[firedrake] Mapping nodal values from parent to extruded mesh

[Fabio Luporini]

Hi Tuomas

Yes, the point of having ASTs instead of C code is for optimisation.
However, you can stick to C strings and care about optimisation only at the
very hand, if you saw a particular hand-written kernel is a bottleneck.

In the future, we hope to integrate a parser to avoid writing ASTs

Thanks

-- Fabio

2015-04-11 0:50 GMT+01:00 Tuomas Karna <tuomas.karna at gmail.com>:

>  Hi David,
>
> Thanks for the clarification, this all makes sense. I think for the time
> being I can live with CG in vertical. The pyop2 kernel documentation is
> great. Is there a reason to prefer AST over hard-coded kernels?
> Optimization?
>
> BTW, any chance of seeing you at FEniCS '15?
>
> Yes, I'm planning to attend, will submit abstract shortly.
>
> - Tuomas
>
>
> On 04/10/2015 03:23 AM, 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> 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> 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
>>>
>>>
>>>
>>> _______________________________________________
>>> firedrake mailing list
>>> firedrake at imperial.ac.uk
>>> 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
>>
>>
>> _______________________________________________
>> firedrake mailing listfiredrake at imperial.ac.ukhttps://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
>
>
> _______________________________________________
> firedrake mailing listfiredrake at imperial.ac.ukhttps://mailman.ic.ac.uk/mailman/listinfo/firedrake
>
>
>
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