Subject: [FFC-dev] Optimization results for Cahn-Hilliard

From: Anders Logg <[email-masked]>
Date: Fri, 7 Oct 2005 16:04:52 -0500

Garth, I tried the form you sent me for testing (CahnHilliard.form).

Here are the results, before and after optimizations:

        |  FFC default mode    FFC BLAS mode (-f blas)
------------------------------------------------------
Before  |  4min 32s, 851MB     5min 31s, 1200MB
After   |  2min 27s,  59MB     1min 13s,  60MB

Memory usage reduced by a factor 20 which is pretty good... :-)

I turned off the computation of integrals for the benchmarks (or it
would have taken forever). Rob has a nice idea for optimization of the
integral computation so that should be fixed in the near future.

The Cahn-Hilliard form is really demanding with lots of coefficients
and terms. Is it possible to choose piecewise constant representation
for some of the coefficients to reduce compile-time?

/Anders

---

From: "Garth N. Wells" <[email-masked]>
Date: Sat, 08 Oct 2005 08:56:26 +0200

>         |  FFC default mode    FFC BLAS mode (-f blas)

Looks great.

> for some of the coefficients to reduce compile-time?

Some piecewise constants could be used to imply reduced integration. It's true
that very few FE codes would use exact integration for such a complex problem.
Most would just look at the order of the test and trial functions in determining
the integation scheme. I see that reduced integration is in the ffc TODO list,
which would offer a nice fix.

Garth

> 
> /Anders
> 
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