New question #136803 on DOLFIN:
https://answers.launchpad.net/dolfin/+question/136803
I try to run the python demo file for the mixed formulation for the poisson
problem. When setting the dirichlet boundary condition I get the error:
*** Error: Unable to create boundary condition. Reason: Illegal value 0 for
value rank, should be 1.
Perhaps this error depends on the compiler statement: "Got expression dimension
= 0" when setting G with
G = BoundarySource()
but I'm not sure.
Please can you help me to understand the error statement. Thanks a lot.
Melanie
ps. here is a part of the source code where the error occurs:
# Define function G such that G \cdot n = g
class BoundarySource(Expression):
def eval_data(self, values, data):
g = sin(5*data.x()[0])
values[0] = g*data.normal()[0]
values[1] = g*data.normal()[1]
def value_shape(self):
return (2,)
G = BoundarySource()
# Define essential boundary
def boundary(x):
return x[1] < DOLFIN_EPS or x[1] > 1.0 - DOLFIN_EPS
bc = DirichletBC(W.sub(0), G, boundary)
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