dolfin team mailing list archive

[logg <logg@xxxxxxxxx>]

On Wed, Oct 21, 2009 at 04:31:12PM -0000, Garth Wells wrote:
>
> oelgaard wrote:
> > Quoting Garth Wells <gnw20@xxxxxxxxx>:
> >
> >> oelgaard wrote:
> >>> Public bug reported:
> >>>
> >>> The following two files will reproduce the bug.
> >>>
> >>> M.ufl:
> >>>
> >>> exact = FiniteElement("Lagrange", triangle, 6)
> >>> approx = FiniteElement("Lagrange", triangle, 1)
> >>>
> >>> u = Function(exact)
> >>> uh = Function(approx)
> >>>
> >>> M = (uh - u)*(uh - u)*dx
> >>>
> >>>
> >>> main.cpp:
> >>>
> >>> #include <dolfin.h>
> >>> #include "M.h"
> >>>
> >>> using namespace dolfin;
> >>>
> >>> class Expr : public Expression
> >>> {
> >>> public:
> >>>
> >>>   Expr() : Expression(2) {}
> >>>
> >>>   void eval(double* values, const double* x) const
> >>>   {
> >>>     values[0] = 10*x[0]*x[1];
> >>>   }
> >>>
> >>> };
> >>>
> >>> class Expr2 : public Expression
> >>> {
> >>> public:
> >>>
> >>>   Expr2() : Expression(2) {}
> >>>
> >>>   void eval(double* values, const double* x) const
> >>>   {
> >>>     values[0] = sin(5*x[0]);
> >>>   }
> >>> };
> >>>
> >>> class Func2 : public Function
> >>> {
> >>> public:
> >>>
> >>>   Func2(FunctionSpace& v) : Function(v) {}
> >>>
> >>>   void eval(double* values, const double* x) const
> >>>   {
> >>>     values[0] = sin(5*x[0]);
> >>>   }
> >>> };
> >>>
> >> The above class shouldn't be possible with the development version of
> >> DOLFIN. Are you using an older version?
> >
> > Yes:
> >
> > changeset:   7392:70596970a173
> > tag:         tip
> > user:        Anders Logg <logg@xxxxxxxxx>
> > date:        Wed Oct 21 17:34:32 2009 +0200
> > summary:     Attempt at bug fix in application of periodic boundary conditions
> > on
> >
> >
> > Why shouldn't it be possible to derive a class from Function?
> >
>
> In the new design, Function is strictly a finite element function, and
> not a user-defined function. We may need to fix something to make it
> impossible to create a Function with a user-provided eval(..).
> Expression should be used instead.

I don't see how to do this. The eval function is virtual so there's
nothing "wrong" with overloading it.

Unless there's some trick we can do with making it private or
protected in Function.

--
Anders


> >>>          Status: New
> >>>
> >>
> >> Status in DOLFIN: New
> >>
> >> Bug description:
> >> The following two files will reproduce the bug.
> >>
> >> M.ufl:
> >>
> >> exact = FiniteElement("Lagrange", triangle, 6)
> >> approx = FiniteElement("Lagrange", triangle, 1)
> >>
> >> u = Function(exact)
> >> uh = Function(approx)
> >>
> >> M = (uh - u)*(uh - u)*dx
> >>
> >>
> >> main.cpp:
> >>
> >> #include <dolfin.h>
> >> #include "M.h"
> >>
> >> using namespace dolfin;
> >>
> >> class Expr : public Expression
> >> {
> >> public:
> >>
> >>   Expr() : Expression(2) {}
> >>
> >>   void eval(double* values, const double* x) const
> >>   {
> >>     values[0] = 10*x[0]*x[1];
> >>   }
> >>
> >> };
> >>
> >> class Expr2 : public Expression
> >> {
> >> public:
> >>
> >>   Expr2() : Expression(2) {}
> >>
> >>   void eval(double* values, const double* x) const
> >>   {
> >>     values[0] = sin(5*x[0]);
> >>   }
> >> };
> >>
> >> class Func2 : public Function
> >> {
> >> public:
> >>
> >>   Func2(FunctionSpace& v) : Function(v) {}
> >>
> >>   void eval(double* values, const double* x) const
> >>   {
> >>     values[0] = sin(5*x[0]);
> >>   }
> >> };
> >>
> >> int main()
> >> {
> >>   // Create mesh and function space
> >>   UnitSquare mesh(8, 8);
> >>   M::CoefficientSpace_u Vu(mesh);
> >>   M::CoefficientSpace_uh Vuh(mesh);
> >>
> >>   Expr exact;
> >> //  Expr2 approx;      // 12.5251
> >> //  Func2 approx(Vuh); // 11.1111
> >>   Func2 approx(Vu);    // 11.1111
> >>
> >>   M::Functional m(mesh);
> >>   m.u = exact;
> >>   m.uh = approx;
> >>
> >>   double error = assemble(m);
> >>
> >>   std::cout << "error: " << error << std::endl;
> >>
> >>   return 0;
> >> }
> >>
> >
>

-- 
function and expression does not give the same result
https://bugs.launchpad.net/bugs/457262
You received this bug notification because you are subscribed to DOLFIN.

Status in DOLFIN: New

Bug description:
The following two files will reproduce the bug.

M.ufl:

exact = FiniteElement("Lagrange", triangle, 6)
approx = FiniteElement("Lagrange", triangle, 1)

u = Function(exact)
uh = Function(approx)

M = (uh - u)*(uh - u)*dx


main.cpp:

#include <dolfin.h>
#include "M.h"

using namespace dolfin;

class Expr : public Expression
{
public:

  Expr() : Expression(2) {}

  void eval(double* values, const double* x) const
  {
    values[0] = 10*x[0]*x[1];
  }

};

class Expr2 : public Expression
{
public:

  Expr2() : Expression(2) {}

  void eval(double* values, const double* x) const
  {
    values[0] = sin(5*x[0]);
  }
};

class Func2 : public Function
{
public:

  Func2(FunctionSpace& v) : Function(v) {}

  void eval(double* values, const double* x) const
  {
    values[0] = sin(5*x[0]);
  }
};

int main()
{
  // Create mesh and function space
  UnitSquare mesh(8, 8);
  M::CoefficientSpace_u Vu(mesh);
  M::CoefficientSpace_uh Vuh(mesh);

  Expr exact;
//  Expr2 approx;      // 12.5251
//  Func2 approx(Vuh); // 11.1111
  Func2 approx(Vu);    // 11.1111

  M::Functional m(mesh);
  m.u = exact;
  m.uh = approx;

  double error = assemble(m);

  std::cout << "error: " << error << std::endl;

  return 0;
}