# Computing Irreducible Inconsistent Subsystem (IIS) to find infeasibility causes

**URL:** <https://discourse.julialang.org/t/computing-irreducible-inconsistent-subsystem-iis-to-find-infeasibility-causes/101864>\
**Category:** Optimization (Mathematical)\
**Created:** [July 21, 2023, 3:37am UTC](https://discourse.julialang.org/t/computing-irreducible-inconsistent-subsystem-iis-to-find-infeasibility-causes/101864 "2023-07-21T03:37:42Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Luiz\_Monteiro](https://avatars.discourse-cdn.com/v4/letter/l/b77776/32.png) [@Luiz\_Monteiro](https://discourse.julialang.org/u/Luiz_Monteiro)\
**Post date:** [July 21, 2023, 3:37am UTC](https://discourse.julialang.org/t/computing-irreducible-inconsistent-subsystem-iis-to-find-infeasibility-causes/101864/1 "2023-07-21T03:37:42Z")

</div>

Hi, I am trying to find infeasibility causes of a MIP model in JuMP with Gurobi solver using the comand: “compute\_conflict!(model1)”.  
The output result is copied below, but I dont know how to translate these result to identify the infeasibility cause in the model. How can I find it?  
Thanks in advance

Model is infeasible  
Best objective -, best bound -, gap -

User-callback calls 426, time in user-callback 0.00 sec

Computing Irreducible Inconsistent Subsystem (IIS)…

```
       Constraints | Bounds | Runtime
  Min Max Guess | Min Max Guess |

```

* * *

```
    0 8545 - 0 21840 - 0s
    0 8540 - 0 5962 - 5s
    0 8539 - 0 5962 - 11s
    1 8538 - 0 5962 - 17s
    1 8537 - 0 5962 - 22s
    3 8537 - 0 5962 - 25s
    3 8536 - 0 5962 - 30s
    3 8536 - 0 5962 - 35s
    4 8535 - 0 5962 - 44s
    4 8534 - 0 5962 - 50s
    4 8533 - 0 5962 - 55s
    5 8533 - 0 5962 - 64s
    5 8533 - 0 5962 - 69s
    5 8533 - 0 5962 - 75s
    6 8533 - 0 5962 - 79s
    6 8533 - 0 5962 - 82s
    6 8533 - 0 5962 - 88s
    6 8533 - 0 5962 - 94s
    6 8532 - 0 5962 - 99s
    6 8532 - 0 5962 - 100s
    6 8532 - 0 5962 - 100s

```

Non-minimal IIS computed: 8532 constraints, 5962 bounds  
IIS runtime: 100.11 seconds (20.50 work units)

---

<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 21, 2023, 1:57pm UTC](https://discourse.julialang.org/t/computing-irreducible-inconsistent-subsystem-iis-to-find-infeasibility-causes/101864/2 "2023-07-21T13:57:44Z")

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Take a read of this part of the docs:

> **[Solutions · JuMP](https://jump.dev/JuMP.jl/stable/manual/solutions/#Conflicts)**
>
> Documentation for JuMP.

See also

> **[Debugging · JuMP](https://jump.dev/JuMP.jl/stable/tutorials/getting_started/debugging/#Debugging-an-infeasible-model)**
>
> Documentation for JuMP.

---

<div class="post-metadata">

**Author:** ![Luiz\_Monteiro](https://avatars.discourse-cdn.com/v4/letter/l/b77776/32.png) [@Luiz\_Monteiro](https://discourse.julialang.org/u/Luiz_Monteiro)\
**Post date:** [July 22, 2023, 10:11pm UTC](https://discourse.julialang.org/t/computing-irreducible-inconsistent-subsystem-iis-to-find-infeasibility-causes/101864/3 "2023-07-22T22:11:03Z")

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Thanks @odow ,  
I am trying to use the code described in Solutions:  
“if get\_attribute(model1, MOI.ConflictStatus()) == MOI.CONFLICT\_FOUND  
iis\_model1, \_ = copy\_conflict(model1)  
print(iis\_model1)  
end”  
But returns the error: “UndefVarError: get\_attribute not defined”  
Dont know if Its a problem related to Gurobi.