Finds the number of permutations for placing chess pieces on an M x N board without the pieces threatening eachother.

Run the solver with parameters for width, height and quantity of each of the pieces:

python solver.py -M 6 -N 9 --kings 2 --queens 1 --bishops 1 --rooks 1 --knights 1
Number of solutions: 20136752

Note: The above problem takes around 3 minutes to solve and uses no more than 4GB of RAM.

Install the python requirements:

pip install requirements.txt

Redis can optionally be used as a solution store. To install redis:

sudo apt install redis

Then use the parameter --store redis to store solutions in redis instead of in python memory. The redis store is slower but more stable.

Tests can be run using:

PYTHONPATH=. pytest tests

• The performance is CPU-bound, so could potentially be improved by using multiprocessing.
• Some memory could be saved by hashing the 'hash_key' of the board. This would be at the expense of visible solutions.
• Code is PEP8 compliant with a max-line-length of 100.