PCNN-preconditioner and "floating domains"

Barry Smith bsmith at mcs.anl.gov
Mon Jun 29 17:20:39 CDT 2009

On Jun 29, 2009, at 4:55 PM, Andreas Grassl wrote:

> Hello,
> Barry Smith schrieb:
>>   To modify the code for elasticity is a big job. There are two  
>> faculty
>> Axel Klawonn and O. Rheinbach
>> at Universität Duisburg-Essen who have implemented a variety of these
>> fast methods for elasticity.
>> I suggest you contact them.
> I wrote an email last week, but I still have no answer.  
> Investigating further my
> code and the source code related to IS I noticed, that there is a flag
> pure_neumann which I guess should handle the singular Neumann  
> problems giving
> the problem, but from my understanding of the code flow there is no  
> situation it
> is set true. Is this flag a remainder from previous implementations  
> or am I just
> looking at the wrong place?

    I have no idea what that flag is for.

> Furthermore I'm wondering about the size of the coarse problem. From  
> my
> understanding it should include all interface DOF's? But the size I  
> get is the
> number of subdomains...
   It should be the number of subdomains times the dimension of the  
null space for the subdomains.
For Laplacian that is just the number of subdomains. For 3d linear  
elasticity it is 6 times the number of subdomains.

> Last but not least I wanted to thank for the fast help you provide  
> and to
> apologize for the questions, which may seem rather stupid but help  
> me to find
> the right understanding.
> cheers,
> ando
> -- 
> /"\                               Grassl Andreas
> \ /    ASCII Ribbon Campaign      Uni Innsbruck Institut f. Mathematik
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