dolfin team mailing list archive

[Johan Hake <hake@xxxxxxxxx>]

On Wednesday 04 June 2008 23:34:16 Martin Sandve Alnæs wrote:
> Nice :)
>
> It should also be easy to extend this to support sympy and swiginac
> expressions, which can easily be converted to C strings.

Does sympy support conversion to C strings?

Btw: Feature request. Add support for abs too, i.e., fabs.

Johan

> --
> 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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