# How to use NLopt with juniper and Alpine
**URL:** https://discourse.julialang.org/t/how-to-use-nlopt-with-juniper-and-alpine/60857
**Category:** Optimization (Mathematical)
**Created:** [May 10, 2021, 7:53am UTC](https://discourse.julialang.org/t/how-to-use-nlopt-with-juniper-and-alpine/60857 "2021-05-10T07:53:21Z")
**Posts on this page:** 10
**Page:** 1
### Author:  [@manoj.centura](https://discourse.julialang.org/u/manoj.centura)
#### Post date: [May 10, 2021, 7:53am UTC](https://discourse.julialang.org/t/how-to-use-nlopt-with-juniper-and-alpine/60857/1 "2021-05-10T07:53:21Z")
Hi,
Can we use NLopt with juniper/Alpine or any other solver for solving MINLP?
Thanks,
Manoj
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### Author:  [@mohamed82008](https://discourse.julialang.org/u/mohamed82008)
#### Post date: [May 10, 2021, 7:56am UTC](https://discourse.julialang.org/t/how-to-use-nlopt-with-juniper-and-alpine/60857/2 "2021-05-10T07:56:57Z")
Yes in theory but my experience has been that an error is thrown sometimes when a node is infeasible in Juniper so it may need a try-catch somewhere.
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### Author:  [@odow](https://discourse.julialang.org/u/odow)
#### Post date: [May 10, 2021, 7:57am UTC](https://discourse.julialang.org/t/how-to-use-nlopt-with-juniper-and-alpine/60857/3 "2021-05-10T07:57:54Z")
Why NLopt instead of Ipopt?
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### Author:  [@manoj.centura](https://discourse.julialang.org/u/manoj.centura)
#### Post date: [May 10, 2021, 8:15am UTC](https://discourse.julialang.org/t/how-to-use-nlopt-with-juniper-and-alpine/60857/4 "2021-05-10T08:15:39Z")
Ipopt is not generating a feasible solution after 3600 second with Juniper and alpine.
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### Author:  [@mohamed82008](https://discourse.julialang.org/u/mohamed82008)
#### Post date: [May 10, 2021, 8:19am UTC](https://discourse.julialang.org/t/how-to-use-nlopt-with-juniper-and-alpine/60857/5 "2021-05-10T08:19:35Z")
How expensive are your functions? Are you using second order Ipopt or first order?
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### Author:  [@manoj.centura](https://discourse.julialang.org/u/manoj.centura)
#### Post date: [May 10, 2021, 8:21am UTC](https://discourse.julialang.org/t/how-to-use-nlopt-with-juniper-and-alpine/60857/6 "2021-05-10T08:21:31Z")
I am defining model as
```
optimizer = Juniper.Optimizer
nl\_solver = optimizer\_with\_attributes(NLopt.Optimizer, “algorithm” =\> 1)
mip\_solver = optimizer\_with\_attributes(Gurobi.Optimizer)
model = Model(optimizer\_with\_attributes(optimizer, “nl\_solver”=\>nl\_solver, “mip\_solver”=\>mip\_solver ,“mip\_gap”=\>25))```
but getting error as
ERROR: LoadError: UndefVarError: NLopt not defined
Stacktrace:
[1] maincalc() at D:\Received\_doc\From\_dhana\Dev julia projectdeflection\Bulk\_Sequencer\_latest\_05\_08\_2021.jl:1524
[2] top-level scope at D:\Received\_doc\From\_dhana\Dev julia projectdeflection\Bulk\_Sequencer\_latest\_05\_08\_2021.jl:1637
[3] top-level scope at util.jl:156
in expression starting at D:\Received\_doc\From\_dhana\Dev julia projectdeflection\Bulk\_Sequencer\_latest\_05\_08\_2021.jl:1636
---
### Author:  [@mohamed82008](https://discourse.julialang.org/u/mohamed82008)
#### Post date: [May 10, 2021, 8:21am UTC](https://discourse.julialang.org/t/how-to-use-nlopt-with-juniper-and-alpine/60857/7 "2021-05-10T08:21:50Z")
You may also want to experiment with the traversing strategy [Options · Juniper](https://lanl-ansi.github.io/Juniper.jl/stable/options/#traverse_strategy::Symbol-%5B:BFS%5D).
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### Author:  [@manoj.centura](https://discourse.julialang.org/u/manoj.centura)
#### Post date: [May 10, 2021, 8:24am UTC](https://discourse.julialang.org/t/how-to-use-nlopt-with-juniper-and-alpine/60857/8 "2021-05-10T08:24:05Z")
I am new to the field.
my constraints are the order of 5. how to use ipot with second order and first?
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### Author:  [@mohamed82008](https://discourse.julialang.org/u/mohamed82008)
#### Post date: [May 10, 2021, 8:27am UTC](https://discourse.julialang.org/t/how-to-use-nlopt-with-juniper-and-alpine/60857/9 "2021-05-10T08:27:25Z")
You have to set the `hessian_approximation` option to `"exact"` for second order or `"limited-memory"` for first order. Are you sure your problem isn’t just infeasible?
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### Author:  [@blegat](https://discourse.julialang.org/u/blegat)
#### Post date: [May 10, 2021, 11:18am UTC](https://discourse.julialang.org/t/how-to-use-nlopt-with-juniper-and-alpine/60857/10 "2021-05-10T11:18:01Z")
> [@manoj.centura](#):
>
> ERROR: LoadError: UndefVarError: NLopt not defined
This error means that you are missing a line `using NLopt`