fix: return empty squares when computing hash

1 files changed, 8 insertions, 7 deletions

diff --git a/src/main.c b/src/main.c
index 7985d41..5fa9f8c 100644
--- a/src/main.c
+++ b/src/main.c
@@ -13,16 +13,16 @@
 #define MIN(x, y) (((x) < (y)) ? (x) : (y))
 
 void generate_zobrist_seed(int* seed) {
-  for (int i = 0; i < 781; i++) {
+  for (int i = 0; i < MAX_ZOBRIST_SEEDS; i++) {
     seed[i] = rand();
   }
 }
 
 int zobrist_hash(int* seed, int* board, int color_to_move) {
-  int result = 1;
+  int hash = 1;
 
   // Last feature means white to move
-  if (color_to_move == WHITE) result ^= seed[MAX_ZOBRIST_SEEDS - 1];
+  if (color_to_move == WHITE) hash ^= seed[MAX_ZOBRIST_SEEDS - 1];
 
   for (int rank = 7; rank >= 0; rank--) {
     for (int file = 0; file < 8; file++) {
@@ -31,10 +31,10 @@ int zobrist_hash(int* seed, int* board, int color_to_move) {
 
       // Unique index of this piece on this position
       int zobrist_index = piece * 128 + position;
-      result ^= seed[zobrist_index];
+      hash ^= seed[zobrist_index];
     }
   }
-  return result;
+  return hash;
 }
 
 int apply_move_zobrist(Move move, int* board, int* zobrist_seed, int hash) {
@@ -42,6 +42,7 @@ int apply_move_zobrist(Move move, int* board, int* zobrist_seed, int hash) {
   int target_piece = board[move.destination];
 
   hash ^= zobrist_seed[MAX_ZOBRIST_SEEDS - 1]; // Flip color
+  hash ^= zobrist_seed[EMPTY * 128 + move.origin]; // Add empty to origin
   hash ^= zobrist_seed[piece * 128 + move.origin]; // Remove piece from origin
   hash ^= zobrist_seed[piece * 128 + move.destination]; // Add piece to destination
   hash ^= zobrist_seed[target_piece * 128 + move.destination]; // Remove target piece from destination
@@ -511,7 +512,7 @@ Move find_best_move(int* board, int color, int depth, int alpha, int beta, int*
     Move available_moves[MAX_AVAILABLE_MOVES];
     int available_moves_count = list_available_moves(available_moves, board, color);
     int cache_hits = sort_moves(available_moves, available_moves_count, board, hash, transposition_table, zobrist_seed);
-    if (cache_hits && (double)cache_hits / (double)available_moves_count > 0.75) printf("More than 75 percent cache hits (%i)\n", cache_hits);
+    if (depth == 0 && cache_hits && (double)cache_hits / (double)available_moves_count > 0.50) printf("More than 50 percent cache hits (%i)\n", cache_hits);
 
     for (int i = 0; i < available_moves_count; i++) {
       *metrics += 1;
@@ -561,7 +562,7 @@ int main() {
   print_board(board);
 
   while (1) {
-    printf("Expected zobrist hash: %i (found %i)\n", hash, zobrist_hash(zobrist_seed, board, color));
+    printf("Zobrist hash: %i\n", hash);
 
     if (color == PLAYER) {
       printf("Enter a move for %s:\n", COLORS[color]);