dolfin team mailing list archive

[Nuno David Lopes <ndl@xxxxxxxxxxxxxx>]

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
and  BiCGStab (the default) "doesn't converge"...
it makes only one iteration:
-------------------------------------------------------------------------------------------------
Solving linear system of size 40121 x 40121 (uBlas Krylov solver).
*** Warning: Requested Krylov method unknown. Using BiCGStab.
Krylov solver converged in 1 iterations.
-------------------------------------------------------------------------------------------------
The results aren't in agreement with the ones i've got with LU.
I didn't change any default parameters....

(I'm testing on a standard heat equation with several boundary conditions and 
two different heat diffusion coefficient subdomains)

On Thursday 15 May 2008, Anders Logg wrote:
> On Thu, May 15, 2008 at 05:24:39PM +0100, Nuno David Lopes wrote:
> > After a great struggle for a clean install in a ubuntu 8.04 box i could
> > compile dolfin, with umfpack and without petsc. Just like i have in my
> > ubuntu 7.10 laptop.
> >
> > After some tests i've found that I'm unable to get a KrylovSolver other
> > than Bicgstag!!!! Is this a Known issue? I guess i've all the blas
> > related libs...
>
> Yes, I think someone else mentioned it to me.
>
> See if it works now. I've attempted to fix it. If not, it should be
> easy to fix.
>
> > libboost
> > atlas3
> > lapack3
> > refblas3
> > with dev's also.
> >
> > if i have something like:
> >
> > KrylovSolver solver(gmres,ilu);
> >
> > KrylovSolver solver(cg);
> >
> > LinearSolver solver(gmres);
> >
> > solve(A,x,b,gmres);
> >
> > i got the following message
> >
> > Solving linear system of size 40121 x 40121 (uBlas Krylov solver).
> > *** Warning: Requested Krylov method unknown. Using BiCGStab.
> >
> > I've no problems with LUSolver.(umfpack seems to be alright)
> >
> > Is this a Known issue?
> > Do i need petsc for that?
> > I can't compile with umfpack and petsc...
> > but as i've seen thru the mailing list that is known and difficult issue
> > about package dependencies, right?
> >
> > Thanks.
> >
> > On Saturday 10 May 2008, Anders Logg wrote:
> > > LinearSolver is now a general wrapper for all linear solvers
> > > (rather than a base class for linear solvers). Creating a LinearSolver
> > > and reusing it instead of calling solve() multiple times gives
> > > about 5% speedup.
> > >
> > > It's a subclass of Parametrized, meaning that it's possible to set
> > > parameters. For example, it should be possible to do
> > >
> > >   LinearSolver solver(gmres, amg);
> > >   solver.set("Krylov relative tolerance", 1e-6);
> > >   solver.set("Krylov absolute tolerance". 1e-6);
> > >   solver.solve(A, x, b);
> > >
> > > and have those parameters passed on to the backend (for example
> > > PETSc).
> > >
> > > For those of you interested in setting special parameters to different
> > > backends, the available parameters are listed in
> > >
> > >   dolfin/parameter/DefaultParameters.h
> > >
> > > and they are accessed in the different backends by for example
> > >
> > >   tol = get("Krylov relative tolerance");
> > >
> > > Supply a patch if there are parameters you think are missing.
> > >
> > > We probably should not support all parameters for all backends.
>
> _______________________________________________
> DOLFIN-dev mailing list
> DOLFIN-dev@xxxxxxxxxx
> http://www.fenics.org/mailman/listinfo/dolfin-dev



-- 
Nuno David Lopes

e-mail:ndl@xxxxxxxxxxxxxx        (FCUL/CMAF)
           nlopes@xxxxxxxxxxxxxxx    (ISEL)
http://ptmat.ptmat.fc.ul.pt/%7Endl/