On Wed, Jun 22, 2016 at 5:13 PM, Matthew Knepley <knep...@gmail.com> wrote:
> On Wed, Jun 22, 2016 at 5:51 AM, Mark Adams <mfad...@lbl.gov> wrote: > >> I'm trying to get block smoothers to work for gamg. We (Garth) tried >> this and got this error: >> >> >> - Another option is use '-pc_gamg_use_agg_gasm true' and use >>> '-mg_levels_pc_type gasm'. >>> >>> >> Running in parallel, I get >> >> ** Max-trans not allowed because matrix is distributed >> ---- >> >> First, what is the difference between asm and gasm? >> > > ASM is very simple Additive Schwarz which can have multiple blocks per > process, but cannot have blocks spanning > processes. GASM was meant to generalize this, but Dmitry wrote it and (to > my knowledge) the support situation is > uncertain. Maybe Barry know better. > > >> Second, I need to fix this to get block smoothers. This used to work. >> Did we lose the capability to have blocks that span processor subdomains? >> > > Did we ever have it? > I thought so but it's been a long time. The code did work at one point but now I (Garth) gets this error. Does anyone know about this error? I don't find it with 'git grep Max-trans' Thanks, Mark > > >> gamg only aggregates across processor subdomains within one layer, so >> maybe I could use one layer of overlap in some way? >> > > ASM can do arbitrary overlap. > > Matt > > >> Thanks, >> Mark >> >> > > > -- > What most experimenters take for granted before they begin their > experiments is infinitely more interesting than any results to which their > experiments lead. > -- Norbert Wiener >