Change to not do static null move when move from tt is a quiet move and change beta condition.

alcides-schulz · alcides-schulz · commit 0177fa5aea61 · 2025-05-10T17:01:30.000-04:00
60s+0.6 Hash=64
Score of tucanoNEW vs tucanoOLD: 1661 - 1593 - 3808  [0.505] 7062
Elo difference: 3.3 +/- 5.5, LOS: 88.3 %, DrawRatio: 53.9 %
SPRT: llr 2.5 (84.8%), lbound -2.94, ubound 2.94

Score of tucanoNEW vs tucanoOLD: 391 - 315 - 914  [0.523] 1620
Elo difference: 16.3 +/- 11.2, LOS: 99.8 %, DrawRatio: 56.4 %
SPRT: llr 2.96 (100.6%), lbound -2.94, ubound 2.94 - H1 was accepted
diff --git a/src/globals.h b/src/globals.h
@@ -522,6 +522,8 @@ int     is_late_moves(MOVE_LIST *ml);
 int     is_bad_capture(MOVE_LIST *ml);
 int     is_mate_score(int score);
 int     is_eval_score(int score);
+int     is_winning_score(int score);
+int     is_losing_score(int score);
 
 //  Move ordering
 void    save_beta_cutoff_data(MOVE_ORDER *move_order, int color, int ply, MOVE best_move, MOVE_LIST *ml, MOVE previous_move);
diff --git a/src/main.c b/src/main.c
@@ -20,7 +20,7 @@
 
 #define ENGINE "Tucano"
 #define AUTHOR "Alcides Schulz"
-#define VERSION "12.10"
+#define VERSION "12.11"
 
 void        develop_workbench(void);
 double      bench(int depth, int print);
diff --git a/src/search.c b/src/search.c
@@ -139,8 +139,10 @@ int search(GAME *game, UINT incheck, int alpha, int beta, int depth, MOVE exclud
         }
 
         // Static null move: eval score + margin is higher that current beta, so it can skip the search.
-        if (depth < STAT_NULL_DEPTH && eval_score - STAT_NULL_MARGIN[depth] >= beta && !is_mate_score(beta)) {
-            return eval_score - STAT_NULL_MARGIN[depth];
+        if (depth < STAT_NULL_DEPTH && eval_score - STAT_NULL_MARGIN[depth] >= beta && !is_losing_score(beta)) {
+            if (trans_move == MOVE_NONE || move_is_capture(trans_move)) {
+                return eval_score - STAT_NULL_MARGIN[depth];
+            }
         }
 
         // Null move heuristic: side to move has advantage that even allowing an extra move to opponent, still keeps advantage.
diff --git a/src/search_utils.c b/src/search_utils.c
@@ -200,6 +200,22 @@ int is_mate_score(int score)
     return FALSE;
 }
 
+//-------------------------------------------------------------------------------------------------
+//  Indicate if is winning score from mate or egtb.
+//-------------------------------------------------------------------------------------------------
+int is_winning_score(int score)
+{
+    return score >= WIN_SCORE;
+}
+
+//-------------------------------------------------------------------------------------------------
+//  Indicate if is losing score from mate or egtb.
+//-------------------------------------------------------------------------------------------------
+int is_losing_score(int score)
+{
+    return score <= -WIN_SCORE;
+}
+
 //-------------------------------------------------------------------------------------------------
 //  Indicate if is an evaluation score
 //-------------------------------------------------------------------------------------------------

Original file line number	Diff line number	Diff line change
`@@ -139,8 +139,10 @@ int search(GAME *game, UINT incheck, int alpha, int beta, int depth, MOVE exclud`
`139`	`139`	`}`
`140`	`140`
`141`	`141`	`// Static null move: eval score + margin is higher that current beta, so it can skip the search.`
`142`		`- if (depth < STAT_NULL_DEPTH && eval_score - STAT_NULL_MARGIN[depth] >= beta && !is_mate_score(beta)) {`
`143`		`- return eval_score - STAT_NULL_MARGIN[depth];`
	`142`	`+ if (depth < STAT_NULL_DEPTH && eval_score - STAT_NULL_MARGIN[depth] >= beta && !is_losing_score(beta)) {`
	`143`	`+ if (trans_move == MOVE_NONE \|\| move_is_capture(trans_move)) {`
	`144`	`+ return eval_score - STAT_NULL_MARGIN[depth];`
	`145`	`+ }`
`144`	`146`	`}`
`145`	`147`
`146`	`148`	`// Null move heuristic: side to move has advantage that even allowing an extra move to opponent, still keeps advantage.`