[petsc-dev] Right-preconditioned GMRES

[Matthew Knepley]

On Thu, Feb 9, 2017 at 7:29 AM, Pierre Jolivet <pierre.jolivet at enseeiht.fr>
wrote:

>
> On Feb 9, 2017, at 2:17 PM, Matthew Knepley <knepley at gmail.com> wrote:
>
> On Thu, Feb 9, 2017 at 7:06 AM, Pierre Jolivet <pierre.jolivet at enseeiht.fr
> > wrote:
>
>>
>> On Feb 9, 2017, at 1:37 PM, Matthew Knepley <knepley at gmail.com> wrote:
>>
>> On Thu, Feb 9, 2017 at 4:56 AM, Pierre Jolivet <pierre.jolivet@
>> enseeiht.fr> wrote:
>>
>>> Hello,
>>> I _might_ be doing something wrong when calling
>>> KSPSetFromOptions/KSPSetUp, but still, am I supposed to get this kind of
>>> error?
>>> [0]PETSC ERROR: No support for this operation for this object type
>>> [0]PETSC ERROR: KSP gmres does not support PRECONDITIONED with RIGHT
>>>
>>> If not, I’ll try to send a MWE (it basically depends on where I set the
>>> option -ksp_pc_side right).
>>>
>>
>> I believe its telling you that it cannot display the preconditioned
>> residual with right preconditioning, which is true.
>> Are you requesting both?
>>
>>
>> No, I’m just using -ksp_view and -ksp_pc_side right. In the “standard”
>> case, it obviously work.
>> However, the error is triggered if I set -ksp_pc_side right after a first
>> call to KSPSetOperators()/KSPSetUp() without destroying the KSP.
>> Should I destroy my KSP before changing from left- (default) to
>> right-preconditioning if KSPSetOperators()/KSPSetUp has already been called?
>>
>
> Its likely you have to use
>
>   http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/KSP/
> KSPSetNormType.html
>
> or
>
>   *-ksp_norm_type unpreconditioned*
>
>
> If I use this after my first call to KSPSetUp, I now end up with:
> [0]PETSC ERROR: KSP gmres does not support UNPRECONDITIONED with LEFT
>

Yes, you would need to use it at the same time that you change the
preconditioning side.

  Thanks,

     Matt

> since we would not have a chance to change it since its been set already.
>
>   Thanks,
>
>      Matt
>
> Thanks.
>>
>>   Thanks,
>>
>>      Matt
>>
>>
>>> Thanks,
>>> Pierre
>>
>>
>>
>>
>> --
>> What most experimenters take for granted before they begin their
>> experiments is infinitely more interesting than any results to which their
>> experiments lead.
>> -- Norbert Wiener
>>
>>
>>
>
>
> --
> What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which their
> experiments lead.
> -- Norbert Wiener
>
>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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