[petsc-dev] asm / gasm

[Barry Smith]

   I suggest focusing on asm. Having blocks that span multiple processes seems like over kill for a smoother ? (Major league overkill) in fact doesn't one want multiple blocks per process, ie. pretty small blocks.

   Barry

> On Jun 22, 2016, at 7:51 AM, Mark Adams <mfadams at 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?
> 
> 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?
> 
> gamg only aggregates across processor subdomains within one layer, so maybe I could use one layer of overlap in some way?
> 
> Thanks,
> Mark
>