# Getting duals for nonlinear programming problem

**URL:** <https://discourse.julialang.org/t/getting-duals-for-nonlinear-programming-problem/11357>\
**Category:** Optimization (Mathematical)\
**Tags:** history\
**Created:** [June 2, 2018, 2:24am UTC](https://discourse.julialang.org/t/getting-duals-for-nonlinear-programming-problem/11357 "2018-06-02T02:24:55Z")\
**Posts on this page:** 1\
**Showing post:** 7

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**Author:** ![WalterMadelim](https://avatars.discourse-cdn.com/v4/letter/w/3e96dc/32.png) [@WalterMadelim](https://discourse.julialang.org/u/WalterMadelim)\
**Post date:** [April 24, 2025, 6:27am UTC](https://discourse.julialang.org/t/getting-duals-for-nonlinear-programming-problem/11357/7 "2025-04-24T06:27:04Z")

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Things are clearer to me now. It’s merely about the KKT system of equations.

At a local optimum, which Ipopt ensures, there are 2 possibilities for an inequality constraint

1. it is binding at this local optimum
2. it is nonbinding, i.e. it can be safely removed, concerning only this specific local optimum

If it is the situation 2, then the multiplier returned is simply `0`.  
If it is the situation 1, then that inequality constraint can be deemed a `==` constraint, which owns a normal lagrange multiplier (typically will be nonzero).

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