[petsc-users] Speed up KSPSolve of dense matrix

[Florian Lindner]

Am Dienstag, 4. November 2014, 19:14:58 schrieb Jed Brown:
> Barry Smith <bsmith at mcs.anl.gov> writes:
> >> I've tried to use a direct solver like suggested on pp 72, but:
> >> 
> >> ./petBench 600 1 -ksp_type preonly -pc_type lu
> >
> >   You cannot use LU with SBAIJ format. Only Cholesky. So use -pc_type cholesky
> 
> And using a sparse matrix format for a dense matrix is a recipe for poor performance.

I'm more or less aware of that, but I'm surprised that the performance is such poor.

I changed the format of matrixC to dense now, but the runtime is still poor. Overall time is now around 9s with 95% spent in KSPSolve and exact the same number of MatMult executions, taking 65% of time.

Thx,
Florian