From 8bf4262e1186713dc7614d863f6551774fba23e7 Mon Sep 17 00:00:00 2001
From: Bruno Raoult <braoult@gmail.com>
Date: Wed, 11 Sep 2024 08:14:55 +0200
Subject: [PATCH] position: use XOR in square clr/set, for castling flags to 8
 bits

---
 src/bitboard.h     | 15 +--------------
 src/chessdefs.h    |  6 ++++--
 src/eval.c         |  2 +-
 src/position.h     | 34 ++++++++++++++++++++++++++++++----
 test/movedo-test.c |  5 +++--
 5 files changed, 39 insertions(+), 23 deletions(-)

diff --git a/src/bitboard.h b/src/bitboard.h
index 4848f7a..31e1fb8 100644
--- a/src/bitboard.h
+++ b/src/bitboard.h
@@ -182,19 +182,6 @@ static __always_inline bitboard_t bb_file(int file)
 }
 */
 
-/**
- * bb_first_bb() - return bitboard of first square of a bitboard.
- * @bb: bitboard
- *
- * bb must be non-zero.
- *
- * @return: bitboard of first square (lsb) of @bb.
- */
-static __always_inline square_t bb_first_bb(bitboard_t bb)
-{
-    return bb & -bb;
-}
-
 /**
  * bb_next() - clear and return next (lsb) square of a bitboard.
  * @bb: &bitboard
@@ -205,7 +192,7 @@ static __always_inline square_t bb_first_bb(bitboard_t bb)
  */
 static __always_inline square_t bb_next(bitboard_t *bb)
 {
-    square_t sq = ctz64(*bb);
+    square_t sq = lsb64(*bb);
     *bb &= *bb - 1;
     return sq;
 }
diff --git a/src/chessdefs.h b/src/chessdefs.h
index 869cf4d..62fbbad 100644
--- a/src/chessdefs.h
+++ b/src/chessdefs.h
@@ -51,7 +51,7 @@
 
 /* castle_t bits structure
  */
-typedef enum {
+enum {
     CASTLE_NONE = 0,
     CASTLE_WK   = (1 << 0),                       /* 0001 */
     CASTLE_WQ   = (1 << 1),                       /* 0010 */
@@ -65,7 +65,9 @@ typedef enum {
     CASTLE_K  = (1 << 0),                         /* generic K/Q, bits 0 and 1 */
     CASTLE_Q  = (1 << 1),
     CASTLE_KQ = (CASTLE_K |CASTLE_Q),
-} castle_rights_t;
+};
+
+typedef u8 castle_rights_t;
 
 /* determine is oo or ooo is possible with castle flags f and color c
  */
diff --git a/src/eval.c b/src/eval.c
index c736c7e..c1bf653 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -41,7 +41,7 @@ s16 calc_phase(pos_t *pos)
 
     phase = max(phase, 0);
 #   ifdef DEBUG_EVAL
-    printf("calc phase:%d\n", phase);
+    printf("calculated phase:%d\n", phase);
 #   endif
     return phase;
 }
diff --git a/src/position.h b/src/position.h
index 38a0e3c..d8c35fd 100644
--- a/src/position.h
+++ b/src/position.h
@@ -88,8 +88,8 @@ static __always_inline void pos_set_sq(pos_t *pos, square_t square, piece_t piec
     bug_on(pos->board[square] != EMPTY);
 
     pos->board[square] = piece;
-    pos->bb[color][type] |= BIT(square);
-    pos->bb[color][ALL_PIECES] |= BIT(square);
+    pos->bb[color][type] ^= BIT(square);
+    pos->bb[color][ALL_PIECES] ^= BIT(square);
     //if (type == KING)
     //    pos->king[color] = square;
 
@@ -114,12 +114,38 @@ static __always_inline void pos_clr_sq(pos_t *pos, square_t square)
     //pos->key ^= zobrist_pieces[piece][square];
 
     pos->board[square] = EMPTY;
-    pos->bb[color][type] &= ~BIT(square);
-    pos->bb[color][ALL_PIECES] &= ~BIT(square);
+    pos->bb[color][type] ^= BIT(square);
+    pos->bb[color][ALL_PIECES] ^= BIT(square);
     //if (type == KING)
     //    pos->king[color] = SQUARE_NONE;
 }
 
+/**
+ * pos_mv_sq - move a piece from a square to another one.
+ * @pos: position
+ * @from: source square
+ * @to: dest square
+ *
+ * Both position board and bitboards are modified.
+ * This function is equivalent to:
+ *      pos_set_sq(pos, to, pos->board[from]);
+ *      pos_clr_sq(pos, from);
+ */
+static __always_inline void pos_mv_sq(pos_t *pos, square_t from, square_t to)
+{
+    piece_t pc = pos->board[from];
+    piece_type_t pt = PIECE(pc);
+    color_t color = COLOR(pc);
+    bitboard_t bb_squares = BIT(from) | BIT(to);
+
+    bug_on(pc == EMPTY || pos->board[to] != EMPTY);
+
+    pos->board[from] = EMPTY;
+    pos->board[to] = pc;
+    pos->bb[color][pt] ^= bb_squares;
+    pos->bb[color][ALL_PIECES] ^= bb_squares;
+}
+
 /**
  * pos_occ() - get position occupation (all pieces)
  * @pos: position
diff --git a/test/movedo-test.c b/test/movedo-test.c
index 897db58..8d6d21a 100644
--- a/test/movedo-test.c
+++ b/test/movedo-test.c
@@ -52,8 +52,8 @@ int main(int __unused ac, __unused char**av)
         for (move = movelist.move; move < last; ++move) {
             //pos_print(pos);
             //printf("i=%d j=%d  turn=%d move=[%s]\n", i, j, pos->turn,
-            //       move_str(movebuf, move, 0));
-            //move_p
+            //       move_to_str(movebuf, *move, 0));
+
             move_do(pos, *move, &state);
             //pos_print(pos);
             //fflush(stdout);
@@ -67,6 +67,7 @@ int main(int __unused ac, __unused char**av)
             move_undo(pos, *move, &state);
             pos->state = state;
             if (!pos_ok(pos, false)) {
+                //pos_print(pos);
                 printf("*** fen %d [%s] move %d [%s] invalid position after move_undo\n",
                        test_line, fen, j, movebuf);
                 exit(0);