dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Sun, Jan 10, 2010 at 07:02:22AM -0000, Ted Kord wrote:
> New question #96848 on DOLFIN:
> https://answers.launchpad.net/dolfin/+question/96848
>
> Hello
>
> Is there away to :
>
> 1. create and bind an object to each node in space.
>
> 2. have the object automatically update its state at every time step.
>
> My original approach was to create a pointer to the object in a subclass of expression ......  but the solution turns out to be the same  the same at each time step. So, I know I'm definitely doing something wrong.
>
> Thanks in advance
>
> Ted

When you create a subclass of Expression, you can do whatever you like
as part of that class, for example by putting a vector of objects as a
member variable of your class.

But remember that for a time-dependent problem, you must yourself
update the value of t between time steps. Here's a sketch:

class MyExpression : public Expression
{
public:

   MyExpression(const Mesh& mesh)
   {
     for (int i = 0; i < mesh.num_vertices(); ++i)
     {
       objects.push_back(...);
     }
   }

   void eval(...)
   {
     ...
   }

   void update(double t)
   {
     this->t = t;
   }

private:

   double t;
   std::vector<Class> objects;

};

Then do something like this in your code:

  MyExpression w(mesh);

  while (t < T)
  {
    w.update(t);

    solve

    t += dt;
  }

--
Anders

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