Reduce depth for move count pruning. from 9 to 6

alcides-schulz · alcides-schulz · commit a74b667d36d3 · 2025-04-18T08:46:38.000-04:00
10s+0.1
Score of tucanoNEW vs tucanoOLD: 2032 - 1952 - 4783  [0.505] 8767
Elo difference: 3.2 +/- 4.9, LOS: 89.8 %, DrawRatio: 54.6 %
SPRT: llr 2.98 (101.2%), lbound -2.94, ubound 2.94 - H1 was accepted

60s+0.6
Score of tucanoNEW vs tucanoOLD: 1229 - 1151 - 2969  [0.507] 5349
Elo difference: 5.1 +/- 6.2, LOS: 94.5 %, DrawRatio: 55.5 %
SPRT: llr 2.97 (100.8%), lbound -2.94, ubound 2.94 - H1 was accepted
diff --git a/README.md b/README.md
@@ -71,7 +71,7 @@ If you compile tucano you can use the command "bench" to get a signature. Just s
 Signature is a number generated after searching a couple of positions to indicate you have the correct compilation. 
 If you don't get the correct signature it means that something is wrong with the compilation process and the program may not perform correctly.
 
-    12.00:  5620048
+    12.00:  1438388
     11.00:  5203395
     10.00:  5734637 (with nn eval file loaded)
      9.00: 21898211
diff --git a/src/main.c b/src/main.c
@@ -20,7 +20,7 @@
 
 #define ENGINE "Tucano"
 #define AUTHOR "Alcides Schulz"
-#define VERSION "12.05"
+#define VERSION "12.06"
 
 void        develop_workbench(void);
 double      bench(int depth, int print);
diff --git a/src/search.c b/src/search.c
@@ -269,12 +269,13 @@ int search(GAME *game, UINT incheck, int alpha, int beta, int depth, MOVE exclud
             if (!is_killer_move(&game->move_order, turn, ply, move)) {
                 if (!is_counter_move(&game->move_order, flip_color(turn), get_last_move_made(&game->board), move)) {
                     int move_has_bad_history = get_has_bad_history(&game->move_order, turn, move);
-                    int free_passer = is_free_passer(&game->board, turn, move);
                     // Move count pruning: prune moves based on move count.
-                    if (!root_node && !pv_node && move_has_bad_history && depth < 8 && !incheck && move_is_quiet(move) && !free_passer) {
-                        int pruning_threshold = 4 + depth * 2 + (improving ? 0 : -3);
-                        if (move_count > pruning_threshold) {
-                            continue;
+                    if (!root_node && !pv_node && move_has_bad_history && depth <= 6 && !incheck && move_is_quiet(move)) {
+                        if (!is_free_passer(&game->board, turn, move)) {
+                            int pruning_threshold = 4 + depth * 2 + (improving ? 0 : -3);
+                            if (move_count > pruning_threshold) {
+                                continue;
+                            }
                         }
                     }
                     // Futility pruning: eval + margin below beta. Uses beta cutoff history.
