SNESSetUp() and matrix-free options

[Barry Smith]

   How about?

   -snes_mf   (means what it currently means)

   -snes_mf operator (means what -snes_mf_operator means)

    Barry

On May 7, 2009, at 6:03 PM, Lisandro Dalcin wrote:

> On Thu, May 7, 2009 at 6:14 PM, Jed Brown <jed at 59a2.org> wrote:
>> Barry Smith wrote:
>>>
>>>    I understand this. I just don't view this as a big deal worth
>>> changing the code over.
>>
>> I agree.  My comment was that *if* the options were to be changed, as
>> Lisandro was suggesting, then it would be better to eliminate
>> unnecessary options conflicts.
>>
>
> Well, now that I'm actually writing the code, things are a bit more  
> clear...
>
> perhaps we should have just two options
>
> 1) -snes_mf, if passed, should be string "full" or "operator" (not
> sure about these)
> 2) -snes_mf_version, if passed, should be integer 1 or 2
>
> In Python pseudocode (thinking options like a Python dict)
>
>
> if "snes_mf" in options:
>
>   version = options.get("snes_mf_version", 1)
>   if version == 1:
>      MatCreateSNESMF(...)
>   elif version == 2:
>      SNESDefaultMatrixFreeCreate2(...)
>   else:
>      raise PetscError
>
>   value = options["snes_mf"]
>   if value == "operator":
>      SNESSetJacobian(J,0,0,...)
>   elif value == "full":
>      SNESSetJacobian(J,J,MatMFFDComputeJacobian)
>   else:
>      raise PetscError
>
>
> Note that I expect snes_mf_version=2 (despite being MatShell based) to
> work with snes_mf="operator"
>
> What do you think?
>
> -- 
> Lisandro Dalcín
> ---------------
> Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
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