On Dec 14, 2011, at 7:07 AM, M.Younas wrote: > Hi, PETSc, Team, > > I have solved a non-symmetric Poisson problem using GMRES(m) as solver and > BoomerAMG (from Hypre) as preconditioner. But I don't understand how the > BoomerAMG works as preconditioner with GMRES(m). Can anyone explain the > procedure? Does it work like BoomerAMG precondition the liner system first > (once only) and then GMRES(m) is being used for stopping criterion?
By default PETSc uses ONE v-cycle of the BoomerAMG as a preconditioner for GMRES. With the option -ksp_type richardson then PETSc is using a bunch of BoomerAMG v-cycles until the convergence criteria is satisfied without using a GMRES Barry Note that a preconditioner can be any stationary linear iterative scheme. That is any linear operation that approximately solves A x = b, no matter how complicated the stationary linear iterative scheme is it can be used as a preconditioner. > > Kind regards, > > Younas > > RUG, Groningen, The Netherlands.
