[petsc-dev] sor smoothers

[Jed Brown]

"Mark F. Adams" <mfadams at lbl.gov> writes:

> On Aug 12, 2013, at 7:19 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
>> 
>>  Jed,
>> 
>>   I don't understand your computations. I run
>> 
>> ./ex29 -ksp_type chebyshev -ksp_max_it 2 -ksp_monitor -pc_type eisenstat -log_summary -ksp_view -ksp_chebyshev_eigenvalues 1.0,2.0 -ksp_norm_type none
>> 
>
> I thought we wanted to use richardson to get PCApplyRichardson_SOR to
> get invoked and save the MatMults in the KSP, because SOR is a strange
> PC that can use an existing solution w/o doing residual correction.
> What am I missing.

Chebyshev allows us to accelerate it (sometimes) relative to Richardson.
The cost of Richardson(2)/SOR is remarkably similar to
Cheby(2)/Eisenstat.
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