feat: add quiscence search

1 files changed, 39 insertions, 2 deletions

diff --git a/src/main.c b/src/main.c
index b950144..15c7618 100644
--- a/src/main.c
+++ b/src/main.c
@@ -494,7 +494,7 @@ int generate_pseudolegal_moves(Move* moves, int* board, int color, int only_capt
 
         while(ray_move && *ray_move) {
           for (int destination = origin + *ray_move; !(destination & 0x88); destination += *ray_move) {
-            if ((board[destination] == EMPTY && !only_captures) || board[destination] % 2 != color) {
+            if ((board[destination] == EMPTY && !only_captures) || (board[destination] != EMPTY && board[destination] % 2 != color)) {
               if (moves) moves[moves_count] = (Move){ origin, destination, 0 };
               moves_count++;
             }
@@ -672,6 +672,43 @@ int order_moves(Move* moves, int moves_count, int* board, long hash, Transpositi
   return cache_hits; // Only needed for display
 }
 
+int quiscence(int* board, int color, int alpha, int beta, int* metrics, long hash, Transposition* transposition_table, long* zobrist_seed, clock_t deadline) {
+  int is_maximizer = (color == 0);
+
+  int evaluation = static_evaluate(board, 0, 0);
+  if(evaluation >= beta ) return beta;
+  if(alpha < evaluation) alpha = evaluation;
+
+  Move pseudolegal_moves[MAX_AVAILABLE_MOVES];
+  int pseudolegal_moves_count = generate_pseudolegal_moves(pseudolegal_moves, board, color, 1);
+  int cache_hits = order_moves(pseudolegal_moves, pseudolegal_moves_count, board, hash, transposition_table, zobrist_seed);
+
+  for (int i = 0; i < pseudolegal_moves_count; i++) {
+    *metrics += 1;
+    Move move = pseudolegal_moves[i];
+
+    long move_hash = hash_after_move(move, board, zobrist_seed, hash);
+    int captured_piece = make_move(move, board);
+    int score = quiscence(board, 1 - color, alpha, beta, metrics, move_hash, transposition_table, zobrist_seed, deadline);
+    unmake_move(move, captured_piece, board);
+
+    if (is_maximizer) {
+      if (score > evaluation) evaluation = score;
+      alpha = MAX(evaluation, alpha);
+    } else {
+      if (score < evaluation) evaluation = score;
+      beta = MIN(evaluation, beta);
+    }
+
+    if (beta <= alpha) break;
+
+    // We ran out of time
+    if (clock() > deadline) break;
+  }
+
+  return evaluation;
+}
+
 /*
  * Alpha-beta pruning
  * Value here is white material advantage over black
@@ -699,7 +736,7 @@ Move minimax_search(int* board, int color, int depth, int alpha, int beta, int*
 
       move.value = depth > 0
         ? minimax_search(board, 1 - color, depth - 1, alpha, beta, metrics, move_hash, transposition_table, zobrist_seed, deadline).value
-        : static_evaluate(board, pseudolegal_moves_count, color);
+        : quiscence(board, 1 - color, alpha, beta, metrics, hash, transposition_table, zobrist_seed, deadline);
 
       if (transposition_table[move_hash].depth < depth) {
         if (transposition_table[move_hash].depth == -1) TRANSPOSITION_TABLE_CARDINALITY++;