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. >
