---
id: faq
title: Frequently Asked Questions
sidebar_label: FAQ
---
### 1. Can OpEn find the global optimum?
No.
OpEn does not offer any guarantees that the solution it returns is a global optimum.
### 2. Can OpEn solve mixed integer problems?
Yes. OpEn solves parametric problems of the form
```text
Minimize f(u; p)
subj. to: u in U(p)
```
Set `U(p)` can be
### 3. Can OpEn solve multi-objective problems?
No.
### 4. How should I choose the L-BFGS memory?
A value between 3 and 20 should suffice, although the performance is not too sensitive to the exact value of the L-BFGS memory. You shouldn't choose too high values as this will increase the memory requirements of your program (esp. for large-scale problems) and might have a negative effect on performance.
Long story short... if you need very high performance, you should experiment with it. Otherwise, stick with any value between 3 and 20.
### 5. How can I cite OpEn?
Please, cite the original PANOC paper as follows:
```bibtex
@inconference{panoc2017,
author = "Stella, L. and Themelis, A. and Sopasakis, P. and Patrinos, P.",
title = "A simple and efficient algorithm for
nonlinear model predictive control",
booktitle = "56th IEEE Conference on Decision and Control (CDC)",
year = "2017",
pages = "1939-1944"
}
```
You may also cite the following papers where we use PANOC in lab experiments - first, for obstacle avoidance on an autonomous ground vehicle carrying a trailer:
```bibtex
@inconference{agv2018,
author = "Sathya, A. and Sopasakis, P. and Van Parys, R. and Themelis, A.
and Pipeleers, G. and Patrinos, P.",
title = "Embedded nonlinear model predictive control for
obstacle avoidance using PANOC",
booktitle = "IEEE European Control Conference (ECC)",
year = "2018",
}
```
and our recent work on obstacle avoidance of an autonomous micro-aerial vehicle:
```bibtex
@inconference{mav2019,
author = "Small, E. and Sopasakis, P. and Fresk, E.
and Patrinos, P. and Nikolakopoulos, G.",
title = "Aerial navigation in obstructed environments with
embedded nonlinear model predictive control",
booktitle = "IEEE European Control Conference (ECC)",
year = "2019"
}
```
### 6. I have a question; whom should I address it to?
You can reach us on Discord and Gitter.
Find out more information [here](http://localhost:3000/optimization-engine/blog/2019/03/06/talk-to-us).
### 7. How can I report an issue?
Please report any issues on [github](https://github.com/alphaville/optimization-engine/issues).