perf(board): making hashing use incremental XORs instead of rebuild from scratch

1 files changed, 33 insertions, 0 deletions

diff --git a/src/zobrist.cpp b/src/zobrist.cpp
index c06f1a2..afef3e6 100644
--- a/src/zobrist.cpp
+++ b/src/zobrist.cpp
@@ -348,6 +348,39 @@ void InitZobrist() {
   SideKey = PolyglotRandom64[idx];
 }
 
+void xorCastleKey(bool color, bool IS_KING_SIDE, Game *g) {
+  const bool WHITE = true;
+
+  if (color == WHITE && IS_KING_SIDE && g->whiteCastleKing) {
+    g->hash ^= CastleKeys[0];
+  };
+  if (color == WHITE && !IS_KING_SIDE && g->whiteCastleQueen) {
+    g->hash ^= CastleKeys[1];
+  };
+  if (color == !WHITE && IS_KING_SIDE && g->blackCastleKing) {
+    g->hash ^= CastleKeys[2];
+  };
+  if (color == !WHITE && !IS_KING_SIDE && g->blackCastleQueen) {
+    g->hash ^= CastleKeys[3];
+  };
+}
+void xorSidekey(Game *g) { g->hash ^= SideKey; }
+void xorEnpassantKey(Game *g) {
+  if (g->canEnpassant && IsEnpassantLegal(g)) {
+    g->hash ^= EnPassantKeys[g->enPassant.file];
+  }
+}
+void xorSquare(uint8_t square, Game *g) {
+  Piece p = g->pieces[square];
+  if (p.type == NONEPIECE) {
+    return;
+  }
+  g->hash ^= PieceKeys[p.color][p.type][square];
+}
+
+/*
+ * should be only called at start of game
+ */
 uint64_t GenerateZobristKey(Game *b) {
   uint64_t key = 0;