cache winner in Move

src/complexagent.rs

@@ -13,6 +13,7 @@ struct Move {
     color: Piece,
     board: Board,
     next_move: Vec<Move>,
+    winner: Option<Piece>,
 }
 
 impl Move {
@@ -21,22 +22,28 @@ impl Move {
             return;
         }
 
-        if self.next_move.is_empty() {
-            self.next_move = problem_space(&self.board, !self.color).collect();
+        // only compute next move if this move doesn't end the game
+        if self.winner.is_none() {
+            if self.next_move.is_empty() {
+                self.next_move = problem_space(&self.board, !self.color).collect();
+            }
+            self.next_move
+                .iter_mut()
+                .for_each(|x| x.populate_next_moves(i - 1));
         }
-        self.next_move
-            .iter_mut()
-            .for_each(|x| x.populate_next_moves(i - 1));
     }
 
     fn value(&self, agent_color: Piece, depth: usize) -> i64 {
         let mut self_value = self.captured as i64;
 
-        if self.board.game_winner(agent_color) != Some(!agent_color) {
+        if self.winner == Some(!agent_color) {
             // if this board results in the opponent winning, MAJORLY negatively weigh this move
             // NOTE! this branch isn't completely deleted because if so, the bot wouldn't make a move.
             // We shouldn't prune branches because we still need to always react to the opponent's moves
             self_value = i64::MIN;
+        } else if self.winner == Some(agent_color) {
+            // this move results in a
+            self_value = i64::MAX;
         } else if agent_color != self.color {
             self_value = -self_value;
         }
@@ -81,7 +88,9 @@ impl Move {
                 color: !color,
                 board: *board,
                 next_move: problem_space(board, color).collect(),
+                winner: board.game_winner(!color),
             }],
+            winner: board.game_winner(color),
         }
     }
 }
@@ -100,6 +109,7 @@ fn problem_space(board: &Board, color: Piece) -> Box<dyn Iterator<Item = Move> +
                 color,
                 board,
                 next_move: Vec::new(),
+                winner: board.game_winner(color),
             }),
     )
 }