dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Wed, Jun 22, 2011 at 10:42:53PM +0200, Anders Logg wrote:
> Dear all,
>
> I have now implemented the discussed changes (in the dolfin/logg
> branch). Problems can now be solved in one of two ways. The interfaces
> look very similar in C++ and Python and very similar for linear and
> nonlinear problems (same number of arguments etc). Here's what it
> looks like now.
>
> 1. Short option
>
>   solve(a == L, u, bc)
>   solve(F == 0, u, bc, J=J)
>
> * The bc argument is optional and can be either a single bc or a list.
>
> * The J=J argument is not yet handled.
>
> 2. Long (advanced) option
>
>   problem = LinearVariationalProblem(a, L, u, bc)
>   solver = LinearVariationalSolver(problem)
>   solver.parameters[...] = ...
>   solver.parameters[...] = ...
>   solver.solve()
>
>   problem = NonlinearVariationalProblem(a, L, u, bc)

It should be

  problem = NonlinearVariationalProblem(F, 0, u, bc)

here.

--
Anders


>   solver = NoninearVariationalSolver(problem)
>   problem.set_jacobian(J)
>   solver.parameters[...] = ...
>   solver.parameters[...] = ...
>   solver.solve()
>
> * The reason for the separate set_jacobian function is that this is
>   not necessary for all nonlinear solvers. We could add other solvers
>   that don't require it.
>
> Let me know if this looks good. It may have implications on the code
> examples in the FEniCS book.
>
> The old VariationalProblem class is still there and gives an
> informative error message.
>