Why there is no need to use degree on C++ version of Expression?

1

Hello!

I am confused when I use Expression because I need to use parameter degree in python version of Expression like this

Expression(("x[0]","x[1]"),degree=2)

However, parameter degree is not used in C++ version of Expression like this

class Source : public Expression
{
public:

    Source() : Expression(2)
    {}

    void eval(Array<double>& values, const Array<double>& x) const
    {
        values[0]= x[0];
        values[1]= x[1];
    }

};

And use like this

Source source;

So, what’s the meaning of degree? We need to project Expression into finite element space before we use it?

2

Hey,

you will need to use the degree parmeter in both cases. In the end in your second example you will have something like this:

cpp_code = "class Source : public Expression
{
public:

    Source() : Expression(2)
    {}

    void eval(Array<double>& values, const Array<double>& x) const
    {
        values[0]= x[0];
        values[1]= x[1];
    }

};"
exp = CompiledExpression(compile_cpp_code(cpp_code).Source(), degree=2)

I interpret it the same as you, as a projection into the finite element space.

Hope this helps :slight_smile:
Emanuel

3

Thank you very much!

So, “exp” has its own function space.