dolfin team mailing list archive

[Stepan Roucka <stepan@xxxxxxxxx>]

I think you use dim() method instead:

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 dim(self):
       return 2

The documentation of demos seems to be outdated?
The demos in the ppa packages use dim(), but in the
sources
http://bazaar.launchpad.net/~dolfin-core/dolfin/main/annotate/head%3A/demo/pde/cahn-hilliard/python/demo.py
value_shape is still used, I don't understand why.

Stepan

On 10 November 2010 18:48, Garth N. Wells <gnw20@xxxxxxxxx> wrote:
>
>
> On 10/11/10 17:44, N.A. Borggren wrote:
>>
>> 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?
>>
>
> Which version of DOLFIN are you using?
>
> Garth
>
>> Thank you very much,
>>     Nathan Borggren
>
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