[petsc-dev] sor smoothers

[Barry Smith]

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.
>> 
>> 
>> 
>