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[Johan Hake <question139524@xxxxxxxxxxxxxxxxxxxxx>]

Question #139524 on DOLFIN changed:
https://answers.launchpad.net/dolfin/+question/139524

Johan Hake proposed the following answer:
On Saturday January 1 2011 00:57:57 S Wood wrote:
> Question #139524 on DOLFIN changed:
> https://answers.launchpad.net/dolfin/+question/139524
> 
> S Wood requested for more information:
> Hi Andres,
> 
> Sorry I am new to dofin and fenics, but I was wondering if you can
> clarify what you mean by "update"? Here is a segment of the code I have
> and I don't get the plot on the same loop!
> 

You are recreating the solution Function each timestep. The plot command can 
then not figure out that you are plotting the same Function.

Change the code to:

 u, v = TrialFunction(V), TestFunction(V)
 Fuv = v*u*dx + ......
 u = Function(V)
 F = action(Fuv, u)
 J = derivative(F, u, du)
 
 # Solve nonlinear variational problem
 problem = VariationalProblem(J, F, bc, nonlinear=True)
 newton =  problem.parameters['newton_solver']
 newton["maximum_iterations"] = 40

 while t <= T:
     problem.solve(u)
 
     # Plot u
     plot(u)
 
     # March in time
     t += dt
     u_prev.assign(u)
 

Johan
 
> Thank you very much.
> 
> S.

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