On Wed, Feb 18, 2009 at 02:04:35PM +0000, A Navaei wrote: > 2009/2/17 Anders Logg <[email protected]>: > > On Tue, Feb 17, 2009 at 03:28:08PM +0000, Garth N. Wells wrote: > >> > >> > >> A Navaei wrote: > >> > The following minimal test for Function in c++ reveals some bugs. I > >> > guess this example can help me with dealing with the current issues of > >> > ImageFunction. > >> > > >> > (1) interpolate.py does not work when a Function is created in c++ and > >> > wrapped (see comment [2]). It seems that the bug is originated from > >> > the copy constructor (see comment [3]) > >> > > >> > (2) In order to perform the interpolation, why is it necessary to > >> > create another Function and then copy it? > >> > > >> > (3) Signature checkes seem not working properly (see comment [1]). The > >> > signature-based assignments are error-prone anyway, why the > >> > object-oriented approach is not used? > >> > > >> > >> Signatures are used to permit reading/writing Functions to a file. They > >> are indeed error prone, so I believe that we reached a consensus a short > >> while ago that we would remove pre-compiled elements. > >> > >> Garth > > > > Instead of signatures, I'd recommend that you define a simple form > > file for each of the different types of FunctionSpace you need, for > > example: > > > > element = FiniteElement("CG", "triangle", 1) > > > > v = TestFunction(element) > > u = TrialFunction(element) > > a = v*u*dx > > > > If you put this in a file named My.form and compile it with FFC using > > -l dolfin, you will get a class named MyFunctionSpace that you can > > then instantiate using just a mesh: > > > > MyFunctionSpace V(mesh); > > > > Create one form file for each of the different types of FunctionSpace > > that you need, name the files to something suitable and use the > > generated code. That way you won't need to worry about signatures, > > dofmaps and finite elements. > > Effectively, I've been using the very same method all this time, it > does not work.
Yes, it does. It's used in about 20 of the demos.
> The copy constructor fix never worked. I've been trying to explain
> this in many different ways, but the right attention was never paid to
> this. Let's see if the sandbox example can convince you this time.
>
> A Function instance still cannot be returned by reference (or value).
> Returning as shared_ptr seems to work initially, but eventually it
> generates segmentation fault -- see attached.
Yes, it can. There's absolutely no problem to return a Function by
reference. See the updated sandbox demo.
The only problem is when you want to copy a Function which is only
defined in terms of an eval() operator. In those cases the Function
cannot be copied.
If you do the following:
class MyFunction : public Function
{
public:
MyFunction(const FunctionSpace& V) : Function(V) {};
void eval(double* values, const double* x) const
{
values[0] = sin(x[0]);
}
};
MyFunction f(V);
Function g = f;
Do you then expect g to return sin(x)? It would be possible to
implement this but it would require g to keep a pointer to f so that
the eval() in g may call the eval() in f.
--
Anders
>
> -Ali
>
> >
> >
> > -----BEGIN PGP SIGNATURE-----
> > Version: GnuPG v1.4.9 (GNU/Linux)
> >
> > iEYEARECAAYFAkma2rQACgkQTuwUCDsYZdHp4ACfSbCXc2FAulzIdDsKvhz/6EGV
> > aY4An0eyftGV3hxR3L25M9LPu3X7KFg+
> > =z1cY
> > -----END PGP SIGNATURE-----
> >
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> > [email protected]
> > http://www.fenics.org/mailman/listinfo/dolfin-dev
> >
> >
> // Place for random tests
>
> #include <dolfin.h>
> #include "Poisson.h"
>
> using namespace dolfin;
>
> class MyFunction : public Function
> {
> public:
>
> MyFunction(const FunctionSpace& V) : Function(V) {};
>
> void eval(double* values, const double* x) const
> {
> message("Calling eval");
> double dx = x[0] - 0.5;
> double dy = x[1] - 0.5;
> values[0] = 500.0*exp(-(dx*dx + dy*dy) / 0.02);
> }
> };
>
> class FunctionContainer
> {
> public:
> FunctionContainer(const FunctionSpace& V)
> {
> _f = Function(V);
> };
>
> const Function& get_function()
> {
> return _f;
> };
> protected:
> Function _f;
> };
>
>
> int main()
> {
> UnitSquare mesh(2, 2);
> PoissonFunctionSpace V(mesh);
> MyFunction f(V);
> Vector x;
>
> message("Interpolating to another vector");
> f.interpolate(x, f.function_space());
> x.disp();
>
> message("Interpolating to the function vector");
> f.interpolate(f.vector(), f.function_space());
> f.vector().disp();
>
> message("Interpolating using initialising by an external function");
> MyFunction f_(f);
> f.interpolate(f_.vector(), f.function_space());
> f.vector().disp();
>
> message("Returning Function by reference");
> FunctionContainer fc(V);
> Function f2 = fc.get_function();
> }
>
> _______________________________________________
> DOLFIN-dev mailing list
> [email protected]
> http://www.fenics.org/mailman/listinfo/dolfin-dev
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