ffc team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Fri, Jun 15, 2007 at 04:29:12PM +0200, Kristian Oelgaard wrote:
> 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

ok, let's try that.

/Anders