stellar

commit 0f8fcd867fd7ddbae2c118b5639acc0c05e9a2af
parent 40ec0f1a8e50396cea47115cda5943fcaa6efbf5
Author: Dimitrije Dobrota <mail@dimitrijedobrota.com>
Date:   Sat,  5 Aug 2023 17:30:48 +0200

Null Move Pruning

Diffstat:
M
CMakeLists.txt
 | 
2
+-
M
src/engine/engine.c
 | 
13
+++++++++++++

2 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -3,7 +3,7 @@ set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
 project(
     Stellar
-	VERSION 0.0.13
+	VERSION 0.0.14
     DESCRIPTION "Chess engine written in C"
 	HOMEPAGE_URL https://git.dimitrijedobrota.com/stellar.git
 	LANGUAGES C
diff --git a/src/engine/engine.c b/src/engine/engine.c
@@ -16,6 +16,7 @@
 #define MAX_PLY 64
 #define FULL_DEPTH 4
 #define REDUCTION_LIMIT 3
+#define REDUCTION_MOVE 2
 
 #define INFINITY 50000
 #define WINDOW 50
@@ -151,6 +152,18 @@ int negamax(Stats *stats, const Board *board, int alpha, int beta, int depth) {
     if (isCheck) depth++;
 
     Board copy;
+
+    if (depth >= 3 && !isCheck && stats->ply) {
+        board_copy(board, &copy);
+        board_side_switch(&copy);
+        board_enpassant_set(&copy, no_sq);
+
+        int score = -negamax(stats, &copy, -beta, -beta + 2,
+                             depth - 1 - REDUCTION_MOVE);
+
+        if (score >= beta) return beta;
+    }
+
     MoveList list;
     move_list_generate(&list, board);