# Start value Gurobi error

**URL:** <https://discourse.julialang.org/t/start-value-gurobi-error/42437>\
**Category:** Optimization (Mathematical)\
**Tags:** question, jump\
**Created:** [July 2, 2020, 3:05pm UTC](https://discourse.julialang.org/t/start-value-gurobi-error/42437 "2020-07-02T15:05:44Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![Miguel\_Goncalves](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/miguel_goncalves/32/10699_2.png) [@Miguel\_Goncalves](https://discourse.julialang.org/u/Miguel_Goncalves)\
**Post date:** [July 2, 2020, 3:05pm UTC](https://discourse.julialang.org/t/start-value-gurobi-error/42437/1 "2020-07-02T15:05:45Z")

</div>

I am a casual/academic user of optimization with Julia/JuMP, and I noticed there is the possibility to include initial solution setting the function set\_start\_value, but I just want to set initially some variables of my whole model. I use Gurobi with solver, and the bellow code is the part that I added the start values:

> ```
> for i in 1:n
> for j in 1:m
> set_start_value(X[i,j], XFITSP[i,j])
> set_start_value(Y[i,j], YFITSP[i,j])
> end
> end
> 
> tempo = time()
> status = optimize!(modelo)
> tempo = time() - tempo
> 
> ```

My model has 3 group of variables: X, Y and W. If I listed only two groups, it returned this error:

> Academic license - for non-commercial use only  
> Academic license - for non-commercial use only  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> Warning, invalid warm-start basis discarded  
> ERROR: LoadError: MathOptInterface.SetAttributeNotAllowed{MathOptInterface.VariablePrimalStart}: Setting attribute MathOptInterface.VariablePrimalStart() cannot be performed. You may want to use a `CachingOptimizer` in `AUTOMATIC` mode or you may need to call `reset_optimizer` before doing this operation if the `CachingOptimizer` is in `MANUAL` mode.  
> Stacktrace:  
> [1] #throw\_set\_error\_fallback#13(::MathOptInterface.SetAttributeNotAllowed{MathOptInterface.VariablePrimalStart}, ::Function, ::Gurobi.Optimizer, ::MathOptInterface.VariablePrimalStart, ::MathOptInterface.VariableIndex, ::Nothing) at C:\Users\Miguel.juliapro\JuliaPro\_v1.1.1.1\packages\MathOptInterface\C3lip\src\attributes.jl:318  
> [2] throw\_set\_error\_fallback(::Gurobi.Optimizer, ::MathOptInterface.VariablePrimalStart, ::MathOptInterface.VariableIndex, ::Nothing) at C:\Users\Miguel.juliapro\JuliaPro\_v1.1.1.1\packages\MathOptInterface\C3lip\src\attributes.jl:317  
> [3] set(::Gurobi.Optimizer, ::MathOptInterface.VariablePrimalStart, ::MathOptInterface.VariableIndex, ::Nothing) at C:\Users\Miguel.juliapro\JuliaPro\_v1.1.1.1\packages\MathOptInterface\C3lip\src\attributes.jl:295  
> [4] \_broadcast\_getindex\_evalf at .\broadcast.jl:578 [inlined]  
> [5] \_broadcast\_getindex at .\broadcast.jl:551 [inlined]  
> [6] getindex at .\broadcast.jl:511 [inlined]  
> [7] macro expansion at .\broadcast.jl:843 [inlined]  
> [8] macro expansion at .\simdloop.jl:73 [inlined]  
> [9] copyto! at .\broadcast.jl:842 [inlined]  
> [10] copyto! at .\broadcast.jl:797 [inlined]  
> [11] copy at .\broadcast.jl:773 [inlined]  
> [12] materialize at .\broadcast.jl:753 [inlined]  
> [13] set(::Gurobi.Optimizer, ::MathOptInterface.VariablePrimalStart, ::Array{MathOptInterface.VariableIndex,1}, ::Array{Union{Nothing, Float64},1}) at C:\Users\Miguel.juliapro\JuliaPro\_v1.1.1.1\packages\MathOptInterface\C3lip\src\attributes.jl:291  
> [14] set(::MathOptInterface.Bridges.LazyBridgeOptimizer{Gurobi.Optimizer,MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Bridges.AllBridgedConstraints{Float64}}}, ::MathOptInterface.VariablePrimalStart, ::Array{MathOptInterface.VariableIndex,1}, ::Array{Union{Nothing, Float64},1}) at C:\Users\Miguel.juliapro\JuliaPro\_v1.1.1.1\packages\MathOptInterface\C3lip\src\Bridges\bridgeoptimizer.jl:222  
> [15] \_pass\_attributes(::MathOptInterface.Bridges.LazyBridgeOptimizer{Gurobi.Optimizer,MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Bridges.AllBridgedConstraints{Float64}}}, ::MathOptInterface.Utilities.UniversalFallback{JuMP.\_MOIModel{Float64}}, ::Bool, ::MathOptInterface.Utilities.IndexMap, ::Array{MathOptInterface.AbstractVariableAttribute,1}, ::Tuple{DataType}, ::Tuple{Array{MathOptInterface.VariableIndex,1}}, ::Tuple{Array{MathOptInterface.VariableIndex,1}}, ::typeof(MathOptInterface.set)) at C:\Users\Miguel.juliapro\JuliaPro\_v1.1.1.1\packages\MathOptInterface\C3lip\src\Utilities\copy.jl:141  
> [16] pass\_attributes at C:\Users\Miguel.juliapro\JuliaPro\_v1.1.1.1\packages\MathOptInterface\C3lip\src\Utilities\copy.jl:111 [inlined]  
> [17] pass\_attributes at C:\Users\Miguel.juliapro\JuliaPro\_v1.1.1.1\packages\MathOptInterface\C3lip\src\Utilities\copy.jl:109 [inlined]  
> [18] default\_copy\_to(::MathOptInterface.Bridges.LazyBridgeOptimizer{Gurobi.Optimizer,MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Bridges.AllBridgedConstraints{Float64}}}, ::MathOptInterface.Utilities.UniversalFallback{JuMP.\_MOIModel{Float64}}, ::Bool) at C:\Users\Miguel.juliapro\JuliaPro\_v1.1.1.1\packages\MathOptInterface\C3lip\src\Utilities\copy.jl:192  
> [19] #automatic\_copy\_to#61 at C:\Users\Miguel.juliapro\JuliaPro\_v1.1.1.1\packages\MathOptInterface\C3lip\src\Utilities\copy.jl:15 [inlined]  
> [20] #automatic\_copy\_to at .\none:0 [inlined]  
> [21] #copy\_to#1 at C:\Users\Miguel.juliapro\JuliaPro\_v1.1.1.1\packages\MathOptInterface\C3lip\src\Bridges\bridgeoptimizer.jl:91 [inlined]  
> [22] (::getfield(MathOptInterface, Symbol(“#kw##copy\_to”)))(::NamedTuple{(:copy\_names,),Tuple{Bool}}, ::typeof(MathOptInterface.copy\_to), ::MathOptInterface.Bridges.LazyBridgeOptimizer{Gurobi.Optimizer,MathOptInterface.Utilities.UniversalFallback{MathOptInterface.Bridges.AllBridgedConstraints{Float64}}}, ::MathOptInterface.Utilities.UniversalFallback{JuMP.\_MOIModel{Float64}}) at .\none:0  
> [23] attach\_optimizer(::MathOptInterface.Utilities.CachingOptimizer{MathOptInterface.AbstractOptimizer,MathOptInterface.Utilities.UniversalFallback{JuMP.\_MOIModel{Float64}}}) at C:\Users\Miguel.juliapro\JuliaPro\_v1.1.1.1\packages\MathOptInterface\C3lip\src\Utilities\cachingoptimizer.jl:130  
> [24] optimize!(::MathOptInterface.Utilities.CachingOptimizer{MathOptInterface.AbstractOptimizer,MathOptInterface.Utilities.UniversalFallback{JuMP.\_MOIModel{Float64}}}) at C:\Users\Miguel.juliapro\JuliaPro\_v1.1.1.1\packages\MathOptInterface\C3lip\src\Utilities\cachingoptimizer.jl:166  
> [25] #optimize!#79(::Bool, ::Bool, ::Function, ::Model, ::Nothing) at C:\Users\Miguel.juliapro\JuliaPro\_v1.1.1.1\packages\JuMP\ibcEh\src\optimizer\_interface.jl:132  
> [26] optimize! at C:\Users\Miguel.juliapro\JuliaPro\_v1.1.1.1\packages\JuMP\ibcEh\src\optimizer\_interface.jl:105 [inlined] (repeats 2 times)  
> [27] top-level scope at none:0  
> in expression starting at C:\Users\Miguel\Documents\model.jl:110

If I include the third group of variable W, it didn’t return any error, just the warning “Warning, invalid warm-start basis discarded” and the solution without any initial solution. I already read the topic [Warning, invalid warm-start basis discarded](https://discourse.julialang.org/t/warning-invalid-warm-start-basis-discarded/26403) , but I didn’t understand how i can fix this situation. Furthermore, i have a friend with a similar code that tested in his computer and had suscess

I doing correctly?

---

<div class="post-metadata">

**Author:** ![Henrique\_Becker](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/henrique_becker/32/15443_2.png) [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)\
**Post date:** [July 2, 2020, 3:25pm UTC](https://discourse.julialang.org/t/start-value-gurobi-error/42437/2 "2020-07-02T15:25:31Z")

</div>

Some extra information would be good.

1. Which are the versions of Julia and the JuMP.jl and Gurobi.jl packages, what version of Gurobi are you using (not the Julia Package, the solver itself)? You can do `] status` (or `import Pkg; Pkg.status()`) inside the Julia REPL to get it. If you use a project (i.e., are running the code in a folder with `Project.toml` and `Manifest.toml`), you need to `Pkg.activate("folder_path")` first.
2. Can you post a complete code that can be run to reproduce the problem?

If the code worked for your friend and not for you, then the problem is probably the versions you are using. If possible ask your friend the questions in (1) too.

---

<div class="post-metadata">

**Author:** ![Miguel\_Goncalves](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/miguel_goncalves/32/10699_2.png) [@Miguel\_Goncalves](https://discourse.julialang.org/u/Miguel_Goncalves)\
**Post date:** [July 2, 2020, 3:44pm UTC](https://discourse.julialang.org/t/start-value-gurobi-error/42437/3 "2020-07-02T15:44:29Z")

</div>

Of course,

The versions you request:  
[2e9cd046] Gurobi v0.6.0 (I downloaded Gurobi 8.1.1 if you need know too)  
[4076af6c] JuMP v0.19.2

The reduced code (with only 2 groups of variable):

> using JuMP, Gurobi
> 
> ```
> modelo = Model(with_optimizer(Gurobi.Optimizer))
> 
> linha=size(C,1)
> coluna=size(C,2)
> n=linha
> m=coluna
> 
> for i in 1:n
> for j in 1:m
> if i==j
> C[i,j]=10^6
> end
> end
> end
> 
> @variable(modelo, X[1:n,1:m], Bin)
> @variable(modelo, G[1:n,1:m]>=0)
> 
> function Caixeiro(C, X)
> SomaObj = 0
> for i in 1:n
> for j in 1:m
> if i!=j
> SomaObj = SomaObj + C[i,j]*X[i,j]
> end
> 
> end
> end
> return SomaObj
> end
> 
> @objective(modelo, Min, Caixeiro(C,X))
> 
> @constraint(modelo, con[i = 1:n], sum(X[i,j] for j in 1:m)-X[i,i]==1)
> @constraint(modelo, con2[j = 1:m], sum(X[i,j] for i in 1:n)-X[j,j]==1)
> 
> for i in 2:n
> @constraint(modelo, sum(G[j,i] for j in 1:n)-sum(G[i,j] for j in 2:n)==1)
> end
> 
> for i in 1:n
> for j in 2:n
> if i != j
> @constraint(modelo, G[i,j]>=0)
> @constraint(modelo, G[i,j]<=(n-1)*X[i,j])
> end
> end
> end
> 
> for i in 1:n
> for j in 1:m
> set_start_value(X[i,j], XFITSP[i,j])
> set_start_value(G[i,j], 0)
> end
> end
> 
> tempo = time()
> status = optimize!(modelo)
> tempo = time() - tempo
> 
> ```

This code return any error, only the warning and without any initial solution, if I exclude

> set\_start\_value(G[i,j], 0)

It returns the same error I quote before

---

<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 2, 2020, 4:07pm UTC](https://discourse.julialang.org/t/start-value-gurobi-error/42437/4 "2020-07-02T16:07:37Z")

</div>

Please update to the latest versions: JuMP 0.21 and Gurobi.jl 0.8. This bug has been fixed.

---

<div class="post-metadata">

**Author:** ![Miguel\_Goncalves](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/miguel_goncalves/32/10699_2.png) [@Miguel\_Goncalves](https://discourse.julialang.org/u/Miguel_Goncalves)\
**Post date:** [July 2, 2020, 4:44pm UTC](https://discourse.julialang.org/t/start-value-gurobi-error/42437/5 "2020-07-02T16:44:46Z")

</div>

Nice, sorry for be so layman in this topic but how can i update?

Cause i did Pkg.update()/Pkg;update(“Gurobi”)/Pkg;update(“JuMP”) and the versions are always the same, returning this to Gurobi update:

> julia\> Pkg.update(“Gurobi”)  
> Updating registry at `C:\Users\Miguel\.juliapro\JuliaPro_v1.1.1.1\registries\JuliaPro`  
> Updating git-repo `https://pkg.juliacomputing.com//registry/JuliaPro`  
> Resolving package versions…  
> Updating `C:\Users\Miguel\.juliapro\JuliaPro_v1.1.1.1\environments\v1.1\Project.toml`  
> [no changes]  
> Updating `C:\Users\Miguel\.juliapro\JuliaPro_v1.1.1.1\environments\v1.1\Manifest.toml`  
> [no changes]

and this to JuMP update:

> julia\> Pkg.update(“JuMP”)  
> Updating registry at `C:\Users\Miguel\.juliapro\JuliaPro_v1.1.1.1\registries\JuliaPro`  
> Updating git-repo `https://pkg.juliacomputing.com//registry/JuliaPro`  
> Resolving package versions…  
> Updating `C:\Users\Miguel\.juliapro\JuliaPro_v1.1.1.1\environments\v1.1\Project.toml`  
> [no changes]  
> Updating `C:\Users\Miguel\.juliapro\JuliaPro_v1.1.1.1\environments\v1.1\Manifest.toml`  
> [no changes]

---

<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 2, 2020, 5:05pm UTC](https://discourse.julialang.org/t/start-value-gurobi-error/42437/6 "2020-07-02T17:05:21Z")

</div>

Don’t use JuliaPro. It uses a different registry which means you don’t get access to the latest fixes. Just install the regular version of Julia.

---

<div class="post-metadata">

**Author:** ![Miguel\_Goncalves](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/miguel_goncalves/32/10699_2.png) [@Miguel\_Goncalves](https://discourse.julialang.org/u/Miguel_Goncalves)\
**Post date:** [July 2, 2020, 5:10pm UTC](https://discourse.julialang.org/t/start-value-gurobi-error/42437/7 "2020-07-02T17:10:48Z")

</div>

Ok, thanks so much!