dolfin team mailing list archive

[Johan Hake <johan.hake@xxxxxxxxx>]

What version of DOLFIN do you use. Just run 

  dolfin-version 

from the command prompt. The itnerface of VariationalProblem has changed 
recently and it seams as you might have an older version.

Johan

On Monday May 30 2011 21:05:47 Praveen C wrote:
> New question #159694 on DOLFIN:
> https://answers.launchpad.net/dolfin/+question/159694
> 
> Hello
> This is my first attempt at dolfin. I am solving a 1-d convection-diffusion
> equation
> 
> (u^2/2)_x - u_xx = f
> u(0) = u(1) = 0
> 
> So I do the following
> 
> 
> # Create mesh and function space
> mesh = UnitInterval(50)
> V = FunctionSpace(mesh, "CG", 1)
> 
> # Sub domain for Dirichlet boundary condition
> def DirichletBoundary(x):
>      return x[0] < DOLFIN_EPS or x[0] > 1.0 - DOLFIN_EPS
> 
> # Define variational problem
> u = Function(V)
> f = Expression("10.0*x[0]*(1.0-x[0])*sin(x[0])")
> 
> du = TrialFunction(V)
> v  = TestFunction(V)
> 
> F = (-0.5*u**2*grad(v) + dot(grad(u), grad(v)))*dx - f*v*dx
> dF= derivative(F, u, du)
> 
> # Define boundary condition
> u0 = Constant(0.0)
> bc = DirichletBC(V, u0, DirichletBoundary)
> 
> problem = VariationalProblem(F, dF, bc)
> u = problem.solve()
> 
> But this gives me following error
> 
> RuntimeError: *** Error: Unable to extract trial space for solution of
> variational problem, is 'a' bilinear?
> 
> Can you help me with this please ?
> 
> Thanks
> praveen