[firedrake] Mapping nodal values from parent to extruded mesh
Tuomas Karna
tuomas.karna at gmail.com
Sat Apr 11 01:20:19 BST 2015
Hi Miklos,
I see. So, if I read this correctly, the reference element
two_product_cell needs get_facet_element and get_facet_transform
methods? But the former needs to be generalized as the facet element
depends on the facet?
- Tuomas
On 04/10/2015 04:04 AM, Miklos Homolya wrote:
> Hi,
>
> facet_support_dofs is the same infrastructure we use to support
> geometric boundary conditions.
>
> I have implemented geometric boundary conditions for (unstructured)
> quadrilaterals, it wasn't too complicated:
> https://bitbucket.org/mapdes/fiat/pull-request/29/geometric-bcs-for-quadrilaterals/diff
>
> For general tensor product elements it would be a bit more
> complicated, as horizontal and vertical facets are in general
> different. For example, a prism has quadrilaterals as vertical facets,
> but triangles as horizontal facets.
>
> Regards,
> Miklos
>
>
> On 10/04/15 11:23, David Ham wrote:
>> Hi Tuomas,
>>
>> Concerning the sets of spaces which this will work for, I think that
>> the current implementation probably works for any horizontal space
>> but only for vertical CG. One could just try relaxing the test in
>> that case.
>>
>> The reason for the restriction to vertical CG is that fs.bt_masks
>> uses the topological association of nodes with mesh entities in order
>> to work out which nodes are on the top or bottom of the cell. In
>> order to allow DG in the vertical, it would be necessary to support
>> the geometric definition (ie which basis functions do not vanish on
>> the top/bottom).
>>
>> If you look at functionspace.py:78 you can see where the bottom and
>> top masks are generated. This uses entity_closure_dofs() from FIAT.
>> In order to use the geometric definition of dofs one would need to
>> support using facet_support_dofs() (which is how BC maps are set up
>> at functionspace.py:375). Currently FIAT TensorFiniteElement objects
>> do support entity_closure_dofs() but nobody has done the legwork to
>> get them to support facet_support_dofs.
>>
>> Concerning documentation, COFFEE is deplorably underdocumented
>> (although the author is on this list so maybe this will change ;).
>> The actual available AST nodes are only "documented" by reading the
>> source:
>> https://github.com/coneoproject/COFFEE/blob/master/coffee/base.py
>> However, you are fundamentally writing a PyOP2 kernel, and the C api
>> for that *is* documented at: http://op2.github.io/PyOP2/kernels.html
>> so that hopefully helps somewhat.
>>
>> Otherwise, keep asking here or in IRC (IRC tends to get faster
>> responses, at least between about 10am and 8pm UK time).
>>
>> BTW, any chance of seeing you at FEniCS '15?
>>
>> Cheers,
>>
>> David
>>
>>
>>
>> On 10 April 2015 at 02:44, Tuomas Karna <tuomas.karna at gmail.com
>> <mailto:tuomas.karna at gmail.com>> wrote:
>>
>> Hi all,
>>
>> A couple of questions regarding those extruded mesh -> parent
>> mesh copy operations,
>>
>> A while back I got the reverse 2d->3d copy working with a
>> hard-coded pyop2 kernel (like in mesh extrusion). I'm not
>> familiar with COFFEE syntax, is there documentation/examples
>> somewhere?
>>
>> The 3d->2d copy routine in extrusion_extraction branch checks
>> that the function space is CG. Does this method easily generalize
>> to other spaces? DGxCG prisms seem to work OK. I'm also
>> interested in using DGxDG and RTxCG/DG spaces.
>>
>>
>> Cheers,
>>
>> Tuomas
>>
>>
>> On 03/05/2015 10:24 AM, Tuomas Karna wrote:
>>> Thanks David,
>>>
>>> This is great, I'll try doing the reverse operation.
>>>
>>> - Tuomas
>>>
>>> On 03/05/2015 08:20 AM, David Ham wrote:
>>>> Hi Tuomas,
>>>>
>>>> This wasn't there this morning but I've implemented one of the
>>>> cases (pulling out the top and bottom maps). The result is in
>>>> the extrusion_extraction branches of both PyOP2 and Firedrake.
>>>> The 2d->3d operation would be rather similar except that you'd
>>>> have to interrogate the fiat_element on the extruded Function
>>>> in order to determine which extruded nodes are "on top of" the
>>>> 2d nodes you have. Unfortunately I won't have time to do that
>>>> one soon (huge amounts to do before SIAM CSE next week) but
>>>> feel free to have a try and complain when it doesn't work!
>>>>
>>>> Cheers,
>>>>
>>>> David
>>>>
>>>> On 4 March 2015 at 22:23, Tuomas Karna <tuomas.karna at gmail.com
>>>> <mailto:tuomas.karna at gmail.com>> wrote:
>>>>
>>>> Hi all,
>>>>
>>>> I'd need to copy nodal values between fields on parent and
>>>> extruded
>>>> meshes. For example, copy 2d->3d (constant over vertical)
>>>> or 3d->2d
>>>> (extract surface/bottom level). The horizontal function
>>>> space is the
>>>> same. Is there an easy way to do this? Is there a map of
>>>> extruded nodes
>>>> somewhere?
>>>>
>>>> Thanks,
>>>>
>>>> Tuomas
>>>>
>>>>
>>>>
>>>> _______________________________________________
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>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> Dr David Ham
>>>> Departments of Mathematics and Computing
>>>> Imperial College London
>>>>
>>>> http://www.imperial.ac.uk/people/david.ham
>>>>
>>>>
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>>>> https://mailman.ic.ac.uk/mailman/listinfo/firedrake
>>>
>>
>>
>>
>>
>> --
>> Dr David Ham
>> Departments of Mathematics and Computing
>> Imperial College London
>>
>> http://www.imperial.ac.uk/people/david.ham
>>
>>
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>
>
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