[petsc-users] Assembling primal Schur matrix in FETI-DP method

[Thomas Witkowski]

Zitat von Jed Brown <jedbrown at mcs.anl.gov>:

> On Mon, Nov 21, 2011 at 08:03, Thomas Witkowski <
> Thomas.Witkowski at tu-dresden.de> wrote:
>
>> Okay, but how to make use of the KSP in MatMatSolve?
>
>
> With this approach, you just call KSPSolve() multiple times.
>

I have to multiple two matrices, one is implicitly defined by a KSP,  
the other one is explicitly assembled. So when using KSPSolve(), it  
must be called for each column of the second matrix? This seems not to  
be very efficient as I thought the matrices are stored row wise? Is  
there a way to get the columns of a SEQAIJ matrix?

Thomas