dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Sat, Feb 14, 2009 at 06:51:44PM +0100, 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? However, Function can make a discrete
> function from MyFunction, then it's ok.
> 
> Martin

This should be fairly easy to do by interpolation. I'll make an
attempt to fix this.

-- 
Anders

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