# How to define an optimizer package?

**URL:** <https://discourse.julialang.org/t/how-to-define-an-optimizer-package/51534>\
**Category:** Optimization (Mathematical)\
**Tags:** question\
**Created:** [December 9, 2020, 3:40pm UTC](https://discourse.julialang.org/t/how-to-define-an-optimizer-package/51534 "2020-12-09T15:40:46Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![RaquelSantos](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/raquelsantos/32/3668_2.png) [@RaquelSantos](https://discourse.julialang.org/u/RaquelSantos)\
**Post date:** [December 9, 2020, 3:40pm UTC](https://discourse.julialang.org/t/how-to-define-an-optimizer-package/51534/1 "2020-12-09T15:40:46Z")

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Whenever I try to compile the solver declaration the following error appears

```julia
using JuMP, JuMPeR, Cbc, MathOptInterface
ModelD = Model(with_optimizer(Cbc.Optimizer))
Error message: UndefVarError: with_optimizer not defined

```

I also tried it that way and it didn’t work

```julia
ModelD = Model(solver=CbcSolver())

```

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**Author:** ![kristoffer.carlsson](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/kristoffer.carlsson/32/22_2.png) [@kristoffer.carlsson](https://discourse.julialang.org/u/kristoffer.carlsson)\
**Post date:** [December 9, 2020, 3:45pm UTC](https://discourse.julialang.org/t/how-to-define-an-optimizer-package/51534/2 "2020-12-09T15:45:29Z")

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What is your JuMP version? The docs for the latest version do not mention `with_optimizer` anymore ([https://jump.dev/JuMP.jl/stable/quickstart/](https://jump.dev/JuMP.jl/stable/quickstart/)). Perhaps

```julia
julia> model = Model(Cbc.Optimizer);

```

works.

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**Author:** ![mtanneau](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mtanneau/32/17787_2.png) [@mtanneau](https://discourse.julialang.org/u/mtanneau)\
**Post date:** [December 9, 2020, 3:49pm UTC](https://discourse.julialang.org/t/how-to-define-an-optimizer-package/51534/3 "2020-12-09T15:49:30Z")

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JuMPeR uses an older version of JuMP (0.18), but it looks like you have a more recent version installed (probably \>0.18).  
If that’s the case, try pinning JuMP v0.18 and using the corresponding JuMP syntax.

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<div class="post-metadata">

**Author:** ![RaquelSantos](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/raquelsantos/32/3668_2.png) [@RaquelSantos](https://discourse.julialang.org/u/RaquelSantos)\
**Post date:** [December 9, 2020, 6:56pm UTC](https://discourse.julialang.org/t/how-to-define-an-optimizer-package/51534/4 "2020-12-09T18:56:54Z")

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Hi @kristoffer.carlsson

I’m using this version v0.18.6  
Unfortunately your suggestion didn’t work.  
Thanks!!

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<div class="post-metadata">

**Author:** ![RaquelSantos](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/raquelsantos/32/3668_2.png) [@RaquelSantos](https://discourse.julialang.org/u/RaquelSantos)\
**Post date:** [December 9, 2020, 7:00pm UTC](https://discourse.julialang.org/t/how-to-define-an-optimizer-package/51534/5 "2020-12-09T19:00:42Z")

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Hi @mtanneau

I’m using this version v0.6.0 of JuMPeR and v0.18.6 of JuMP

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**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:** [December 9, 2020, 7:01pm UTC](https://discourse.julialang.org/t/how-to-define-an-optimizer-package/51534/6 "2020-12-09T19:01:10Z")

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Please read the warning at the top of the documentation: [Introduction · JuMP](https://jump.dev/JuMP.jl/stable/)

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<div class="post-metadata">

**Author:** ![RaquelSantos](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/raquelsantos/32/3668_2.png) [@RaquelSantos](https://discourse.julialang.org/u/RaquelSantos)\
**Post date:** [January 6, 2021, 5:38pm UTC](https://discourse.julialang.org/t/how-to-define-an-optimizer-package/51534/7 "2021-01-06T17:38:32Z")

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Hi @odow  
Thanks for the suggestion, but I’m still unable to use the Cbc solver