Johan Hake wrote:
> On Wednesday 19 August 2009 15:48:43 Garth N. Wells wrote:
>> Johan Hake wrote:
>>> On Wednesday 19 August 2009 15:12:21 Garth N. Wells wrote:
>>>> Johan Hake wrote:
>>>>> On Wednesday 19 August 2009 14:57:20 Garth N. Wells wrote:
>>>>>> Johan Hake wrote:
>>>>>>> On Wednesday 19 August 2009 14:21:12 Garth N. Wells wrote:
>>>>>>>> Garth N. Wells wrote:
>>>>>>>>> Kent Andre wrote:
>>>>>>>>>>> Not sure what we have to do actually. I suppose I want get any
>>>>>>>>>>> clue from the
>>>>>>>>>>> demo/function/restriction
>>>>>>>>>>>
>>>>>>>>>>> demo?
>>>>>>>>>>> I see that Kent has modified the dolfin.FunctionSpace to reflect
>>>>>>>>>>> the present (broken) implementation of restriction, anything in
>>>>>>>>>>> that line? Should such an implementation has been done in
>>>>>>>>>>> FunctionSpaceBase instead of FunctionSpace? Kent?
>>>>>>>>>>>
>>>>>>>>>>> Johan
>>>>>>>>>> This restriction is different in the sense that the restriction is
>>>>>>>>>> made by the standard element on a sub mesh.
>>>>>>>>>> The restriction in focus now is on the complete mesh but for only
>>>>>>>>>> a part of the element.
>>>>>>>>>> Combined, these two features will be very powerful. I guess the
>>>>>>>>>> sub-mesh restriction stuff is broken due to the parallel mesh.
>>>>>>>>> I've attached an example solver. To make it work for P^k with k > 2
>>>>>>>>> we need to restrict some functions to cell facets. Using FFC, we do
>>>>>>>>>
>>>>>>>>> scalar = FiniteElement("Lagrange", "triangle", 3)
>>>>>>>>> dscalar = FiniteElement("Discontinuous Lagrange", "triangle",
>>>>>>>>> 3)
>>>>>>>>>
>>>>>>>>> # This syntax restricts the space 'scalar' to cell facets.
>>>>>>>>> mixed = scalar["facet"] + dscalar
>>>>>>>>>
>>>>>>>>> In PyDOLFIN we could do
>>>>>>>>>
>>>>>>>>> V_dg = FunctionSpace(mesh, "DG", 3)
>>>>>>>>> V_cg = FunctionSpace(mesh, "CG", 3, "facet")
>>>>>>>>>
>>>>>>>>> mixed = V_cg + V_dg
>>>>>>>> I see now that we need to have the above option since the everything
>>>>>>>> (e.g. the dof map) is created and compiled inside functionspace.py.
>>>>>>> We could implement it in FunctionSpaceBase, as an operator, returning
>>>>>>> a new FunctionSpaceBase, with the restricted element as arguemnt.
>>>>>>>
>>>>>>> However my concerns go to a sub space of a restricted mixed space (if
>>>>>>> such exists) see the other email.
>>>>>>>
>>>>>>> If we go for 1, (as you have already done ;) ), we cannot create a
>>>>>>> restricted mixed space using the addition syntax.
>>>>>>>
>>>>>>> mixed = V1 + V2
>>>>>> Do you mean to then restrict mixed? I'm already doing
>>>>> Precisely.
>>>>>
>>>>> After a second thought I think that doing it in the constructor is more
>>>>> clean. Makes life simpler. Is this also possible i UFL, I mean:
>>>>>
>>>>> e = FiniteElement("CG",cell,0,"facet")
>>>>>
>>>>> Should it?
>>>> Is that a PyDOLFIN finite element? If it is, then yes, that's how it
>>>> should work.
>>> I meant UFL.FiniteElement.
>> OK. I don't know if that is the syntax. Kristian will know.
>>
>>>> Somewhat related, it's a bit annoying in PyDOLFIN that the code is
>>>> recompiled when the mesh is changed. Can we avoid this? Should one then
>>>> create a finite element and a dof map with which to initialise the
>>>> Pythin FunctionSpace?
>>> Do you mean when one has refined a mesh?
>> Yes, or just changed from one simulation to the next.
>
> Are you sure we get a recompilation, or is the module just loaded from cache?
>
It's recompiling. It seems to create code for each mesh I use. If I go
back to a previously used mesh, it's super fast.
Garth
>> As far as I understand it is the
>>
>>> reason for this that we need to recompute the dofmap.
>> In C++ we create a dolfin::FunctionSpace from a dolfin::FiniteElement, a
>> dolfin::DofMap and a dolfin::Mesh. The FiniteElement and DofMap are
>> created with a ufc::finite_element and a ufc::dof_map, respectively.
>>
>> In the Python interface, in addition to what we have now, we would need
>> FiniteElement and DofMap objects, with which we could create a
>> FunctionSpace (together with a Mesh). Then, hopefully we could avoid
>> recompilation when just the mesh is changed.
>
> If a mesh is refined it is the same mesh, and then it would be cool to just
> reinitialize the FunctionSpace, or the DofMap. Wouldn't this also be a
> feature
> in C++?
>
> FunctionSpace::reinitialize()
> FunctionSpace::reinitialize(shared_ptr<Mesh> Mesh)
>
> or something like that. The first one when the same mesh is being used, for
> example after a refinement, and the second one when another mesh is being
> used. Then we do not have to create a new FunctionSpace.
>
> Johan
>
>> Garth
>>
>>> How is this done in the C++ interface.
>>>
>>> Johan
>>>
>>>> Garth
>>>>
>>>>> Johan
>>>>>
>>>>>> V0 = FunctionSpace(mesh, "CG", 3, "facet")
>>>>>> V1 = FunctionSpace(mesh, "DG", 3)
>>>>>>
>>>>>> mixed = V0 + V1
>>>>>>
>>>>>> and it works. This type of restriction (we'll need to sort out our
>>>>>> terminology) impacts the dofmap, which I why I think it needs to be
>>>>>> involved in the creation of the function space.
>>>>>>
>>>>>> Garth
>>>>>>
>>>>>>> If we want a restricted mixed space we need to use the constructor.
>>>>>>>
>>>>>>> mixed = MixedFunctionSpace((V1,V2),restriction="facet")
>>>>>>>
>>>>>>> Johan
>>>>>>>
>>>>>>>> Garth
>>>>>>>>
>>>>>>>>> or
>>>>>>>>>
>>>>>>>>> V_dg = FunctionSpace(mesh, "DG", 3)
>>>>>>>>> V_cg = FunctionSpace(mesh, "CG", 3)
>>>>>>>>>
>>>>>>>>> mixed = V_cg["scalar"] + V_dg
>>>>>>>>>
>>>>>>>>> Garth
>>>>>>>>>
>>>>>>>>>> Kent
>>>>>>>>>>
>>>>>>>>>> _______________________________________________
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