dolfin team mailing list archive

[Marie Rognes <meg@xxxxxxxxx>]

Garth N. Wells wrote:
> Johan Hake wrote:
> > On Thursday 02 July 2009 15:17:08 Garth N. Wells wrote:
> > > 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)
>
> Oops, I meant that I removed
>
>     Pi_f.interpolate(f, Q_h)
>
> and added
>
>     Pi_f.interpolate(f)
>
> I think that we should remove interpolate.py. It's now a wrapper for 
> only two lines of code.


If so, if I want to interpolate f (defined on V_h) onto the space Q_h, I 
should do ...?


--
Marie