

On Tue, Mar 10, 2015 at 5:50 PM, Mark Adams wrote: > Penalty methods are hell on solvers. There is a good change that GAMG > will do the right thing with a finite threshold. and keep this stiff > section separate. You might want to start wit a small number of levels and > a large coarse grid an

Re: [petsc-users] Near nullspace for preconditioners other than GAMG?

Penalty methods are hell on solvers. There is a good change that GAMG will do the right thing with a finite threshold. and keep this stiff section separate. You might want to start wit a small number of levels and a large coarse grid and get it working. Then add more levels and see if it breaks.

Re: [petsc-users] Near nullspace for preconditioners other than GAMG?

On Sun, Mar 8, 2015 at 10:31 AM, Mark Adams wrote: > > > >> Another situation I've been meaning to ask about: If the elasticity model >> includes some "near rigid" regions (very high Young's modulus) >> > > Do you mean Poisson ratio? > No, just high Young's modulus in subregions. Engineers some

Re: [petsc-users] Near nullspace for preconditioners other than GAMG?

On Sat, Mar 7, 2015 at 6:27 PM, David Knezevic wrote: > OK, thanks for letting me know. > > I've tried GAMG and ML with MatNullSpaceCreateRigidBody and those both > work well for me. (I tried ML after Jed pointed out that ML also uses the > near nullspace.) > > I have also tried hypre but the con

Re: [petsc-users] Near nullspace for preconditioners other than GAMG?

On Sat, Mar 7, 2015 at 5:52 PM, Barry Smith wrote: > > > On Mar 7, 2015, at 5:27 PM, David Knezevic > wrote: > > > > OK, thanks for letting me know. > > > > I've tried GAMG and ML with MatNullSpaceCreateRigidBody and those both > work well for me. (I tried ML after Jed pointed out that ML also u

Re: [petsc-users] Near nullspace for preconditioners other than GAMG?

> On Mar 7, 2015, at 5:27 PM, David Knezevic wrote: > > OK, thanks for letting me know. > > I've tried GAMG and ML with MatNullSpaceCreateRigidBody and those both work > well for me. (I tried ML after Jed pointed out that ML also uses the near > nullspace.) > > I have also tried hypre but th

Re: [petsc-users] Near nullspace for preconditioners other than GAMG?

OK, thanks for letting me know. I've tried GAMG and ML with MatNullSpaceCreateRigidBody and those both work well for me. (I tried ML after Jed pointed out that ML also uses the near nullspace.) I have also tried hypre but the convergence hasn't been as good for the elasticity models I've been usi

Re: [petsc-users] Near nullspace for preconditioners other than GAMG?

FYI, stüben used classical AMG for elasticity but he has articulated his code for elasticity more than Hypre as I understand it. Hypre can work OK for elasticity in my experience. Its worth a try. Mark On Thu, Mar 5, 2015 at 5:27 PM, David Knezevic wrote: > OK, got it, thanks! > > David > > >

Re: [petsc-users] Near nullspace for preconditioners other than GAMG?

OK, got it, thanks! David On Thu, Mar 5, 2015 at 5:08 PM, Jed Brown wrote: > David Knezevic writes: > > I was just wondering if its possible to achieve the same sort of thing > with > > other AMG solvers (e.g. BoomerAMG)? I assume that MatSetNearNullSpace > does > > nothing for external solve

Re: [petsc-users] Near nullspace for preconditioners other than GAMG?

David Knezevic writes: > I was just wondering if its possible to achieve the same sort of thing with > other AMG solvers (e.g. BoomerAMG)? I assume that MatSetNearNullSpace does > nothing for external solvers like hypre, right? It is used by ML (smoothed aggregation), but not BoomerAMG (classical

[petsc-users] Near nullspace for preconditioners other than GAMG?

Hi all, I found that using MatNullSpaceCreateRigidBody as per example 49 works well with GAMG for a standard elasticity problem, so that's great. I was just wondering if its possible to achieve the same sort o