[petsc-dev] sor smoothers

[Barry Smith]

On Sep 12, 2013, at 4:39 PM, "Mark F. Adams" <mfadams at lbl.gov> wrote:

> I'm not sure what to do with:
> 
> PetscErrorCode  PCMGSetResidual(PC pc,PetscInt l,PetscErrorCode (*residual)(Mat,Vec,Vec,Vec),Mat mat) ?
> 
> I'm thinking to have this in the code:
> 
>  mglevels[l]->A = mat;
>  mglevels[l]->residual = residual;
> 
> and change the calls from using PCMGResidualDefault to using MatResidualDefault.

   Seems ok to me.

>  This will keep from breaking code that uses this to set the Mat also.  And should this be called PCMGSetResidualAndMat?

   No.

   Barry

> 
> Mark
> 
> On Sep 9, 2013, at 9:25 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> 
>> 
>> On Sep 9, 2013, at 8:03 PM, "Mark F. Adams" <mfadams at lbl.gov> wrote:
>> 
>>> OK, so its ground hog day.  The plan?:
>>> 
>>> 1) I should add a residual method to Mat, make a MatResidualDefault, and have all (yuck) SetUp_MatXXX set this default.  I guess there is no base class SetUp ….  then make a MatResidual_SeqAIJ that just does a dumb residual for now, with testing logic if Jed's stuff is available.
>> 
>>  Take a look at MatCreate_SeqAIJ. These fill up all the function points in one swoop with the big function table, this is why there is not "base class setup".
>> 
>>> 
>>> 2) Have PCMGResidualDefault call MatResidual instead MatMult & VecAYPX.  Or do we want to nuke PCMGResidualDefault?
>> 
>>  You don't really need PCMGResidualDefault, just make the residual function pointer in PCMG point to MatResidual
>> 
>>> Jed's defect correction argument might sound like a typical Jed, e.g., what if a Martian gets hepatitis during mardi gras, but defect correction is really useful and I would like to see its support supported …
>> 
>>  Don't need it to support defect correction  but anyways :-)
>> 
>>> 
>>> 3) Add fields in Mat: mat_res_state, vec_res_state, vec_res_id.  I need to know the types but I can do this in the next phase.
>> 
>>  Look in _p_PetscObject for the types of state and id, both currently PetscInt.
>> 
>>> 
>> 
>>> Mark
>>> 
>>> On Sep 9, 2013, at 5:35 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>>> 
>>>> 
>>>> On Sep 9, 2013, at 4:32 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
>>>> 
>>>>> Barry Smith <bsmith at mcs.anl.gov> writes:
>>>>>> I don't care if PCMGSetResidual stays around for now but I do not
>>>>>> think we should "point to it" as a standard way for people to do
>>>>>> things; I think we should improve how the two slots are used with
>>>>>> PCMG, it really has never been thought about at all and whenever
>>>>>> possible I think using the two slots appropriately is better than
>>>>>> PCMGSetResidual and will solve most of the "use" cases.
>>>>> 
>>>>> Fine, I was just not eager to _delete_ PCMGSetResidual until we had
>>>>> established a complete replacement, and even then, it might be enough to
>>>>> leave it as "advanced" and suggest the preferred alternative in the man
>>>>> page.  It just doesn't seem expensive to support and I don't think it
>>>>> causes people to tangle themselves up in bad design.
>>>> 
>>>> It doesn't have its own object which is kind of limiting.
>>>> 
>>>> 
>>>> 
>>> 
>> 
>