dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Fri, Aug 22, 2008 at 10:37:14AM +0200, Martin Sandve Alnæs wrote:
> 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.

The only issue I see is with the first special case. Yes, this won't
be solved by UFL. What I meant was, I won't solve it (creating a
function from a given element which means we need to generate the dof
map) before we will need to fix this code anyway to work with UFL.

-- 
Anders

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