dolfin team mailing list archive

[Johan Hake <johan.hake@xxxxxxxxx>]

> in the question 102501, I found similar question and it actually solved my
> problem. I can write the tensor as the answers in question 102501. FEniCS
> doesn't complain about it. But I think that it's not solving problem.
> Here are code and the result

No you are probably not solving you problem. u1c is here interpreted as a 
scalar value, which is initiated to 0. You can set the value of that scalar 
by:

  f00.u1c = some_value

but I guess that ulc really is a Function or another Expression. Then you need 
a bit more elaborated Expression. Something like:

code = """
class MyExpr: public Expression
{
public:
  boost::shared_ptr<dolfin::GenericFunction> ulc;
  MyExpr():Expression()
  {}

  void eval(dolfin::Array<double>& values, const dolfin::Array<double>& x) 
const
  {
   assert(ulc);
   ulc->eval(values, x);
   values[0] = (10.45-9.96)/10.45*values[0];
  }
};
"""

f00 = Expression(code)
f00.ulc = ulc
ulc.vector()[:]=1
f00(0,0,0)

=> 0.046889952153109919

But... I now see that your expression can be writte directly in ufl which is 
much easier:

  f00 = (10.45-9.96)/10.45 *u1c
  f11 = (5.58-6.05)/5.58 *u1c
  f22 = (4.86-4.74)/4.86 *u1c
  z = 0
  F2= as_matrix(((f00,z,z),(z,f11,z),(z,z,f22)))

Johan