lots of intersect type errors from `copy_to`

[lkapelevich]

This should probably be a Julia issue, but it might be worth starting here.
On Julia master, if I run:

using JuMP, Hypatia
MOIU = MOI.Utilities
model = Model(Hypatia.Optimizer)
backend = JuMP.backend(model)
MOIU.attach_optimizer(backend)
m = backend.optimizer.model
indexmap = MOI.copy_to(m.optimizer, m.model_cache, copy_names = false)

I get a very long error:

Internal error: encountered unexpected error in runtime:
StackOverflowError()
intersect at /home/thoth/julia/src/subtype.c:2944
intersect at /home/thoth/julia/src/subtype.c:3044
intersect at /home/thoth/julia/src/subtype.c:3060
intersect_unionall_ at /home/thoth/julia/src/subtype.c:2538
intersect_unionall at /home/thoth/julia/src/subtype.c:2587
intersect at /home/thoth/julia/src/subtype.c:3096
intersect_all at /home/thoth/julia/src/subtype.c:3186
intersect_aside at /home/thoth/julia/src/subtype.c:2092 [inlined]
intersect_aside at /home/thoth/julia/src/subtype.c:2079 [inlined]
intersect_var at /home/thoth/julia/src/subtype.c:2306
intersect at /home/thoth/julia/src/subtype.c:3044
intersect at /home/thoth/julia/src/subtype.c:3044
intersect at /home/thoth/julia/src/subtype.c:3044
intersect at /home/thoth/julia/src/subtype.c:3044
intersect at /home/thoth/julia/src/subtype.c:3060
intersect_unionall_ at /home/thoth/julia/src/subtype.c:2538
intersect_unionall at /home/thoth/julia/src/subtype.c:2587
intersect at /home/thoth/julia/src/subtype.c:3096
intersect_all at /home/thoth/julia/src/subtype.c:3186
intersect_aside at /home/thoth/julia/src/subtype.c:2092 [inlined]
intersect_aside at /home/thoth/julia/src/subtype.c:2079 [inlined]
intersect_var at /home/thoth/julia/src/subtype.c:2306
intersect at /home/thoth/julia/src/subtype.c:3044
intersect at /home/thoth/julia/src/subtype.c:3044
intersect at /home/thoth/julia/src/subtype.c:3044
intersect at /home/thoth/julia/src/subtype.c:3044
intersect at /home/thoth/julia/src/subtype.c:3060
intersect_unionall_ at /home/thoth/julia/src/subtype.c:2538
intersect_unionall at /home/thoth/julia/src/subtype.c:2587
intersect at /home/thoth/julia/src/subtype.c:3096
intersect_all at /home/thoth/julia/src/subtype.c:3186
intersect_aside at /home/thoth/julia/src/subtype.c:2092 [inlined]
intersect_aside at /home/thoth/julia/src/subtype.c:2079 [inlined]
intersect_var at /home/thoth/julia/src/subtype.c:2306
intersect at /home/thoth/julia/src/subtype.c:3044
intersect at /home/thoth/julia/src/subtype.c:3044
intersect at /home/thoth/julia/src/subtype.c:3044
intersect at /home/thoth/julia/src/subtype.c:3044
intersect at /home/thoth/julia/src/subtype.c:3060
...etc

This is on Julia master (haven't triggered it on 1.6), Ubuntu, and JuMP v0.21.6

[odow]

I guess you distilled this case from a larger model calling optimize!?

Does it happen with something like this?

using Hypatia
const MOI = Hypatia.MOI
model = Hypatia.Optimizer()
cache = MOI.Utilities.UniversalFallback(MOI.Utilities.Model{Float64}())
MOI.copy_to(model, cache, copy_names = false)

What about on MathOptInterface#master?

[lkapelevich]

Yes, the errors are from calling optimize! on any model. Your code snippet triggered the same error, on MathOptInterface#master as well.

[odow]

What if you remove the UniversalFallback? And copy_names?

[lkapelevich]

All those still trigger the errors.
New finding- from Atom the errors don't happen, and I think the difference might be that JULIA_NUM_THREADS is set now it's happening from Atom too

[odow]

It's probably worth opening a Julia issue. Given that things are okay on 1.6, I don't think it's our problem.