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[Johan Hake <question104471@xxxxxxxxxxxxxxxxxxxxx>]

Question #104471 on DOLFIN changed:
https://answers.launchpad.net/dolfin/+question/104471

    Status: Open => Answered

Johan Hake proposed the following answer:
Hello Chris!

When defining MixedFunction spaces with more than one component you should 
use:

  W = MixedFunctionSpace([V,Q,R])

The add operator in FunctionSpace returns a MixedFunctionSpace of its two 
components, so

  V+Q+R

would result in:

  W = MixedFunctionSpace([MixedFunctionSpace([V,Q]),R])

Johan

On Monday 15 March 2010 14:13:12 Chris Richardson wrote:
> New question #104471 on DOLFIN:
> https://answers.launchpad.net/dolfin/+question/104471
> 
> I want to solve for a vector and two scalars, and I have specified the
>  FunctionSpace W intuitively correctly, but the BC complains that my
>  dimension is incorrect (for the vector). What am I doing wrong?
> 
> mesh=UnitSquare(10,10)
> 
> V=VectorFunctionSpace(mesh,"CG",2)
> Q=FunctionSpace(mesh,"CG",1)
> R=FunctionSpace(mesh,"CG",1)
> W=V+Q+R
> 
> def bound0(x):
>     x[0]<DOLFIN_EPS
> 
> v0=Constant((0.0,0.0))
> 
> bc=DirichletBC(W.sub(0),v0,bound0)
> 
> 
>     bc=DirichletBC(W.sub(0),v0,bound0)
>   File "/usr/lib/python2.6/dist-packages/dolfin/mesh/bcs.py", line 56, in
>  __init__ cpp.DirichletBC.__init__(self, *args)
>   File "/usr/lib/python2.6/dist-packages/dolfin/cpp.py", line 9390, in
>  __init__ _cpp.DirichletBC_swiginit(self,_cpp.new_DirichletBC(*args))
> RuntimeError: *** Error: Unable to create boundary condition. Reason:
>  Illegal value 2 for value dimension, should be 3.
>

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