ffc team mailing list archive

[jhoffman@xxxxxxxxxxx]

Hi Anders,

I have started to look at how to solve the stabilization problem in the
best way. I first tried the approach with a piecewise constant function
for the stabilization parameter, but I seem to have missed something? Do
you find anything obvious wrong with the form-file below?

/Johan


name = "NSEContinuity"
scalar_element = FiniteElement("Lagrange", "tetrahedron", 1)
vector_element = FiniteElement("Vector Lagrange", "tetrahedron", 1)
disc_scalar_element = FiniteElement("Discontinuous Lagrange",
"tetrahedron", 0)

q = BasisFunction(scalar_element)
p = BasisFunction(scalar_element)
uc = Function(vector_element)
f = Function(vector_element)
d1 = Function(disc_scalar_element)

i0 = Index()
i1 = Index()
i2 = Index()

a = q.dx(i0)*p.dx(i0)*dx
L = q.dx(i0)*f[i0]*dx - q.dx(i0)*uc[i1]*uc[i0].dx(i1)*dx -
(1/d1)*q*uc[i0].dx(i0)*dx




skalman:~/local> ffc NSEContinuity.form
This is FFC, the FEniCS Form Compiler, version 0.1.8.
For further information, go to http://www/fenics.org/ffc/.

Parsing NSEContinuity.form
Output written to NSEContinuity.py
[[((-1.0, -1.0, -1.0),), ((1.0, -1.0, -1.0),), ((-1.0, 1.0, -1.0),),
((-1.0, -1.0, 1.0),)], [(), (), (), (), (), ()], [(), (), (), ()], [()]]
((-1.0, -1.0, -1.0), (1.0, -1.0, -1.0), (-1.0, 1.0, -1.0), (-1.0, -1.0, 1.0))
Warning: element untested
Traceback (most recent call last):
  File "/usr/bin/ffc", line 81, in ?
    main(sys.argv[1:])
  File "/usr/bin/ffc", line 59, in main
    execfile(outname)
  File "NSEContinuity.py", line 32, in ?
    disc_scalar_element = FiniteElement("Discontinuous Lagrange",
"tetrahedron", 0)
  File "/home/hoffman/local/lib/python/ffc/compiler/finiteelement.py",
line 66, in __init__
    self.element = DiscontinuousLagrange(fiat_shape, degree)
  File "/home/hoffman/local/lib/python/FIAT/DiscontinuousLagrange.py",
line 87, in DiscontinuousLagrange
    if n == 0: return P0.P0( shape )
  File "/home/hoffman/local/lib/python/FIAT/P0.py", line 35, in __init__
    Udual = P0Dual( shape , U )
  File "/home/hoffman/local/lib/python/FIAT/P0.py", line 21, in __init__
    d = shapes_new.dims[ shape ]
AttributeError: 'module' object has no attribute 'dims'






> On Fri, Jul 08, 2005 at 11:02:04PM +0200, Garth N. Wells wrote:
>> Hi Anders,
>>
>> I'm trying to stabilise a problem and for this I need a measure of the
>> element
>> area. Do you have any plans to make this sort of information available
>> through
>> ffc? I have seen that Johan H. hasn't yet defined the element length in
>> the
>> Navier-Stokes module yet. Johan, do you have a plan how to do this? It
>> could be
>> done easily by defining a constant in the .form file and then adding a
>> line c4 =
>> sqrt(det), but this would destroy the beauty of the ffc generated file.
>
> I will probably add a default Function h(x) that gives you the size of
> the element. Do you need the side length (diameter) or the area?
>
> This will probably not be until after the summer though, so what you
> can do now is to define a piecewise constant function that is defined
> as the mesh size or area or whatever, like so:
>
>    P0 = FiniteElement("Discontinuous Lagrange", "triangle", 0)
>    h  = Function(P0)
>
> and then define a corresponding Function in DOLFIN from a Vector and
> set the values of the Vector to the local mesh size (x(i) area of
> triangle i).
>
>> A more general question - do you have a plan on how more complicated
>> nonlinear
>> problems, such as plasticity, will fit in with ffc + DOLFIN? I mean here
>> solving
>> equations in which the coefficients of an equation themselves come from
>> the
>> solution of a non-trivial nonlinear problem, such a plasticity return
>> mapping
>> algorithm.
>>
>> Garth
>
> This is already implemented. When you define a Function in FFC, then
> this corresponds to a Function in DOLFIN, and the DOLFIN Function
> could be either defined by an expression or it can be the solution of
> another problem.
>
> The Function concept is really central to both FFC and DOLFIN, and it
> is the key to working with FFC and DOLFIN. Each Function in FFC
> corresponds to a Function in DOLFIN, and it should not matter how the
> Function is defined in DOLFIN. There are a couple of things missing,
> like reading Functions from file, projection between different
> function spaces, but the basic stuff is implemented. (Take a look at
> Function.cpp, it's pretty short.)
>
> Ask again if something is unclear.
>
> /Anders
>
> _______________________________________________
> FFC-dev mailing list
> FFC-dev@xxxxxxxxxx
> http://www.fenics.org/cgi-bin/mailman/listinfo/ffc-dev
>