pv.h (empty)

I am still unsure if I will go to thread or process...

Makefile

@@ -39,7 +39,9 @@ OBJ       := $(addprefix $(OBJDIR)/,$(SRC_FN:.c=.o))
 TSTSRC    := $(wildcard $(TSTDIR)/*.c)
 
 LIB       := br_$(shell uname -m)                           # library name
-LIBS      := $(strip -l$(LIB))
+LIB       := $(strip $(LIB))
+LIBFILE   := ${BRLIBDIR}/lib$(strip ${LIB}).a
+LIBS      := $(addprefix -l,$(strip $(LIB)))
 
 DEP_FN    := $(SRC_FN)
 DEP       := $(addprefix $(DEPDIR)/,$(DEP_FN:.c=.d))
@@ -102,7 +104,7 @@ endif
 # if no version, use last commit and date.
 # else, if last commit != last tag commit, add commit and date to version number
 ifeq ($(VERSION),)
-  VERSION := $(build)-$(COMMIT)-$(DATE)
+  VERSION := $(build)-git.$(COMMIT)-$(DATE)
 else ifneq ($(COMMIT), $(TAG_COMMIT))
   VERSION := $(VERSION)-next-$(build)-$(COMMIT)-$(DATE)
 endif
@@ -124,13 +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
@@ -344,6 +347,7 @@ brlib:
 	$(info calling with build=$(build))
 	$(MAKE) -e -C $(BRLIB) lib-static
 unexport build
+
 ##################################### brchess binaries
 .PHONY: targets cleanbin cleanbindir
 
@@ -355,9 +359,9 @@ cleanbin:
 cleanbindir:
 	$(call rmdir,$(BINDIR),binaries)
 
-$(TARGET): libs $(OBJ) | $(BINDIR)
+$(TARGET): $(LIBFILE) $(OBJ) | $(BINDIR) libs
 	@echo linking $@.
-	$(CC) $(LDFLAGS) $(OBJ) $(LIBS) -o $@
+	$(CC) $(ALL_LDFLAGS) $(OBJ) -o $@
 
 ##################################### pre-processed (.i) and assembler (.s) output
 .PHONY: cleanasmcpp
@@ -490,6 +494,7 @@ wtf:
 	@#echo LIBSRC=$(LIBSRC)
 
 zob:
+	echo $(LIBFILE)
 	@#$(CC) $(LDFLAGS) $(CPPFLAGS) $(CFLAGS) $< $(LIBS) src/util.c -o util
 
 ##################################### End of multi-targets

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/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 */

src/eval-defs.h

@@ -36,18 +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:
  */
-phase_t 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 @@ phase_t calc_phase(pos_t *pos)
 
     phase = max(phase, 0);
 #   ifdef DEBUG_EVAL
-    printf("calc phase:%d\n", phase);
+    printf("calc phase:%d verif=%d\n", phase, calc_phase(pos));
 #   endif
     return phase;
 }

src/eval.h

@@ -20,6 +20,11 @@
 #include "eval-defs.h"
 
 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/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);
@@ -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;
 }
 

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;
         };
     };

src/move-do.c

@@ -79,16 +79,21 @@ pos_t *move_do(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->ply50 = 0;
-        bug_on(pos->board[to] == EMPTY || COLOR(pos->captured) != them);
+        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);
@@ -105,6 +110,7 @@ pos_t *move_do(pos_t *pos, const move_t move, state_t *state)
         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)];
@@ -112,6 +118,8 @@ pos_t *move_do(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);
         }
@@ -155,7 +163,12 @@ pos_t *move_do(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;
 }

src/move-gen.c

@@ -480,3 +480,18 @@ finish:
     return movelist;
     //return movelist->nmoves = moves - movelist->move;
 }
+
+/**
+ * pos_gen_legal() - generate position legal moves
+ * @pos: position
+ * @movelist: &movelist_t array to store moves
+ *
+ * Generate all @pos legal moves for player-to-move.
+ * @movelist is filled with the moves.
+ *
+ * @Return: movelist
+ */
+movelist_t *pos_gen_legal(pos_t *pos, movelist_t *movelist)
+{
+    return pos_legal(pos, pos_gen_pseudo(pos, movelist));
+}

src/move-gen.h

@@ -27,5 +27,6 @@ movelist_t *pos_legal_dup(const pos_t *pos, movelist_t *pseudo, movelist_t *lega
 movelist_t *pos_legal(const pos_t *pos, movelist_t *list);
 
 movelist_t *pos_gen_pseudo(pos_t *pos, movelist_t *movelist);
+movelist_t *pos_gen_legal(pos_t *pos, movelist_t *movelist);
 
 #endif  /* MOVEGEN_H */

src/perft.c

@@ -20,59 +20,79 @@
 #include "move-do.h"
 
 /**
- * perft() - Perform perft on position
+ * do_perft() - perft engine
  * @pos:    &position to search
  * @depth:  Wanted depth.
- * @ply:    current perft depth level (root = 1)
- * @divide: output total for 1st level moves.
  *
- * Run perft on a position. This function displays the available moves at @depth
- * level for each possible first move, and the total of moves.
+ * Run perft on a position.
  *
  * This version uses the algorithm:
- *    if last depth
- *      return 1;
  *    gen legal moves
+ *    if last depth
+ *      return number of legal move
  *    loop for legal move
  *      do-move
- *      perft (depth -1)
+ *      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 subnodes = 0, nodes = 0;
+    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;
 
-    for (move = movelist.move; move < last; ++move) {
-        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 (pos->plyroot >= 3) {
-            hentry_t *entry = tt_probe_perft(pos->key, depth);
-            if (entry != TT_MISS) {
-                subnodes = HASH_PERFT_VAL(entry->data);
-            } else {
-                subnodes = do_perft(pos, depth - 1);
-                tt_store_perft(pos->key, depth, subnodes);
+    //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);
             }
-        } else {
-            subnodes = do_perft(pos, depth - 1);
-        }
-        move_undo(pos, *move, &state);
-        nodes += subnodes;
+            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;
 }

src/position.c

@@ -185,8 +185,8 @@ bitboard_t pos_checkers(const pos_t *pos, const color_t color)
  * pos_repcount() - return position repetition count.
  * @pos: &position to search
  *
- * Attention: positions before (and including) root position repcount is
- * decreased by one. See do_moves() in uci.c.
+ * 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.
  */

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

@@ -15,6 +15,8 @@
 
 #include <brlib.h>
 
+#include "chessdefs.h"
+
 #include "position.h"
 #include "move-gen.h"
 #include "move-do.h"
@@ -22,6 +24,8 @@
 #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
@@ -47,35 +51,57 @@ bool is_draw(pos_t *pos)
  *
  * @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

@@ -16,8 +16,21 @@
 
 #include "position.h"
 
+/**
+ * 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);
+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/thread.c

@@ -0,0 +1,70 @@
+/* thread.c - thread management.
+ *
+ * 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 <brlib.h>
+#include <pthread.h>
+#include <poll.h>
+#include <sys/socket.h>
+
+#include "thread.h"
+
+/* Still have to decide: thread or process ?
+ *
+ */
+thread_pool_t threadpool;
+
+
+/**
+ * thrd_create - initialize thrd.
+ */
+int thrd_create(__unused int num)
+{
+    int fd[2];
+    /* shall we make a communication channel via a pipe or socket ? */
+    int __unused ret = socketpair(AF_LOCAL, SOCK_SEQPACKET, PF_LOCAL, fd);
+    return 1;
+}
+
+/**
+ * thread_init - initialize thread pool.
+ */
+int thread_init(int nb)
+{
+    nb = clamp(nb, MIN_THRDS, MAX_THRDS);
+
+    /* stop unwanted threads, always keep 1 */
+    for (int i = nb + 1; i < threadpool.nb; ++i) {
+        printf("stopping thread %d - status = \n", i);
+        threadpool.thread[i].cmd = THRD_DO_QUIT;
+    }
+    for (int i = threadpool.nb; i < nb; ++i) {
+        printf("creating thread %d - status = \n", i);
+        thrd_create(i);
+
+    }
+
+    return nb;
+}
+
+/*
+  communication:
+  main thread -> thread
+           commands via memory
+  thread -> main thread
+           status via memory
+           output via pipe/socket
+  thread output will be output/filtered by main thread
+
+ */

src/thread.h

@@ -0,0 +1,55 @@
+/* thread.h - thread management.
+ *
+ * Copyright (C) 2021-2024 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>
+ *
+ */
+
+#ifndef THREAD_H
+#define THREAD_H
+
+#include <pthread.h>
+
+#include <brlib.h>
+
+#include "position.h"
+
+#define MIN_THRDS 1
+#define MAX_THRDS 16
+
+typedef enum {
+    THRD_DEAD,
+    THRD_IDLE,
+    THRD_WORKING,
+} thread_status_t;
+
+typedef enum {
+    /* main thread to subs */
+    THRD_DO_SEARCH,
+    THRD_DO_STOP,
+    THRD_DO_QUIT,
+} thread_cmd_t;
+
+typedef struct {
+    int id;
+    thread_status_t status;
+    thread_cmd_t cmd;
+    int fd[2];
+    pos_t pos;
+} thread_t;
+
+typedef struct {
+    int nb;
+    thread_t thread[MAX_THRDS + 1];
+} thread_pool_t;
+
+int thrd_create(__unused int num);
+int thread_init(int nb);
+
+#endif  /* THREAD_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);
@@ -374,13 +377,56 @@ int do_position(pos_t *pos, char *arg)
     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;
+}
+
 int do_moves(__unused pos_t *pos, char *arg)
 {
     char *saveptr = NULL, *token, check[8];
     move_t move;
     movelist_t movelist;
 
-    saveptr = NULL;
     token = strtok_r(arg, " ", &saveptr);
     while (token) {
         move = move_from_str(token);