[petsc-dev] Right-preconditioned GMRES

[Pierre Jolivet]

There, attached.

Thanks.

PS: here is the patch also, just in case
diff --git a/src/ksp/ksp/examples/tutorials/ex1.c b/src/ksp/ksp/examples/tutorials/ex1.c
index 6382c09..d9dc69a 100644
--- a/src/ksp/ksp/examples/tutorials/ex1.c
+++ b/src/ksp/ksp/examples/tutorials/ex1.c
@@ -123,6 +123,11 @@ int main(int argc,char **args)
     routines.
   */
   ierr = KSPSetFromOptions(ksp);CHKERRQ(ierr);
+  ierr = KSPSetUp(ksp);CHKERRQ(ierr);
+  char right_options[] = "-ksp_norm_type unpreconditioned -ksp_pc_side right";
+  PetscOptionsInsertString(NULL,right_options);
+  ierr = KSPSetFromOptions(ksp);CHKERRQ(ierr);
+  ierr = KSPSetUp(ksp);CHKERRQ(ierr);

   if (nonzeroguess) {
     PetscScalar p = .5;



> On Feb 9, 2017, at 2:56 PM, Matthew Knepley <knepley at gmail.com> wrote:
> 
> On Thu, Feb 9, 2017 at 7:48 AM, Pierre Jolivet <pierre.jolivet at enseeiht.fr <mailto:pierre.jolivet at enseeiht.fr>> wrote:
>> On Feb 9, 2017, at 2:31 PM, Matthew Knepley <knepley at gmail.com <mailto: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.
> 
> Can you make an example do it (SNES ex5)? Or can you send a small example that does it?
> 
>   Thanks,
> 
>     Matt
>  
> 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
> 
> 
> 
> 
> -- 
> 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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