Following up on my previous email, I have found a workaround to those issues, but now I have a problem with the solvers:

Traceback (most recent call last):

  File "/Users/matak/Downloads/Inequality-constraint-Rockafellar/solvers.py", line 32, in solver_F

    F_problem = NonlinearVariationalProblem(F_solve, w)#, aP=Ap)

  File "/Users/matak/firedrake/src/firedrake/firedrake/variational_solver.py", line 47, in __init__

    raise ValueError("Provided residual is not a linear form")

ValueError: Provided residual is not a linear form

There two issues here:

1. I cannot give a preconditioning matrix aP -- is this not possible for nonlinear problems?

2. I suspect the error above is because I have functions that depend on the solution, and I don’t know if that is acceptable in firedrake. I have something like the following:

u = Function(V)

v = TestFunction(V)

maximum = interpolate(0.5*(u
 + abs(u)), V)

F = v*(u + maximum)*dx

Best wishes,

Anna.