movegen: pseudo_is_legal() and pos_legalmoves()

src/attack.c

@@ -20,6 +20,9 @@
 #include "hyperbola-quintessence.h"
 #include "attack.h"
 
+
+// #define DEBUG_ATTACK_ATTACKERS1
+
 /**
  * sq_attackers() - find attackers on a square
  * @pos: position
@@ -36,9 +39,6 @@
  *
  * @Return: a bitboard of attackers.
  */
-
-// #define DEBUG_ATTACK_ATTACKERS1
-
 bitboard_t sq_attackers(const pos_t *pos, const square_t sq, const color_t c)
 {
     bitboard_t attackers = 0, tmp;
@@ -96,24 +96,24 @@ bitboard_t sq_attackers(const pos_t *pos, const square_t sq, const color_t c)
 }
 
 /**
- * sq_pinners() - find pinners on a square
+ * sq_pinners() - get "pinners" on a square
  * @pos: position
  * @sq:  square to test
- * @c:   attacker color
+ * @color:   attacker color
  *
  * Find all @c pieces which are separated from @sq by only one piece (of
  * any color).
  *
- * @Return: a bitboard of attackers.
+ * @Return: bitboard of pinners.
  */
-bitboard_t sq_pinners(const pos_t *pos, const square_t sq, const color_t c)
+bitboard_t sq_pinners(const pos_t *pos, const square_t sq, const color_t color)
 {
     bitboard_t attackers, pinners = 0;
     bitboard_t occ = pos_occ(pos);
     bitboard_t maybe_pinner, tmp, lines;
 
     /* bishop type */
-    attackers = pos->bb[c][BISHOP] | pos->bb[c][QUEEN];
+    attackers = pos->bb[color][BISHOP] | pos->bb[color][QUEEN];
     /* occupancy on sq diag and antidiag */
     lines = (bb_sqdiag[sq] | bb_sqanti[sq]) & occ;
     bit_for_each64(maybe_pinner, tmp, attackers) {
@@ -124,7 +124,7 @@ bitboard_t sq_pinners(const pos_t *pos, const square_t sq, const color_t c)
     }
 
     /* same for rook type */
-    attackers = pos->bb[c][ROOK] | pos->bb[c][QUEEN];
+    attackers = pos->bb[color][ROOK] | pos->bb[color][QUEEN];
     lines = (bb_sqrank[sq] | bb_sqfile[sq]) & occ;
     bit_for_each64(maybe_pinner, tmp, attackers) {
         bitboard_t between = bb_between_excl[maybe_pinner][sq];

src/fen.c

@@ -133,7 +133,8 @@ static int fen_check(pos_t *pos)
     if (!(error = pos_check(pos, 0))) {
         /* TODO: Should it really be here ? */
         pos->checkers = pos_checkers(pos, pos->turn);
-        pos->pinners  = pos_pinners(pos, pos->turn);
+        pos->pinners = pos_king_pinners(pos, pos->turn);
+        pos->blockers = pos_king_blockers(pos, pos->turn, pos->pinners);
     }
     return error ? -1: warning;
 }

src/move-gen.c

@@ -30,66 +30,59 @@
 /**
  * pseudo_is_legal() - check if a move is legal.
  * @pos:  position
- * @move: move_t
- *
- * We check all possible invalid moves:
- * (1) King:
- *  - K moves to a controlled square
- * (1) Castling:
- *  - K passes a controlled square   - already done in pseudomove gen
- *
- *
- * (3) En-passant:
- *  - pinned taking pawn, done in (3)
- *  - taking and taken pawn on same rank than king, discovered check on rank
- *
- * (3) Pinned pieces:
- *  - if destination square quits "pinned line"
+ * @move: move_t to verify
  *
  * @return: true if move is valid, false otherwise.
  */
 bool pseudo_is_legal(pos_t *pos, move_t move)
 {
-    int from = move_from(move);
-    int to = move_to(move);
-    int us = pos->turn;
-    int them = OPPONENT(us);
-    int piece = pos->board[from];
+    color_t us = pos->turn, them = OPPONENT(us);
+    square_t from = move_from(move), to = move_to(move);
+    int piece = PIECE(pos->board[from]), sq;
+    bitboard_t tmp;
 
-    /* (1) - castling, skipped */
+    /* (1) - King
+     * For castling, we already tested intermediate squares attacks
+     * in pseudo move generation, so we only care destination square here.
+     */
+    if (piece == KING)
+        return !sq_attackers(pos, to, them);
 
-    /* (2) - King */
-    if (piece == KING) {
-        /* For castling, we already intermediate and destination squares
-         * attacks in pseudo move generation, so we only care destination
-         * square here.
-         */
-        return sq_attackers(pos, to, them) ? false: true;
+    /* (2) - pinned pieces
+     * We verify here that pinned piece P stays on line King-P.
+     */
+    if (mask(from) & pos->blockers & pos->bb[us][ALL_PIECES]) {
+        bitboard_t line = bb_line[from][pos->king[us]];
+        return line & mask(to);                   /* to is not on pin line */
     }
 
-    /* 3 - en-passant */
-
-
-    /*
-     * if (bb_test(pins, from) && !bb_test(Ray[king][from], to))
-     *         return false;
-     * // En-passant special case: also illegal if self-check through the en-passant captured pawn
-     * if (to == pos->epSquare && piece == PAWN) {
-     *     const int us = pos->turn, them = opposite(us);
-     *     bitboard_t occ = pos_pieces(pos);
-     *     bb_clear(&occ, from);
-     *     bb_set(&occ, to);
-     *     bb_clear(&occ, to + push_inc(them));
-     *     return !(bb_rook_attacks(king, occ) & pos_pieces_cpp(pos, them, ROOK, QUEEN)) &&
-     *         !(bb_bishop_attacks(king, occ) & pos_pieces_cpp(pos, them, BISHOP, QUEEN));
-     * } else
-     *     return true;
+    /* (3) - En-passant
+     * We only care the situation where our King and enemy R/Q are on
+     * from rank ()
      */
+    if (move & M_CAPTURE && PIECE(pos->board[to]) == EMPTY) {
+         /* from square rank bitboard */
+        bitboard_t rank5 = bb_sqrank[sq_rank(from)];
+        /* enemy rooks/queens on from rank */
+        bitboard_t rooks = (pos->bb[them][ROOK] | pos->bb[them][QUEEN]) & rank5;
+
+        if ((pos->bb[us][KING] & rank5) && rooks) { /* K and enemy R/Q on rank */
+            /* captured pawn square (beside from square) */
+            square_t captured = sq_make(sq_file(pos->en_passant), sq_rank(from));
+            /* occupation bitboard without the two "disappearing" pawns */
+            bitboard_t occ = pos_occ(pos) ^ mask(from) ^ mask(captured);
+
+            bit_for_each64(sq, tmp, rooks)        /* check all rooks/queens */
+                if (hyperbola_rank_moves(occ, sq) & pos->bb[us][KING])
+                    return false;
+        }
+        return true;
+    }
     return true;
 }
 
 /**
- * gen_all_pseudomoves() - generate all pseudo moves
+ * pos_gen_pseudomoves() - generate position pseudo-legal moves
  * @pos: position
  *
  * Generate all @pos pseudo moves for player-to-move.
@@ -108,9 +101,10 @@ bool pseudo_is_legal(pos_t *pos, move_t move)
  *
  * @Return: The total number of moves.
  */
-int gen_all_pseudomoves(pos_t *pos)
+int pos_gen_pseudomoves(pos_t *pos)
 {
-    color_t us = pos->turn, them = OPPONENT(us);
+    color_t us               = pos->turn;
+    color_t them             = OPPONENT(us);
 
     bitboard_t my_pieces     = pos->bb[us][ALL_PIECES];
     bitboard_t not_my_pieces = ~my_pieces;
@@ -277,3 +271,24 @@ int gen_all_pseudomoves(pos_t *pos)
      */
     return (pos->moves.nmoves = nmoves);
 }
+
+/**
+ * pos_legalmoves() - generate position legal moves from pseudo-legal ones.
+ * @pos:  position
+ * @dest: address where to store legal moves
+ *
+ * The pseudo-legal moves must be already calculated before calling this function.
+ *
+ * @Return: @dest
+ */
+movelist_t *pos_legalmoves(pos_t *pos, movelist_t *dest)
+{
+    int pseudo;
+    movelist_t *src = &pos->moves;
+    dest->nmoves = 0;
+    for (pseudo = 0; pseudo < src->nmoves; ++pseudo) {
+        if (pseudo_is_legal(pos, src->move[pseudo]))
+            dest->move[dest->nmoves++] = src->move[pseudo];
+    }
+    return dest;
+}

src/move-gen.h

@@ -21,7 +21,8 @@
 #include "piece.h"
 #include "move.h"
 
-bool pseudo_is_legal(pos_t *pos, move_t move);
-int gen_all_pseudomoves(pos_t *pos);
+extern bool pseudo_is_legal(pos_t *pos, move_t move);
+extern int pos_gen_pseudomoves(pos_t *pos);
+extern movelist_t *pos_legalmoves(pos_t *pos, movelist_t *dest);
 
 #endif  /* MOVEGEN_H */

src/move.c

@@ -89,8 +89,8 @@
  */
 
 /**
- * move_print() - print a move
- * @pos: position
+ * moves_print() - print movelist moves.
+ * @moves: &movelist_t moves list
  * @flags: moves selection and display options.
  *
  * Possible flags are:
@@ -101,15 +101,12 @@
  * M_PR_NL:    print a newline after move
  * M_PR_EVAL:  print move eval
  */
-void moves_print(pos_t *pos, __unused int flags)
+void moves_print(movelist_t *moves, __unused int flags)
 {
-    move_t *moves = pos->moves.move;
-    int nmoves = pos->moves.nmoves;
-
-    printf("%2d:", nmoves);
-    for (int m = 0; m < nmoves; ++m) {
-        square_t from = move_from(moves[m]);
-        square_t to   = move_to(moves[m]);
+    printf("%2d:", moves->nmoves);
+    for (int m = 0; m < moves->nmoves; ++m) {
+        square_t from = move_from(moves->move[m]);
+        square_t to   = move_to(moves->move[m]);
         printf(" %s-%s", sq_to_string(from), sq_to_string(to));
     }
     printf("\n");
@@ -133,14 +130,14 @@ static int _moves_cmp_bysquare(const void *p1, const void *p2)
 }
 
 /**
- * move_sort_by_sq() - sort moves by from/to squares ascending
- * @pos: position.
+ * move_sort_by_sq() - sort moves list by from/to squares ascending
+ * @moves: &movelist_t
  *
  * Used for perft, for easier comparison.
  */
-void move_sort_by_sq(pos_t *pos)
+void move_sort_by_sq(movelist_t *moves)
 {
-    qsort(pos->moves.move, pos->moves.nmoves, sizeof(move_t), _moves_cmp_bysquare);
+    qsort(moves->move, moves->nmoves, sizeof(move_t), _moves_cmp_bysquare);
 }
 
 /*

src/move.h

@@ -127,8 +127,8 @@ static inline move_t move_make_promote_capture(square_t from, square_t to,
 
 //int move_print(int movenum, move_t *move, move_flags_t flags);
 
-extern void moves_print(pos_t *pos, int flags);
-extern void move_sort_by_sq(pos_t *pos);
+extern void moves_print(movelist_t *moves, int flags);
+extern void move_sort_by_sq(movelist_t *moves);
 
 //extern int pseudo_moves_castle(pos_t *pos, bool color, bool doit, bool do_king);
 //int pseudo_moves_gen(pos_t *pos, piece_list_t *piece, bool doit, bool do_king);

src/position.c

@@ -132,18 +132,46 @@ bitboard_t pos_checkers(const pos_t *pos, const color_t color)
 }
 
 /**
- * pos_pinners() - find all pinners on a king.
+ * pos_king_pinners() - get the "pinners" on a king "pinners".
  * @pos:   &position
- * @color: king color
+ * @color: king color.
  *
- * Get a bitboard of all pinners on @color king.
- * Just a wrapper over @sq_pinners().
+ * get position "pinners" on @color king. Here, pinner means a piece separated from king
+ * by one piece (any color) only.
+ * This is just a wrapper over @sq_pinners().
  *
- * @return: a bitboard of pinners.
+ * @return: pinners bitboard.
  */
-bitboard_t pos_pinners(const pos_t *pos, const color_t color)
+bitboard_t pos_king_pinners(const pos_t *pos, const color_t color)
 {
-    return sq_pinners(pos, pos->king[color], OPPONENT(color));
+    return sq_pinners(pos, pos->king[color], OPPONENT(pos->turn));
+}
+
+/**
+ * pos_king_blockers() - get the pin blockers on a king.
+ * @pos:   &position
+ * @color: king color.
+ * @pinners: pinners bitboard.
+ *
+ * get @pinners blockers pieces on @color king.
+ *
+ * @return: blockers bitboard.
+ */
+bitboard_t pos_king_blockers(const pos_t *pos, const color_t color, const bitboard_t pinners)
+{
+    bitboard_t tmp, blockers = 0, occ = pos_occ(pos);
+    square_t pinner, king = pos->king[color];
+
+    bit_for_each64(pinner, tmp, pinners) {
+        bitboard_t blocker = bb_between_excl[pinner][king] & occ;
+        warn_on(popcount64(blocker) != 1);
+        if (popcount64(blocker) != 1) {
+            printf("n blockers = %d\n", popcount64(blocker));
+            bb_print("blockers", blocker);
+        }
+        blockers |= blocker;
+    }
+    return blockers;
 }
 
 /**
@@ -233,6 +261,7 @@ void pos_print(const pos_t *pos)
     printf("fen %s\n", pos2fen(pos, str));
     printf("checkers: %s\n", pos_checkers2str(pos, str, sizeof(str)));
     printf("pinners : %s\n", pos_pinners2str(pos, str, sizeof(str)));
+    printf("blockers: %s\n", pos_blockers2str(pos, str, sizeof(str)));
 }
 
 /**

src/position.h

@@ -39,10 +39,13 @@ typedef struct __pos_s {
     bitboard_t controlled[2];                     /* unsure */
     bitboard_t checkers;                          /* opponent checkers */
     bitboard_t pinners;                           /* opponent pinners */
+    bitboard_t blockers;                          /* pieces blocking pin */
     piece_t board[BOARDSIZE];
     movelist_t moves;
 } pos_t;
 
+#define pos_pinned(p)                  (p->blockers & p->bb[p->turn][ALL_PIECES])
+
 /**
  * pos_set_sq - unconditionally set a piece on a square
  * @pos: position
@@ -120,7 +123,7 @@ static __always_inline int pos_between_count(const pos_t *pos,
 
 /**
  * pos_checkers2str() - get of string of checkers.
- * @pos:   position
+ * @p:   position
  * @str:   destination string
  * @len:   max @str len.
  *
@@ -128,8 +131,9 @@ static __always_inline int pos_between_count(const pos_t *pos,
  *
  * @return: @str.
  */
-#define pos_checkers2str(pos, str, len)  bb_sq2str((pos)->checkers, (str), (len))
-#define pos_pinners2str(pos, str, len)   bb_sq2str((pos)->pinners, (str), (len))
+#define pos_checkers2str(p, str, len)  bb_sq2str(p->checkers, str, len)
+#define pos_pinners2str(p, str, len)   bb_sq2str(p->pinners, str, len)
+#define pos_blockers2str(p, str, len)  bb_sq2str(p->blockers, str, len)
 
 //void bitboard_print(bitboard_t bb, char *title);
 //void bitboard_print2(bitboard_t bb1, bitboard_t bb2, char *title);
@@ -140,7 +144,9 @@ extern void pos_del(pos_t *pos);
 extern pos_t *pos_clear(pos_t *pos);
 
 extern bitboard_t pos_checkers(const pos_t *pos, const color_t color);
-extern bitboard_t pos_pinners(const pos_t *pos, const color_t color);
+extern bitboard_t pos_king_pinners(const pos_t *pos, const color_t color);
+extern bitboard_t pos_king_blockers(const pos_t *pos, const color_t color, const bitboard_t );
+//extern bitboard_t set_king_pinners_blockers(pos_t *pos);
 //extern char *pos_checkers2str(const pos_t *pos, char *str);
 //extern char *pos_pinners2str(const pos_t *pos, char *str);