[petsc-dev] Right-preconditioned GMRES

[Pierre Jolivet]

> On Feb 9, 2017, at 2:31 PM, Matthew Knepley <knepley at gmail.com> wrote:
> 
> On Thu, Feb 9, 2017 at 7:29 AM, Pierre Jolivet <pierre.jolivet at enseeiht.fr <mailto:pierre.jolivet at enseeiht.fr>> wrote:
> 
>> On Feb 9, 2017, at 2:17 PM, Matthew Knepley <knepley at gmail.com <mailto:knepley at gmail.com>> wrote:
>> 
>> On Thu, Feb 9, 2017 at 7:06 AM, Pierre Jolivet <pierre.jolivet at enseeiht.fr <mailto:pierre.jolivet at enseeiht.fr>> wrote:
>> 
>>> On Feb 9, 2017, at 1:37 PM, Matthew Knepley <knepley at gmail.com <mailto:knepley at gmail.com>> wrote:
>>> 
>>> On Thu, Feb 9, 2017 at 4:56 AM, Pierre Jolivet <pierre.jolivet at enseeiht.fr <mailto:pierre.jolivet at 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 <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.

Yes, I’m using PetscOptionsInsert, and whether I let PETSc parse "-ksp_pc_side right -ksp_norm_type unpreconditioned” or "-ksp_norm_type unpreconditioned -ksp_pc_side right” I end up with the same error afterwards.

Thanks.

>   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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