ffc team mailing list archive

["Garth N. Wells" <g.n.wells@xxxxxxxxxxxxxxx>]

Anders,

I can't try the forms that you gave, because I can't get FFC 0.1.7 + FIAT 0.2.1
to run. The output from 'ffc Poisson.form' (using the Poisson.form demo in
ffc-0.1.7/src/demo) is 

mech136/<4>ffc-0.1.7/src/demo>ffc Poisson.form
This is FFC, the FEniCS Form Compiler, version 0.1.7.
For further information, go to http://www/fenics.org/ffc/.

Parsing Poisson.form
Output written to Poisson.py

Compiling form: (dXa0/dxb0)(dXa1/dxb0) | ((d/dXa0)vi1)*((d/dXa1)vi0)*dX
Finite element of test space:  Lagrange finite element of degree 1 on a Triangle
Finite element of trial space: Lagrange finite element of degree 1 on a Triangle
Computing 36 integrals, this may take some time
...............................................................................
Traceback (most recent call last):
  File "/usr/bin/ffc", line 80, in ?
    main(sys.argv[1:])
  File "/usr/bin/ffc", line 58, in main
    execfile(outname)
  File "Poisson.py", line 38, in ?
    compile([a, L], name, "0.1.7", "C++", "GNU GPL Version 2")
  File "/usr/lib/python2.3/site-packages/ffc/compiler/compiler.py", line 75, in
compile
    form.AKi = ElementTensor(form.sum, "interior", format)
  File "/usr/lib/python2.3/site-packages/ffc/compiler/elementtensor.py", line
41, in __init__
    gK_used = set()
NameError: global name 'set' is not defined

Garth


Quoting Anders Logg <logg@xxxxxxxxx>:

> You were right, there was a (serious) bug in FFC for handling constant
> indices. Thanks for pointing this out.
> 
> It has been fixed in the latest CVS version of FFC. However, the new
> version of FFC uses FIAT directly to generate vector-valued elements
> (previously handled in FFC), and FIAT assumes that a vector-valued
> Lagrange element on a triangle has two components. I think Rob will
> fix this shortly. Until then, try the following forms and see that you
> get the expected results:
> 
> element = FiniteElement("Vector Lagrange", "triangle", 1)
> 
> v  = BasisFunction(element)
> u1 = BasisFunction(element)
> 
> # Form 1
> #a = v[1] *(u1[0].dx(0) + u1[1].dx(1)) * dx
> 
> #Form 2
> #a = v[1] *(u1[0] + u1[1]) * dx
> 
> #Form 3
> a = v[1] *(u1[0].dx(0) + u1[1].dx(1)) * dx
> 
> #Form 4
> #a = v[1] *(u1[i].dx(i) ) * dx
> 
> /Anders
> 
> On Mon, May 02, 2005 at 05:19:37PM +0200, Garth N. Wells wrote:
> > Dear Anders,
> > 
> > I've been trying to use FFC for some forms which cannot be written using
> > summation convention, so I've been writing out the forms explicitly.
> > However, I have a problem with terms that involve a derivative, e.g.
> > u1[0].dx(0). Terms like u1[i].dx(i) (using indices) work fine.
> > 
> > Below is the code from an FFC file. What I've labelled Form 1 is basically
> the
> > continuity equation for 2D Navier-Stokes. Form 1 and Form 2 produce
> erroneously
> > exactly the same header file. In the case of Form 1, the resulting header
> file
> > does not involve any terms from the Jacobian (g00, g10, etc.) which it
> should
> > do. I would expect Form 3 and Form 4 to produce the same result. However,
> Form 4
> > produces the expected result, and Form 3 does not. Is there something wrong
> with
> > the synatax that I'm using? Notably, terms like u1[0].dx() do produce the
> > expected result (no index between the round brackets).
> > 
> > We're having some trouble with our mail server here, so I'd be grateful if
> you
> > could send a cc of any response to gnwells@xxxxxxxxxxx.
> > 
> > Regards,
> > Garth
> > 
> > name = "Test"
> > vector = FiniteElement("Lagrange", "triangle", 1, 3)
> > 
> > v    = BasisFunction(vector)
> > u1   = BasisFunction(vector)
> > 
> > # Form 1
> > a = v[2] *(u1[0].dx(0) + u1[1].dx(1)) * dx
> > 
> > #Form 2
> > #a = v[2] *(u1[0] + u1[1]) * dx
> > 
> > #Form 3
> > #a = v[2] *(u1[0].dx(0) + u1[1].dx(1) + u1[2].dx(2)) * dx
> > 
> > #Form 4
> > #a = v[2] *(u1[i].dx(i) ) * dx
> > 
> > 
> 
> -- 
> Anders Logg
> Research Assistant Professor
> Toyota Technological Institute at Chicago
> http://www.tti-c.org/logg/
>