ffc team mailing list archive

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

On 21 June 2010 23:16, Kent Andre <kent-and@xxxxxxxxx> wrote:
>
> Strange. I used dorsal to compile the dev versions of the various
> packages. Dolfin, ffc, and sfc are only a few days old.
>
> But do you have any suggestions for how to optimize the FFC generated
> code ? I have used quadrature here, tensor representation is not good
> in this application.

I had a look at the generated code from FFC and SyFi
(which by the way is a real pain when PyDOLFIN is involved)

and realised that your comparison is not fair.
FFC uses the UFL algorithm estimate_total_polynomial_degree() to
compute the quadrature_degree.
SFC uses (in this case) the UFL algorithm estimate_quadrature_degree()
which is less conservative.

This results in FFC using 25 integration points to compute the
integral while SFC just uses 3.

If you use the option:

parameters ["form_compiler"]["quadrature_degree"] = "2"

the comparison is _more_ fair and the numbers are almost the same.
SFC still uses 3 points, while FFC now uses 4 points which leads to my
answer to your first question:
"How should I optimize FFC?" :)

https://blueprints.launchpad.net/ffc/+spec/simplex-quadrature

Kristian

> Kent
>
>
> On Mon, 2010-06-21 at 23:05 +0200, Kristian Oelgaard wrote:
>> I tried to run the code against the dev versions of FEniCS and got the
>> following error after successfully finishing the FFC part:
>>
>> Traceback (most recent call last):
>>   File "demo.py", line 15, in <module>
>>     V = FunctionSpace(mesh, "CG", 1)
>>   File "/home/oelgaard/software/fenics/dolfin/local/lib/python2.6/site-packages/dolfin/function/functionspace.py",
>> line 230, in __init__
>>     FunctionSpaceBase.__init__(self, mesh, element)
>>   File "/home/oelgaard/software/fenics/dolfin/local/lib/python2.6/site-packages/dolfin/function/functionspace.py",
>> line 44, in __init__
>>     ufc_element, ufc_dofmap = jit(self._ufl_element)
>>   File "/home/oelgaard/software/fenics/dolfin/local/lib/python2.6/site-packages/dolfin/compilemodules/jit.py",
>> line 44, in mpi_jit
>>     return local_jit(*args, **kwargs)
>>   File "/home/oelgaard/software/fenics/dolfin/local/lib/python2.6/site-packages/dolfin/compilemodules/jit.py",
>> line 87, in jit
>>     p = form_compiler.default_parameters()
>> AttributeError: 'module' object has no attribute 'default_parameters'
>>
>> Kristian
>>
>> On 21 June 2010 15:42,  <kent-and@xxxxxxxxx> wrote:
>> >
>> > Hi, just portet SFC to dolfin-dev and ufl-dev and made some simple
>> > comparisons with FFC. I
>> > don't know exactly how representative these are, but I thought I'd try to
>> > compare
>> > them for fun.
>> >
>> > I have used the following code:
>> >
>> > from dolfin import *
>> > import time
>> >
>> > for compiler in ["ffc", "sfc"]:
>> >
>> >    for N in [200, 400, 800]:
>> >
>> >        parameters["form_compiler"]["name"]=compiler
>> >        if compiler == "ffc":
>> >            parameters["form_compiler"]["optimize"] = True
>> >            parameters ["form_compiler"]["cpp_optimize"] = True
>> >
>> >        mesh = UnitSquare(N, N)
>> >        V = FunctionSpace(mesh, "CG", 1)
>> >
>> >        P=6
>> >        U = Function(V)
>> >        energy = U**6*(U*U + inner(grad(U), grad(U)))*dx
>> >
>> >        v = TestFunction(V)
>> >        u = TrialFunction(V)
>> >
>> >        F = derivative(energy, U, v)
>> >        J = derivative(F, U, u)
>> >
>> >        print ""
>> >        print "First time"
>> >        print ""
>> >        t0 = time.time()
>> >        A = assemble(J)
>> >        t1 = time.time()
>> >        print "First time for ", compiler, " was ", t1 - t0
>> >
>> >        print ""
>> >        print "Second time"
>> >        print ""
>> >        t0 = time.time()
>> >        A = assemble(J)
>> >        t1 = time.time()
>> >
>> >        print "Second time for ", compiler, " was ", t1 - t0
>> >
>> >
>> > With these options SFC is about 3 times faster than FFC. How should I
>> > optimize FFC ?
>> >
>> > Kent
>> >
>> >
>> >
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>
>
>