This Python library, implemented in C, offers an efficient approximate solution for the Travelling Salesman Problem (TSP). It leverages the 2-opt heuristic and simulated annealing approach to find optimal routes.

This library has no dependencies and can be used by building a wheel (whl) file.

First, let's download build, which will help us build this library:

pip install build

Then run this command:

python -m build

This will generate a dist directory containing our library's wheel (whl) file.

Now, you can either install the library globally, but I would recommend creating a virtual environment:

python3 -m venv venv
source venv/bin/activate

Now let's install the library.

pip install dist/tsp-...whl

This library provides two methods to solve TSP problems: one employs a classic hill climb with random restart, and the other uses a simulated annealing approach. Both methods utilize the 2-opt heuristic to find the nearest neighbor.

To use this module, you need a distance matrix dist_mat representing the pairwise distances between all nodes. Here, dist_mat[i][j] denotes the distance from node i to node j.

cost = [
    [0, 2451, ...,1420, 2145, 1972],
    ...
    [1972, 579, ..., 1200, 504, 0],
]

from tspsolver import tsp2opt

# The first argument is dist_mat,
# and the second argument is the number of random restart iterations.
k = tsp2opt(cost, 4)
print(k)

This will output:

{'order': [7, 0, 9, 5, 10, 11, 1, 8, 6, 12, 4, 3, 2], 'cost': 7293}

Here, 'order' represents the sequence to follow, and it is cyclic. The 'cost' is the total distance traveled for this sequence.

from tspsolver import tspsa

# The first argument is the cost matrix,
# the second argument is the number of iterations for simulated annealing,
# the third argument is the initial temperature,
# and the fourth argument is the cooling factor (alpha)

result = tspsa(cost, 500, 1000, 0.03)
print(result)

This will yield the same result as the classic hill climb with random restart.

For cooling scheduling, the simulated annealing uses an exponential function

double current_temp = temp * exp(-(alpha * i));

If you encounter any issues or have questions about using the library, please feel free to open an issue on the GitHub repository. Your feedback and contributions are welcome!

This library was developed with the help of the following resources:

• Solving header files issue
• Used py2opt lib readme as base for this readme
• C extension learning
• C extension learning
• Original Python docs for C API
• Example inspiration
• Packaging the extension
• Guide for publishing the library