Expression and class(UserExpression) don't yield the same results

[nate]

@Cou

    def eval(self, value, x):
        
        u_e = 1.0 + x[0]*x[0] + self.alpha*x[1]*x[1] + self.beta*self.t
    
        value = u_e

I haven’t run your code, but I’m pretty sure the above needs the following correction:

    def eval(self, value, x):
        
        u_e = 1.0 + x[0]*x[0] + self.alpha*x[1]*x[1] + self.beta*self.t
    
        value[0] = u_e

In your original implementation you overwrite the variable value whereas you should assign quantities to its members.