mctspy : python implementation of Monte Carlo Tree Search algorithm

Basic python implementation of Monte Carlo Tree Search (MCTS) intended to run on small game trees.

Installation

pip3 install mctspy

Running tic-tac-toe example

to run tic-tac-toe example:

import numpy as np
from mctspy.tree.nodes import TwoPlayersGameMonteCarloTreeSearchNode
from mctspy.tree.search import MonteCarloTreeSearch
from mctspy.games.examples.tictactoe import TicTacToeGameState

state = np.zeros((3,3))
initial_board_state = TicTacToeGameState(state = state, next_to_move=1)

root = TwoPlayersGameMonteCarloTreeSearchNode(state = initial_board_state)
mcts = MonteCarloTreeSearch(root)
best_node = mcts.best_action(10000)

Running MCTS for your own 2 players zero-sum game

If you want to apply MCTS for your own game, its state implementation should derive from
mmctspy.games.common.TwoPlayersGameState

(lookup mctspy.games.examples.tictactoe.TicTacToeGameState for inspiration)

Example Game Play

import numpy as np
from mctspy.tree.nodes import TwoPlayersGameMonteCarloTreeSearchNode
from mctspy.tree.search import MonteCarloTreeSearch
from mctspy.games.examples.connect4 import Connect4GameState

# define inital state
state = np.zeros((7, 7))
board_state = Connect4GameState(
    state=state, next_to_move=np.random.choice([-1, 1]), win=4)

# link pieces to icons
pieces = {0: " ", 1: "X", -1: "O"}

# print a single row of the board
def stringify(row):
    return " " + " | ".join(map(lambda x: pieces[int(x)], row)) + " "

# display the whole board
def display(board):
    board = board.copy().T[::-1]
    for row in board[:-1]:
        print(stringify(row))
        print("-"*(len(row)*4-1))
    print(stringify(board[-1]))
    print()

display(board_state.board)
# keep playing until game terminates
while board_state.game_result is None:
    # calculate best move
    root = TwoPlayersGameMonteCarloTreeSearchNode(state=board_state)
    mcts = MonteCarloTreeSearch(root)
    best_node = mcts.best_action(total_simulation_seconds=1)

    # update board
    board_state = best_node.state
    # display board
    display(board_state.board)

# print result
print(pieces[board_state.game_result])