dolfin team mailing list archive

["Garth N. Wells" <gnw20@xxxxxxxxx>]

Anders Logg wrote:
> On Fri, May 16, 2008 at 10:55:09AM +0100, Nuno David Lopes wrote:
> > GMRES seems to work: 
> > -------------------------------------------------------------------------------------------------
> > Solving linear system of size 40121 x 40121 (uBlas Krylov solver).
> > Krylov solver converged in 14 iterations.
> > -------------------------------------------------------------------------------------------------
> > I've got the same results for factorized LU.
> >
> >
> > CG isn't recognized
>
> CG isn't implemented for uBLAS. 

I'll add it once we can apply boundary conditions without destroying 
symmetry.

Check line 130 and onward in
> uBlasKrylovSolver.h.
>
> > and  BiCGStab (the default) "doesn't converge"...
> > it makes only one iteration:
>
> I'm not sure how well tested the BiCGStab implementation is, but it's
> not very unusual for an iterative method to not converge.

BiCGStab was pretty well tested. Make sure that a preconditioner is 
being used, and if you're solving a steady diffusion problem, start 
testing with a coarse mesh. The iterative methods will struggle with 
steady diffusion and mesh refinement.

Garth