TSP

An optimization app for the Traveling Salesman Problem.

Execution

Python

To run locally, please install Python libraries included in the file requirements.txt

pip install -r requirements.txt

And include separately google ortools lib, which has conflicting dependencies with streamlit.

pip install --no-deps ortools==9.7.2996

Then, exexcute streamlit via command line:

streamlit run app.py

Docker

To build an image locally, make sure you have docker installed in your computer and run the following command:

docker build -t tsp_app:latest .

You can replace tsp_app by any repository name you would like and latest by any version.

Then you can run your app by running

docker run -p 8501:8501 tsp_app:latest

Solutions

Heuristic

The heuristic strategies for the TSP provided in google ortools are unlikely to prove optimality, but can provide good quality solutions for large instances in a short time. They are based on a greedy constructive phase + local search.

MIP

The model adopted considers a directed graph $G(V, A)$ connecting nodes $V$ through arcs $A$. The decision variables are binaries that indicate if an arc $i, j$ is part of the solution. Our goal is to minimize the total cost, which for each arc is $c_{i, j}$.

$$ \begin{align} \text{min} \quad & \sum_{i, j \in A} c_{i, j} x_{i, j} \\ \text{s.t.} \quad & \sum_{j \in V \setminus{{i}}} x_{i, j} = \sum_{j \in V \setminus{{i}}} x_{j, i} = 1 & \forall ; i \in V \\ & \sum_{i \in S} \sum_{j \in V \setminus{{S}}} x_{i, j} \geq 1 & \forall ; S \subseteq V, |S| \leq |V| / 2 \\ & x_{i, j} \in {0, 1} & \forall ; i, j \in A\\ \end{align} $$

Contact

You can reach out to me at bruscalia12@gmail.com