ffc team mailing list archive

[Kristian Oelgaard <k.b.oelgaard@xxxxxxxxxx>]

Quoting Anders Logg <logg@xxxxxxxxx>:

> On Fri, Jun 15, 2007 at 04:07:12PM +0200, Kristian Oelgaard wrote:
> > 
> > 
> > Currently I'm compiling simple forms like:
> > 
> > e_u   = FiniteElement("Lagrange", "triangle", 10)
> > e_uh  = FiniteElement("Lagrange", "triangle", 5)
> > u   = Function(e_u)
> > uh  = Function(e_uh)
> > a = (u - uh)*(u - uh)*dx
> > 
> > which takes roughly 2min to compile. The code generation is very fast but
> > formatting the output takes forever. With quadrature the above form
> compiles in
> > 1-2s and so does tensor representation if I do:
> > 
> > #ufc_code["tabulate_tensor"] = remove_unused(body)
> > ufc_code["tabulate_tensor"] = body
> > 
> > in __generate_cell_integral() (ufcformat.py)
> > 
> > So avoiding the use of remove_unused(), at least when generating code for
> > tabulate_tensor() would be preferable.
> > 
> > Currently the code generation in tensorgenerator.py is executed in the
> same
> > order as the code appear in the resulting header file i.e.
> > 
> > coefficients -> geometry -> sign_code -> element_code
> > 
> > and then in ufcformat.py we put the jacobian in front of everything after
> which
> > we hand over the code to remove_unused()
> > 
> > I suggest we instead do something like this:
> > 
> > # generate element code + set of used geometry terms + set of used signs
> > element_code, geo_set, sign_set = __generate_element_tensor()
> > 
> > sign_code = __generate_signs(sign_set)
> > 
> > # generate geometry code + set of used coefficients + set of jacobi terms
> > geo_code, coeff_set, jacobi_set = __generate_geometry_tensors(geo_set)
> > 
> > code = __generate_jacobian(jacobi_set)
> > code += __generate_coefficients(coeff_set)
> > code += geo_code + sign_code + element_code
> > 
> > with this approach we should be able to speed up code generation (at the
> expense
> > of memory consumption, which will be small I think?)
> > 
> > or is the above not possible because of something that I missed?
> > 
> > Kristian
> 
> We did something like this before (keeping track of which variables
> are used when we generate the code). I added the remove_unused() as a
> postprocessing step for simplicity.
> 
> I have no objections to fixing this, but perhaps we can wait until
> after the release? (So we don't break anything.)

Yes, we should definitely wait until after the release.

> Another thing to look at would be if it's possible to optimize the
> remove_unused() function.

I think that remove_unused() is OK as long as we don't use it for the
tabulate_tensor() code. For the other parts of the formatting where we use it,
it is quite handy.

Kristian

> /Anders
> _______________________________________________
> FFC-dev mailing list
> FFC-dev@xxxxxxxxxx
> http://www.fenics.org/mailman/listinfo/ffc-dev
>