ffc team mailing list archive

[Andy Ray Terrel <aterrel@xxxxxxxxxxxx>]

On Tue, Jun 22, 2010 at 10:31 AM, Garth N. Wells <gnw20@xxxxxxxxx> wrote:
>
>
> On 22/06/10 07:05, Andy Ray Terrel wrote:
>>
>> On Tue, Jun 22, 2010 at 6:15 AM, Anders Logg<logg@xxxxxxxxx>  wrote:
>>>
>>> On Tue, Jun 22, 2010 at 01:04:27PM +0200, Kristian Oelgaard wrote:
>>>>
>>>> On 21 June 2010 23:16, Kent Andre<kent-and@xxxxxxxxx>  wrote:
>>>>>
>>>>> Strange. I used dorsal to compile the dev versions of the various
>>>>> packages. Dolfin, ffc, and sfc are only a few days old.
>>>>>
>>>>> But do you have any suggestions for how to optimize the FFC generated
>>>>> code ? I have used quadrature here, tensor representation is not good
>>>>> in this application.
>>>>
>>>> I had a look at the generated code from FFC and SyFi
>>>> (which by the way is a real pain when PyDOLFIN is involved)
>>>>
>>>> and realised that your comparison is not fair.
>>>> FFC uses the UFL algorithm estimate_total_polynomial_degree() to
>>>> compute the quadrature_degree.
>>>> SFC uses (in this case) the UFL algorithm estimate_quadrature_degree()
>>>> which is less conservative.
>>>>
>>>> This results in FFC using 25 integration points to compute the
>>>> integral while SFC just uses 3.
>>>>
>>>> If you use the option:
>>>>
>>>> parameters ["form_compiler"]["quadrature_degree"] = "2"
>>>>
>>>> the comparison is _more_ fair and the numbers are almost the same.
>>>> SFC still uses 3 points, while FFC now uses 4 points which leads to my
>>>> answer to your first question:
>>>> "How should I optimize FFC?" :)
>>>>
>>>> https://blueprints.launchpad.net/ffc/+spec/simplex-quadrature
>>>
>>> I think either Andy Terrel or Peter Brune mentioned having worked out
>>> some code for computing more efficient quadrature on simplices. There
>>> was some discussion on adding that either to FIAT or FFC.
>>>
>>> What ever happened to that?
>>
>> The only fast quadrature I was working on was for the BCR wavelet
>> rules for Calderon Zygmund operators.  Rob has some recent stuff on
>> fast quadrature using Bernstein basis.  I'm not sure what Peter might
>> have been doing.
>>
>> The local expert on quadrature at TACC, tells me the fastest schemes
>> for quadrature for simplices is Grundmann-Möller for lower orders (<
>> 20 ish) and the standard conical product for higher orders.
>>
>> @article{grundmann:282,
>> author = {Axel Grundmann and H. M. M\"{o}ller},
>> collaboration = {},
>> title = {Invariant Integration Formulas for the $n$-Simplex by
>> Combinatorial Methods},
>> publisher = {SIAM},
>> year = {1978},
>> journal = {SIAM Journal on Numerical Analysis},
>> volume = {15},
>> number = {2},
>> pages = {282-290},
>> url = {http://link.aip.org/link/?SNA/15/282/1},
>> doi = {10.1137/0715019}
>> }
>>
>
> I've pasted the above into
>
>    https://blueprints.launchpad.net/ffc/+spec/simplex-quad
>
> Garth
>

I added a few more notes and links on the blueprint.

-- Andy

>>>
>>> --
>>> Anders
>>>
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>>>
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>>
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