[petsc-users] about pclu

[Ryan Yan]

One more ask, :-)

Which one is more efficient, richardson, preonly or no difference, if I am
going to use direct solver for many times steps.

Thanks,

Yan

On Tue, Apr 5, 2011 at 11:06 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> On Apr 5, 2011, at 9:52 PM, Ryan Yan wrote:
>
> > Hi,
> > I am wondering is there a way of checking the residual of a direct
> solver. It should
> > be one shot and very small.  I tried -ksp_monitor_true_residual, but no
> thing shows up. I guess a piece of code
> > $Ax-b$ will do the trick?
>
>    The reason that the monitor doesn't display anything is not the direct
> solver but because you are using LU with KSPType of KSPPREONLY  if you run
> with -ksp_type richardson or -ksp_type gmres then -ksp_monitor_true_residual
> will print the residual as you want.
>
>   Barry
>
> >
> > Thanks,
> >
> > Yan
>
>
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