Use quiesce in the prob-cut before the normal search.

alcides-schulz · alcides-schulz · commit 241d35e03680 · 2025-04-28T11:18:51.000-04:00
10s+0.1 Hash=8
Score of tucanoNEW vs tucanoOLD: 719 - 639 - 1599  [0.514] 2957
Elo difference: 9.4 +/- 8.5, LOS: 98.5 %, DrawRatio: 54.1 %
SPRT: llr 2.95 (100.2%), lbound -2.94, ubound 2.94 - H1 was accepted

60s+0.6 Hash=64
Score of tucanoNEW vs tucanoOLD: 686 - 609 - 1636  [0.513] 2931
Elo difference: 9.1 +/- 8.3, LOS: 98.4 %, DrawRatio: 55.8 %
SPRT: llr 2.95 (100.3%), 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 "12.08"
+#define VERSION "12.09"
 
 void        develop_workbench(void);
 double      bench(int depth, int print);
diff --git a/src/search.c b/src/search.c
@@ -162,7 +162,7 @@ int search(GAME *game, UINT incheck, int alpha, int beta, int depth, MOVE exclud
             }
         }
 
-        //  Prob-Cut: after a capture a low depth with reduced beta indicates it is safe to ignore this node
+        //  Prob-Cut: after a capture a low depth search with reduced beta indicates it is safe to ignore this node
         if (depth >= 5 && !is_mate_score(beta)) {
             int pc_beta = beta + 100;
             if (!tt_record.data || score_from_tt(tt_record.info.score, ply) >= pc_beta || tt_record.info.depth < depth - 3) {
@@ -179,7 +179,13 @@ int search(GAME *game, UINT incheck, int alpha, int beta, int depth, MOVE exclud
                         }
                         make_move(&game->board, pc_move);
                         int pc_incheck = is_incheck(&game->board, side_on_move(&game->board));
-                        int pc_score = -search(game, pc_incheck, -pc_beta, -pc_beta + 1, depth - 4, MOVE_NONE);
+                        int pc_score = 0;
+                        if (depth > 10) {
+                            pc_score = -quiesce(game, pc_incheck, -pc_beta, -pc_beta - 1, 0);
+                        }
+                        if (depth <= 10 || pc_score >= pc_beta) {
+                            pc_score = -search(game, pc_incheck, -pc_beta, -pc_beta + 1, depth - 4, MOVE_NONE);
+                        }
                         undo_move(&game->board);
                         if (game->search.abort) return 0;
                         if (pc_score >= pc_beta) {
@@ -197,6 +203,7 @@ int search(GAME *game, UINT incheck, int alpha, int beta, int depth, MOVE exclud
             }
         }
 
+        // Depth reduction for recaptures that are not promissing.
         if (move_is_capture(get_last_move_made(&game->board))) {
             if (!improving && depth > 3 && depth <= 10 && eval_score + MAX(200, get_best_capture(&game->board)) < alpha) {
                 depth--;

Original file line number	Diff line number	Diff line change
`@@ -162,7 +162,7 @@ int search(GAME *game, UINT incheck, int alpha, int beta, int depth, MOVE exclud`
`162`	`162`	`}`
`163`	`163`	`}`
`164`	`164`
`165`		`- // Prob-Cut: after a capture a low depth with reduced beta indicates it is safe to ignore this node`
	`165`	`+ // Prob-Cut: after a capture a low depth search with reduced beta indicates it is safe to ignore this node`
`166`	`166`	`if (depth >= 5 && !is_mate_score(beta)) {`
`167`	`167`	`int pc_beta = beta + 100;`
`168`	`168`	`if (!tt_record.data \|\| score_from_tt(tt_record.info.score, ply) >= pc_beta \|\| tt_record.info.depth < depth - 3) {`
`@@ -179,7 +179,13 @@ int search(GAME *game, UINT incheck, int alpha, int beta, int depth, MOVE exclud`
`179`	`179`	`}`
`180`	`180`	`make_move(&game->board, pc_move);`
`181`	`181`	`int pc_incheck = is_incheck(&game->board, side_on_move(&game->board));`
`182`		`- int pc_score = -search(game, pc_incheck, -pc_beta, -pc_beta + 1, depth - 4, MOVE_NONE);`
	`182`	`+ int pc_score = 0;`
	`183`	`+ if (depth > 10) {`
	`184`	`+ pc_score = -quiesce(game, pc_incheck, -pc_beta, -pc_beta - 1, 0);`
	`185`	`+ }`
	`186`	`+ if (depth <= 10 \|\| pc_score >= pc_beta) {`
	`187`	`+ pc_score = -search(game, pc_incheck, -pc_beta, -pc_beta + 1, depth - 4, MOVE_NONE);`
	`188`	`+ }`
`183`	`189`	`undo_move(&game->board);`
`184`	`190`	`if (game->search.abort) return 0;`
`185`	`191`	`if (pc_score >= pc_beta) {`
`@@ -197,6 +203,7 @@ int search(GAME *game, UINT incheck, int alpha, int beta, int depth, MOVE exclud`
`197`	`203`	`}`
`198`	`204`	`}`
`199`	`205`
	`206`	`+ // Depth reduction for recaptures that are not promissing.`
`200`	`207`	`if (move_is_capture(get_last_move_made(&game->board))) {`
`201`	`208`	`if (!improving && depth > 3 && depth <= 10 && eval_score + MAX(200, get_best_capture(&game->board)) < alpha) {`
`202`	`209`	`depth--;`