I am trying to code a small chess engine, but I am confused with what the sign of the score means. This is my current minimax algorithm:

INFINITY = 999999
def minimax(self, depth, color):
    if depth == 0:
        return (1 if color else -1) * self.evaluate()
    if color == WHITE:
        max_value = -INFINITY
        for move in board.generate_moves():
            score = minimax(depth - 1, not color)
            max_value = max(score, max_value)
        return max_value
        min_value = INFINITY
        for move in board.generate_moves():
            score = minimax(depth - 1, not color)
            min_value = min(score, min_value)
        return min_value

def evaluate(self):
    score = 0
    if board.detect_checkmate():
        return INFINITY
    score += (piece_values[KING] * (piece_count(KING, WHITE) - piece_count(KING, BLACK))
            + piece_values[QUEEN] * (piece_count(QUEEN, WHITE) - piece_count(QUEEN, BLACK))
            + piece_values[ROOK] * (piece_count(ROOK, WHITE) - piece_count(ROOK, BLACK))
            + piece_values[KNIGHT] * (piece_count(KNIGHT, WHITE) - piece_count(KNIGHT, BLACK))
            + piece_values[BISHOP] * (piece_count(BISHOP, WHITE) - piece_count(BISHOP, BLACK))
            + piece_values[PAWN] * (piece_count(PAWN, WHITE) - piece_count(PAWN, BLACK)))
    return score

See, what is important isn't the lousy evaluation function I have, I think it is about the sign the evaluation function returns. I am confused about the colors of the players and the maximizing player and minimizing player. Is it that if the engine is playing black, it is the maximizing player? Or is the white always the maximizing player?

1 Answer 1


Evaluation sign should be the colour. Your implementation looks correct to me. I compared yours with:


What you did is conceptually identical to the pseudocode on the page.

  • So for example, if the engine is black, +100 means black is basically up by a hundred points? Oct 27, 2017 at 2:16
  • It's white winning for about a pawn.
    – SmallChess
    Oct 27, 2017 at 2:22
  • Ah I misinterpreted your original answer. Thanks for clarifying! Oct 27, 2017 at 2:27

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