A parallel example using HiGHS was recently published here : Parallelism · JuMP

However, when I change the model used to something that requires several iterations instead of just `presolve`

it prints a bunch of `Iteration total error ${} + ${} + ${} + ${} = ${} != ${}`

messages.

MWE : I’ve found this instance to be fairly reliable on my system, but potentially the seed may influence your results. Typically the larger `N`

is, the more messages are printed.

Julia Version 1.8.5

Commit 17cfb8e65ea (2023-01-08 06:45 UTC)

Platform Info:

OS: macOS (x86_64-apple-darwin21.4.0)HiGHS v1.5.0

JuMP v1.9.0

```
# Multi-threading the right way from https://jump.dev/JuMP.jl/stable/tutorials/algorithms/parallelism/#With-multi-threading
using JuMP
using HiGHS
solutions = Pair{Int,Float64}[]
my_lock = Threads.ReentrantLock()
# Copy of multi-objective knapsack problem from https://jump.dev/JuMP.jl/stable/tutorials/linear/multi_objective_knapsack/
# With changed input data and simplified objective to remove dependence on MultiObjectiveAlgorithms
function generate_model()
profit = [79, 91, 79, 66, 72, 83, 65, 93, 59, 94, 82, 55, 74, 68, 57, 62, 62]
desire = [99, 62, 95, 77, 55, 66, 77, 88, 59, 61, 86, 68, 50, 82, 51, 89, 56]
weight = [85, 53, 72, 56, 75, 51, 74, 62, 61, 54, 93, 56, 52, 53, 66, 80, 64]
capacity = 900
N = length(profit)
model = Model(HiGHS.Optimizer)
@variable(model, x[1:N], Bin)
@constraint(model, sum(weight[i] * x[i] for i in 1:N) <= capacity)
@expression(model, profit_expr, sum(profit[i] * x[i] for i in 1:N))
@expression(model, desire_expr, sum(desire[i] * x[i] for i in 1:N))
@objective(model, Max, profit_expr + desire_expr)
set_silent(model)
optimize!(model)
solution_summary(model)
return argmax(i -> objective_value(model; result = i), 1:result_count(model))
end
Threads.@threads for i in 1:Threads.nthreads()
@show Threads.threadid()
res = generate_model()
Threads.lock(my_lock) do
push!(solutions, i => res)
end
end
@show solutions
```

The only mention I can find of HiGHS being thread-safe is this docstring : Docstrings · HiGHS_jll.jl

I guess the question is : is HiGHS thread-safe? Is this the intended behaviour? Is there are problem with the JuMP doc examples or my MWE?