Inference problems

[ericphanson]

The tests don't finish on Julia 1.2+. Even locally with MOI v0.8 it seems slow, so it could be different than JuliaLang/julia#32167. I will try all platforms on Travis with compat set to MOI v0.8 to see if that helps.

[ericphanson]

CI: https://travis-ci.com/ericphanson/TravelingSalesmanExact.jl/builds/126257518

Stalls out on the big problem on 1.2+ even with MOI v0.8. It’s a bit weird because it can solve the smaller problems ok (I moved the big problem to the end to check).

[ericphanson]

One thing special about the problem that gets stuck is that verbose=true. So it could be a problem with unicode plots, for example. I set verbose=true for an earlier problem that was solved on all versions, so when CI finishes, that could show if it's a problem with verbose=true or with something else.

CI: https://travis-ci.com/ericphanson/TravelingSalesmanExact.jl/builds/126275354

[ericphanson]

I turned on verbose=true on a small problem also specified by cities so that plots are generated. That works fine (CI: https://travis-ci.com/ericphanson/TravelingSalesmanExact.jl/builds/126635605). It's weird because I don't see why it should be doing more type inference at this point-- it should've run basically the same code already, just on a smaller problem. (And JuMP converts everything to Float64, so the fact that the file uses integers shouldn't matter). I'll need to do some profiling / put in debug logging etc and figure out exactly where it gets stuck and what it's doing, but I don't have time right now.

[ericphanson]

Locally 6f6150a fixes the inference problems (CI in progress here. edit: passes). I really don't understand why, but it seems like the inference hang is deciding in the case of cities::Vector{Any} whether to call the method with signature

get_optimal_tour(cost::AbstractMatrix, with_optimizer =  get_default_optimizer(); verbose = false, symmetric = issymmetric(cost))

or the method with signature

get_optimal_tour(cities::AbstractVector, with_optimizer = get_default_optimizer(); verbose = false, distance = euclidean_distance, symmetric = true)

and it can't figure out which. Adding the type information for cities to be Vector{Vector{Int}} instead of Vector{Any} somehow lets it figure out which one to call much faster.