# JuMP problem get conflicting constraints when using small values

**URL:** <https://discourse.julialang.org/t/jump-problem-get-conflicting-constraints-when-using-small-values/79425>\
**Category:** Optimization (Mathematical)\
**Tags:** question, package, jump\
**Created:** [April 13, 2022, 9:48am UTC](https://discourse.julialang.org/t/jump-problem-get-conflicting-constraints-when-using-small-values/79425 "2022-04-13T09:48:23Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![this\_josh](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/this_josh/32/42679_2.png) [@this\_josh](https://discourse.julialang.org/u/this_josh)\
**Post date:** [April 13, 2022, 9:48am UTC](https://discourse.julialang.org/t/jump-problem-get-conflicting-constraints-when-using-small-values/79425/1 "2022-04-13T09:48:23Z")

</div>

In JuMP I’m having problems getting conflicting equality constraints when using small values

```nohighlight
using JuMP
using Gurobi

model = Model(Gurobi.Optimizer)
@variable(model, x)
a = 5e-5
b = 3e-3

@constraint(model, c1, x == 0)
@constraint(model, c2, 1 == (a * x^2 +b*x))

@objective(model, Min, x)

optimize!(model)

compute_conflict!(model)

MOI.get.(model, MOI.ConstraintConflictStatus(), c1)

MOI.get.(model, MOI.ConstraintConflictStatus(), c2)
# Without broadcasting
MOI.get.(model, MOI.ConstraintConflictStatus(), c2)

```

However, this gives (sorry for long traceback)

```nohighlight
julia> MOI.get.(model, MOI.ConstraintConflictStatus(), c1)
IN_CONFLICT::ConflictParticipationStatusCode = 1

julia> MOI.get.(model, MOI.ConstraintConflictStatus(), c2)
ERROR: ArgumentError: Gurobi.Optimizer does not support getting the attribute MathOptInterface.ConstraintConflictStatus().
Stacktrace:
  [1] get_fallback(model::Gurobi.Optimizer, attr::MathOptInterface.ConstraintConflictStatus, #unused#::MathOptInterface.ConstraintIndex{MathOptInterface.ScalarQuadraticFunction{Float64}, MathOptInterface.EqualTo{Float64}})
    @ MathOptInterface ~/.julia/packages/MathOptInterface/IIN1o/src/attributes.jl:361
  [2] get(model::Gurobi.Optimizer, attr::MathOptInterface.ConstraintConflictStatus, args::MathOptInterface.ConstraintIndex{MathOptInterface.ScalarQuadraticFunction{Float64}, MathOptInterface.EqualTo{Float64}})
    @ MathOptInterface ~/.julia/packages/MathOptInterface/IIN1o/src/attributes.jl:330
  [3] get(b::MathOptInterface.Bridges.LazyBridgeOptimizer{Gurobi.Optimizer}, attr::MathOptInterface.ConstraintConflictStatus, ci::MathOptInterface.ConstraintIndex{MathOptInterface.ScalarQuadraticFunction{Float64}, MathOptInterface.EqualTo{Float64}})
    @ MathOptInterface.Bridges ~/.julia/packages/MathOptInterface/IIN1o/src/Bridges/bridge_optimizer.jl:1239
  [4] get(model::MathOptInterface.Utilities.CachingOptimizer{MathOptInterface.Bridges.LazyBridgeOptimizer{Gurobi.Optimizer}, MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Utilities.Model{Float64}}}, attr::MathOptInterface.ConstraintConflictStatus, index::MathOptInterface.ConstraintIndex{MathOptInterface.ScalarQuadraticFunction{Float64}, MathOptInterface.EqualTo{Float64}})
    @ MathOptInterface.Utilities ~/.julia/packages/MathOptInterface/IIN1o/src/Utilities/cachingoptimizer.jl:862
  [5] _moi_get_result(::MathOptInterface.Utilities.CachingOptimizer{MathOptInterface.Bridges.LazyBridgeOptimizer{Gurobi.Optimizer}, MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Utilities.Model{Float64}}}, ::MathOptInterface.ConstraintConflictStatus, ::Vararg{Any})
    @ JuMP ~/.julia/packages/JuMP/lnUbA/src/JuMP.jl:1226
  [6] get(model::Model, attr::MathOptInterface.ConstraintConflictStatus, cr::ConstraintRef{Model, MathOptInterface.ConstraintIndex{MathOptInterface.ScalarQuadraticFunction{Float64}, MathOptInterface.EqualTo{Float64}}, ScalarShape})
    @ JuMP ~/.julia/packages/JuMP/lnUbA/src/JuMP.jl:1289
  [7] _broadcast_getindex_evalf
    @ ./broadcast.jl:670 [inlined]
  [8] _broadcast_getindex
    @ ./broadcast.jl:643 [inlined]
  [9] getindex
    @ ./broadcast.jl:597 [inlined]
 [10] copy
    @ ./broadcast.jl:875 [inlined]
 [11] materialize(bc::Base.Broadcast.Broadcasted{Base.Broadcast.DefaultArrayStyle{0}, Nothing, typeof(MathOptInterface.get), Tuple{Base.RefValue{Model}, Base.RefValue{MathOptInterface.ConstraintConflictStatus}, Base.RefValue{ConstraintRef{Model, MathOptInterface.ConstraintIndex{MathOptInterface.ScalarQuadraticFunction{Float64}, MathOptInterface.EqualTo{Float64}}, ScalarShape}}}})
    @ Base.Broadcast ./broadcast.jl:860
 [12] top-level scope
    @ REPL[16]:1

julia> # Without broadcasting
       MOI.get(model, MOI.ConstraintConflictStatus(), c2)
ERROR: ArgumentError: Gurobi.Optimizer does not support getting the attribute MathOptInterface.ConstraintConflictStatus().
Stacktrace:
 [1] get_fallback(model::Gurobi.Optimizer, attr::MathOptInterface.ConstraintConflictStatus, #unused#::MathOptInterface.ConstraintIndex{MathOptInterface.ScalarQuadraticFunction{Float64}, MathOptInterface.EqualTo{Float64}})
   @ MathOptInterface ~/.julia/packages/MathOptInterface/IIN1o/src/attributes.jl:361
 [2] get(model::Gurobi.Optimizer, attr::MathOptInterface.ConstraintConflictStatus, args::MathOptInterface.ConstraintIndex{MathOptInterface.ScalarQuadraticFunction{Float64}, MathOptInterface.EqualTo{Float64}})
   @ MathOptInterface ~/.julia/packages/MathOptInterface/IIN1o/src/attributes.jl:330
 [3] get(b::MathOptInterface.Bridges.LazyBridgeOptimizer{Gurobi.Optimizer}, attr::MathOptInterface.ConstraintConflictStatus, ci::MathOptInterface.ConstraintIndex{MathOptInterface.ScalarQuadraticFunction{Float64}, MathOptInterface.EqualTo{Float64}})
   @ MathOptInterface.Bridges ~/.julia/packages/MathOptInterface/IIN1o/src/Bridges/bridge_optimizer.jl:1239
 [4] get(model::MathOptInterface.Utilities.CachingOptimizer{MathOptInterface.Bridges.LazyBridgeOptimizer{Gurobi.Optimizer}, MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Utilities.Model{Float64}}}, attr::MathOptInterface.ConstraintConflictStatus, index::MathOptInterface.ConstraintIndex{MathOptInterface.ScalarQuadraticFunction{Float64}, MathOptInterface.EqualTo{Float64}})
   @ MathOptInterface.Utilities ~/.julia/packages/MathOptInterface/IIN1o/src/Utilities/cachingoptimizer.jl:862
 [5] _moi_get_result(::MathOptInterface.Utilities.CachingOptimizer{MathOptInterface.Bridges.LazyBridgeOptimizer{Gurobi.Optimizer}, MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Utilities.Model{Float64}}}, ::MathOptInterface.ConstraintConflictStatus, ::Vararg{Any})
   @ JuMP ~/.julia/packages/JuMP/lnUbA/src/JuMP.jl:1226
 [6] get(model::Model, attr::MathOptInterface.ConstraintConflictStatus, cr::ConstraintRef{Model, MathOptInterface.ConstraintIndex{MathOptInterface.ScalarQuadraticFunction{Float64}, MathOptInterface.EqualTo{Float64}}, ScalarShape})
   @ JuMP ~/.julia/packages/JuMP/lnUbA/src/JuMP.jl:1289
 [7] top-level scope
   @ REPL[17]:2

```

As you can see `c1` is fine, but `c2` encounters an error, I’ve also tried this with Ipopt.

Versions tried:  
Julia 1.7.2 (2022-02-06)  
[2e9cd046] Gurobi v0.10.1  
[4076af6c] JuMP v0.22.2

Julia 1.8.0-beta3 (2022-03-29)  
[2e9cd046] Gurobi v0.11.1  
[4076af6c] JuMP v1.0.0

---

<div class="post-metadata">

**Author:** ![blob](https://avatars.discourse-cdn.com/v4/letter/b/ebca7d/32.png) [@blob](https://discourse.julialang.org/u/blob)\
**Post date:** [April 13, 2022, 12:49pm UTC](https://discourse.julialang.org/t/jump-problem-get-conflicting-constraints-when-using-small-values/79425/2 "2022-04-13T12:49:50Z")

</div>

It seems that the problem is not with small values, but with the fact that the equality constraint is quadratic. This works:

```julia
using JuMP
using Gurobi

model = Model(Gurobi.Optimizer)
@variable(model, x)
a = 5e-5
b = 3e-3

@constraint(model, c1, x == 0)
@constraint(model, c2, 1 == (a * x +b*x))

@objective(model, Min, x)

optimize!(model)

compute_conflict!(model)

MOI.get.(model, MOI.ConstraintConflictStatus(), c1)

MOI.get.(model, MOI.ConstraintConflictStatus(), c2)

```

Gives:  
 ![image](https://global.discourse-cdn.com/julialang/original/3X/9/6/9667a7cc8a283a6fca60c9e424137bfba1c6137f.png)

Can Gurobi always support quadratic equality constraints? The example works with inequality:

```julia
using JuMP
using Gurobi

model = Model(Gurobi.Optimizer)
@variable(model, x)
a = 5e-5
b = 3e-3

@constraint(model, c1, x == 0)
@constraint(model, c2, 1 <= (a * x^2 +b*x))

@objective(model, Min, x)

optimize!(model)

compute_conflict!(model)

# MOI.get.(model, MOI.ConstraintConflictStatus(), c1)

MOI.get.(model, MOI.ConstraintConflictStatus(), c2)
# # Without broadcasting
MOI.get.(model, MOI.ConstraintConflictStatus(), c2)

```

and gives:

 ![image](https://global.discourse-cdn.com/julialang/original/3X/a/3/a3ac275447e476c43f99ef48f2a05a565a9e131a.png)

I am unfortunately not familiar with Gurobi enough to offer more help.

---

<div class="post-metadata">

**Author:** ![this\_josh](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/this_josh/32/42679_2.png) [@this\_josh](https://discourse.julialang.org/u/this_josh)\
**Post date:** [April 13, 2022, 1:18pm UTC](https://discourse.julialang.org/t/jump-problem-get-conflicting-constraints-when-using-small-values/79425/3 "2022-04-13T13:18:04Z")

</div>

Thanks for your response. Given the error message I hadn’t considered that it could be a Gurobi limitation. Reviewing but after reviewing the Gurobi documentation they state [“Quadratic equality constraints are always non-convex; they will give a `GRB_ERROR_QCP_EQUALITY_CONSTRAINT` error with default settings”](https://www.gurobi.com/documentation/9.0/refman/constraints.html) so it’s likely that’s causing the error. But why is JuMP giving the error message `ArgumentError: Gurobi.Optimizer does not support getting the attribute MathOptInterface.ConstraintConflictStatus().`

To further support your point if I set `c2` to a linear equality constraint `@constraint(model, c2, 1 == (a * x + b * x))` I’m able to get the conflict status.

It seems to me that my problem is I’m trying to do something Gurobi isn’t able to and that JuMP is giving a misleading error message.

---

<div class="post-metadata">

**Author:** ![blob](https://avatars.discourse-cdn.com/v4/letter/b/ebca7d/32.png) [@blob](https://discourse.julialang.org/u/blob)\
**Post date:** [April 13, 2022, 1:59pm UTC](https://discourse.julialang.org/t/jump-problem-get-conflicting-constraints-when-using-small-values/79425/4 "2022-04-13T13:59:22Z")

</div>

After some digging - it seems that JuMP doesn’t handle this particular conflict code. For your problem:  
 ![image](https://global.discourse-cdn.com/julialang/original/3X/7/a/7ad0c2cab9fb575f43cf802c9e7dae9300b3dc4c.png)

But JuMP seems to check:  
 ![image](https://global.discourse-cdn.com/julialang/original/3X/a/e/ae67440516d8c4ebd43626e516c86bd6d37004aa.png)

Then it throws an error that we see. Maybe open an issue with JuMP? Although someone more experienced may be more helpful

---

<div class="post-metadata">

**Author:** ![this\_josh](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/this_josh/32/42679_2.png) [@this\_josh](https://discourse.julialang.org/u/this_josh)\
**Post date:** [April 13, 2022, 2:04pm UTC](https://discourse.julialang.org/t/jump-problem-get-conflicting-constraints-when-using-small-values/79425/5 "2022-04-13T14:04:04Z")

</div>

Thanks, I’ll look at opening a ticket tomorrow.