dolfin team mailing list archive

[Johan Hake <hake@xxxxxxxxx>]

Hello!

This is just insanely cool!

I got a 20 time speed up while assembling a simple advection form.

I suppose with more complex forms the speedup would be much more!

This levels the python users with the cpp users even more!

And of course instant caches the compiled functions so no recompile for each 
time.

Thanks!

Johan

On Wednesday 04 June 2008 12:44:17 Martin Sandve Alnæs wrote:
> 2008/6/3 Anders Logg <logg@xxxxxxxxx>:
> > On Tue, Jun 03, 2008 at 11:23:41PM +0200, Martin Sandve Alnæs wrote:
> >> It's easy with some helper functions I have, I can show you tomorrow.
> >> It only depends on dolfin::Function (i.e. dolfin.cpp_Function) and
> >> Instant.
> >
> > ok, nice. Maybe we can add the helper functions to assemble.py.
>
> Now you can do things like this:
>
> A = assemble(..., coefficients=[myfunction, 1.23, "sin(x[0])"])
>
> 1.23 is wrapped in a cpp_Function (i.e. a constant Function), and
> the string is compiled as a C++ dolfin::Function like "v[0] = ...;".
>
> If you want more control over the implementation
> (i.e. temporary variables in eval for efficiency, if-checks, etc.)
> you can also do this:
>
> code = """
> class F: dolfin::Function {
>  ...
> };
> class G: dolfin::Function {
>  ...
> };
> """
>
> f, g = compile_functions(code, mesh)
>
>
> Or, if you just want to precompile but don't need anything too fancy:
>
> expressions = ["sin(x[0])",
>                          ("a*x[1]", "b*x[0]")]
> f, g = compile_functions(expressions, mesh)
> assert f.rank() == 0
> assert g.rank() == 1
> g.a = 1.23
> g.b = 3.21
>
> Note that:
> - a tuple is interpreted as a vector expression
>
> - a tuple of tuples is interpreted as a matrix expression
>
> - variables like a and b in the strings above are detected
>   automatically, but this requires all builtin names to be
>   registered in the variable dolfin.compile_functions._builtins,
>   which currently contains some common mathematical
>   functions like sqrt, pow, exp, sin, pi etc.
>
> - variables are initialized to 0.0, so use compile_functions if
>   you need control over variable values.
>
> - assemble also accepts tuples like in compile_functions
>
> - assemble only calls on instant once independently of
>   the number of string expressions, to reduce compilation time
>
> - Error checks are not extensive!
>
> --
> Martin
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