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>