hash: add hash_short macro, state_s: add prev and move

src/hash.h

@@ -30,6 +30,11 @@
 
 typedef u64 hkey_t;                               /* cannot use typedef for key_t */
 
+/**
+ * hash_short: return the value of a hash first 7 MSB.
+ */
+#define hash_short(hash)  ((hash) >> (64 - 8))
+
 /**
  * hentry_t: hashtable bucket.
  *

src/position.c

@@ -30,6 +30,7 @@
 #include "misc.h"
 #include "board.h"
 #include "attack.h"
+#include "hist.h"
 
 /**
  * pos_new() - allocate a new position
@@ -123,8 +124,6 @@ pos_t *pos_clear(pos_t *pos)
     pos->pinners = 0;
     pos->blockers = 0;
 
-    pos->repeat.moves = 0;
-
     return pos;
 }
 
@@ -167,10 +166,12 @@ bool pos_cmp(const pos_t *pos1, const pos_t *pos2)
     if (_cmpf(checkers) ||_cmpf(pinners) || _cmpf(blockers))
         goto end;
 
-    if (_cmpf(repeat.moves) ||
-        memcmp(pos1->repeat.key, pos2->repeat.key,
-               pos1->repeat.moves * sizeof pos1->repeat.key))
-        goto end;
+    /*
+     * if (_cmpf(repeat.moves) ||
+     *     memcmp(pos1->repeat.key, pos2->repeat.key,
+     *            pos1->repeat.moves * sizeof pos1->repeat.key))
+     *     goto end;
+     */
 
     ret = true;
 end:
@@ -429,7 +430,7 @@ void pos_print(const pos_t *pos)
     char str[128];
 
     board_print(pos->board);
-    printf("key:%lx ", pos->key);
+    printf("key:%lx (#%lx)", pos->key, hash_short(pos->key));
     printf("fen: %s\n", pos2fen(pos, str));
     printf("checkers:%s ", pos_checkers2str(pos, str, sizeof(str)));
     printf("pinners: %s ", pos_pinners2str(pos, str, sizeof(str)));

src/position.h

@@ -28,13 +28,6 @@
 #include "move.h"
 #include "board.h"
 
-#define REPEAT_SIZE 1024
-
-typedef struct {
-    hkey_t key[REPEAT_SIZE];
-    int moves;
-} repeat_t;
-
 typedef struct __pos_s {
     u64 node_count;                               /* evaluated nodes */
     int turn;                                     /* WHITE or BLACK */
@@ -56,6 +49,8 @@ typedef struct __pos_s {
                         int clock_50;
                         int plycount;             /* plies so far, start from 1 */
                         piece_t captured;         /* only used in move_undo */
+                        move_t move;
+                        struct state_s *prev;
         );
     bitboard_t checkers;                          /* opponent checkers */
     bitboard_t pinners;                           /* opponent pinners */
@@ -64,7 +59,6 @@ typedef struct __pos_s {
     piece_t board[BOARDSIZE];
     bitboard_t bb[2][PIECE_TYPE_MAX];             /* bb[0][PAWN], bb[1][ALL_PIECES] */
     square_t king[2];                             /* dup with bb, faster retrieval */
-    repeat_t repeat;                              /* for repetition detection */
 } pos_t;
 
 typedef struct state_s state_t;