These are AMPL scripts for nonlinear optimization problems from the paper:

 H. D. Mittelmann and H. Maurer, Solving Elliptic Control Problems with 
 Interior Point and SQP Methods: Control and State Constraints, 
 J. Comp. Appl. Math. 120, 175-195 (2000)


Characteristics of the problems
-------------------------------

Notation: RHS:   right-hand side of PDE
          BC:    boundary condition
          CC/SC: control/state constraints
          NOREG: no regularization (zero factor with integral over control)
          OP:    nature of optimization problem

Example 1:  heat conduction problem, boundary control, mixed BC,
               OP: convex QP

Example 2: same as Ex. 1, except NOREG, bang-bang control

Example 3: logistic type from population dynamics, nonconvex objective,
           homogeneous Neumann BC. CC/SC both active, OP: quadr. constr. QP

Example 4: same as Ex. 3, except NOREG, bang-bang control