[petsc-dev] asm / gasm

[Boyce Griffith]

> On Jun 22, 2016, at 2:06 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> 
> 
>   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.

And with lots of small blocks, remember to configure with --with-viewfromoptions=0. :-)

-- Boyce

> 
>   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
>> 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20160622/bbbbdd4e/attachment.html>