Transposition tables! I’ve added zobrist hashing so that I can create a dictionary that contains all of the board states I have already evaluated. Since many different moves can lead to the same position it means that I can save computing power by just getting the score of that board state instead of having to re-evaluate the board again. Zobrist hashes are just a way to represent the board in hash. This is useful as I can use them as the keys in my dictionary and quickly see if the current board state has been evaluated yet. I also fixed a bug that let the bot play illegal moves as there wasn’t a legality check after the aspiration window failed. An abort flag was also added that is set to True when the user undos or redos a move. This lets me instantly stop that thread’s search for the best move ensuring it doesn’t use unneccessary computing power. Next I am going to try and implement iterative deepening so that I can force the bot to move within a certain amount of time. This would let me make the bot play different ‘time controls’ by altering how long it has to think about what move it should play.

I tested it against some bots from chess.com and it managed to beat Wally (a 1800 bot) but lost to Li (a 2000 bot)