# Gurobi Error 10003: Name too long

**URL:** <https://discourse.julialang.org/t/gurobi-error-10003-name-too-long/101752>\
**Category:** Optimization (Mathematical)\
**Tags:** question, package, jump\
**Created:** [July 18, 2023, 10:02pm UTC](https://discourse.julialang.org/t/gurobi-error-10003-name-too-long/101752 "2023-07-18T22:02:22Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![math\_opt](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/math_opt/32/25317_2.png) [@math\_opt](https://discourse.julialang.org/u/math_opt)\
**Post date:** [July 18, 2023, 10:02pm UTC](https://discourse.julialang.org/t/gurobi-error-10003-name-too-long/101752/1 "2023-07-18T22:02:22Z")

</div>

So, I get the error that probably the variable (and likely constraints as well) have a name longer than 255 characters. I have some custom types that I use as indices of the variables. I am sure this is leading to the issue. However, I was wondering if there is a way around this problem. Having the objects of these custom types as variables indices make the formulation more intuitive. A MWE (rather poorly written but does reproduce the error) reproducing the problem is shown below:

```julia
using JuMP, Gurobi

struct Type1
    a::Int
    b::Int
end

struct Type2
    f::Vector{Type1}
end

struct Data
    g::Vector{Type2}
end

type1_vec1 = Type1[]
for i in 1:50
    push!(type1_vec1, Type1(i, i+1))
end

type1_vec2 = Type1[]
for i in 51:100
    push!(type1_vec2, Type1(i, i+1))
end

data = Data([Type2(type1_vec1), Type2(type1_vec2)])
model = Model(Gurobi.Optimizer)

@variable(model, y[v in data.g], Bin)

optimize!(model)

```

I understand that the error is generated by Gurobi software and not `Gurobi.jl`, but I am looking for suggestions on how to define indices if I actually want them to be custom type objects which can rather be lengthy. For example, a `person` object with lots of attributes. Also, I understand may be I can have a unique identifier for each object but then I have some objects that are _automatically_ generated based on the user defined objects, so I am not sure to what extent I can keep defining these unique identifiers.

Thanks!

---

<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:** [July 18, 2023, 11:36pm UTC](https://discourse.julialang.org/t/gurobi-error-10003-name-too-long/101752/2 "2023-07-18T23:36:44Z")

</div>

You can work around this with `set_string_names_on_creation(model, false)`.

> **[JuMP · JuMP](https://jump.dev/JuMP.jl/stable/api/JuMP/#set_string_names_on_creation)**
>
> Documentation for JuMP.

You could also explicitly set different names with `set_name`

> **[Variables · JuMP](https://jump.dev/JuMP.jl/stable/manual/variables/#Variable-names)**
>
> Documentation for JuMP.

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<div class="post-metadata">

**Author:** ![math\_opt](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/math_opt/32/25317_2.png) [@math\_opt](https://discourse.julialang.org/u/math_opt)\
**Post date:** [July 19, 2023, 12:17am UTC](https://discourse.julialang.org/t/gurobi-error-10003-name-too-long/101752/3 "2023-07-19T00:17:09Z")

</div>

Hi @odow,

Thanks for referring to these links. This is immensely helpful. Just a follow-up question – When I set `set_string_names_on_creation(model, false)`, I see that the variables are defined as anonymous variables. However, their indexing is still retained. So, I should still be able to access their values after optimization as usual. Right? For example, `value(y[data.g[1]])`, and so on. (I checked and it works but just confirming if I am thinking it correctly.)

So, if I understand correctly, setting `set_string_names_on_creation(model, false)`, or giving some other name via `set_name`, only deregisters the default string name which eventually affects the name by which it is passed to the solver as well as how the user accesses the variable (or their values) later. Right?

Is there some example problem that showcases this functionality of accessing variable values and constraint expressions when the default name is set to off? This has always confused me for some reason, so I am looking to clarify all this. 😅

Thanks.

---

<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:** [July 19, 2023, 2:43am UTC](https://discourse.julialang.org/t/gurobi-error-10003-name-too-long/101752/4 "2023-07-19T02:43:39Z")

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Yes. The bindings are unaffected. All that changes is the string named used when printing. See

> **[Variables · JuMP](https://jump.dev/JuMP.jl/stable/manual/variables/#variable_names_and_bindings)**
>
> Documentation for JuMP.