Use OrderedDict

[bkraske]

Propose using ordered dictionaries for reproducibility/fixing of seeds (see branch: ordered_dictionaries)

Both expand! and branching_sim iterate over a dictionary (odict), which may not have consistent order (Why don’t Julia dictionaries preserve order?). As I understand it, the seeding scheme is dependent on these dictionaries having a consistent order. There are cases with unordered dictionaries where lower bound values may be different with the same seed due to the scenarios being evaluated in a different order. Using ordered dictionaries fixes this as evaluation order will be consistent.

Tests are currently passing, but I haven't compared benchmark times yet.

[zsunberg]

I went ahead and created a PR (#32 ) so that it is easier to see the changes.

We'll talk about this more in a meeting sometime.