dolfin team mailing list archive

[Garth Wells <gnw20@xxxxxxxxx>]

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.

Garth

> Kristian
> 
>> 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
>> You received this bug notification because you are a direct subscriber
>> of the bug.
>>
>> 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;
}