dolfin team mailing list archive

["Garth N. Wells" <gnw20@xxxxxxxxx>]

Martin Sandve Alnæs wrote:
> On Sat, Feb 14, 2009 at 6:08 PM, Johan Hake <hake@xxxxxxxxx> wrote:
> > On Saturday 14 February 2009 17:45:44 Martin Sandve Alnæs wrote:
> > > On Sat, Feb 14, 2009 at 5:34 PM, Johan Hake <hake@xxxxxxxxx> wrote:
> > > > On Saturday 14 February 2009 17:28:18 Garth N. Wells wrote:
> > > > > Johan Hake wrote:
> > > > > > On Saturday 14 February 2009 13:48:05 A Navaei wrote:
> > > > > > > It seems that the error can be re-produced even without sub-classing
> > > > > > > and using existing dolfin classes in pure c++. Based on the
> > > > > > > itk-dolfin interface code, the below minimal code should generate the
> > > > > > > error (note that I use the binary distribution which uses std::tr1,
> > > > > > > replacing it with boost shared pointer should not have any effect).
> > > > > > Not in c++ but swig only support std::tr1::shared_ptr from version
> > > > > > 1.3.37. But if you intend to use shared_ptr only internally there
> > > > > > whould not be any problems.
> > > > > >
> > > > > > > After wrapping in python:
> > > > > > >
> > > > > > > (1) Calling FunctionTest.CreateFunction(), which returns by value,
> > > > > > > results this error:
> > > > > > >
> > > > > > > RuntimeError: *** Error: Unable to assign to function, missing
> > > > > > > coefficients (user-defined function).
> > > > > > You cannot assign another user-defined function to another Function.
> > > > > > It must be a discrete function, which has an initialized _vector. This
> > > > > > is probably a feature that other developers should answer for.
> > > > > >
> > > > > > However this means that you cannot copy a userdefined function, with
> > > > > > the side effect of not beeing able to return a user-defined Function
> > > > > > by value.
> > > > > >
> > > > > > > Since dolfin::Function does come with the required copy ctors, the
> > > > > > > problem cannot be stemmed from this.
> > > > > > This use the assignment operator which requires the Function to be a
> > > > > > discrete and not a user-defined Function.
> > > > > >
> > > > > > I consider this to be a bug in the library. Any other comments from
> > > > > > the C++ DOLFIN developers (I am mostly dealing with the python
> > > > > > interface)?
> > > > > In a nutshell, are you suggesting that the Function copy constructor
> > > > > should work for user-defined Functions?
> > > > Yes. Why shouldn't it?
> > > >
> > > > I can see why the assigment operator should not work.
> > > If I understand this right, what you propose is probably not
> > > technically possible in C++ with the current design. The old design
> > > which used the envelope-letter could have dealt with this.
> > Why's that?
> >
> > The only data that needs to be copied are the FunctionSpace, when _vector is
> > null, and this is shared? Am I missing somthing wrt to the copting of any
> > derived class of Function?
> >
> > Johan
>
> I haven't followed this in detail, so I may misunderstand, but if you
> have a subclass MyFunction of Function, copying it to a Function can't
> possibly work. How could it? 

It doesn't work, but it is now possible to copy a MyFunction to a 
MyFunction, which wasn't possible before.

Garth

However, Function can make a discrete
> function from MyFunction, then it's ok.
>
> Martin