dolfin team mailing list archive

["Martin Sandve Alnæs" <martinal@xxxxxxxxx>]

2008/8/22 Anders Logg <logg@xxxxxxxxx>:
> On Fri, Aug 22, 2008 at 10:08:07AM +0200, Martin Sandve Alnæs wrote:
>> 2008/8/22 Anders Logg <logg@xxxxxxxxx>:
>> > On Thu, Aug 21, 2008 at 11:43:41PM +0200, Johan Hake wrote:
>> >> On Thursday 21 August 2008 23:05:57 Evan Lezar wrote:
>> >> > Hi
>> >> >
>> >> > I added a simple warning message to the Function constructor in function.py
>> >> > which is displayed if the constructor is called with 3 arguments and the
>> >> > last one is not an instance of dolfin.Vector or Matrix.
>> >> >
>> >> > I know that a warning is not a necessarily a long-term solution, but it
>> >> > would at least assist new users such as myself in tracking down the source
>> >> > of errors in their code.
>> >>
>> >> Fine that you found out what your problem was!
>> >>
>> >> Your issue again illustrates the limitation Function in pydolfin. We should
>> >> really update at least the docstrings, together with more exstensive
>> >> testings. For example could these lines be expanded:
>> >>
>> >>      # Otherwise give all to DOLFIN
>> >>      else:
>> >>          dolfin.cpp_Function.__init__(self, *((element,) + others))
>> >>
>> >> so that we only send valid arguments to the cpp_Function constructor.
>> >>
>> >> A while ago I implemented a way of instantiate a discrete function using a
>> >> numpy array. I promised Martin to send a patch to him for inclusion but faild
>> >> to do it. Please apply Evans patch then I can hand a patch for the numpy
>> >> array initialization after that.
>> >
>> > Done.
>> >
>>
>> This check is wrong in many ways:
>>
>>         # Check arguments
>>         if len(others) == 2:
>>             if not isinstance(others[1], (dolfin.Vector, dolfin.GenericVector)):
>>                 error("Coefficients should be dolfin Vector or Matrix")
>>
>> First, the len(others) == 2 is a very very ugly hack that hides
>> some of the dolfin::Function::Function signatures.
>>
>> Second, checking for dolfin.Vector is superfluous and misleading for
>> people reading the code (they might repeat the practice and forget
>> the GenericVector part in other code).
>>
>> Third, the term "Coefficients" in the message has no clear no meaning.
>>
>> Fourth, "or Matrix" should of course be removed.
>>
>> I'll leave it up to those who use dolfin.Function to fix this mess the
>> way they want it.
>
> Yes, you are right. The Function class in PyDOLFIN is a hack. It needs
> to be fixed, but probably won't before UFL is ready.

The issues here won't change with UFL.

--
Martin