syfi team mailing list archive

["Martin Sandve Alnæs" <martinal@xxxxxxxxx>]

2007/11/8, Anders Logg <logg@xxxxxxxxx>:
> Which form is "source element vector"? Is it the linear form
>
>   L = v*f*dx?

Yes.

> How is this computed by SyFi (tabulate_tensor)? It would be
> interesting to compare with the FFC code.

I can post the code tomorrow. SyFi is faster than FFC in this case,
while FFC is faster than SyFi for the Laplace matrix. Mass matrices
don't differ. Also, the SyFi-generated quadrature can be faster than
both FFC and "regular" SyFi code in some cases, in particular for the
convection vector L = dot(dot(u,grad(u)),v)*dx.

> I'm not sure what your timeframe is but maybe you should also include
> timings for FErari-optimized FFC code (in which case you need to bug
> me about activating the optimization again in FFC).

Bug bug :)

> We did a series of
> benchmarks for comparing plain FFC code with FErari code a while back
> and the local speedups were typically between a factor 1-4:
>
>     http://www.femcenter.org/pub/preprints/phiprint-2007-04.pdf

I'll read this tomorrow. Also, Ola is working on implementing a
factorization algorithm I found in an article earlier, and if he
manages to get it working we could test that as well or use it to
replace the current optimization (a naive implementation of "common
subexpression elimination"). The current naive algorithm gives speedup
factors of around 0.9 to 3.5, not easily predictable.

Most of the article will be unchanged by these additional results, so
if we can get them in time (don't know when "in time" is), we can
include them.

--
Martin