[petsc-dev] [petsc-users] FETI-DP

[Thomas Witkowski]

Jed Brown wrote:
> On Wed, Apr 20, 2011 at 17:05, Thomas Witkowski 
> <thomas.witkowski at tu-dresden.de 
> <mailto:thomas.witkowski at tu-dresden.de>> wrote:
>
>     Following the mathematical representation wouldn't make it more
>     sense to store B but B^T, because the local matrices B_i^T are
>     real local and would have no off-diagonal elements?
>
>
> They really can't because sometimes the Lagrange multiplier itself 
> will be stored on a different process. Also, this representation has 
> lots of empty rows where as storing B, every row has entries (usually 
> 2 entries).
Why could it happen to define a Lagrange multiplier, that "connects" to 
subdomains, i.e. two processes, on a third process? The last argument is 
clear to me!