# Invertible Constraint in JuMP

**URL:** <https://discourse.julialang.org/t/invertible-constraint-in-jump/54031>\
**Category:** Optimization (Mathematical)\
**Created:** [January 27, 2021, 4:09am UTC](https://discourse.julialang.org/t/invertible-constraint-in-jump/54031 "2021-01-27T04:09:47Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![cheng\_chen](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/cheng_chen/32/20899_2.png) [@cheng\_chen](https://discourse.julialang.org/u/cheng_chen)\
**Post date:** [January 27, 2021, 4:09am UTC](https://discourse.julialang.org/t/invertible-constraint-in-jump/54031/1 "2021-01-27T04:09:47Z")

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How can I add a constraint in JuMP model with ProxSDP optimizer such that the solution is invertible?

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<div class="post-metadata">

**Author:** ![blegat](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/blegat/32/217090_2.png) [@blegat](https://discourse.julialang.org/u/blegat)\
**Post date:** [January 27, 2021, 8:03am UTC](https://discourse.julialang.org/t/invertible-constraint-in-jump/54031/2 "2021-01-27T08:03:31Z")

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Do you mean creating an SDP variable which is invertible?  
You can do

```julia
@variable(model, Q[1:n, 1:n], PSD)
using LinearAlgebra
eps = 1e-5
X = Q + eps * I

```

X is then positive definite hence invertible