Increase null move base depth from 4 to 5

alcides-schulz · alcides-schulz · commit 7d12360e47b4 · 2024-10-15T21:21:26.000-04:00
Score of tucanoNEW vs tucanoOLD: 1024 - 947 - 2490  [0.509] 4461
Elo difference: 6.0 +/- 6.8, LOS: 95.9 %, DrawRatio: 55.8 %
SPRT: llr 2.95 (100.2%), lbound -2.94, ubound 2.94 - H1 was accepted
diff --git a/src/main.c b/src/main.c
@@ -20,7 +20,7 @@
 
 #define ENGINE "Tucano"
 #define AUTHOR "Alcides Schulz"
-#define VERSION "11.26"
+#define VERSION "11.27"
 
 void        develop_workbench(void);
 double      bench(int depth, int print);
diff --git a/src/search.c b/src/search.c
@@ -126,13 +126,12 @@ int search(GAME *game, UINT incheck, int alpha, int beta, int depth, MOVE exclud
             return eval_score - STAT_NULL_MARGIN[depth];
         }
 
-        // TODO test depth - 5 
         // Null move heuristic: side to move has advantage that even allowing an extra move to opponent, still keeps advantage.
         if (has_pieces(&game->board, turn) && !has_recent_null_move(&game->board)) {
             // null move search
             if (depth >= 2 && eval_score >= beta) {
                 MOVE last_move = get_last_move_made(&game->board);
-                int null_depth = depth - 4 - ((depth - 4) / 4) - MIN(3, (eval_score - beta) / 200) - (move_is_quiet(last_move) ? 0 : 1);
+                int null_depth = depth - 5 - ((depth - 4) / 4) - MIN(3, (eval_score - beta) / 200) - (move_is_quiet(last_move) ? 0 : 1);
                 make_move(&game->board, NULL_MOVE);
                 int null_score = -search(game, FALSE, -beta, -beta + 1, null_depth, MOVE_NONE);
                 undo_move(&game->board);
