dolfin team mailing list archive

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

Nice :)

It should also be easy to extend this to support sympy and swiginac
expressions, which can easily be converted to C strings.

--
Martin


2008/6/4 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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>
>
>