pv.h (empty)

- hist.c: add hist_next() - get next entry in history
- state_t: remove plycount, clock_50 -> ply50, add phase, repcount
- pos_t: add plycount, plyroot
- state_t moved to chessdefs.h
- perft-test: split perft from do_perft (todo for perft_alt)
- position.c: add pos_repcount()
- search.c: add is_draw()
- uci: set root position (after moves), adjust history moves repcount

Makefile

@@ -126,13 +126,14 @@ else # ifeq ($(build),dev)
         #        fen.c
         #CPPFLAGS  += -DDEBUG_FEN                           # FEN decoding
         #        hash / TT
-        CPPFLAGS  += -DZOBRIST_VERIFY                       # double chk zobrist
+        #CPPFLAGS  += -DZOBRIST_VERIFY                      # incr. zobrist check
         #CPPFLAGS  += -DPERFT_MOVE_HISTORY                  # perft, keep prev moves
         #        attack.c
         #CPPFLAGS  += -DDEBUG_ATTACK_ATTACKERS              # sq_attackers
         #CPPFLAGS  += -DDEBUG_ATTACK_PINNERS                # sq_pinners details
         #        eval.c eval-simple.c
-        CPPFLAGS  += -DDEBUG_EVAL                           # eval
+        CPPFLAGS  += -DDEBUG_EVAL                          # eval
+        CPPFLAGS  += -DPHASE_VERIFY                        # incr. phase check
 
         #        old unused flags
         #CPPFLAGS  += -DDEBUG_POS                           # position.c
@@ -159,22 +160,22 @@ ifeq ($(build),release)
         #CFLAGS    += -g
         #CFLAGS    += -ginline-points                   # inlined funcs debug info
         LDFLAGS   += -flto
-else ifeq ($(build),perf)
-        CFLAGS    += -O3
-        CFLAGS    += -ggdb0                            # symbols (gdb, perf, etc.)
-        CFLAGS    += -ginline-points                   # inlined funcs debug info
-        CFLAGS    += -funroll-loops
 else ifeq ($(build),dev)
-        CFLAGS    += -O1
-        CFLAGS    += -ggdb                             # symbols (gdb, perf, etc.)
+        CFLAGS    += -Og
+        CFLAGS    += -g                                # symbols (gdb, perf, etc.)
         CFLAGS    += -ginline-points                   # inlined funcs debug info
         #CFLAGS += -pg                                 # gprof
         # Next one may be useful for valgrind (when invalid instructions)
         #CFLAGS += -mno-tbm
+else ifeq ($(build),perf)
+        CFLAGS    += -O3
+        CFLAGS    += -g                                # symbols (gdb, perf, etc.)
+        CFLAGS    += -ginline-points                   # inlined funcs debug info
+        CFLAGS    += -funroll-loops
 else ifeq ($(build),debug)
-        CFLAGS    += -O0                               # -Og hides some variables
-        CFLAGS    += -ggdb3                            # symbols (including macro)
-        #CFLAGS    += -ginline-points                   # inlined funcs debug info
+        CFLAGS    += -Og
+        CFLAGS    += -g                                # symbols (gdb, perf, etc.)
+        CFLAGS    += -ginline-points                   # inlined funcs debug info
         # for gprof
         #CFLAGS += -pg
         # Next one may be useful for valgrind (when invalid instructions)
@@ -229,16 +230,16 @@ else
 all: libs testing $(TARGET)
 
 release:
-	$(MAKE) build=release clean all
+	$(MAKE) BUILD=release clean all
 
 dev:
-	$(MAKE) build=dev clean all
+	$(MAKE) BUILD=dev clean all
 
 perf:
-	$(MAKE) build=perf clean all
+	$(MAKE) BUILD=perf clean all
 
 debug:
-	$(MAKE) build=debug clean all
+	$(MAKE) BUILD=debug clean all
 
 compile: brlib objs
 

scripts/fetch-all.sh

@@ -29,6 +29,9 @@ readarray -t orig_b  < <(git for-each-ref --format='%(refname:short)' \
 # bugs:
 #  - We only check local branch existence, not tracking information correctness.
 #  - What about sub-branches ? Like remote/a and remote/a/b not being tracked ?
+#for i in `git branch -a | grep remote | grep -v HEAD | grep -v master`; do
+#    git branch --track ${i#remotes/origin/} $i
+#done
 for remote_b in "${orig_b[@]}"; do
     short=${remote_b#"$origin"/};
     # OR (??): short=${remote_b##*/}

src/bitboard.h

@@ -182,6 +182,19 @@ 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
@@ -192,7 +205,7 @@ static __always_inline bitboard_t bb_file(int file)
  */
 static __always_inline square_t bb_next(bitboard_t *bb)
 {
-    square_t sq = lsb64(*bb);
+    square_t sq = ctz64(*bb);
     *bb &= *bb - 1;
     return sq;
 }

src/brchess.c

@@ -37,10 +37,10 @@ int main(int ac, char **av)
     pos_t *pos;
     int opt;
 
+    printf("brchess " VERSION "\n");
     init_all();
     pos = pos_new();
-    hist_link(pos);
-    printf("\nWelcome to brchess " VERSION "\nEngine ready.\n");
+    printf("Engine ready.\n");
 
     // size_t len = 0;
     // char *str = NULL;

src/chessdefs.h

@@ -16,10 +16,9 @@
 
 #include <brlib.h>                                /* brlib types */
 
+#define ONE                1ul
 #define U64(const_u64)     const_u64##UL
-#define BIT(i)             ( U64(1) << (i) )
-#define BIT_NONE           ( U64(0) )
-#define BIT_ALL            ( ~BIT_NONE )
+#define BIT(i)             ( (u64) (ONE << (i)) )
 
 #define BOARDSIZE          (8*8)
 #define GAMESIZE           1024                   /* max game size (512 moves) */
@@ -51,7 +50,7 @@
 
 /* castle_t bits structure
  */
-enum {
+typedef enum {
     CASTLE_NONE = 0,
     CASTLE_WK   = (1 << 0),                       /* 0001 */
     CASTLE_WQ   = (1 << 1),                       /* 0010 */
@@ -65,9 +64,7 @@ enum {
     CASTLE_K  = (1 << 0),                         /* generic K/Q, bits 0 and 1 */
     CASTLE_Q  = (1 << 1),
     CASTLE_KQ = (CASTLE_K |CASTLE_Q),
-};
-
-typedef u8 castle_rights_t;
+} castle_rights_t;
 
 /* determine is oo or ooo is possible with castle flags f and color c
  */
@@ -88,9 +85,9 @@ typedef struct __movelist_s movelist_t;
 
 /* basic types
  */
-
 typedef u64 bitboard_t;
 typedef s16 eval_t;
+typedef s8 phase_t;
 
 /* forward enum definition is impossible in C11.
  * To simplify cross-dependancies, all important enum are moved here.

src/eval-defs.c

@@ -22,6 +22,10 @@
 //#include "eval-simple.h"
 //#include "eval.h"
 
+phase_t piece_phase[PIECE_TYPE_NB] = {
+    0, P_PHASE, N_PHASE, B_PHASE, R_PHASE, Q_PHASE, 0
+};
+
 /* eval parameters definition. */
 static const struct ev_params ev_param_def [EV_PARAMS_NB] = {
     /*                type      setable def   min    max  name */
@@ -256,7 +260,8 @@ static const struct pst {
              * A1 ..... H1
              */
             [PAWN] = {
-                {                                 /* midgame */
+                { /* H1                                 H8 */
+                    /* midgame */
                     +0,  0,   0,   0,   0,   0,  0,  0,
                     50, 50,  50,  50,  50,  50, 50, 50,
                     10, 10,  20,  30,  30,  20, 10, 10,
@@ -574,8 +579,8 @@ void pst_init(int set)
         eval_t mid_pc = piece_midval(pt);
         eval_t end_pc = piece_endval(pt);
         for (square_t sq = 0; sq < SQUARE_NB; ++sq) {
-            eval_t mid_pst = pst->val[pt][MIDGAME][sq];
-            eval_t end_pst = pst->val[pt][ENDGAME][sq];
+            eval_t mid_pst = pst->val[MIDGAME][pt][sq];
+            eval_t end_pst = pst->val[ENDGAME][pt][sq];
 
             pst_mg[BLACK][pt][sq] = (mid_pc * wmat + mid_pst * wpst) / 100;
             pst_eg[BLACK][pt][sq] = (end_pc * wmat + end_pst * wpst) / 100;

src/eval-defs.h

@@ -14,7 +14,6 @@
 #ifndef EVAL_DEFS_H
 #define EVAL_DEFS_H
 
-
 #include "chessdefs.h"
 #include "piece.h"
 #include "eval.h"
@@ -26,7 +25,6 @@ enum {
     ENDGAME,
     PHASE_NB
 };
-typedef s16 phase_t;
 
 /* pieces weight in phase calculation.
  */
@@ -38,18 +36,24 @@ enum {
     Q_PHASE = 4,
     ALL_PHASE = P_PHASE*16 + N_PHASE*4 + B_PHASE*4 + R_PHASE*4 + Q_PHASE*2
 };
+extern phase_t piece_phase[PIECE_TYPE_NB];
+
+static inline phase_t pt_phase(piece_type_t pt)
+{
+    return piece_phase[pt];
+}
 
 /* max pieces eval is 9*QUEEN_VALUE + 2*ROOK_VALUE + 2*BISHOP_VALUE
  * + 2*KNIGHT_VALUE which is (for a pawn valued at 100) well less than 15,000.
  */
 #define EVAL_MAX     (SHRT_MAX)                   /* 32767 */
 #define EVAL_MIN     (-EVAL_MAX)
-
+#define EVAL_DRAW    0
 #define EVAL_INV     EVAL_MIN
 
 #define EVAL_MATE    30000
 
-/* eval parameters */
+/* engine parameters */
 enum {
     WT_MAT,
     WT_PST,

src/eval-simple.c

@@ -48,19 +48,15 @@ eval_t eval_material(pos_t *pos)
  * eval_simple() - simple and fast position evaluation
  * @pos: &position to evaluate
  *
- * This function is normally used only during initialization,
- * or when changing phase (middlegame <--> endgame), as the eval
- * will be done incrementally when doing moves.
- *
  * @return: the @pos evaluation in centipawns
  */
 eval_t eval_simple(pos_t *pos)
 {
-    eval_t eval[2] = { 0, 0 };
+    eval_t eval[2] = { 0, 0 }, res;
     eval_t mg_eval[2], eg_eval[2];
-    //struct pc_sq = sq_ int (*gg)[6 + 2][64] = eg? pc_sq_eg: pc_sq_mg;
 
-    //pos->eval_simple_phase = ENDGAME;
+    int eg_weight = clamp((int) pos->phase, ALL_PHASE, 0);
+    int mg_weight = ALL_PHASE - pos->phase;
 
     for (color_t color = WHITE; color < COLOR_NB; ++color) {
         mg_eval[color] = 0;
@@ -80,10 +76,15 @@ eval_t eval_simple(pos_t *pos)
 
         }
     }
+    eval[WHITE] = mg_eval[WHITE] * mg_weight + eg_eval[WHITE] * eg_weight;
+    eval[BLACK] = mg_eval[BLACK] * mg_weight + eg_eval[BLACK] * eg_weight;
+    res = (eval[WHITE] - eval[BLACK]) / ALL_PHASE;
 #   ifdef DEBUG_EVAL
-    printf("phase:%d mg[WHITE]:%d mg[BLACK]:%d eg[WHITE]:%d eg[BLACK]:%d\n",
-           pos->phase, mg_eval[WHITE], mg_eval[BLACK], eg_eval[WHITE], eg_eval[BLACK]);
+    printf("phase:%d mg:%d/%d eg:%d/%d ev:%d/%d RES=%d\n",
+           pos->phase, mg_eval[WHITE], mg_eval[BLACK],
+           eg_eval[WHITE], eg_eval[BLACK],
+           eval[WHITE], eval[BLACK], res
+        );
 #   endif
-
-    return eval[WHITE] - eval[BLACK];
+    return res;
 }

src/eval.c

@@ -19,6 +19,50 @@
 #include "position.h"
 #include "eval.h"
 #include "eval-simple.h"
+#include "hist.h"
+
+/**
+ * calc_phase - calculate position phase
+ * @pos: &position
+ *
+ * This function should be calculated when a new position is setup, or as
+ * a verification of an incremental one.
+ * Note: phase is *not* clamped, to avoid update errors.
+ *
+ * @return: phase value
+ */
+phase_t calc_phase(pos_t *pos)
+{
+    int phase = ALL_PHASE;
+    for (piece_type_t pt = PAWN; pt < KING; ++pt)
+        phase -= piece_phase[pt] * popcount64(pos->bb[WHITE][pt] | pos->bb[BLACK][pt]);
+#   ifdef DEBUG_PHASE
+    printf("calc phase:%d\n", phase);
+#   endif
+    return phase;
+}
+
+/**
+ * phase_verify() - verify position phase.
+ * @pos: &position
+ *
+ * Verify that position phase is correct (a full recalculation is performed).
+ * This function is inactive if PHASE_VERIFY is not set.
+ *
+ * @return: True if phase key is OK, no return otherwise.
+ */
+#ifdef PHASE_VERIFY
+bool phase_verify(pos_t *pos)
+{
+    phase_t verif = calc_phase(pos);
+    if (pos->phase != verif) {
+        warn(true, "warn phase=%d verif=%d\n", pos->phase, verif);
+        hist_print(pos);
+        bug_on(pos->phase != verif);
+    }
+    return true;
+}
+#endif
 
 /**
  * calc_phase - calculate position phase
@@ -30,7 +74,7 @@
  *
  * @return:
  */
-s16 calc_phase(pos_t *pos)
+__unused static phase_t calc_phase2(pos_t *pos)
 {
     int phase = ALL_PHASE;
     phase -= P_PHASE * popcount64(pos->bb[WHITE][PAWN]   | pos->bb[BLACK][PAWN]);
@@ -41,7 +85,7 @@ s16 calc_phase(pos_t *pos)
 
     phase = max(phase, 0);
 #   ifdef DEBUG_EVAL
-    printf("calculated phase:%d\n", phase);
+    printf("calc phase:%d verif=%d\n", phase, calc_phase(pos));
 #   endif
     return phase;
 }

src/eval.h

@@ -19,7 +19,12 @@
 #include "chessdefs.h"
 #include "eval-defs.h"
 
-s16 calc_phase(pos_t *pos);
+phase_t calc_phase(pos_t *pos);
+#ifdef PHASE_VERIFY
+bool phase_verify(pos_t *pos);
+#else
+#define phase_verify(p) true
+#endif
 
 eval_t eval_mobility(pos_t *pos, bool color);
 eval_t eval_square_control(pos_t *pos, bool color);

src/fen.c

@@ -230,12 +230,12 @@ pos_t *fen2pos(pos_t *pos, const char *fen)
 
     /* 5) half moves since last capture or pawn move (50 moves rule)
      */
-    tmppos.clock_50 = 0;
+    tmppos.ply50 = 0;
     tmppos.plycount = 1;
     if (sscanf(cur, "%hd%n", &tmp, &consumed) != 1)
         goto end;                                 /* early end, ignore w/o err */
 
-    tmppos.clock_50 = tmp;
+    tmppos.ply50 = tmp;
     cur += consumed;
     SKIP_BLANK(cur);
 
@@ -350,7 +350,7 @@ char *pos2fen(const pos_t *pos, char *fen)
     /* 5) moves since last capture or pawn move (50 moves rule)
      * 6) current full move number, starting with 1
      */
-    sprintf(fen+cur, "%d %d", pos->clock_50,
+    sprintf(fen+cur, "%d %d", pos->ply50,
             1 + (pos->plycount - (pos->turn == BLACK)) / 2);
     return fen;
 }

src/hash.c

@@ -97,12 +97,11 @@ hkey_t zobrist_calc(pos_t *pos)
  * @pos: &position
  *
  * Verify that position Zobrist key matches a full Zobrist calculation.
- * This function cannot be called if ZOBRIST_VERIFY is not set.
+ * This function is inactive if ZOBRIST_VERIFY is not set.
  *
- * @return: True if Zobrist key is OK.
+ * @return: True if Zobrist key is OK, no return otherwise.
  */
 #ifdef ZOBRIST_VERIFY
-
 bool zobrist_verify(pos_t *pos)
 {
     hkey_t diff, key = zobrist_calc(pos);
@@ -202,7 +201,7 @@ int tt_create(s32 sizemb)
         hash_tt.bytes    = hash_tt.nbuckets * sizeof(bucket_t);
         hash_tt.mb       = hash_tt.bytes / 1024 / 1024;
 
-        hash_tt.mask     = BIT_ALL >> (64 - nbits);
+        hash_tt.mask     = -1ull >> (64 - nbits);
 
         hash_tt.keys     = safe_alloc_aligned_hugepage(hash_tt.bytes);
 
@@ -267,10 +266,8 @@ hentry_t *tt_probe(hkey_t key)
     for (i = 0; i < ENTRIES_PER_BUCKET; ++i) {
         entry = bucket->entry + i;
         if (key == entry->key)
-            break;
+            return entry;
     }
-    if (i < ENTRIES_PER_BUCKET)
-        return entry;
     return NULL;
 }
 
@@ -295,7 +292,6 @@ hentry_t *tt_probe_perft(const hkey_t key, const u16 depth)
     /* find key in buckets */
     for (i = 0; i < ENTRIES_PER_BUCKET; ++i) {
         entry = bucket->entry + i;
-        bug_on(entry->key && (key & hash_tt.mask) != (entry->key & hash_tt.mask));
         if (key == entry->key && HASH_PERFT_DEPTH(entry->data) == depth) {
             hash_tt.hits++;
             /*
@@ -391,7 +387,7 @@ hentry_t *tt_store_perft(const hkey_t key, const u16 depth, const u64 nodes)
 void tt_info()
 {
     if (hash_tt.keys) {
-        printf("TT: Mb:%d buckets:%'lu (bits:%u mask:%#lx) entries:%'lu\n",
+        printf("TT: Mb:%d buckets:%'lu (bits:%u mask:%#x) entries:%'lu\n",
                hash_tt.mb, hash_tt.nbuckets, hash_tt.nbits,
                hash_tt.mask, hash_tt.nkeys);
     } else {

src/hash.h

@@ -44,14 +44,16 @@ typedef u64 hkey_t;                               /* cannot use typedef for key_
  * 16 bytes in future, it should be updated to be exactly 32 bytes.
  */
 typedef struct {
-    hkey_t key;                                   /* zobrist */
+    hkey_t key;                                   /* position key */
     union {
         u64 data;
         struct {
-            u16 depth;                            /* ply in search */
-            s16 eval;
-            move_t move;
-            //u8 flags;                             /* maybe for locking, etc... */
+            s16 eval;                             /* 16: eval */
+            move_t move;                          /* 16: best move */
+            u8 depth;                             /*  8: search depth */
+            u8 gen8;                              /*  8: search generation */
+
+            //flags;                             /* maybe for locking, etc... */
             //u8 filler;
         };
     };
@@ -76,15 +78,15 @@ typedef struct {
 
     /* memory size in bytes/mb */
     size_t bytes;
-    u32 mb;
+    u32  mb;
 
     /* size in buckets/keys */
     size_t nbuckets;
     size_t nkeys;                                 /* nbuckets * NBUCKETS */
 
     /* internal representation */
-    u32 nbits;                                    /* #buckets in bits, power of 2 */
-    u64 mask;                                     /* nbuckets - 1, bucket mask */
+    u32  nbits;                                   /* #buckets in bits, power of 2 */
+    u32  mask;                                    /* nbuckets - 1, key mask */
 
     /* stats - unsure about usage */
     //size_t used_buckets;
@@ -106,8 +108,8 @@ typedef struct {
 
 extern hkey_t zobrist_pieces[16][64];
 extern hkey_t zobrist_castling[4 * 4 + 1];
-extern hkey_t zobrist_turn;                       /* for black, XOR each ply */
-extern hkey_t zobrist_ep[9];                      /* 0-7: ep file, 8: SQUARE_NONE */
+extern hkey_t zobrist_turn;                        /* for black, XOR each ply */
+extern hkey_t zobrist_ep[9];                       /* 0-7: ep file, 8: SQUARE_NONE */
 
 extern hasht_t hash_tt;                           /* main transposition table */
 

src/hist.c

@@ -37,6 +37,16 @@ void hist_init(void)
     hist.state[0].prev = &hist.state[0];
 }
 
+/**
+ * hist_next() - get next history slot.
+ *
+ * return: @state_t next history slot.
+ */
+state_t *hist_next(void)
+{
+    return hist.state + hist.nstates++;
+}
+
 /**
  * hist_push() - add a state to hist list
  * @st:   &state_t to add
@@ -134,9 +144,10 @@ void hist_static_print(void)
 
     printf("UCI state history: ");
     while (true) {
-        printf("%s(#%lx) ",
+        printf("%s(#%lx r=%d) ",
                move_to_str(movestr, st->move, 0),
-               hash_short(st->key));
+               hash_short(st->key),
+               st->repcount);
         if (st == HIST_START)
             break;
         st = hist_prev(st);
@@ -154,9 +165,10 @@ void hist_print(pos_t *pos)
     state_t *st = &pos->state;
     printf("position states history: ");
     while (true) {
-        printf("%s(#%lx) ",
+        printf("%s(#%lx r=%d) ",
                move_to_str(movestr, st->move, 0),
-               hash_short(st->key));
+               hash_short(st->key),
+               st->repcount);
         if (st == HIST_START)
             break;
         st = hist_prev(st);

src/hist.h

@@ -48,6 +48,7 @@ extern hist_t hist;
 #define HIST_START  (hist.state)
 
 void hist_init(void);
+state_t *hist_next(void);
 void hist_push(state_t *st); //, move_t *move);
 void hist_link(pos_t *pos);
 state_t *hist_pop(void);

src/move-do.c

@@ -24,20 +24,7 @@
 #include "position.h"
 #include "move-do.h"
 #include "hash.h"
-
-/**
- * sq_castle - castling rights per square.
- *
- * position castling rights mask has to be AND'ed with this array 'from' and 'to'.
- */
-castle_rights_t sq_castle[64] = {
-    [A1] = ~CASTLE_WQ, [B1 ... D1] = CASTLE_ALL,
-    [E1] = ~CASTLE_W,  [F1 ... G1] = CASTLE_ALL,
-    [H1] = ~CASTLE_WK, [A2 ... H7] = CASTLE_ALL,
-    [A8] = ~CASTLE_BQ, [B8 ... D8] = CASTLE_ALL,
-    [E8] = ~CASTLE_B,  [F8 ... G8] = CASTLE_ALL,
-    [H8] = ~CASTLE_BK,
-};
+#include "hist.h"
 
 /**
  * move_do() - do move.
@@ -73,180 +60,16 @@ pos_t *move_do(pos_t *pos, const move_t move, state_t *state)
     hkey_t key = pos->key;
 
     *state = pos->state;                          /* save irreversible changes */
-
-    /* update key: switch turn, reset ep */
-    key ^= zobrist_turn;
-    key ^= zobrist_ep[EP_ZOBRIST_IDX(pos->en_passant)];
-
-    ++pos->clock_50;
-    ++pos->plycount;
-    pos->en_passant = SQUARE_NONE;
-    pos->turn = them;
-    pos->captured = captured;
-    pos->move = move;
-
-    bug_on(COLOR(piece) != us);
-
-    /* special moves: captures, pawn double push, en-passant, castling.
-     * All these moves are exclusive (so we use if ... else)
-     */
-    if (captured != EMPTY) {                      /* capture: remove piece */
-        pos->clock_50 = 0;
-        bug_on(pos->board[to] == EMPTY || COLOR(pos->captured) != them);
-        key ^= zobrist_pieces[captured][to];
-        pos_clr_sq(pos, to);
-    } else if (ptype == PAWN) {
-        pos->clock_50 = 0;
-        if (from + up + up == to) {               /* double push: set e.p. */
-            square_t ep = from + up;
-            /* check that opponent can e.p. */
-            if (bb_pawn_attacks[us][ep] & pos->bb[them][PAWN]) {
-                pos->en_passant = ep;
-                key ^= zobrist_ep[EP_ZOBRIST_IDX(pos->en_passant)];
-            }
-        } else if (is_enpassant(move)) {          /* e.p.: clear grabbed pawn */
-            square_t grabbed = to - up;
-            piece_t pc = pos->board[grabbed];
-            key ^= zobrist_pieces[pc][grabbed];
-            pos_clr_sq(pos, grabbed);
-        }
-    } else if (is_castle(move)) {                 /* castling: handle rook move */
-        square_t rookfrom, rookto;
-        if (to > from) {                          /* o-o */
-            rookfrom = to + 1;
-            rookto = to - 1;
-        } else {                                  /* o-o-o */
-            rookfrom = to - 2;
-            rookto = to + 1;
-        }
-        key ^= zobrist_pieces[pos->board[rookfrom]][rookto] ^
-            zobrist_pieces[pos->board[rookfrom]][rookfrom];
-        pos_set_sq(pos, rookto, pos->board[rookfrom]);
-        pos_clr_sq(pos, rookfrom);
-    }
-
-    /* common part: captures and non captures
-     * We could improve slightly, as en-passant and double push will make
-     * the following tests.
-     * Improvement could be to add promotion test and king test twice above.
-     * (in capture and after ).
-     */
-    if (is_promotion(move)) {
-        bug_on(sq_rank(to) != sq_rel_rank(RANK_8, us));
-        new_piece = MAKE_PIECE(move_promoted(move), us);
-    }
-
-    key ^= zobrist_pieces[piece][from] ^ zobrist_pieces[new_piece][to];
-    pos_clr_sq(pos, from);
-    pos_set_sq(pos, to, new_piece);
-
-    /* update castling flags */
-    key ^= zobrist_castling[pos->castle];
-    pos->castle &= sq_castle[from] & sq_castle[to];
-    key ^= zobrist_castling[pos->castle];
-
-    //if (ptype == KING) {
-    //    pos->king[us] = to;
-    //} else
-    /* do this always, cheaper than test on K move */
-    pos->king[us] = ctz64(pos->bb[us][KING]);
-
-    pos->key = key;
-
-    zobrist_verify(pos);
-
-    return pos;
-}
-
-/**
- * move_undo() - undo move.
- * @pos:    &pos_t position
- * @move:   move to undo
- * @state:  &state_t address where irreversible changes were saved
- *
- * @move is applied to @pos:
- * - bitboards and board are updated
- * - previous information is restored:
- *   - castling
- *   - en-passant
- *   - captured piece (excl. en-passant)
- *   - move count
- *   - 50-moves rule count
- *
- * @return: pos.
- */
-pos_t *move_undo(pos_t *pos, const move_t move, const state_t *state)
-{
-    color_t them = pos->turn, us = OPPONENT(them);
-    square_t from = move_from(move), to = move_to(move);
-    piece_t piece = pos->board[to];
-    int up = sq_up(them);
-
-    /* common part: captures and non captures
-     * We could improve slightly, as en-passant and double push will make
-     * the following tests.
-     * Improvement could be to add promotion test and king test twice above.
-     * (in capture and after ).
-     */
-    if (is_promotion(move))
-        piece = MAKE_PIECE(PAWN, us);
-
-    pos_clr_sq(pos, to);
-    pos_set_sq(pos, from, piece);
-
-    /* special moves: capture, king (+ castling), en-passant
-     */
-    if (pos->captured != EMPTY) {                 /* captured: restore piece */
-        pos_set_sq(pos, to, pos->captured);
-    } else if (is_castle(move)) {                 /* castle: rook move */
-        square_t rookfrom, rookto;
-        if (to > from) {                          /* o-o */
-            rookfrom = to - 1;
-            rookto = to + 1;
-        } else {                                  /* o-o-o */
-            rookfrom = to + 1;
-            rookto = to - 2;
-        }
-        pos_set_sq(pos, rookto, pos->board[rookfrom]);
-        pos_clr_sq(pos, rookfrom);
-    } else if (is_enpassant(move)) {              /* e.p.: restore grabbed pawn */
-        square_t grabbed = to + up;
-        pos_set_sq(pos, grabbed, MAKE_PIECE(PAWN, them));
-    }
-
-    /* do this always, cheaper than test on K move */
-    pos->king[us] = ctz64(pos->bb[us][KING]);
-    //if (PIECE(piece) == KING)
-    //    pos->king[us] = from;
-
-    pos->state = *state;                          /* restore irreversible changes */
-    pos->turn = us;
-    return pos;
-}
-
-/**
- * move_{do,undo}_alt - alternative move_do/move_undo (to experiment)
- */
-pos_t *move_do_alt(pos_t *pos, const move_t move, state_t *state)
-{
-    color_t us = pos->turn, them = OPPONENT(us);
-    square_t from = move_from(move), to = move_to(move);
-    piece_t piece = pos->board[from];
-    piece_t captured = pos->board[to];
-    piece_type_t ptype = PIECE(piece);
-    piece_t new_piece = piece;
-    int up = sq_up(us);
-    hkey_t key = pos->key;
-
-    *state = pos->state;                          /* save irreversible changes */
+    pos->prev = state;
 
     /* update key: switch turn, reset castling and ep */
     key ^= zobrist_turn;
     key ^= zobrist_castling[pos->castle];
     key ^= zobrist_ep[EP_ZOBRIST_IDX(pos->en_passant)];
 
-    ++pos->clock_50;
+    ++pos->ply50;
     ++pos->plycount;
+    ++pos->plyroot;
     pos->en_passant = SQUARE_NONE;
     pos->turn = them;
     pos->captured = captured;
@@ -256,17 +79,21 @@ pos_t *move_do_alt(pos_t *pos, const move_t move, state_t *state)
 
     if (is_promotion(move)) {
         bug_on(sq_rank(to) != sq_rel_rank(RANK_8, us));
-        new_piece = MAKE_PIECE(move_promoted(move), us);
+        piece_t promoted = move_promoted(move);
+        new_piece = MAKE_PIECE(promoted, us);
+        pos->phase += pt_phase(PAWN) - pt_phase(promoted);
     }
 
     if (captured != EMPTY) {
-        pos->clock_50 = 0;
-        //pos->captured = pos->board[to];           /* save capture info */
-        bug_on(pos->board[to] == EMPTY || COLOR(pos->captured) != them);
+        pos->ply50 = 0;
+        pos->phase += pt_phase(PIECE(captured));
+
+        bug_on(COLOR(captured) != them);
         key ^= zobrist_pieces[captured][to];
         pos_clr_sq(pos, to);                      /* clear square */
     } else if (is_castle(move)) {                 /* handle rook move */
         square_t rookfrom, rookto;
+
         if (to > from) {
             rookfrom = sq_rel(H1, us);
             rookto = sq_rel(F1, us);
@@ -280,9 +107,10 @@ pos_t *move_do_alt(pos_t *pos, const move_t move, state_t *state)
         pos_clr_sq(pos, rookfrom);
         pos->castle = clr_castle(pos->castle, us);
     } else if (ptype == PAWN) {                   /* pawn non capture or e.p. */
-        pos->clock_50 = 0;
+        pos->ply50 = 0;
         if (from + up + up == to) {               /* if pawn double push, set e.p. */
             square_t ep = from + up;
+
             if (bb_pawn_attacks[us][ep] & pos->bb[them][PAWN]) {
                 pos->en_passant = ep;
                 key ^= zobrist_ep[EP_ZOBRIST_IDX(pos->en_passant)];
@@ -290,13 +118,15 @@ pos_t *move_do_alt(pos_t *pos, const move_t move, state_t *state)
         } else if (is_enpassant(move)) {          /* clear grabbed pawn */
             square_t grabbed = to - up;
             piece_t pc = pos->board[grabbed];
+
+            pos->phase += pt_phase(PAWN);
             key ^= zobrist_pieces[pc][grabbed];
             pos_clr_sq(pos, grabbed);
         }
     }
 
     key ^= zobrist_pieces[piece][from] ^ zobrist_pieces[new_piece][to];
-    pos_clr_sq(pos, from);
+    pos_clr_sq(pos, from);                        /* clear "from" and set "to" */
     pos_set_sq(pos, to, new_piece);
 
     if (ptype == KING)
@@ -332,6 +162,185 @@ pos_t *move_do_alt(pos_t *pos, const move_t move, state_t *state)
 
     pos->key = key;
 
+    pos->repcount = pos_repcount(pos);
+
+    /* consistency checks.
+     * Checks done only if compiled with '-DZOBRIST_VERIFY' or '-DPHASE_VERIFY'
+     */
+    zobrist_verify(pos);
+    phase_verify(pos);
+
+    return pos;
+}
+
+/**
+ * move_undo() - undo move.
+ * @pos:    &pos_t position
+ * @move:   move to undo
+ * @state:  &state_t address where irreversible changes were saved
+ *
+ * @move is applied to @pos:
+ * - bitboards and board are updated
+ * - previous information is restored:
+ *   - castling
+ *   - en-passant
+ *   - captured piece (excl. en-passant)
+ *   - move count
+ *   - 50-moves rule count
+ *
+ * @return: pos.
+ */
+pos_t *move_undo(pos_t *pos, const move_t move, const state_t *state)
+{
+    color_t them = pos->turn, us = OPPONENT(them);
+    square_t from = move_from(move), to = move_to(move);
+    piece_t piece = pos->board[to];
+    int up = sq_up(them);
+
+    if (is_promotion(move))
+        piece = MAKE_PIECE(PAWN, us);
+
+    pos_clr_sq(pos, to);                          /* always clear "to" ... */
+    pos_set_sq(pos, from, piece);                 /* ... and set "from" */
+
+    if (PIECE(piece) == KING)
+        pos->king[us] = from;
+
+    if (pos->captured != EMPTY) {
+        pos_set_sq(pos, to, pos->captured);       /* restore captured piece */
+    } else if (is_castle(move)) {                 /* make reverse rook move */
+        square_t rookfrom, rookto;
+        if (to > from) {
+            rookfrom = sq_rel(F1, us);
+            rookto = sq_rel(H1, us);
+        } else {
+            rookfrom = sq_rel(D1, us);
+            rookto = sq_rel(A1, us);
+        }
+        pos_set_sq(pos, rookto, pos->board[rookfrom]);
+        pos_clr_sq(pos, rookfrom);
+    } else if (is_enpassant(move)) {              /* restore grabbed pawn */
+        square_t grabbed = to + up;
+        pos_set_sq(pos, grabbed, MAKE_PIECE(PAWN, them));
+    }
+
+    pos->state = *state;                          /* restore irreversible changes */
+    pos->turn = us;
+    --pos->plycount;
+    --pos->plyroot;
+    return pos;
+}
+
+/**
+ * move_{do,undo}_alt - alternative move_do/move_undo (to experiment)
+ */
+pos_t *move_do_alt(pos_t *pos, const move_t move, state_t *state)
+{
+    color_t us = pos->turn, them = OPPONENT(us);
+    square_t from = move_from(move), to = move_to(move);
+    piece_t piece = pos->board[from];
+    piece_t captured = pos->board[to];
+    piece_type_t ptype = PIECE(piece);
+    piece_t new_piece = piece;
+    int up = sq_up(us);
+    hkey_t key = pos->key;
+
+    *state = pos->state;                          /* save irreversible changes */
+    pos->prev = state;
+
+    /* update key: switch turn, reset castling and ep */
+    key ^= zobrist_turn;
+    key ^= zobrist_castling[pos->castle];
+    key ^= zobrist_ep[EP_ZOBRIST_IDX(pos->en_passant)];
+
+    ++pos->ply50;
+    ++pos->plycount;
+    ++pos->plyroot;
+    pos->en_passant = SQUARE_NONE;
+    pos->turn = them;
+    pos->captured = captured;
+    pos->move = move;
+
+    bug_on(COLOR(piece) != us);
+
+    if (is_promotion(move)) {
+        bug_on(sq_rank(to) != sq_rel_rank(RANK_8, us));
+        new_piece = MAKE_PIECE(move_promoted(move), us);
+    }
+
+    if (captured != EMPTY) {
+        pos->ply50 = 0;
+        bug_on(pos->board[to] == EMPTY || COLOR(pos->captured) != them);
+        key ^= zobrist_pieces[captured][to];
+        pos_clr_sq(pos, to);                      /* clear square */
+    } else if (is_castle(move)) {                 /* handle rook move */
+        square_t rookfrom, rookto;
+        if (to > from) {
+            rookfrom = sq_rel(H1, us);
+            rookto = sq_rel(F1, us);
+        } else {
+            rookfrom = sq_rel(A1, us);
+            rookto = sq_rel(D1, us);
+        }
+        key ^= zobrist_pieces[pos->board[rookfrom]][rookto] ^
+            zobrist_pieces[pos->board[rookfrom]][rookfrom];
+        pos_set_sq(pos, rookto, pos->board[rookfrom]);
+        pos_clr_sq(pos, rookfrom);
+        pos->castle = clr_castle(pos->castle, us);
+    } else if (ptype == PAWN) {                   /* pawn non capture or e.p. */
+        pos->ply50 = 0;
+        if (from + up + up == to) {               /* if pawn double push, set e.p. */
+            square_t ep = from + up;
+            if (bb_pawn_attacks[us][ep] & pos->bb[them][PAWN]) {
+                pos->en_passant = ep;
+                key ^= zobrist_ep[EP_ZOBRIST_IDX(pos->en_passant)];
+            }
+        } else if (is_enpassant(move)) {          /* clear grabbed pawn */
+            square_t grabbed = to - up;
+            piece_t pc = pos->board[grabbed];
+            key ^= zobrist_pieces[pc][grabbed];
+            pos_clr_sq(pos, grabbed);
+        }
+    }
+
+    key ^= zobrist_pieces[piece][from] ^ zobrist_pieces[new_piece][to];
+    pos_clr_sq(pos, from);                        /* clear "from" and set "to" */
+    pos_set_sq(pos, to, new_piece);
+
+    if (ptype == KING)
+        pos->king[us] = to;
+
+    /* update castling flags
+     * As we always consider flags are valid, we :
+     * - adjust our flags if relative from is "E1", "A1", H1"
+     * - adjust opp flags if relative to   if "A8", H8"
+     */
+    if (can_castle(pos->castle, us)) {            /* do we save time with this test ? */
+        square_t rel_e1 = sq_rel(E1, us);
+        square_t rel_a1 = sq_rel(A1, us);
+        square_t rel_h1 = sq_rel(H1, us);
+        if (from == rel_e1)
+            pos->castle = clr_castle(pos->castle, us);
+        else if (from == rel_a1)
+            pos->castle = clr_ooo(pos->castle, us);
+        else if (from == rel_h1)
+            pos->castle = clr_oo(pos->castle, us);
+    }
+    if (can_castle(pos->castle, them)) {
+        square_t rel_a8 = sq_rel(A8, us);
+        square_t rel_h8 = sq_rel(H8, us);
+        if (to == rel_a8)
+            pos->castle = clr_ooo(pos->castle, them);
+        else if (to == rel_h8)
+            pos->castle = clr_oo(pos->castle, them);
+    }
+
+    /* update castling rights key */
+    key ^= zobrist_castling[pos->castle];
+
+    pos->key = key;
+
+    pos->repcount = pos_repcount(pos);
     zobrist_verify(pos);
 
     return pos;
@@ -373,5 +382,7 @@ pos_t *move_undo_alt(pos_t *pos, const move_t move, const state_t *state)
 
     pos->state = *state;                          /* restore irreversible changes */
     pos->turn = us;
+    --pos->plycount;
+    --pos->plyroot;
     return pos;
 }

src/move-do.h

@@ -14,11 +14,8 @@
 #ifndef MOVE_DO_H
 #define MOVE_DO_H
 
-#include "chessdefs.h"
 #include "position.h"
 
-extern castle_rights_t sq_castle[64];             /* to adjust castling rights */
-
 pos_t *move_do(pos_t *pos, const move_t move, state_t *state);
 pos_t *move_undo(pos_t *pos, const move_t move, const state_t *state);
 

src/perft.c

@@ -19,6 +19,84 @@
 #include "move-gen.h"
 #include "move-do.h"
 
+/**
+ * do_perft() - perft engine
+ * @pos:    &position to search
+ * @depth:  Wanted depth.
+ *
+ * Run perft on a position.
+ *
+ * This version uses the algorithm:
+ *    gen legal moves
+ *    if last depth
+ *      return number of legal move
+ *    loop for legal move
+ *      do-move
+ *      if depth == 2
+ *
+ *      do_perft (depth -1)
+ *      undo-move
+ *
+ * @return: total moves found at @depth level.
+ */
+static u64 do_perft(pos_t *pos, int depth)
+{
+    u64 nodes = 0;
+    movelist_t movelist;
+    move_t *move, *last;
+    state_t state;
+
+    pos_set_checkers_pinners_blockers(pos);
+    pos_legal(pos, pos_gen_pseudo(pos, &movelist));
+
+    //if (depth == 1)
+    //    return movelist.nmoves;
+
+    last = movelist.move + movelist.nmoves;
+    switch (depth) {
+        case 1:
+            /* This case could be removed if 'case 2' is handled in perft()
+             */
+            return movelist.nmoves;
+            break;
+        case 2:
+            /* For depth 2, we directly calculate the possible legal moves
+             * after each possible moves.
+             */
+            for (move = movelist.move; move < last; ++move) {
+                move_do(pos, *move, &state);
+                movelist_t movelist2;
+                pos_set_checkers_pinners_blockers(pos);
+                nodes += pos_legal(pos, pos_gen_pseudo(pos, &movelist2))->nmoves;
+                move_undo(pos, *move, &state);
+            }
+            break;
+        default:
+            /* Default: Search in TT for same key+depth. Use it if found, create
+             * it otherwise.
+             */
+            for (move = movelist.move; move < last; ++move) {
+                move_do(pos, *move, &state);
+                hentry_t *entry = tt_probe_perft(pos->key, depth);
+                if (entry != TT_MISS) {
+                    nodes += HASH_PERFT_VAL(entry->data);
+                } else {
+                    u64 subnodes = do_perft(pos, depth - 1);
+                    tt_store_perft(pos->key, depth, subnodes);
+                    nodes += subnodes;
+                }
+                move_undo(pos, *move, &state);
+            }
+            //} else {
+            //subnodes = do_perft(pos, depth - 1);
+    }
+        //move_undo(pos, *move, &state);
+        //nodes += subnodes;
+    //}
+
+    return nodes;
+}
+
 /**
  * perft() - Perform perft on position
  * @pos:    &position to search
@@ -40,7 +118,7 @@
  *
  * @return: total moves found at @depth level.
  */
-u64 perft(pos_t *pos, int depth, int ply, bool divide)
+u64 perft(pos_t *pos, int depth, bool divide)
 {
     u64 subnodes = 0, nodes = 0;
     movelist_t movelist;
@@ -56,30 +134,15 @@ u64 perft(pos_t *pos, int depth, int ply, bool divide)
             subnodes = 1;
         } else {
             move_do(pos, *move, &state);
-            if (depth == 2) {
-                movelist_t movelist2;
-                pos_set_checkers_pinners_blockers(pos);
-                subnodes = pos_legal(pos, pos_gen_pseudo(pos, &movelist2))->nmoves;
-            } else if (ply >= 3) {
-                hentry_t *entry = tt_probe_perft(pos->key, depth);
-                if (entry != TT_MISS) {
-                    subnodes = HASH_PERFT_VAL(entry->data);
-                } else {
-                    subnodes = perft(pos, depth - 1, ply + 1, divide);
-                    tt_store_perft(pos->key, depth, subnodes);
-                }
-            } else {
-                subnodes = perft(pos, depth - 1, ply + 1, divide);
-            }
+            subnodes = do_perft(pos, depth - 1);
             move_undo(pos, *move, &state);
         }
-        nodes += subnodes;
-        if (ply == 1 && divide) {
+        if (divide) {
             char movestr[8];
             printf("%s: %lu\n", move_to_str(movestr, *move, 0), subnodes);
         }
+        nodes += subnodes;
     }
-
     return nodes;
 }
 

src/perft.h

@@ -16,7 +16,7 @@
 
 #include "position.h"
 
-u64 perft(pos_t *pos, int depth, int ply, bool output);
+u64 perft(pos_t *pos, int depth,/* int ply,*/ bool divide);
 u64 perft_alt(pos_t *pos, int depth, int ply, bool output);
 
 #endif  /* PERFT_H */

src/position.c

@@ -108,6 +108,7 @@ pos_t *pos_clear(pos_t *pos)
 
     pos->king[WHITE] = SQUARE_NONE;
     pos->king[BLACK] = SQUARE_NONE;
+    pos->prev = HIST_START;
 
     return pos;
 }
@@ -130,7 +131,7 @@ bool pos_cmp(const pos_t *pos1, const pos_t *pos2)
 
     /* move_do/undo position state */
     if (_cmpf(key) || _cmpf(en_passant) || _cmpf(castle) ||
-        _cmpf(clock_50) || _cmpf(plycount) || _cmpf(captured))
+        _cmpf(ply50) || _cmpf(plycount) || _cmpf(captured))
         goto end;
 
     if (_cmpf(checkers) || _cmpf(pinners) || _cmpf(blockers))
@@ -180,6 +181,36 @@ bitboard_t pos_checkers(const pos_t *pos, const color_t color)
     return sq_attackers(pos, occ, pos->king[color], OPPONENT(color));
 }
 
+/**
+ * pos_repcount() - return position repetition count.
+ * @pos: &position to search
+ *
+ * Attention: positions before (and including) root position repcount are
+ * already decreased by one. See do_moves() in uci.c.
+ *
+ * @return: The number of repetitions in history, zero otherwise.
+ */
+u8 pos_repcount(pos_t *pos)
+{
+    int c50 = pos->ply50;
+    state_t *st = &pos->state;
+    hkey_t key = pos->key;
+
+    st = hist_prev4(st);
+    //printf("is rep: START=%p ", HIST_START);
+    //printf("state=%p diff=%zd c50=%d k1=%#lx k2=%#lx\n",
+    //       st, st - HIST_START, c50, hash_short(pos->key), hash_short(st->key));
+
+    /* attention, what about root position ? Isn't it dangerous to compare with
+     * its key ? like: st->prev != HIST_START
+     */
+    for (; c50 >= 0 && st != HIST_START; st = hist_prev2(st), c50 -= 2) {
+        if (key == st->key)
+            return st->repcount + 1;
+    }
+    return false;
+}
+
 /**
  * pos_set_checkers_pinners_blockers() - calculate checkers, pinners and blockers.
  * @pos:   &position

src/position.h

@@ -27,6 +27,7 @@
 #include "piece.h"
 #include "move.h"
 #include "board.h"
+#include "eval-defs.h"
 
 typedef struct __pos_s {
     u64 node_count;                               /* evaluated nodes */
@@ -50,14 +51,14 @@ typedef struct __pos_s {
 
                         /* 16 bits */
                         move_t move;
-                        u16 plycount;             /* plies so far, start from 1 */
-                        s16 phase;
 
                         /* 8 bits */
                         square_t en_passant;
                         castle_rights_t castle;
                         piece_t captured;         /* only used in move_undo */
-                        u8 clock_50;
+                        phase_t phase;
+                        u8 ply50;
+                        u8 repcount;              /* repetition count */
         );
     eval_t eval;
     bitboard_t checkers;                          /* opponent checkers */
@@ -66,6 +67,8 @@ typedef struct __pos_s {
     piece_t board[BOARDSIZE];
     bitboard_t bb[2][PT_NB];                      /* bb[0][PAWN], bb[1][ALL_PIECES] */
     square_t king[2];                             /* dup with bb, faster retrieval */
+    u16 plycount;                                 /* plies in game, start from 1 */
+    u8 plyroot;                                   /* plies since search root. root=0 */
 } pos_t;
 
 typedef struct state_s state_t;
@@ -88,8 +91,8 @@ 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;
 
@@ -114,38 +117,12 @@ 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
@@ -209,6 +186,7 @@ void pos_del(pos_t *pos);
 pos_t *pos_clear(pos_t *pos);
 bool pos_cmp(const pos_t *pos1, const pos_t *pos2);
 
+u8 pos_repcount(pos_t *pos);
 void pos_set_checkers_pinners_blockers(pos_t *pos);
 void pos_set_pinners_blockers(pos_t *pos);
 bitboard_t pos_checkers(const pos_t *pos, const color_t color);

src/pv.h

@@ -0,0 +1,53 @@
+/* pv.c - Principal variation.
+ *
+ * Copyright (C) 2024 Bruno Raoult ("br")
+ * Licensed under the GNU General Public License v3.0 or later.
+ * Some rights reserved. See COPYING.
+ *
+ * You should have received a copy of the GNU General Public License along with this
+ * program. If not, see <https://www.gnu.org/licenses/gpl-3.0-standalone.html>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later <https://spdx.org/licenses/GPL-3.0-or-later.html>
+ *
+ */
+
+#include <stdio.h>
+#include <ctype.h>
+
+#include <brlib.h>
+
+#include "move.h"
+
+/*
+ * For PV, we use a triangular structure. The following table is adapted from
+ * https://www.chessprogramming.org/Triangular_PV-Table.
+ *
+ * ply     Search   maxLengthPV
+ *         Depth
+ *                  +--------------------------------------------+
+ * 0=root  N        |N                                           |
+ *                  +------------------------------------------+-+
+ * 1       N-1      |N-1                                       |
+ *                  +----------------------------------------+-+
+ * 2       N-2      |N-2                                     |
+ *                  +----------------------------------------+-+
+ * ...                                     /
+ *                  +-----+-+
+ * N-3     3        |3    |
+ *                  +---+-+
+ * N-2     2        |2  |
+ *                  +-+-+
+ * N-1     1        |1|
+ *                  +-+
+ *
+ * The offsets will be:
+ * Depth (=size):  1  2  3  4  5  6  7 ...
+ * Offset:         0  1  3  6 10 15 21 ...
+ *
+ * Off(n)     = n * (n - 1) / 2      (direct calc)
+ * Off(n + 1) = Off(n) + n           (calc from previous)
+ */
+
+typedef struct {
+    move[];
+} foo;

src/search.c

@@ -15,11 +15,30 @@
 
 #include <brlib.h>
 
+#include "chessdefs.h"
+
 #include "position.h"
 #include "move-gen.h"
 #include "move-do.h"
 #include "search.h"
 #include "attack.h"
+#include "hist.h"
+
+search_uci_t search_uci;
+
+/**
+ * is_draw() - check if position is draw by 50 or repetition rule.
+ * @pos: &position to search
+ *
+ * Note that states before (and including) root position state have
+ * their repcount decreased by one.
+ *
+ * @return: The @pos negamax evaluation.
+ */
+bool is_draw(pos_t *pos)
+{
+    return (pos->ply50 > 100 || pos->repcount);
+}
 
 /**
  * negamax() - search position negamax.
@@ -32,35 +51,57 @@
  *
  * @return: The @pos negamax evaluation.
  */
-/*
- * eval_t negamax(pos_t *pos, int depth, int color)
- * {
- *     move_t *move;
- *     pos_t *newpos;
- *     eval_t best = EVAL_MIN, score;
- *
- *     pos->node_count++;
- *     if (depth == 0) {
- *         moves_gen_all_nomoves(pos);
- *         score = eval(pos) * color;
- *         return score;
- *     }
- *     moves_gen_all(pos);
- *     list_for_each_entry(move, &pos->moves[pos->turn], list) {
- *         newpos = move_do(pos, move);
- *         score = -negamax(newpos, depth - 1, -color);
- *         pos->node_count += newpos->node_count;
- *         move->negamax = score;
- *         if (score > best) {
- *             best = score;
- *             pos->bestmove = move;
- *         }
- *         move_undo(newpos, move);
- *     }
- *     return best;
- * }
- */
+eval_t negamax(pos_t *pos, int depth, int color)
+{
+    move_t *move, *last;
+    state_t state;
+    eval_t best = EVAL_MIN, score;
+    movelist_t movelist;
 
+    pos->node_count++;
+
+    if (pos_repcount(pos))                        /* repetition */
+        return EVAL_DRAW * color;
+
+    pos_set_checkers_pinners_blockers(pos);
+    pos_gen_legal(pos, &movelist);
+
+    if (!movelist.nmoves)                         /* no move: mate ot draw */
+        return (pos->checkers? EVAL_MATE: EVAL_DRAW) * color;
+
+    if (depth == 0) {
+        score = eval(pos) * color;
+        return score;
+    }
+
+    last = movelist.move + movelist.nmoves;
+    for (move = movelist.move; move < last; ++move) {
+        move_do(pos, *move, &state);
+        score = -negamax(pos, depth - 1, -color);
+        if (score > best) {
+            best = score;
+            pos->eval = best;
+        }
+        move_undo(pos, *move, &state);
+    }
+    return best;
+}
+
+/**
+ * search() - do (iterative) search.
+ * @pos: &position to search
+ * @depth: wanted depth.
+ * @alpha: alpha.
+ * @beta: beta.
+ * @color: 1 for white, -1 for black.
+ *
+ *
+ * @return: The @pos PVS evaluation.
+ */
+void search(__unused pos_t *pos)
+{
+
+}
 
 /**
  * pvs() - Principal Variation Search.

src/search.h

@@ -16,7 +16,21 @@
 
 #include "position.h"
 
-//eval_t negamax(pos_t *pos, int depth, int color);
+/**
+ * search_values_t - search values given by "go" command
+ * @depth: max depth "go depth X", MAX_DEPTH for no limit
+ *
+ *
+ */
+typedef struct {
+    u16 depth;                                    /* go depth X */
+} search_uci_t;
+
+extern search_uci_t search_uci;
+
+bool is_draw(pos_t *pos);
+eval_t negamax(pos_t *pos, int depth, int color);
+void search(pos_t *pos);
 //eval_t pvs(pos_t *pos, int depth, int alpha, int beta, int color);
 
 #endif  /* SEARCH_H */

src/uci.c

@@ -17,6 +17,7 @@
 #include <ctype.h>
 
 #include <brlib.h>
+#include <bug.h>
 
 #include "chessdefs.h"
 #include "util.h"
@@ -50,6 +51,7 @@ int do_quit(pos_t *, char *);
 
 int do_setoption(pos_t *, char *);
 int do_position(pos_t *, char *);
+int do_go(pos_t *, char *);
 
 /* commands *NOT* in UCI standard */
 int do_moves(pos_t *, char *);
@@ -66,6 +68,8 @@ struct command commands[] = {
     { "isready",    do_isready, "" },
     { "setoption",  do_setoption, ""},
     { "position",   do_position, "position startpos|fen [moves ...]" },
+    { "go",         do_go, "go" },
+
 
     { "perft",      do_perft, "(not UCI) perft [divide] [alt] depth" },
     { "moves",      do_moves, "(not UCI) moves ..." },
@@ -334,13 +338,12 @@ int do_setoption(__unused pos_t *pos, __unused char *arg)
 
 int do_position(pos_t *pos, char *arg)
 {
-    char *saveptr, *token, *fen, *moves;
+    char *saveptr = NULL, *token, *fen, *moves;
 
     hist_init();
 
     /* separate "moves" section */
     moves = str_token(arg, "moves");
-    saveptr = NULL;
     token = strtok_r(arg, " ", &saveptr);
     if (!strcmp(token, "startpos")) {
         startpos(pos);
@@ -370,7 +373,51 @@ int do_position(pos_t *pos, char *arg)
     }
     /* link last position t history */
     //hist_pop();
-    hist_link(pos);
+    //hist_link(pos);
+    return 1;
+}
+
+
+int do_go(pos_t *pos, char *arg)
+{
+    char *ptr = NULL, *tok, *val;
+
+    //token = strtok_r(arg, " ", &saveptr);
+    for (tok = strtok_r(arg, " ", &ptr); tok; tok = strtok_r(arg, " ", &ptr)) {
+        /* TODO: Find a "clever" way to get the different values without
+         * multiple "strcmp"
+         */
+
+        if (!strcmp(tok, "searchmoves")) {        /* moves list */
+            ;
+        } else if (!strcmp(tok, "wtime")) {       /* integer */
+            ;
+        } else if (!strcmp(tok, "btime")) {       /* integer */
+            ;
+        } else if (!strcmp(tok, "winc")) {        /* integer */
+            ;
+        } else if (!strcmp(tok, "binc")) {        /* integer */
+            ;
+        } else if (!strcmp(tok, "movestogo")) {   /* integer */
+            ;
+        } else if (!strcmp(tok, "depth")) {       /* integer */
+            if ((val = strtok_r(arg, " ", &ptr)))
+                search_uci.depth = atoi(val);
+            ;
+        } else if (!strcmp(tok, "nodes")) {       /* integer */
+            ;
+        } else if (!strcmp(tok, "mate")) {        /* integer */
+            ;
+        } else if (!strcmp(tok, "movetime")) {    /* integer */
+            ;
+        } else if (!strcmp(tok, "ponder")) {      /* no param */
+            ;
+        } else if (!strcmp(tok, "infinite")) {    /* no param */
+            ;
+        }
+
+    }
+    search(pos);
     return 1;
 }
 
@@ -378,9 +425,8 @@ int do_moves(__unused pos_t *pos, char *arg)
 {
     char *saveptr = NULL, *token, check[8];
     move_t move;
-    state_t state;
     movelist_t movelist;
-    saveptr = NULL;
+
     token = strtok_r(arg, " ", &saveptr);
     while (token) {
         move = move_from_str(token);
@@ -395,13 +441,26 @@ int do_moves(__unused pos_t *pos, char *arg)
             return 1;
         }
         //printf("move: %s\n", move_to_str(check, move, 0));
-        hist_push(&pos->state);                   /* push previous state */
-        move_do(pos, move, &state);
-        pos_print(pos);
+        //hist_push(&pos->state);                   /* push previous state */
+        move_do(pos, move, hist_next());
+        printf("repet=%d\n", pos->repcount);
+        //if (is_repetition(pos))
+        //    printf("rep detected\n");
+        //else if(is_draw(pos))
+        //    printf("draw detected\n");
         hist_static_print();
         token = strtok_r(NULL, " ", &saveptr);
     }
-    //hist_static_print();
+    /* reset position root, and decrease history moves repcounts.
+     * TODO: Maybe use "ucinewgame" to decide when to perform this decrease ?
+     */
+    pos->plyroot = 0;
+    for (state_t *st = &pos->state; st != HIST_START; st = hist_prev(st)) {
+        //printf("adjust rep=%d->\n");
+        st->repcount = max(0, st->repcount - 1);
+    }
+    pos_print(pos);
+    hist_print(pos);
     return 1;
 }
 
@@ -429,7 +488,7 @@ int do_perft(__unused pos_t *pos, __unused char *arg)
     printf("perft: divide=%d alt=%d depth=%d\n", divide, alt, depth);
     if (depth > 0) {
         if (!alt)
-            perft(pos, depth, 1, divide);
+            perft(pos, depth, divide);
         else
             perft_alt(pos, depth, 1, divide);
     }
@@ -438,7 +497,7 @@ int do_perft(__unused pos_t *pos, __unused char *arg)
 
 int do_hist(__unused pos_t *pos, __unused char *arg)
 {
-    hist_static_print();
+    hist_print(pos);
     return 0;
 }
 

test/common-test.h

@@ -198,10 +198,6 @@ struct fentest {
     /*****************************************************
      * tests from talkchess                              *
      *****************************************************/
-    { __LINE__, FEN | MOVEGEN | MOVEDO | PERFT,
-      "https://talkchess.com/viewtopic.php?t=21343",
-      "8/k7/3p4/p2P1p2/P2P1P2/8/8/K7 w - - 0 1"
-    },
     { __LINE__, FEN | MOVEGEN | MOVEDO | PERFT,
       "https://www.talkchess.com/forum3/viewtopic.php?f=7&t=71379",
       "8/6kR/8/8/8/bq6/1rqqqqqq/K1nqnbrq b - - 0 1"
@@ -451,12 +447,7 @@ struct fentest {
 
 static int fentest_cur = -1;
 
-static __unused void restart_fen(void)
-{
-    fentest_cur = -1;
-}
-
-static __unused char *next_fen(uint module)
+static char *next_fen(uint module)
 {
     fentest_cur++;
 

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_to_str(movebuf, *move, 0));
-
+            //       move_str(movebuf, move, 0));
+            //move_p
             move_do(pos, *move, &state);
             //pos_print(pos);
             //fflush(stdout);
@@ -67,7 +67,6 @@ 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);

test/perft-test.c

@@ -242,9 +242,7 @@ static int usage(char *prg)
     fprintf(stderr, "Usage: %s [-cms][-d depth] [-p version] [-t size:\n", prg);
     fprintf(stderr, "\t-c:         do *not* print FEN comments\n");
     fprintf(stderr, "\t-d depth:   perft depth (default: 6)\n");
-    fprintf(stderr, "\t-l line:    start from 'line' test\n");
     fprintf(stderr, "\t-m:         print moves details\n");
-    fprintf(stderr, "\t-n number:  do 'number' tests (default: all)\n");
     fprintf(stderr, "\t-s:         use Stockfish to validate perft result\n");
     fprintf(stderr, "\t-t size:    Transposition Table size (Mb). Default: 32\n");
     fprintf(stderr,
@@ -254,7 +252,7 @@ static int usage(char *prg)
 
 int main(int ac, char**av)
 {
-    int curtest = 0, totalfen = 0;
+    int curtest = 0;
     u64 sf_count = 0, my_count;
     bool comment = true, sf_run = false, divide = false;
     char *fen;
@@ -264,8 +262,6 @@ int main(int ac, char**av)
     FILE *outfd = NULL;
     s64 ms, lps;
     int opt, depth = 6, run = 3, tt, newtt = HASH_SIZE_DEFAULT;
-    int startline = 1, ntests = INT_MAX;
-
     struct {
         s64 count, countskipped, ms;
         s64 minlps, maxlps;
@@ -277,8 +273,7 @@ int main(int ac, char**av)
         { .minlps = LONG_MAX },
     };
 
-    printf("Perft " VERSION "\n");
-    while ((opt = getopt(ac, av, "cd:l:mn:p:st:")) != -1) {
+    while ((opt = getopt(ac, av, "cd:mp:st:")) != -1) {
         switch (opt) {
             case 'c':
                 comment = false;
@@ -288,15 +283,9 @@ int main(int ac, char**av)
                 if (depth <= 0)
                     depth = 6;
                 break;
-            case 'l':
-                startline = atoi(optarg);
-                break;
             case 'm':
                 divide = true;
                 break;
-            case 'n':
-                ntests = atoi(optarg);
-                break;
             case 'p':
                 run = atoi(optarg);
                 break;
@@ -336,23 +325,14 @@ int main(int ac, char**av)
     if (sf_run)
         outfd = open_stockfish();
 
-    /* count total fen tests we will do */
-    while (next_fen(PERFT | MOVEDO))
-        totalfen++;
-    restart_fen();
-
     CLOCK_DEFINE(clock, CLOCK_MONOTONIC);
     while ((fen = next_fen(PERFT | MOVEDO))) {
-        if (cur_line() < startline)
-            continue;
-        if (curtest >= ntests)
-            break;
         if (!(fenpos = fen2pos(pos, fen))) {
             printf("wrong fen line:%d fen:%s\n\n", cur_line(), fen);
             continue;
         }
         curtest++;
-        printf("test:%d/%d line:%d fen:%s\n", curtest, totalfen, cur_line(), fen);
+        printf("test:%d line:%d fen:%s\n", curtest, cur_line(), fen);
         if (comment)
             printf("\t\"%s\"\n",
                    *cur_comment()? cur_comment(): "no test desc");
@@ -384,7 +364,7 @@ int main(int ac, char**av)
 
         if (run & 1) {
             clock_start(&clock);
-            my_count = perft(pos, depth, 1, divide);
+            my_count = perft(pos, depth, divide);
             ms = clock_elapsed_ms(&clock);
             if (!ms) {
                 res[0].skipped++;