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I made a perft function to test the speed of my chess engine, and the function takes 205 seconds (>2 minutes) to go 3 ply deep and evaluate all the leaves (~42,000 leaves, because 35^3 = 42,000). Is this slowness supposed to happen? It's only 42,000 nodes, which is very few. I hope that some people with chess engine experience can help me figure out what's wrong. Perf results in chess: https://www.chessprogramming.org/Perft_Results#Perft_10

The running of the perft function doesn't involve using minimax or alpha-beta pruning at all, so it can't be those that is causing the slowness.

My perft function:

a = GameState()

def perft(game_state, nodes, counter):
    if nodes == 0:
        return 1
    internal_count = 0
    if game_state.player_turn == 'w':
        for piece in game_state.w_pieces:
            # I call .copy() after game_state because I don't want the set holding the pieces in 
            # game_state to change when I call all_possible_moves() on it. .copy() in GameState 
            # calls deepcopy on the internal sets and dicts in game_state. Every piece in the 
            # game_state set has a method called .all_possible_moves(GameState) that 
            # generates all the possible moves for that piece. 
            for move in piece.all_possible_moves(game_state.copy()):
                counter += perft(game_state.copy().make_move(piece.coor, move), nodes - 1, 0)
    else:
        for piece in game_state.b_pieces:
            for move in piece.all_possible_moves(game_state.copy()):
                counter += perft(game_state.copy().make_move(piece.coor, move), nodes - 1, 0)
    return counter

counter = perft(a, 3, 0)
print(counter)

There shouldn't be anything overtly wrong with my perft function, right? I have no idea why it would run so long. I expected finding 42,000 nodes to take under a second, but it took more than 2 minutes as you can see here: https://i.stack.imgur.com/NzUB7.jpg

For those who want to look at my full code, here it is: https://repl.it/@kasparov/WarmHightechKeygen-1

Garry Kasparov
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    I'm voting to close this question as off-topic because it belongs on https://codereview.stackexchange.com – Selcuk Sep 24 '19 at 22:53
  • 205 seconds is too much, I agree. We don't have all the relevant code to look at, but in chess, using an UndoMove() (i.e. store what you changed in Move() so that it can be undone) approach is usually faster than copying the game state for each probe. – 500 - Internal Server Error Sep 26 '19 at 11:44

0 Answers0