Option with HYPRE and KSP

[Ben Tay]

Ok thank you very much

On 4/9/07, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
>
>
> On Mon, 9 Apr 2007, Ben Tay wrote:
>
> > Hi,
> >
> > I am solving a poisson eqn and using hypre as a preconditioner has
> greatly
> > increased the speed. I am trying to do some more tuning and I have some
> > questions:
> >
> > 1. Is boomerAMG the only option?
>
> Yes, but all will suck on the poisson compared to boomeramg, so stick to
> boomer
>
> What are the other hypre conditioners
> > available? Is there any documentation somewhere?
>
> Run with -help and check the hypre users manual
>
> >Is hypre just a
> > preconditioner or can it be a solver as well?
>
> Run with -ksp_type richardson to use it as a "solver"
> >
> > 2. what does the preonly in ksp_type mean? Is the eqns solved?
>
>   It means apply the preconditioner ONCE, unless the preconditioner is
> a direct solver it does not solve the equations. Richardson means run
> some number of iterations of the preconditioner and can solve the
> equations
>
> >
> > 3. why can't I use bcgs  or bicg with hypre?
>
>   hypre doesn't support applying the transpose of the preconditioner that
> bcgs and bicg need?
>
>
> > Also, can cg be used for
> > non-symmetric matrix. It seems to work.
>
> Sometimes it works, but it is dangerous and not worth risking.
>
>   Barry
>
> >
> > Thank you very much.
> >
> > Regards.
> >
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20070409/4ebca96e/attachment.htm>