# Unable to optimize using Alpine.jl

**URL:** https://discourse.julialang.org/t/unable-to-optimize-using-alpine-jl/52088
**Category:** Optimization (Mathematical)
**Tags:** question, jump, nlp
**Created:** [December 19, 2020, 2:05pm UTC](https://discourse.julialang.org/t/unable-to-optimize-using-alpine-jl/52088 "2020-12-19T14:05:24Z")
**Posts on this page:** 3
**Page:** 1

<div class="post-metadata">

### Author: ![hassanis](https://avatars.discourse-cdn.com/v4/letter/h/4491bb/32.png) [@hassanis](https://discourse.julialang.org/u/hassanis)
#### Post date: [December 19, 2020, 2:05pm UTC](https://discourse.julialang.org/t/unable-to-optimize-using-alpine-jl/52088/1 "2020-12-19T14:05:24Z")

</div>

I’m havinng trouble using Alpine.jl. I know that it’s compatible with MOI now, and the new version was presented at INFORMS this year. Yet, when I try using it, I get the following error:

```julia
MethodError: no method matching initialize(::Nothing, ::Array{Symbol,1})
Closest candidates are:
  initialize(!Matched::JuMP.NLPEvaluator, ::Array{Symbol,1}) at /Users/Hassan/.julia/packages/JuMP/qhoVb/src/nlp.jl:309
  initialize(!Matched::MathOptInterface.Test.FeasibilitySenseEvaluator, ::Array{Symbol,1}) at /Users/Hassan/.julia/packages/MathOptInterface/VjkSQ/src/Test/nlp.jl:184
  initialize(!Matched::MathOptInterface.Test.HS071, ::Array{Symbol,1}) at /Users/Hassan/.julia/packages/MathOptInterface/VjkSQ/src/Test/nlp.jl:16
  ...
load!(::Alpine.Optimizer) at solver.jl:484
optimize!(::Alpine.Optimizer) at algorithm.jl:17
optimize!(::MathOptInterface.Bridges.LazyBridgeOptimizer{Alpine.Optimizer}) at bridge_optimizer.jl:264
optimize!(::MathOptInterface.Utilities.CachingOptimizer{MathOptInterface.AbstractOptimizer,MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Utilities.Model{Float64}}}) at cachingoptimizer.jl:215
optimize!(::JuMP.Model, ::Nothing; bridge_constraints::Bool, ignore_optimize_hook::Bool, kwargs::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}) at optimizer_interface.jl:130
optimize! at optimizer_interface.jl:106 [inlined]
optimize! at optimizer_interface.jl:106 [inlined]

```

It seems that it cannot launch any solvers. My code for running Alpine is

```julia
nl_solver = optimizer_with_attributes(Ipopt.Optimizer, "print_level"=>0, "tol"=>1e-12);
mip_solver = optimizer_with_attributes(Gurobi.Optimizer, "OutputFlag"=>0, "FeasibilityTol"=>1e-6, "OptimalityTol"=>1e-8);
m = Model(optimizer_with_attributes(Alpine.Optimizer, "nlp_solver"=>nl_solver, "mip_solver"=>mip_solver, "time_limit"=>tlim, "relgap"=>gap,"loglevel" => 100));

```

Any help would be appreciated. Thank you.

---

<div class="post-metadata">

### Author: ![pixel27](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/pixel27/32/8902_2.png) [@pixel27](https://discourse.julialang.org/u/pixel27)
#### Post date: [December 19, 2020, 4:16pm UTC](https://discourse.julialang.org/t/unable-to-optimize-using-alpine-jl/52088/2 "2020-12-19T16:16:30Z")

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Looking at the error it appears `initialize()` does not take `nothing` as the first parameter, at least when an array of Symbols is passed in as the second.

From the error the closest candidates are:

```julia
  initialize(!Matched::JuMP.NLPEvaluator, ::Array{Symbol,1}) at /Users/Hassan/.julia/packages/JuMP/qhoVb/src/nlp.jl:309
  initialize(!Matched::MathOptInterface.Test.FeasibilitySenseEvaluator, ::Array{Symbol,1}) at /Users/Hassan/.julia/packages/MathOptInterface/VjkSQ/src/Test/nlp.jl:184
  initialize(!Matched::MathOptInterface.Test.HS071, ::Array{Symbol,1}) at /Users/Hassan/.julia/packages/MathOptInterface/VjkSQ/src/Test/nlp.jl:16

```

One takes a `JuMP.NLPEvaluator`, the second takes a `MathOptInterface.Test.FeasibilitySenseEvaluator` and the third takes a `MathOptInterface.Test.HS071`.

You might try entering `initialize(` into the REPL then hit tab, that appears to show various forms of the function that may show you other arguments you could pass as the first parameter.

---

<div class="post-metadata">

### Author: ![joaquimg](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/joaquimg/32/223_2.png) [@joaquimg](https://discourse.julialang.org/u/joaquimg)
#### Post date: [December 19, 2020, 6:48pm UTC](https://discourse.julialang.org/t/unable-to-optimize-using-alpine-jl/52088/3 "2020-12-19T18:48:15Z")

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Please provide a “minimal working example”, **MWE**. Also, take a look at: [Please read: make it easier to help you](https://discourse.julialang.org/t/psa-make-it-easier-to-help-you/14757)