dolfin team mailing list archive

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

Johan Hake wrote:
> On Thursday 02 July 2009 22:48:18 Marie Rognes wrote:
> > Johan Hake wrote:
> > > On Thursday 02 July 2009 13:24:28 Garth N. Wells wrote:
> > > > Johan Hake wrote:
> > > > > On Thursday 02 July 2009 13:07:47 Garth N. Wells wrote:
> > > > > > Marie Rognes wrote:
> > > > > > > Garth N. Wells wrote:
> > > > > > > > Marie Rognes wrote:
> > > > > > > > > The following code gives r = 0.0. It is not supposed to be.
> > > > > > > > >
> > > > > > > > > The problem seems to be that f's vector is still all zeros at the
> > > > > > > > > call to interpolate. Could this be easily fixed?
> > > > > > > > This example should have led to an error message since f is not a
> > > > > > > > discrete function. I'll take a look.
> > > > > > > Ok, thanks!
> > > > > > >
> > > > > > > However,
> > > > > > >
> > > > > > > (a) Why is f not a discrete function? (It is defined on a finite
> > > > > > > element space?)
> > > > > > On second thought, it may be a discrete function. I think that this is
> > > > > > defined in the Python interface and not the C++ interface, so I'll
> > > > > > take a look.
> > > > > A user defined function is not a discrete function untill you either
> > > > > call interpolate() or vector, also in python. The problem with the
> > > > > later is that you then create a vector which is initialized to 0.
> > > > >
> > > > > I think this has been discussed before, but should we populate the
> > > > > vector using f.interpolate() when vector is called on a userdefined
> > > > > function?
> > > > Or perhaps Function::vector() should throw an error if the vector has
> > > > not already been allocated.
> > > I vote for this.
> > >
> > > The error message can include information about the user might want to
> > > call interpolate?
> > What is wrong with actually populating the vector with the values one
> > expects it to have?
> > (When would one not want this?)
>
> Nothing is wrong with that. It just changes the state of the userdefined 
> function. The question is should this change be the implicit result of a call 
> to Function::vector() or should it be a result of an explicit action: a call 
> to Function::interpolate().
>
> > Also note that it is not intuitive to me that one must call
> > f.interpolate() before
> >
> > 	Pi_f = interpolate(f, Q_h)

I thought that I removed the above function from the C++ interface and added

    Pi_f = interpolate(f)

Garth

> I agree... Not easy to satisfy every one. 
>
> Should we put in a:
>
>   if not f.has_vector():
>       info("Interpolating userdefined function.")
>       f.interpolate()
>
> in the python part of the interpolate function?
>
> johan