dolfin team mailing list archive

[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?

Garth

> 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;
> }
> 
> ** Affects: dolfin
>      Importance: Undecided
>          Status: New
>

-- 
function and expression does not give the same result
https://bugs.launchpad.net/bugs/457262
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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;
}