Branch prioritisation functionality

[ieva-phasecraft]

Hi folks, I've spent a decent amount of time trying to figure out if there is any way whatsoever to have a custom variable prioritisation in the branch-and-bound algorithm. This seems like basic functionality that should be accessible but as far as I can tell there's no option to set or other easy way to include such a thing. If I just can't find it in the code/docs, please let me know!

Otherwise, is this something that's currently in the works? It would be extremely useful.

Thanks in advance!

[jajhall]

This is not a feature that we've considered adding, but it might not be difficult to do so, depending on what information users want: just the primal solution at the node just solved? In the original space, or the presolved space?

[Opt-Mucca]

I guess the biggest design choice internally (not including how to make the interface) would be: Do we then bypass our standard branching entirely if a user provides branching priorities or would we do our branching (mainly concerned with strong branching) and then ignore the candidate we've found and use the user provided order.

[ieva-phasecraft]

Amazing if it's easy to implement! I'd say it would make sense to give the user total control over the branching, since the whole point is often to test different branching strategies. I can envision there being an issue if some variables are given equal priority, in which case there could be some sort of strong branching fallback? For a first pass, the easiest thing would be to simply use the priorities given by the user entirely, with some tie-breaking strategy in case of equal priorities among variables. More complex, dynamic strategies might be fun and useful in the future but probably a lot more intensive to imeplement.