ENH Order of branches in BranchCollector

[ybilodid]

Hi!
My branching in Serpent looks like:

coef 12 0.0 0.1 0.5 1.0 3.0 5.0 7.0 10.0 12.0 14.0 17.0 21.0
5 ro09 ro08 ro07 ro06 ro05
3 cb0 cb1000 cb2000
3 tf500 tf900 tf1800
2 no_spa zirc
1 no_cr

after reading the .coe file and collecting branches with the BranchCollector, the collected states look like:

collector.states
(('ro05', 'ro06', 'ro07', 'ro08', 'ro09'),
('cb0', 'cb1000', 'cb2000'),
('tf1800', 'tf500', 'tf900'),
('no_spa', 'zirc'),
('no_cr',))

As you see, the order is different from the Serpent input card, which is especially not convenient in the case of fuel temperature.
As far as I understand, the order in collector.states coincide with order in collector.xsTables. Those tables are later printed into XS-library for a diffusion code, and the order of values is important.

Describe the solution you'd like
Would it be possible to keep the original branching order as in Serpent input (and, correspondently, in a .coe file)?

[drewejohnson]

After a brief dig, I think the problem is we sort the states based on their name

serpent-tools/src/serpentTools/xs.py

Line 496 in ec46c96

self._states = tuple([tuple(sorted(s)) for s in branchSets])

@ybilodid can you check if removing that sorted call accomplishes your goal? If so, I would ask that you (or whomever wants to pick this up) puts forward a PR with the change

[drewejohnson]

FWIW this would be an API incompatible change since we're changing how the public states attribute is structured.