Hello,
I am having some issues overloading eval for the class Expression
when I try to use vector valued functions. For example the error occurs
for me in the Cahn-Hilliard demo copied directly from
http://www.fenicsproject.org/doc/demos/pde/cahn-
hilliard/python/documentation.html
$ python cahn.py
Got expression dimension = 0
Traceback (most recent call last):
File "cahn.py", line 56, in<module>
u.interpolate(u_init)
File "cahn.py", line 10, in eval
values[1] = 0.0
IndexError: index out of bounds
the problematic definition is:
class InitialConditions(Expression):
def __init__(self):
random.seed(2 + MPI.process_number())
def eval(self, values, x):
values[0] = 0.63 + 0.02*(0.5 - random.random())
values[1] = 0.0
def value_shape(self):
return (2,)
What is this value_shape accomplishing? The expression dimension seems
to still be zero. How do I resolve this?
