"highs" solver doesn't seem to be installed by default

[bertrandkerres]

Hi,

I'm encountering an error following the default installation on Ubuntu (i.e. having libminizinc installed automatically and using "highs" as solver):

Config exception: no solver with tag highs found

The issue seems to be that the default artifact installation does not come with HiGHS bundled.

Artifact installation:

~/.julia/artifacts/0a92a5f3d4d8e6995368215f66510c82887bbf6e/bin$ ./minizinc --solvers
MiniZinc driver.
Available solver configurations:
  CPLEX <unknown version> (org.minizinc.mip.cplex, mip, float, api)
  Gurobi <unknown version> (org.minizinc.mip.gurobi, mip, float, api)
  SCIP <unknown version> (org.minizinc.mip.scip, mip, float, api)
  Xpress <unknown version> (org.minizinc.mip.xpress, mip, float, api)
Search path for solver configurations:
  /home/bertrand/.julia/artifacts/0a92a5f3d4d8e6995368215f66510c82887bbf6e/share/minizinc/solvers
  /usr/local/share/minizinc/solvers
  /usr/share/minizinc/solvers

Standalone installation (ie. via snap):

$ minizinc --solvers
MiniZinc driver.
Available solver configurations:
  Chuffed 0.13.2 (org.chuffed.chuffed, cp, lcg, int)
  COIN-BC 2.10.12/1.17.10 (org.minizinc.mip.coin-bc, mip, float, api, osicbc, coinbc, cbc)
  CPLEX <unknown version> (org.minizinc.mip.cplex, mip, float, api)
  findMUS 0.7.0 (org.minizinc.findmus)
  Gecode 6.3.0 (org.gecode.gecode, default solver, cp, int, float, set, restart)
  Gecode Gist 6.3.0 (org.gecode.gist, cp, int, float, set, restart)
  Globalizer 0.1.7.2 (org.minizinc.globalizer, experimental, tool)
  Gurobi <unknown version> (org.minizinc.mip.gurobi, mip, float, api)
  HiGHS 1.9.0 (org.minizinc.mip.highs, mip, float, api, highs)
  OR Tools CP-SAT 9.12.4544 (cp-sat, cp-sat, cp, lcg, int)
  SCIP <unknown version> (org.minizinc.mip.scip, mip, float, api)
  Xpress <unknown version> (org.minizinc.mip.xpress, mip, float, api)
Search path for solver configurations:
  /snap/minizinc/1157/share/minizinc/solvers
  /usr/local/share/minizinc/solvers
  /usr/share/minizinc/solvers

MWE:

(@v1.11) pkg> activate --temp
(jl_g25dKx) pkg> add JuMP MiniZinc HiGHS

# Then run the example from the README
using JuMP
import MiniZinc
model = Model(() -> MiniZinc.Optimizer{Float64}("highs"))
@variable(model, 1 <= x[1:3] <= 3, Int)
@constraint(model, x in MOI.AllDifferent(3))
@objective(model, Max, sum(i * x[i] for i in 1:3))
optimize!(model)
@show value.(x)

Version info:

> versioninfo()
Julia Version 1.11.6
Commit 9615af0f269 (2025-07-09 12:58 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 28 × Intel(R) Core(TM) i7-14700KF
  WORD_SIZE: 64
  LLVM: libLLVM-16.0.6 (ORCJIT, alderlake)
Threads: 1 default, 0 interactive, 1 GC (on 28 virtual cores)
Environment:
  JULIA_PKG_SERVER = juliahub.com

[odow]

Pkg.status()? Do you have an older version of MiniZinc.jl?

[odow]

I can't reproduce:

(mzn) pkg> st
Status `/private/tmp/mzn/Project.toml`
  [3677d96b] MiniZinc_jll v2.8.5+0

julia> import MiniZinc_jll

julia> MiniZinc_jll.artifact_dir
"/Users/odow/.julia/artifacts/3075df7c2eb9064d5e52c61c22cdc230d875715b"

shell> /Users/odow/.julia/artifacts/3075df7c2eb9064d5e52c61c22cdc230d875715b/bin/minizinc --solvers
MiniZinc driver.
Available solver configurations:
  CPLEX <unknown version> (org.minizinc.mip.cplex, mip, float, api)
  Gurobi <unknown version> (org.minizinc.mip.gurobi, mip, float, api)
  HiGHS <unknown version> (org.minizinc.mip.highs, mip, float, api, highs)
  SCIP <unknown version> (org.minizinc.mip.scip, mip, float, api)
  Xpress <unknown version> (org.minizinc.mip.xpress, mip, float, api)
Search path for solver configurations:
  /Users/odow/.julia/artifacts/3075df7c2eb9064d5e52c61c22cdc230d875715b/share/minizinc/solvers
  /usr/share/minizinc/solvers
  /opt/homebrew/share/minizinc/solvers

Please ensure that you have the latest version installed.

Your artefact hash is the same as #88, which seems to suggest that you have also installed an old version.

[odow]

Pre-emptively closing this because it doesn't seem to be a bug in MiniZinc.jl.

If you still have an issue after updating your packages, please comment below and I can re-open to investigate further.

[bertrandkerres]

You are correct, it was indeed an old version of MiniZinc (0.2.1) that got installed. Forcing MiniZinc to its latest version made it work.

The incompatibility seems to come from HiGHS.jl, which got downgraded when I upgraded MiniZinc:

(jl_ygaAIg) pkg> add MiniZinc@0.3.12
   Resolving package versions...
   Installed Chuffed_jll ── v0.13.2+0
   Installed MiniZinc_jll ─ v2.8.5+0
   Installed HiGHS_jll ──── v1.7.1+0
   Installed MiniZinc ───── v0.3.12
   Installed HiGHS ──────── v1.17.0
  Downloaded artifact: MiniZinc
  Downloaded artifact: Chuffed
  Downloaded artifact: HiGHS
    Updating `/tmp/jl_ygaAIg/Project.toml`
⌃ [87dc4568] ↓ HiGHS v1.19.0 ⇒ v1.17.0
  [a7f392d2] ↑ MiniZinc v0.2.1 ⇒ v0.3.12

(jl_ygaAIg) pkg> st -m --outdated
Status `/tmp/jl_ygaAIg/Manifest.toml`
⌃ [87dc4568] HiGHS v1.17.0 (<v1.19.0)
⌅ [aea7be01] PrecompileTools v1.2.1 (<v1.3.3): julia
⌅ [8fd58aa0] HiGHS_jll v1.7.1+0 (<v1.11.0+1): HiGHS, MiniZinc_jll

For me personally, it's OK to have HiGHS in a slightly lower version so it's up to you how important you see this incompatibility. Either way, thanks for your help and all the work you're doing with the JuMP ecosystem :) 👏

[odow]

Ah, okay, it's because of

https://github.com/JuliaPackaging/Yggdrasil/blob/056c7be0b102fe81087b902e5303ac7cb1b745d6/M/MiniZinc/build_tarballs.jl#L49-L51

I'll see if I can update it: JuliaPackaging/Yggdrasil#12135