> On 30 Jul 2015, at 13:54, Jan Blechta <blec...@karlin.mff.cuni.cz> wrote:
>
> On Thu, 30 Jul 2015 12:27:47 +0100
> "Garth N. Wells" <gn...@cam.ac.uk <mailto:gn...@cam.ac.uk>> wrote:
>
>> On 30 July 2015 at 12:18, Mikael Mortensen
>> <mikael.morten...@gmail.com> wrote:
>>
>>> Hi
>>>
>>> Back from vacation and very pleased :-) to find that I can update my
>>> Fenics installation to version 1.6 in less than 10 minutes! Used to
>>> take at least a few days.
>>>
>>> Now I’m trying to upgrade my applications to 1.6 and I just found
>>> that some of the common preconditioners (jacobi, bjacobi,
>>> additive_schwarz) have gone missing. Any reason for this or is it a
>>> mistake? They seem to have disappeared recently from the map
>>> _methods_descr in PETScPreconditioner.cpp.
>>>
>>>
>> The code in question was a mess and the wrapping approach
>> unsustainable, which is why it was removed.
Including these three lines in creating _methods_descr in
PETScPreconditioner.cpp seems to work. Why do you consider it messy?
{"jacobi", "Jacobi iteration"},
{"bjacobi", "Block Jacobi iteration"},
{"additive_schwarz", "Additive Schwarz"},
Jacobi and additive_schwarz are the two best preconditioners for a momentum
solve in Navier-Stokes and I don’t think they should have been removed without
even making the ChangeLog.
>
> The demand for the wrapping comes from the requirement of having
> certain amount of control portable across backends. Is this requirement
> getting abandoned, or at least weakened?
Another issue is that most users will simply print
list_krylov_solver_preconditioners, and they will then not know that they can
actually create a jacobi preconditioner. If they do find out they will have to
do something (not portable across backends) like
p = PETScPreconditioner(‘jacobi’)
solver = PETScKrylovSolver(‘cg’, p)
where they used to be able to do
solver = KrylovSolver(“cg”, ‘jacobi’)
Not much more complex, but certainly not very user-friendly to hide
preconditioners like this.
>
> Jan
>
>>
>> You can control the PETSc preconditioners via PETSc options. This
>> gives you far greater control, makes DOLFIN code simpler and provides
>> greater consistency when using PETSc solver. There will be more
>> changes in DOLFIN 1.7 to give greater control over preconditioning.
Ok, what are actually the plans for 1.7?
Mikael
>>
>> Garth
>>
>>
>>
>>
>>> Best regards
>>>
>>> Mikael
>>>
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