### Author:  [@slwu89](https://discourse.julialang.org/u/slwu89)
#### Post date: [July 3, 2024, 3:54pm UTC](https://discourse.julialang.org/t/question-about-when-minizinc-will-return-feasible-solutions/116595/1 "2024-07-03T15:54:20Z")
Hi all. I have a question about the following MiniZinc model. I am able to give a feasible solution with `primal_feasibility_report` but nothing is found by the solver. I’m aware of the silliness of the presented model, this is a minimal example of this behavior extracted from a larger model. Thanks!
```julia
jumpmod = GenericModel{Int}(() -> MiniZinc.Optimizer{Int}("chuffed"))
x = @variable(
jumpmod,
x[i=1:3],
Bin
)
@constraint(jumpmod, sum(x[[1]]) == 1)
@constraint(jumpmod, sum(x[[2]]) == 1)
@constraint(jumpmod, sum(x[[3]]) == 1)
optimize!(jumpmod)
value.(x)
primal_feasibility_report(jumpmod, Dict(x[1] => 1, x[2] => 1, x[3] => 1))
```
---
### Author:  [@blegat](https://discourse.julialang.org/u/blegat)
#### Post date: [July 4, 2024, 8:02am UTC](https://discourse.julialang.org/t/question-about-when-minizinc-will-return-feasible-solutions/116595/2 "2024-07-04T08:02:38Z")
I just tried your code and I get
```julia
julia> solution_summary(jumpmod)
* Solver : MiniZinc
* Status
Result count : 1
Termination status : OPTIMAL
Message from the solver:
"SATISFIABLE"
* Candidate solution (result #1)
Primal status : FEASIBLE_POINT
Dual status : NO_SOLUTION
Objective value : 0
* Work counters
Solve time (sec) : 6.42982e-01
julia> value.(x)
3-element Vector{Int64}:
1
1
1
```
What does `solution_summary` prints for you ?
---
### Author:  [@slwu89](https://discourse.julialang.org/u/slwu89)
#### Post date: [July 4, 2024, 3:21pm UTC](https://discourse.julialang.org/t/question-about-when-minizinc-will-return-feasible-solutions/116595/3 "2024-07-04T15:21:46Z")
Thank you for helping check @blegat. For reference, I’m on JuMP v1.22.2 and MiniZinc v0.3.9. The below code is as close as possible to what is going on in my actual use case, I show the example and the result from `solution_summary` below.
```julia
using JuMP, MiniZinc, DataFrames
workflow = DataFrame(Step=[1,2,3],ChoiceSets=[missing,missing,missing])
jumpmod = GenericModel{Int}(() -> MiniZinc.Optimizer{Int}("chuffed"))
set_attribute(jumpmod, MOI.SolutionLimit(), 10)
x = @variable(
jumpmod,
x[axes(workflow,1)],
Bin
)
@constraint(jumpmod, sum(x[[1]]) == 1)
@constraint(jumpmod, sum(x[[2]]) == 1)
@constraint(jumpmod, sum(x[[3]]) == 1)
optimize!(jumpmod)
solution_summary(jumpmod)
value.(x)
```
Calling summary:
```julia
julia> solution_summary(jumpmod)
* Solver : MiniZinc
* Status
Result count : 0
Termination status : OTHER_ERROR
Message from the solver:
"=====ERROR=====
Warning: included file "count.mzn" overrides a global constraint file from the standard library. This is deprecated. For a solver-specific redefinition of a global constraint, override "fzn_.mzn" instead.
/workspace/srcdir/chuffed/chuffed/core/engine.cpp:419: Not yet supported
"
* Candidate solution (result #1)
Primal status : NO_SOLUTION
Dual status : NO_SOLUTION
* Work counters
Solve time (sec) : 4.46848e-01
```
---
### Author:  [@slwu89](https://discourse.julialang.org/u/slwu89)
#### Post date: [July 10, 2024, 2:50pm UTC](https://discourse.julialang.org/t/question-about-when-minizinc-will-return-feasible-solutions/116595/4 "2024-07-10T14:50:01Z")
@blegat did you have a chance to take a look at the error I was getting?
---
### Author:  [@odow](https://discourse.julialang.org/u/odow)
#### Post date: [July 13, 2024, 12:39am UTC](https://discourse.julialang.org/t/question-about-when-minizinc-will-return-feasible-solutions/116595/5 "2024-07-13T00:39:22Z")
> /workspace/srcdir/chuffed/chuffed/core/engine.cpp:419: Not yet supported
I can reproduce, but I assume this is a bug in Chuffed where you have a degenerate solution with `x = 1` but you are asking for multiple solutions? There does’t seem to be any issue in MiniZinc.jl
---
### Author:  [@slwu89](https://discourse.julialang.org/u/slwu89)
#### Post date: [July 13, 2024, 4:55am UTC](https://discourse.julialang.org/t/question-about-when-minizinc-will-return-feasible-solutions/116595/6 "2024-07-13T04:55:24Z")
Thanks. I was curious why it was giving that error and not able to return the single feasible solution despite being degenerate. But it seems like it worked for @blegat based on his previous response?
---
### Author:  [@remi-garcia](https://discourse.julialang.org/u/remi-garcia)
#### Post date: [July 15, 2024, 6:03am UTC](https://discourse.julialang.org/t/question-about-when-minizinc-will-return-feasible-solutions/116595/7 "2024-07-15T06:03:23Z")
Your first example works for me but not the second one.
If I remove from the second example `set_attribute(jumpmod, MOI.SolutionLimit(), 10)`, it works. If I add it to the first example, it fails.
~~The error seems to come from chuffed which includes some `count.mzn` file when counting solutions.~~
HiGHS fails with a different error message:
`minizinc: Unrecognized option or bad format `–num-solutions’`
---
### Author:  [@remi-garcia](https://discourse.julialang.org/u/remi-garcia)
#### Post date: [July 15, 2024, 7:34am UTC](https://discourse.julialang.org/t/question-about-when-minizinc-will-return-feasible-solutions/116595/8 "2024-07-15T07:34:00Z")
I believe that the issue is from the current artifact available for chuffed (v0.10.4): [Yggdrasil/C/Chuffed/build\_tarballs.jl at master · JuliaPackaging/Yggdrasil · GitHub](https://github.com/JuliaPackaging/Yggdrasil/blob/master/C/Chuffed/build_tarballs.jl)
It should be possible to update the `build_tarballs.jl` to work with the latest version (0.13.2): [Tags · chuffed/chuffed · GitHub](https://github.com/chuffed/chuffed/tags)
I am trying to do so: [[Chuffed] Update from v0.10.4 to v0.13.2 by remi-garcia · Pull Request #9082 · JuliaPackaging/Yggdrasil · GitHub](https://github.com/JuliaPackaging/Yggdrasil/pull/9082)
---
### Author:  [@slwu89](https://discourse.julialang.org/u/slwu89)
#### Post date: [July 15, 2024, 3:09pm UTC](https://discourse.julialang.org/t/question-about-when-minizinc-will-return-feasible-solutions/116595/9 "2024-07-15T15:09:24Z")
Thank you for the help @remi-garcia. It’s nice that this also led to finding some fixes that need to be applied in chuffed itself!
---
### Author:  [@odow](https://discourse.julialang.org/u/odow)
#### Post date: [July 15, 2024, 10:59pm UTC](https://discourse.julialang.org/t/question-about-when-minizinc-will-return-feasible-solutions/116595/10 "2024-07-15T22:59:33Z")
Agree that this is an upstream issue in Chuffed, and that updating to the latest version might fix it.
HiGHS fails because it doesn’t support returning multiple solutions.
---
### Author:  [@remi-garcia](https://discourse.julialang.org/u/remi-garcia)
#### Post date: [July 16, 2024, 8:20am UTC](https://discourse.julialang.org/t/question-about-when-minizinc-will-return-feasible-solutions/116595/11 "2024-07-16T08:20:14Z")
New artifact is available 🎉 . MiniZinc compat with chuffed is currently “=0.10.4”.
@odow Could you update the Project.toml? I don’t know which way is best for MiniZinc.jl 🙂
---
### Author:  [@odow](https://discourse.julialang.org/u/odow)
#### Post date: [July 16, 2024, 8:23am UTC](https://discourse.julialang.org/t/question-about-when-minizinc-will-return-feasible-solutions/116595/12 "2024-07-16T08:23:42Z")
See [Update to Chuffed\_jll@0.13.2 by odow · Pull Request #74 · jump-dev/MiniZinc.jl · GitHub](https://github.com/jump-dev/MiniZinc.jl/pull/74)
---
### Author:  [@remi-garcia](https://discourse.julialang.org/u/remi-garcia)
#### Post date: [July 22, 2024, 6:06am UTC](https://discourse.julialang.org/t/question-about-when-minizinc-will-return-feasible-solutions/116595/13 "2024-07-22T06:06:17Z")
It works with the last MiniZinc.jl release, @slwu89 .
```julia
julia> using JuMP, MiniZinc
julia> jumpmod = GenericModel{Int}(() -> MiniZinc.Optimizer{Int}("chuffed"))
A JuMP Model
Feasibility problem with:
Variables: 0
Model mode: AUTOMATIC
CachingOptimizer state: EMPTY_OPTIMIZER
Solver name: MiniZinc
julia> x = @variable(
jumpmod,
x[i=1:3],
Bin
)
3-element Vector{GenericVariableRef{Int64}}:
x[1]
x[2]
x[3]
julia> @constraint(jumpmod, sum(x[[1]]) == 1)
x[1] = 1
julia> @constraint(jumpmod, sum(x[[2]]) == 1)
x[2] = 1
julia> @constraint(jumpmod, sum(x[[3]]) == 1)
x[3] = 1
julia> set_attribute(jumpmod, MOI.SolutionLimit(), 10)
julia> optimize!(jumpmod)
julia> solution_summary(jumpmod)
* Solver : MiniZinc
* Status
Result count : 1
Termination status : OPTIMAL
Message from the solver:
"SATISFIABLE"
* Candidate solution (result #1)
Primal status : FEASIBLE_POINT
Dual status : NO_SOLUTION
Objective value : 0
* Work counters
Solve time (sec) : 5.46820e-01
```