dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Thu, Jul 07, 2011 at 02:44:20PM -0700, Johan Hake wrote:
> On Thursday July 7 2011 12:21:26 Anders Logg wrote:
> > On Thu, Jul 07, 2011 at 02:20:44PM +0200, Marie E. Rognes wrote:
> > > Is the plan for 1.0-beta to fix
> > >
> > > https://bugs.launchpad.net/ffc/+bug/787010
> > >
> > > and then release?
> >
> > Yes + decide on the interface for NonlinearVariationalProblem.
> >
> > I think that should be all.
> >
> > It would be good to hear more comments on the two suggestions:
> >
> > 1. (current)
> >
> >   NonlinearVariationalProblen(lhs, rhs, u, bcs, [J])
> >
> >   This is consistent with LinearVariationalProblem and the solve()
> >   functions; same order of arguments.
> >
> > 2. (Garth)
> >
> >   NonlinearVariationalProblen(lhs, u, bcs, [J])
> >
> >   This removes the unnecessary rhs argument which always has to be
> >   zero.
> >
> > I think there are good arguments for both but not very strong so it's
> > a matter of taste.
>
> If:
>
>   The point is that it makes the interface for all variational problems
>   (linear or nonlinear) the same:
>
> is the only reason, I go with Garth.

Another reason is complications in the implementation, both in C++ and
the Python layer. Nothing I can't handle but it leads to complications.
I have started to implement it but it's looking messy.

I also would like to keep the set_jacobian function. The constructors
will otherwise be a mess: there will be very many constructors with
varying order of arguments which is both error prone and tedious to
implement/maintain.

We would need the following variations of constructors for linear and
nonlinear variational problems:

  a, L, u
  a, L, u, bc
  a, L, u, bcs
  F, u
  F, u, J
  F, u, bc
  F, u, bc, J
  F, u, bcs
  F, u, bcs, J

Instead of one common signature:

  lhs, rhs, u, [bcs]

Of course there will still need to be some variations to implement,
but those are only handling various ways to specify the boundary
conditions, either none, bc or bcs.

The advantage is clarity: only needing to remember lhs, rhs, u, [bcs].

--
Anders