|-pc_hypre_type||- One of euclid, pilut, parasails, boomeramg, ams, ads|
|Too many others to list, run with||- pc_type hypre -pc_hypre_type XXX -help to see options for the XXX preconditioner|
The options -pc_hypre_boomeramg_max_iter and -pc_hypre_boomeramg_tol refer to the number of iterations (V-cycles) and tolerance that boomeramg does EACH time it is called. So for example, if -pc_hypre_boomeramg_max_iter is set to 2 then 2-V-cycles are being used to define the preconditioner (-pc_hypre_boomeramg_tol should be set to 0.0 - the default - to strictly use a fixed number of iterations per hypre call). -ksp_max_it and -ksp_rtol STILL determine the total number of iterations and tolerance for the Krylov solver. For example, if -pc_hypre_boomeramg_max_iter is 2 and -ksp_max_it is 10 then AT MOST twenty V-cycles of boomeramg will be called.
Note that the option -pc_hypre_boomeramg_relax_type_all defaults to symmetric relaxation (symmetric-SOR/Jacobi), which is required for Krylov solvers like CG that expect symmetry. Otherwise, you may want to use -pc_hypre_boomeramg_relax_type_all SOR/Jacobi. If you wish to use BoomerAMG WITHOUT a Krylov method use -ksp_type richardson NOT -ksp_type preonly and use -ksp_max_it to control the number of V-cycles. (see the PETSc FAQ.html at the PETSc website under the Documentation tab).
2007-02-03 Using HYPRE-1.11.1b, the routine HYPRE_BoomerAMGSolveT and the option -pc_hypre_parasails_reuse were failing with SIGSEGV. Dalcin L.
MatSetNearNullSpace() - if you provide a near null space to your matrix it is ignored by hypre UNLESS you also use
|-pc_hypre_boomeramg_nodal_coarsen <n>||- where n is from 1 to 6 (see HYPRE_BOOMERAMGSetNodal())|
|-pc_hypre_boomeramg_vec_interp_variant <v>||- where v is from 1 to 3 (see HYPRE_BoomerAMGSetInterpVecVariant())|
Depending on the linear system you may see the same or different convergence depending on the values you use.
See PCPFMG for access to the hypre Struct PFMG solver