# AmplNLWriter : supports\_constraint() is ambiguous in MathOptInterface

**URL:** <https://discourse.julialang.org/t/amplnlwriter-supports-constraint-is-ambiguous-in-mathoptinterface/31390>\
**Category:** Optimization (Mathematical)\
**Created:** [November 22, 2019, 3:04pm UTC](https://discourse.julialang.org/t/amplnlwriter-supports-constraint-is-ambiguous-in-mathoptinterface/31390 "2019-11-22T15:04:12Z")\
**Posts on this page:** 10\
**Page:** 1

<div class="post-metadata">

**Author:** ![dmit](https://avatars.discourse-cdn.com/v4/letter/d/f1d935/32.png) [@dmit](https://discourse.julialang.org/u/dmit)\
**Post date:** [November 22, 2019, 3:04pm UTC](https://discourse.julialang.org/t/amplnlwriter-supports-constraint-is-ambiguous-in-mathoptinterface/31390/1 "2019-11-22T15:04:12Z")

</div>

Hi there you beautiful people!

Complete Julia newbie here, so the problem I’m having may be trivial.  
I’m trying to use Couenne optimizer with [AmplNLWriter](https://github.com/JuliaOpt/AmplNLWriter.jl) interface, but can’t make it work.  
Here’s my hello-world level model (that works with Juniper for example).

```julia
using JuMP, AmplNLWriter
model = Model(with_optimizer(AmplNLWriter.Optimizer, "/usr/local/bin/couenne"))
@variable(model, 0 <= x <= 2 )
@variable(model, 0 <= y <= 30 )
@objective(model, Max, 5x + 3*y )
@constraint(model, 1x + 5y <= 3.0 )
status = optimize!(model)

```

I get an error when I try to run it:

```julia
ERROR: LoadError: MethodError: supports_constraint(::AmplNLWriter.InnerModel{Float64}, ::Type{MathOptInterface.SingleVariable}, ::Type{MathOptInterface.GreaterThan{Float64}}) is ambiguous. Candidates:
  supports_constraint(model::AmplNLWriter.InnerModel{#76#T}, ::Type{#s21} where #s21<:Union{MathOptInterface.SingleVariable, MathOptInterface.ScalarAffineFunction{#76#T}, MathOptInterface.ScalarQuadraticFunction{#76#T}}, ::Type{#s20} where #s20<:Union{MathOptInterface.Integer, MathOptInterface.ZeroOne, MathOptInterface.EqualTo{#76#T}, MathOptInterface.GreaterThan{#76#T}, MathOptInterface.Interval{#76#T}, MathOptInterface.LessThan{#76#T}}) where #76#T in AmplNLWriter at /home/dmitry/.julia/packages/MathOptInterface/A2UPd/src/Utilities/model.jl:1020
  supports_constraint(::MathOptInterface.Utilities.AbstractModel{T}, ::Type{MathOptInterface.SingleVariable}, ::Type{#s118} where #s118<:Union{MathOptInterface.Integer, MathOptInterface.ZeroOne, MathOptInterface.EqualTo{T}, MathOptInterface.GreaterThan{T}, MathOptInterface.Interval{T}, MathOptInterface.LessThan{T}, MathOptInterface.Semicontinuous{T}, MathOptInterface.Semiinteger{T}}) where T in MathOptInterface.Utilities at /home/dmitry/.julia/packages/MathOptInterface/A2UPd/src/Utilities/model.jl:489
Possible fix, define
  supports_constraint(::AmplNLWriter.InnerModel{T}, ::Type{MathOptInterface.SingleVariable}, ::Type{#s118} where #s118<:Union{MathOptInterface.Integer, MathOptInterface.ZeroOne, MathOptInterface.EqualTo{T}, MathOptInterface.GreaterThan{T}, MathOptInterface.Interval{T}, MathOptInterface.LessThan{T}, MathOptInterface.Semicontinuous{T}, MathOptInterface.Semiinteger{T}})
Stacktrace:
 [1] supports_constraint(::MathOptInterface.Utilities.UniversalFallback{AmplNLWriter.InnerModel{Float64}}, ::Type{MathOptInterface.SingleVariable}, ::Type{MathOptInterface.GreaterThan{Float64}}) at /home/dmitry/.julia/packages/AmplNLWriter/V1gW5/src/MOI_wrapper.jl:34
 [2] is_bridged(::MathOptInterface.Bridges.LazyBridgeOptimizer{MathOptInterface.Utilities.UniversalFallback{AmplNLWriter.InnerModel{Float64}}}, ::Type{MathOptInterface.GreaterThan{Float64}}) at /home/dmitry/.julia/packages/MathOptInterface/A2UPd/src/Bridges/lazy_bridge_optimizer.jl:385
 [3] add_constrained_variable(::MathOptInterface.Bridges.LazyBridgeOptimizer{MathOptInterface.Utilities.UniversalFallback{AmplNLWriter.InnerModel{Float64}}}, ::MathOptInterface.GreaterThan{Float64}) at /home/dmitry/.julia/packages/MathOptInterface/A2UPd/src/Bridges/bridge_optimizer.jl:1160
 [4] copy_single_variable(::MathOptInterface.Bridges.LazyBridgeOptimizer{MathOptInterface.Utilities.UniversalFallback{AmplNLWriter.InnerModel{Float64}}}, ::MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Utilities.Model{Float64}}, ::MathOptInterface.Utilities.IndexMap, ::Type{MathOptInterface.GreaterThan{Float64}}) at /home/dmitry/.julia/packages/MathOptInterface/A2UPd/src/Utilities/copy.jl:203
 [5] (::getfield(MathOptInterface.Utilities, Symbol("##115#123")){MathOptInterface.Bridges.LazyBridgeOptimizer{MathOptInterface.Utilities.UniversalFallback{AmplNLWriter.InnerModel{Float64}}},MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Utilities.Model{Float64}},MathOptInterface.Utilities.IndexMap})(::Type) at ./none:0
 [6] iterate(::Base.Generator{Array{DataType,1},getfield(MathOptInterface.Utilities, Symbol("##115#123")){MathOptInterface.Bridges.LazyBridgeOptimizer{MathOptInterface.Utilities.UniversalFallback{AmplNLWriter.InnerModel{Float64}}},MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Utilities.Model{Float64}},MathOptInterface.Utilities.IndexMap}}) at ./generator.jl:47
 [7] collect(::Base.Generator{Array{DataType,1},getfield(MathOptInterface.Utilities, Symbol("##115#123")){MathOptInterface.Bridges.LazyBridgeOptimizer{MathOptInterface.Utilities.UniversalFallback{AmplNLWriter.InnerModel{Float64}}},MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Utilities.Model{Float64}},MathOptInterface.Utilities.IndexMap}}) at ./array.jl:606
 [8] default_copy_to(::MathOptInterface.Bridges.LazyBridgeOptimizer{MathOptInterface.Utilities.UniversalFallback{AmplNLWriter.InnerModel{Float64}}}, ::MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Utilities.Model{Float64}}, ::Bool) at /home/dmitry/.julia/packages/MathOptInterface/A2UPd/src/Utilities/copy.jl:325
 [9] #automatic_copy_to#97(::Bool, ::typeof(MathOptInterface.Utilities.automatic_copy_to), ::MathOptInterface.Bridges.LazyBridgeOptimizer{MathOptInterface.Utilities.UniversalFallback{AmplNLWriter.InnerModel{Float64}}}, ::MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Utilities.Model{Float64}}) at /home/dmitry/.julia/packages/MathOptInterface/A2UPd/src/Utilities/copy.jl:15
 [10] (::getfield(MathOptInterface.Utilities, Symbol("#kw##automatic_copy_to")))(::NamedTuple{(:copy_names,),Tuple{Bool}}, ::typeof(MathOptInterface.Utilities.automatic_copy_to), ::MathOptInterface.Bridges.LazyBridgeOptimizer{MathOptInterface.Utilities.UniversalFallback{AmplNLWriter.InnerModel{Float64}}}, ::MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Utilities.Model{Float64}}) at ./none:0
 [11] #copy_to#3(::Base.Iterators.Pairs{Symbol,Bool,Tuple{Symbol},NamedTuple{(:copy_names,),Tuple{Bool}}}, ::typeof(MathOptInterface.copy_to), ::MathOptInterface.Bridges.LazyBridgeOptimizer{MathOptInterface.Utilities.UniversalFallback{AmplNLWriter.InnerModel{Float64}}}, ::MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Utilities.Model{Float64}}) at /home/dmitry/.julia/packages/MathOptInterface/A2UPd/src/Bridges/bridge_optimizer.jl:254
 [12] (::getfield(MathOptInterface, Symbol("#kw##copy_to")))(::NamedTuple{(:copy_names,),Tuple{Bool}}, ::typeof(MathOptInterface.copy_to), ::MathOptInterface.Bridges.LazyBridgeOptimizer{MathOptInterface.Utilities.UniversalFallback{AmplNLWriter.InnerModel{Float64}}}, ::MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Utilities.Model{Float64}}) at ./none:0
 [13] attach_optimizer(::MathOptInterface.Utilities.CachingOptimizer{MathOptInterface.AbstractOptimizer,MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Utilities.Model{Float64}}}) at /home/dmitry/.julia/packages/MathOptInterface/A2UPd/src/Utilities/cachingoptimizer.jl:149
 [14] optimize!(::MathOptInterface.Utilities.CachingOptimizer{MathOptInterface.AbstractOptimizer,MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Utilities.Model{Float64}}}) at /home/dmitry/.julia/packages/MathOptInterface/A2UPd/src/Utilities/cachingoptimizer.jl:185
 [15] #optimize!#78(::Bool, ::Bool, ::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::typeof(optimize!), ::Model, ::Nothing) at /home/dmitry/.julia/packages/JuMP/MsUSY/src/optimizer_interface.jl:141
 [16] optimize!(::Model, ::Nothing) at /home/dmitry/.julia/packages/JuMP/MsUSY/src/optimizer_interface.jl:111 (repeats 2 times)
 [17] top-level scope at /home/dmitry/Documents/projects/practice/julia/optimization/src/optimus.jl:39
 [18] include at ./boot.jl:328 [inlined]
 [19] include_relative(::Module, ::String) at ./loading.jl:1094
 [20] include(::Module, ::String) at ./Base.jl:31
 [21] exec_options(::Base.JLOptions) at ./client.jl:295
 [22] _start() at ./client.jl:464
in expression starting at /home/dmitry/Documents/projects/practice/julia/optimization/src/optimus.jl:39

```

I tried it with Julia v1.2.0 and with v1.3.0-rc5, get same results.  
Google has shown me a similar [issue](https://github.com/JuliaOpt/MathOptInterface.jl/commit/7712852ac7fc4b6dbdc61a0825c1e1b7e4e48750#diff-7ea74237ccd02743bef881d37f4ebe09) that was fixed for Julia v1.3, but I’m not sure how relevant that problem was.

Any help, comments are greatly appreciated. Thanks.

---

<div class="post-metadata">

**Author:** ![blegat](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/blegat/32/217090_2.png) [@blegat](https://discourse.julialang.org/u/blegat)\
**Post date:** [November 22, 2019, 3:16pm UTC](https://discourse.julialang.org/t/amplnlwriter-supports-constraint-is-ambiguous-in-mathoptinterface/31390/2 "2019-11-22T15:16:38Z")

</div>

This should be fixed on the master branch thanks to [https://github.com/JuliaOpt/AmplNLWriter.jl/pull/91](https://github.com/JuliaOpt/AmplNLWriter.jl/pull/91). We should tag a new version.

---

<div class="post-metadata">

**Author:** ![dmit](https://avatars.discourse-cdn.com/v4/letter/d/f1d935/32.png) [@dmit](https://discourse.julialang.org/u/dmit)\
**Post date:** [November 22, 2019, 6:36pm UTC](https://discourse.julialang.org/t/amplnlwriter-supports-constraint-is-ambiguous-in-mathoptinterface/31390/3 "2019-11-22T18:36:48Z")

</div>

Thanks a lot!  
The error is gone after that fix. Although, Couenne doesn’t produce any result: when I try to printout results of the optimization

```julia
println(JuMP.termination_status(model))
println("Objective value: ", JuMP.objective_value(model))
println("x = ", JuMP.value(x))
println("y = ", JuMP.value(y))

```

I get this

```julia
OTHER_ERROR
Objective value: NaN
x = NaN
y = NaN

```

Even though Juniper gives normal result and Couenne does too if I run it with AMPL or as a standalone solver. Any ideas where I go from here?

---

<div class="post-metadata">

**Author:** ![odow](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/odow/32/28685_2.png) [@odow](https://discourse.julialang.org/u/odow)\
**Post date:** [November 22, 2019, 6:39pm UTC](https://discourse.julialang.org/t/amplnlwriter-supports-constraint-is-ambiguous-in-mathoptinterface/31390/4 "2019-11-22T18:39:05Z")

</div>

What’s the result of `AmplNLWriter.mpb_solution_attribute(model)`?

---

<div class="post-metadata">

**Author:** ![dmit](https://avatars.discourse-cdn.com/v4/letter/d/f1d935/32.png) [@dmit](https://discourse.julialang.org/u/dmit)\
**Post date:** [November 22, 2019, 6:44pm UTC](https://discourse.julialang.org/t/amplnlwriter-supports-constraint-is-ambiguous-in-mathoptinterface/31390/5 "2019-11-22T18:44:29Z")

</div>

> [@odow](#):
>
> AmplNLWriter.mpb\_solution\_attribute(model)

gives an error

```julia
ERROR: LoadError: MethodError: no method matching mpb_solution_attribute(::Model)
Closest candidates are:
  mpb_solution_attribute(!Matched::MathOptInterface.Utilities.UniversalFallback{AmplNLWriter.InnerModel{Float64}}) at /home/dmitry/.julia/packages/AmplNLWriter/V1gW5/src/MOI_wrapper.jl:396
Stacktrace:
 [1] top-level scope at /home/dmitry/Documents/projects/practice/julia/optimization/src/optimus.jl:34
 [2] include at ./boot.jl:328 [inlined]
 [3] include_relative(::Module, ::String) at ./loading.jl:1094
 [4] include(::Module, ::String) at ./Base.jl:31
 [5] exec_options(::Base.JLOptions) at ./client.jl:295
 [6] _start() at ./client.jl:464
in expression starting at /home/dmitry/Documents/projects/practice/julia/optimization/src/optimus.jl:34

```

---

<div class="post-metadata">

**Author:** ![odow](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/odow/32/28685_2.png) [@odow](https://discourse.julialang.org/u/odow)\
**Post date:** [November 22, 2019, 8:23pm UTC](https://discourse.julialang.org/t/amplnlwriter-supports-constraint-is-ambiguous-in-mathoptinterface/31390/6 "2019-11-22T20:23:55Z")

</div>

I guess I meant

```julia
AmplNLWriter.mpb_solution_attribute(backend(model).optimizer.model)

```

---

<div class="post-metadata">

**Author:** ![dmit](https://avatars.discourse-cdn.com/v4/letter/d/f1d935/32.png) [@dmit](https://discourse.julialang.org/u/dmit)\
**Post date:** [November 22, 2019, 8:30pm UTC](https://discourse.julialang.org/t/amplnlwriter-supports-constraint-is-ambiguous-in-mathoptinterface/31390/7 "2019-11-22T20:30:41Z")

</div>

```julia
AmplNLWriter.mpb_solution_attribute(backend(model).optimizer.model)

```

gives no output.  
If I print out that, like

```julia
println(AmplNLWriter.mpb_solution_attribute(backend(model).optimizer.model))

```

I get

```julia
AmplNLWriter.MPBSolution(:Error, NaN, Dict(MathOptInterface.VariableIndex(2) => NaN,MathOptInterface.VariableIndex(1) => NaN))

```

---

<div class="post-metadata">

**Author:** ![odow](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/odow/32/28685_2.png) [@odow](https://discourse.julialang.org/u/odow)\
**Post date:** [November 22, 2019, 8:48pm UTC](https://discourse.julialang.org/t/amplnlwriter-supports-constraint-is-ambiguous-in-mathoptinterface/31390/8 "2019-11-22T20:48:18Z")

</div>

The solver errored for some reason. Can you post a log of the solve? Do you have write permission to `~/.julia`?

---

<div class="post-metadata">

**Author:** ![dmit](https://avatars.discourse-cdn.com/v4/letter/d/f1d935/32.png) [@dmit](https://discourse.julialang.org/u/dmit)\
**Post date:** [November 22, 2019, 9:10pm UTC](https://discourse.julialang.org/t/amplnlwriter-supports-constraint-is-ambiguous-in-mathoptinterface/31390/9 "2019-11-22T21:10:37Z")

</div>

I do have the permission.  
How do I get the solve (solver?) log?

---

<div class="post-metadata">

**Author:** ![dmit](https://avatars.discourse-cdn.com/v4/letter/d/f1d935/32.png) [@dmit](https://discourse.julialang.org/u/dmit)\
**Post date:** [November 27, 2019, 8:41pm UTC](https://discourse.julialang.org/t/amplnlwriter-supports-constraint-is-ambiguous-in-mathoptinterface/31390/10 "2019-11-27T20:41:43Z")

</div>

Couenne writes its output to a .sol file if executed as standalone solver. Is there a way to access its output / log when it’s used as a solver in JuMP?