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Re: Image to Function data structure conversion

 



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




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