Benchmark VectorDomain

[dourouc05]

For ConstraintSolver.jl's VectorDomain, @Wikunia uses a matrix, while this package's VectorDomain uses a set of vectors. We should test the performance of both approaches before making a final decision on the best way to represent this set, but also brainstorm about the pros and cons of each approach.

Matrix

Pros:

• easy to enforce that each element has the same size (Julia does it when the user builds a matrix)

Cons:

• enforces some kind of order between the elements, while this is not really required

Set of vectors

Pros:

• no order between the elements

Cons:

• the constructor must enforce that each element has the same size