How to add a new problem

• How to add a new problem
• • Find a description
  • Create a new file with an empty template
  • Code the model and the solution
  • Add a unit test

Find a description

Let us assume you want to add a planar orbital time minimisation transfer problem from space mechanics. This problem will be described by a Description, cf. CTBase.jl, following the nomenclature given in src/CTProblems.jl. For instance:

(:orbital, :time, :x_dim_4, u_dim_2, :mayer)

Nomenclature:

• :name_of_the_problem, and other symbols for a clear description
• if the objective is classical, you can mention it: :time, :energy, :consumption

then

• dimensions: :x_dim_1, :x_dim_2... :u_dim_1, :u_dim_2...
• objective type: :lagrange, :mayer, :bolza
• constraint arc (active on the solution): :x_cons, :u_cons, :mixed_constraint
• singular arc (on the solution): :singular_arc
• differentiability: :non_diff_wrt_x, :non_diff_wrt_u

Create a new file with an empty template

You have to create a new file in the directory src/problems. For instance:

touch src/problems/orbital_planar.jl

Add it to the list of problems, in src/CTProblems.jl:

list_of_problems_files = [
    "...",
    "orbital_planar.jl",
]

Then, you can write into this file the following empty template.

EXAMPLE=(:orbital, :time, :x_dim_4, u_dim_2, :mayer)

@eval function OCPDef{EXAMPLE}()

    # the description
    title = "Planar orbital transfer"

    # the model: to be completed
    ocp = Model()

    # the solution: to be completed
    sol = OptimalControlSolution()

    sol.message = "structure: ..."  # Give the structure as an additional info. 
                                    # For instance, B+S for positive bang followed
                                    # a by singular arc.
                                    
    sol.infos[:resolution] = :numerical # Either :numerical or :analytical
                                        # depending on how you get the solution

    #
    return OptimalControlProblem(title, ocp, sol)

end

Code the model and the solution

For now, you have to complete the model and the solution. You can take example from the already existing problems in src/problems. See also the documentation of CTBase.jl. Try to fulfill all the fields of OptimalControlSolution.

Add a unit test

To complete the process, a unit test must be created. See the test directory for examples. The unit test should be written by a different person to robustify the process.