[petsc-users] Richardson: damping factor=0

[Barry Smith]

   Mark,

   Thanks for pointing this out. Perhaps this is a bug, since all the   PCApplyRichardson_*() have an (implicit) damping of 1 perhaps we should error out when the damping is not one and one attempts to use a PCApplyRichardson_*().

   The current code is questionable since people get a different result then they expect with no explanation why.

  Barry

> On Dec 19, 2014, at 9:23 AM, Mark Adams <mfadams at lbl.gov> wrote:
> 
> Oh, SOR probably grabs the iteration ...
> 
> Never mind.
> 
> On Fri, Dec 19, 2014 at 10:20 AM, Mark Adams <mfadams at lbl.gov> wrote:
> Richardson damping factor does not seem to do anything.  I set it to zero and the solve was fine.
> 
> Am I missing something?
> 
> Thanks,
> Mark
> 
>   Down solver (pre-smoother) on level 3 -------------------------------
>     KSP Object:    (mg_levels_3_)     1024 MPI processes
>       type: richardson
>         Richardson: damping factor=0
>       maximum iterations=4
>       tolerances:  relative=1e-05, absolute=1e-50, divergence=10000
>       left preconditioning
>       using nonzero initial guess
>       using NONE norm type for convergence test
>     PC Object:    (mg_levels_3_)     1024 MPI processes
>       type: sor
>         SOR: type = local_symmetric, iterations = 1, local iterations = 1, omega = 1
>       linear system matrix followed by preconditioner matrix:
>       Mat Object:       1024 MPI processes
>         type: shell
>         rows=33427584, cols=33427584
>       Mat Object:       1024 MPI processes
>         type: mpiaij
>         rows=33427584, cols=33427584
>         total: nonzeros=1.7272e+09, allocated nonzeros=3.4544e+09
>         total number of mallocs used during MatSetValues calls =0
>           not using I-node (on process 0) routines
>