amansinha09 / a-star

A very simple A* implementation in C++ callable from Python for pathfinding on a two-dimensional grid.

A*

This is a very simple C++ implementation of the A* algorithm for pathfinding on a two-dimensional grid. The compiled astar.so file is callable from Python. See pyastar.py for the Python wrapper and examples.py for example usage.

Motivation

I recently needed an implementation of the A* algorithm in Python. Normally I would simply use networkx, but for graphs with millions of nodes the overhead incurred to construct the graph can be expensive. Considering that my use case was so simple, I decided to implement it myself.

Usage

1. Run make to build the shared object file astar.so.
2. Set the MAZE_FPATH and OUTP_FPATH as desired in examples.py.
3. Run python examples.py.

Example Results

To test the implementation, I grabbed two nasty mazes from Wikipedia. They are included in the mazes directory, but are originally from here: Small and Large. I load the .png files as grayscale images, and set the white pixels to 1 (open space) and the black pixels to INF (walls).

Run the code on the small maze:

time python examples.py
loaded maze of shape (1802, 1802)
found path of length 10031 in 0.258270s
plotting path to solns/maze_small_soln.png
done

real  0m2.319s
user  0m0.403s
sys 0m1.691s

The solution is visualized below:

Run the code on the large maze:

loaded maze of shape (4002, 4002)
found path of length 783736 in 3.886067s
plotting path to solns/maze_large_soln.png
done

real  0m6.495s
user  0m4.007s
sys 0m2.273s

The solution is visualized below:

References

1. A* search algorithm on Wikipedia
2. Pathfinding with A* on Red Blob Games