4 * ----------------------------------------------------------------------
5 * Copyright (c) 1993, 1994, 1995 Matthias Mutz
6 * Copyright (c) 1999 Michael Vanier and the Free Software Foundation
8 * GNU SHOGI is based on GNU CHESS
10 * Copyright (c) 1988, 1989, 1990 John Stanback
11 * Copyright (c) 1992 Free Software Foundation
13 * This file is part of GNU SHOGI.
15 * GNU Shogi is free software; you can redistribute it and/or modify it
16 * under the terms of the GNU General Public License as published by the
17 * Free Software Foundation; either version 3 of the License,
18 * or (at your option) any later version.
20 * GNU Shogi is distributed in the hope that it will be useful, but WITHOUT
21 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
22 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
25 * You should have received a copy of the GNU General Public License along
26 * with GNU Shogi; see the file COPYING. If not, see
27 * <http://www.gnu.org/licenses/>.
28 * ----------------------------------------------------------------------
34 /* #define DONTUSE_HEURISTIC */
38 static struct leaf *node;
39 static short sqking, sqxking;
40 static short InCheck = false, GenerateAllMoves = false;
41 static short check_determined = false;
43 short deepsearchcut = true;
44 short tas = false, taxs = false, ssa = false;
46 short generate_move_flags = false;
50 * Ply limits for deep search cut. No moves or drops flagged with "stupid"
51 * are considered beyond ply BEYOND_STUPID. Only moves or drops flagged
52 * with "kingattack" are considered beyond ply BEYOND_KINGATTACK. No moves
53 * or drops flagged with "questionable" are considered beyond ply
54 * BEYOND_QUESTIONABLE. Only moves or drops flagged with "tesuji" are
55 * considered beyond ply BEYOND_TESUJI. No drops are considered beyond ply
56 * BEYOND_DROP. Exceptions: moves or drops that prevent check or give
57 * check are always considered.
60 #define BEYOND_STUPID 0
61 #define BEYOND_TIMEOUT 2
62 #define BEYOND_KINGATTACK 6
63 #define BEYOND_QUESTIONABLE 8
64 #define BEYOND_TESUJI 8
65 #define BEYOND_DROP 10
67 #ifdef DONTUSE_HEURISTIC
68 static short MaxNum[MAXDEPTH] =
70 -1, 40, 80, 20, 40, 10, 5, 5, 5, 5,
71 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
72 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
73 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
78 extern int CheckHashKey();
79 extern char mvstr[4][6];
84 * Update Arrays board[] and color[] to reflect the new board
85 * position obtained after making the move pointed to by node.
89 GenMakeMove(short side,
92 short *tempb, /* piece at to square */
93 short *tempc, /* color of to square */
96 short piece, upiece, n;
102 piece = f - NO_SQUARES;
104 if (piece > NO_PIECES)
109 n = (Captured[side][piece])--;
110 UpdateDropHashbd(side, piece, n);
111 UpdateHashbd(side, piece, -1, t);
112 UpdatePieceList(side, t, ADD_PIECE);
119 if (*tempb != no_piece)
121 n = ++Captured[side][upiece = unpromoted[*tempb]];
122 UpdateDropHashbd(side, upiece, n);
123 UpdateHashbd(*tempc, *tempb, -1, t);
124 UpdatePieceList(*tempc, t, REMOVE_PIECE);
128 Pindex[t] = Pindex[f];
129 PieceList[side][Pindex[t]] = t;
136 UpdateHashbd(side, piece, f, -1);
137 board[t] = promoted[piece];
138 UpdateHashbd(side, board[t], -1, t);
143 UpdateHashbd(side, piece, f, t);
151 printf("error in GenMakeMove: %s\n", mvstr[0]);
164 GenUnmakeMove(short side,
171 short piece, upiece, n;
177 piece = f - NO_SQUARES;
179 if (piece > NO_PIECES)
184 n = ++Captured[side][piece];
185 UpdateDropHashbd(side, piece, n);
186 UpdateHashbd(side, piece, -1, t);
187 UpdatePieceList(side, t, REMOVE_PIECE);
194 Pindex[f] = Pindex[t];
195 PieceList[side][Pindex[f]] = f;
197 if (tempb != no_piece)
199 /* FIXME: make this next line a bit more reasonable... */
200 n = (Captured[side][upiece = unpromoted[tempb]])--;
201 UpdateDropHashbd(side, upiece, n);
202 UpdateHashbd(tempc, tempb, -1, t);
203 UpdatePieceList(tempc, t, ADD_PIECE);
210 UpdateHashbd(side, piece, -1, t);
211 board[f] = unpromoted[piece];
212 UpdateHashbd(side, board[f], f, -1);
217 UpdateHashbd(side, piece, f, t);
225 printf("error in GenUnmakeMove: %s\n", mvstr[0]);
234 gives_check_flag(unsigned short *flags, short side, short f, short t)
236 short tempb, tempc, blockable, promote_piece;
237 promote_piece = (*flags & promote) != 0;
238 GenMakeMove(side, f, t, &tempb, &tempc, promote_piece);
240 if (SqAttacked(sqxking, side, &blockable))
243 GenUnmakeMove(side, f, t, tempb, tempc, promote_piece);
249 short from, short to, unsigned short local_flag, short s)
253 dsp->ShowMessage("TREE overflow\n");
258 node->t = (local_flag & promote) ? (to | 0x80) : to;
260 node->flags = local_flag;
262 node->INCscore = INCscore;
264 if (GenerateAllMoves)
266 /* FIXME: gimme a break! */
271 /* only moves out of check */
272 short tempb, tempc, sq, threat, blockable, promote_piece;
273 promote_piece = (node->flags & promote) != 0;
274 GenMakeMove(side, node->f, node->t,
275 &tempb, &tempc, promote_piece);
276 sq = (from == sqking) ? to : sqking;
277 threat = SqAttacked(sq, side ^ 1, &blockable);
278 GenUnmakeMove(side, node->f, node->t,
279 tempb, tempc, promote_piece);
283 /* FIXME! Gimme a break! */
289 /* only moves that give check */
290 if (!(node->flags & check) && !check_determined)
292 /* determine check flag */
293 gives_check_flag(&node->flags, side, node->f, node->t);
296 if (node->flags & check)
298 /* FIXME! Gimme a break! */
304 /* FIXME! Gimme a break! */
312 PromotionPossible(short color, short f, short t, short p)
316 if ((!InWhiteCamp(f)) && (!InWhiteCamp(t)))
321 if ((!InBlackCamp(f)) && (!InBlackCamp(t)))
325 /* FIXME: this can be simplified... */
344 NonPromotionPossible(short color,
354 : (generate_move_flags ? ILLEGAL_TRAPPED : false));
360 : (generate_move_flags ? ILLEGAL_TRAPPED : false));
369 : (generate_move_flags ? ILLEGAL_TRAPPED : false));
375 : (generate_move_flags ? ILLEGAL_TRAPPED : false));
383 : (generate_move_flags ? ILLEGAL_TRAPPED : false));
389 : (generate_move_flags ? ILLEGAL_TRAPPED : false));
398 #if defined FIELDBONUS || defined DROPBONUS
400 /* bonus for possible next moves */
403 field_bonus(short side, short piece,
404 short f, short t, unsigned short *local_flag)
407 unsigned char *ppos, *pdir;
417 check_determined = true;
419 ptyp = ptype[side][piece];
422 u = first_direction(ptyp, &d, t);
424 ppos = (*nextpos[ptyp])[t];
425 pdir = (*nextdir[ptyp])[t];
431 short coloru = color[u];
433 if (piece != king && GameCnt > 40)
435 if (distance(u, EnemyKing) <= 1)
437 /* can reach square near own king */
439 *local_flag |= kingattack;
441 else if (distance(u, OwnKing) <= 1)
443 /* can reach square near enemy king */
445 *local_flag |= kingattack;
451 /* impossible next move */
453 u = next_direction(ptyp, &d, t);
460 /* possible next move */
461 if (PromotionPossible(side, t, u, piece))
463 /* possible promotion in next move */
468 if (!InPromotionZone(side, t))
470 *local_flag |= tesuji; /* The dangling pawn */
481 if (coloru == neutral)
483 /* next move to an empty square */
486 /* opponent has just left this square */
491 u = next_position(ptyp, &d, t, u);
498 /* attack opponents piece */
500 short boardu, upiece, rvupiece, rvuboard;
504 if (u == TOsquare) /* opponent has moved to TOsquare */
507 if ((boardu = board[u]) == king)
509 s += 20; INCscore -= 18;
510 *local_flag |= check; /* move threatens
515 upiece = unpromoted[piece];
516 rvupiece = relative_value[upiece];
517 rvuboard = relative_value[unpromoted[boardu]];
519 if ((upiece == pawn) && (Captured[side][pawn] > 1))
521 *local_flag |= tesuji; /* The joining pawn attack */
525 if (rvupiece <= rvuboard)
527 *local_flag |= tesuji; /* The striking pawn
538 /* CHECKME: is this right? */
539 if (((rvupiece == rvuboard) && (upiece == pawn))
540 || (upiece == bishop)
542 || (upiece == knight)
546 s++; /* The opposing pawn (piece) */
555 u = next_direction(ptyp, &d, t);
575 * Add a move to the tree. Assign a bonus to order the moves as follows:
576 * 1. Principle variation 2. Capture of last moved piece 3. Other captures
577 * (major pieces first) 4. Killer moves 5. Tesuji drops 6. Other Moves
578 * 7. Other drops. 8. Non-promoting moves
579 * If the flag.tsume is set, assign a high bonus for checks.
583 LinkMove(short ply, short f,
585 unsigned short local_flag,
587 short score_if_impossible)
590 short side, piece, mv;
591 short flag_tsume, try_link = true;
592 short c1, c2, ds, is_drop = f > NO_SQUARES;
593 unsigned long as = 0;
595 flag_tsume = flag.tsume;
597 c1 = side = xside ^ 1;
601 * Is it determined whether the move gives check ?
604 check_determined = ((local_flag & check) != 0);
606 mv = (f << 8) | ((local_flag & promote) ? (t | 0x80) : t);
610 piece = f - NO_SQUARES;
612 if (piece > NO_PIECES)
620 if (score_if_impossible < 0)
622 /* The move is flagged as illegal. */
624 f, t, local_flag, score_if_impossible);
632 s += history[hindex(side, mv)];
635 /* If we're running short of tree nodes, go into tsume mode. */
637 if (!(local_flag & capture))
639 if (*TrP > (TREE - 300))
641 /* too close to tree table limit */
646 /* Guess strength of move and set flags. */
648 if ((piece != king) && (!in_opening_stage))
650 if (distance(t, EnemyKing) <= 1)
652 /* bonus for square near enemy king */
655 local_flag |= kingattack;
657 else if (distance(t, OwnKing) <= 1)
659 /* bonus for square near own king */
662 local_flag |= kingattack;
666 if (tas) /* own attack array available */
668 /* square t defended by own piece (don't count piece to move) ? */
670 ? (as = attack[side][t])
671 : (as = ((attack[side][t] & CNT_MASK) > 1)))
672 s += (ds = in_endgame_stage ? 100 : 10);
675 if (taxs) /* opponents attack array available */
677 /* square t not threatened by opponent or
678 * defended and only threatened by opponents king ?
682 if (!(axs = attack[xside][t])
683 || (tas && as && (axs & control[king]) && (axs & CNT_MASK) == 1))
685 /* FIXME: this is a mess; clean up. */
686 s += (ds = in_endgame_stage
689 ? (InPromotionZone(side, t)
690 ? 40 + relative_value[piece]
696 /* target square near area of action */
699 s += (9 - distance(TOsquare, t));
702 s += (9 - distance(FROMsquare, t)) / 2;
704 /* target square near own or enemy king */
706 if (!in_opening_stage && piece != king)
708 if (balance[c1] < 50)
709 s += (9 - distance(EnemyKing, t)) * (50 - balance[c1]) / 20;
711 s += (9 - distance(OwnKing, t)) * (balance[c1] - 50) / 20;
716 /* bonus for drops, in order to place
717 * drops before questionable moves */
718 s += in_endgame_stage ? 25 : 10;
722 /* drop to the square the opponent has just left */
727 s -= 32 / Captured[side][gold];
728 else if (piece == silver)
729 s -= 16 / Captured[side][silver];
731 #if defined DROPBONUS
732 s += field_bonus(side, piece, f, t, &local_flag);
734 if (s == 10 && piece != pawn)
735 local_flag |= questionable;
740 /* bonus for moves (non-drops) */
741 int consider_last = false;
743 if (in_endgame_stage && Captured[side][gold])
750 /* move to the square the opponent has just left */
751 s += in_endgame_stage ? 10 : 1;
754 if (color[t] != neutral)
757 if (in_endgame_stage)
759 s += relative_value[board[t]] - relative_value[piece];
763 s += (*value)[stage][board[t]] - relative_value[piece];
766 if (t == TOsquare) /* Capture of last moved piece */
767 s += in_endgame_stage ? 5 : 50;
770 if (local_flag & promote)
772 /* bonus for promotions */
774 INCscore += value[stage][promoted[piece]] - value[stage][piece];
778 /* bonus for non-promotions */
779 if (PromotionPossible(side, f, t, piece))
782 /* Look at non-promoting silver or knight */
789 local_flag |= tesuji; /* Non-promotion */
795 consider_last = true;
797 if (piece == pawn || piece == bishop || piece == rook)
799 local_flag |= stupid;
804 local_flag |= questionable;
813 if (local_flag & stupid)
820 #if defined FIELDBONUS
821 s += field_bonus(side, piece, f, t, &local_flag);
826 #if defined CHECKBONUS
827 /* determine check flag */
828 if (!(local_flag & check) && !check_determined)
830 gives_check_flag(&local_flag, side, f, t);
832 if (local_flag & check)
837 /* check conditions for deep search cut (flag.tsume = true) */
840 if (!flag.tsume && deepsearchcut)
842 if ((ply > BEYOND_STUPID) && (local_flag & stupid))
844 try_link = flag.force || ((ply == 1) && (side != computer));
846 else if (hard_time_limit && (ply > BEYOND_TIMEOUT) && flag.timeout)
850 else if ((ply > BEYOND_KINGATTACK) && !(local_flag & kingattack))
854 else if ((ply > BEYOND_QUESTIONABLE) && (local_flag & questionable))
859 else if ((ply > BEYOND_TESUJI) && !(local_flag & tesuji))
864 else if ((ply > BEYOND_DROP) && (f > NO_SQUARES))
871 if (try_link || GenerateAllMoves)
873 Link(side, f, t, local_flag,
874 s - ((SCORE_LIMIT + 1000) * 2));
877 flag.tsume = flag_tsume;
883 DropPossible(short piece, short side, short sq)
885 short r = row(sq), possible = true;
887 if (board[sq] != no_piece)
891 else if (piece == pawn)
893 if ((side == black) && (r == 8))
895 possible = (generate_move_flags ? ILLEGAL_TRAPPED : false);
897 else if ((side == white) && (r == 0))
899 possible = (generate_move_flags ? ILLEGAL_TRAPPED : false);
901 else if (PawnCnt[side][column(sq)])
903 possible = (generate_move_flags ? ILLEGAL_DOUBLED : false);
906 /* Pawn drops are invalid if they mate the opponent. */
909 short f, tempb, tempc;
910 f = pawn + NO_SQUARES;
915 GenMakeMove(side, f, sq, &tempb, &tempc, false);
917 if (IsCheckmate(side^1, -1, -1))
918 possible = (generate_move_flags ? ILLEGAL_MATE : false);
920 GenUnmakeMove(side, f, sq, tempb, tempc, false);
924 else if (piece == lance)
926 if ((side == black) && (r == 8))
927 possible = (generate_move_flags ? ILLEGAL_TRAPPED : false);
928 else if ((side == white) && (r == 0))
929 possible = (generate_move_flags ? ILLEGAL_TRAPPED : false);
931 else if (piece == knight)
933 if ((side == black) && (r >= 7))
934 possible = (generate_move_flags ? ILLEGAL_TRAPPED : false);
935 else if ((side == white) && (r <= 1))
936 possible = (generate_move_flags ? ILLEGAL_TRAPPED : false);
944 #if defined DONTUSE_HEURISTIC
950 for (p = TrPnt[ply]; p < TrPnt[ply+1]; p++)
951 pick(p, TrPnt[ply+1] - 1);
953 #endif /* DONTUSE_HEURISTIC */
956 #ifdef DONTUSE_HEURISTIC
959 DontUseMoves(short ply, short n)
964 /* k = number of check moves + number of captures */
965 for (i = TrPnt[ply], k = 0; i < TrPnt[ply+1]; i++)
969 if ((p->flags & check) || (p->flags & capture))
977 for (i = TrPnt[ply]; i < TrPnt[ply+1]; i++)
981 if (!((p->flags & check) || (p->flags & capture)))
998 * Generate moves for a piece. The moves are taken from the precalculated
999 * array nextpos/nextdir. If the board is free, next move is chosen from
1000 * nextpos else from nextdir.
1004 GenMoves(short ply, short sq, short side,
1008 short ptyp, possible;
1012 unsigned char *ppos, *pdir;
1016 ptyp = ptype[side][piece];
1019 u = first_direction(ptyp, &d, sq);
1021 ppos = (*nextpos[ptyp])[sq];
1022 pdir = (*nextdir[ptyp])[sq];
1028 unsigned short local_flag;
1031 if ((c = color[u]) == xside)
1032 local_flag = capture;
1036 if (c != side && board[u] != king)
1038 if (PromotionPossible(color[sq], sq, u, piece))
1040 LinkMove(ply, sq, u, local_flag | promote, xside, true);
1043 = NonPromotionPossible(color[sq], u, piece)))
1045 LinkMove(ply, sq, u, local_flag, xside, possible);
1050 LinkMove(ply, sq, u, local_flag, xside, true);
1057 u = next_position(ptyp, &d, sq, u);
1061 u = next_direction(ptyp, &d, sq);
1080 * Drop each piece in hand of "side" to square "u" (if allowed).
1084 DropToSquare(short side, short xside, short ply, short u)
1088 for (i = pawn; i < king; i++)
1090 if (Captured[side][i])
1092 if ((possible = DropPossible(i, side, u)))
1100 LinkMove(ply, f, u, (dropmask | i), xside, possible);
1109 * Add drops of side that prevent own king from being in check
1110 * from xside's sweeping pieces.
1114 LinkPreventCheckDrops(short side, short xside, short ply)
1119 unsigned char *ppos, *pdir;
1121 short piece, u, xu, square, ptyp;
1122 short n, drop_square[9];
1124 if (board[square = PieceList[side][0]] != king)
1127 for (piece = pawn+1; piece <= rook; piece++)
1133 piece == bishop || piece == rook)
1135 /* check for threat of xside piece */
1136 ptyp = ptype[side][piece];
1139 u = first_direction(ptyp, &d, square);
1141 ppos = (*nextpos[ptyp])[square];
1142 pdir = (*nextdir[ptyp])[square];
1148 if (color[u] == neutral)
1152 xu = next_position(ptyp, &d, square, u);
1154 if (xu == next_direction(ptyp, &dd, square))
1156 n = 0; /* oops new direction */
1160 drop_square[n++] = u;
1164 if ((xu = ppos[u]) == pdir[u])
1166 n = 0; /* oops new direction */
1170 drop_square[n++] = u;
1177 if (color[u] == xside && (unpromoted[board[u]] == piece))
1179 /* king is threatened by opponents piece */
1182 DropToSquare(side, xside, ply, drop_square[--n]);
1190 u = next_direction(ptyp, &d, square);
1196 while (u != square);
1204 * Add drops that check enemy king.
1208 LinkCheckDrops(short side, short xside, short ply)
1213 unsigned char *ppos, *pdir;
1216 short square, piece;
1218 if (board[square = PieceList[xside][0]] != king)
1221 for (piece = pawn; piece < king; piece++)
1223 if (Captured[side][piece])
1226 * "side" has "piece" in hand. Try to make a piece move from
1227 * opponents king square and drop this piece to each reachable
1228 * empty square. This definitely gives check! For a pawn drop
1229 * it must not double pawns and it must not be checkmate!
1232 ptyp = ptype[xside][piece];
1234 u = first_direction(ptyp, &d, square);
1236 ppos = (*nextpos[ptyp])[square];
1237 pdir = (*nextdir[ptyp])[square];
1242 if (color[u] == neutral)
1244 if (piece != pawn || DropPossible(pawn, side, u))
1247 f = NO_SQUARES + piece;
1253 (dropmask | piece | check), xside, true);
1257 u = next_position(ptyp, &d, square, u);
1265 u = next_direction(ptyp, &d, square);
1271 while (u != square);
1279 * Fill the array Tree[] with all available moves for side to play. Array
1280 * TrPnt[ply] contains the index into Tree[] of the first move at a ply.
1281 * in_check = 0 side is not in check
1282 * in_check > 1 side is in check
1283 * in_check < 0 don't know
1284 * in_check -2 indicates move generation for book moves
1288 MoveList(short side, short ply,
1289 short in_check, short blockable)
1292 struct leaf *firstnode;
1293 short flag_tsume, num;
1296 unsigned short hiHt = 0, hi0 = 0, hi1 = 0, hi2 = 0, hi3 = 0, hi4 = 0;
1299 flag_tsume = flag.tsume;
1303 sqking = PieceList[side][0];
1304 sqxking = PieceList[xside][0];
1312 InCheck = (board[sqking] == king)
1313 ? SqAttacked(sqking, xside, &blockable)
1317 GenerateAllMoves = (in_check == -2) || generate_move_flags;
1319 if (InCheck /* && (ply > 1 || side == computer) */)
1321 /* Own king in check */
1325 TrP = &TrPnt[ply + 1];
1328 firstnode = node = &Tree[*TrP];
1331 Swag0 = killr0[ply];
1335 Swag1 = killr1[ply];
1336 Swag2 = killr2[ply];
1337 Swag3 = killr3[ply];
1340 Swag4 = killr1[ply - 2];
1347 history[hiHt = hindex(side, SwagHt)] += 5000;
1348 history[hi0 = hindex(side, Swag0)] += 2000;
1349 history[hi1 = hindex(side, Swag1)] += 60;
1350 history[hi2 = hindex(side, Swag2)] += 50;
1351 history[hi3 = hindex(side, Swag3)] += 40;
1352 history[hi4 = hindex(side, Swag4)] += 30;
1356 for (i = PieceCnt[side]; i >= 0; i--)
1357 GenMoves(ply, PieceList[side][i], side, xside);
1359 if (!InCheck || blockable)
1363 /* special drop routine for tsume problems */
1365 LinkPreventCheckDrops(side, xside, ply);
1367 LinkCheckDrops(side, xside, ply);
1371 for (u = 0; u < NO_SQUARES; u++)
1372 DropToSquare(side, xside, ply, u);
1379 history[hiHt] -= 5000;
1380 history[hi0] -= 2000;
1388 SwagHt = 0; /* SwagHt is only used once */
1390 if (flag.tsume && node == firstnode)
1393 GenCnt += (num = (TrPnt[ply+1] - TrPnt[ply]));
1395 #ifdef DONTUSE_HEURISTIC
1396 /* remove some nodes in case of wide spread in depth */
1397 if (!flag.tsume && (i = MaxNum[ply]) > 0 && num > i)
1400 DontUseMoves(ply, i);
1404 flag.tsume = flag_tsume;
1410 * Fill the array Tree[] with all available captures for side to play. If
1411 * there is a non-promote option, discard the non-promoting move. Array
1412 * TrPnt[ply] contains the index into Tree[] of the first move at a ply.
1413 * If flag.tsume is set, only add captures (but also the non-promoting)
1414 * that threaten the opponents king.
1416 * in_check = 0: side is not in check
1417 * in_check > 1: side is in check
1418 * in_check < 0: we don't know
1422 CaptureList(short side, short ply,
1423 short in_check, short blockable)
1429 unsigned char *ppos, *pdir;
1431 short i, piece, flag_tsume;
1436 TrP = &TrPnt[ply + 1];
1440 flag_tsume = flag.tsume;
1442 sqking = PieceList[side][0];
1443 sqxking = PieceList[xside][0];
1451 InCheck = (board[sqking] == king)
1452 ? SqAttacked(sqking, xside, &blockable)
1456 GenerateAllMoves = (in_check == -2);
1458 if (InCheck && (ply > 1 || side == computer))
1460 /* Own king is in check */
1464 check_determined = false;
1466 PL = PieceList[side];
1468 for (i = 0; i <= PieceCnt[side]; i++)
1473 ptyp = ptype[side][piece];
1475 u = first_direction(ptyp, &d, sq);
1477 ppos = (*nextpos[ptyp])[sq];
1478 pdir = (*nextdir[ptyp])[sq];
1483 if (color[u] == neutral)
1486 u = next_position(ptyp, &d, sq, u);
1493 if (color[u] == xside && board[u] != king)
1497 if ((PP = PromotionPossible(color[sq], sq, u, piece)))
1500 sq, u, capture | promote,
1501 (*value)[stage][board[u]]
1502 #if !defined SAVE_SVALUE
1505 - relative_value[piece]);
1508 if (!PP || flag.tsume)
1512 (*value)[stage][board[u]]
1513 #if !defined SAVE_SVALUE
1516 - relative_value[piece]);
1521 u = next_direction(ptyp, &d, sq);
1530 flag.tsume = flag_tsume;
1532 SwagHt = 0; /* SwagHt is only used once */
1539 * If the king is in check, try to find a move that prevents check.
1540 * If such a move is found, return false, otherwise return true.
1541 * in_check = 0: side is not in check
1542 * in_check > 1: side is in check
1543 * in_check < 0: don't know
1544 * blockable > 0 && check: check can possibly be prevented by a drop
1545 * blockable = 0 && check: check can definitely not be prevented by a drop
1546 * blockable < 0 && check: nothing known about type of check
1550 IsCheckmate(short side, short in_check, short blockable)
1556 unsigned char *ppos, *pdir;
1560 short tempb, tempc, ksq, threat, dummy, sqking;
1565 sqking = PieceList[side][0];
1568 * Checkmate is possible only if king is in check.
1573 else if (board[sqking] == king)
1574 InCheck = SqAttacked(sqking, xside, &blockable);
1582 * Try to find a move that prevents check.
1585 PL = PieceList[side];
1587 for (i = 0; i <= PieceCnt[side]; i++)
1592 ptyp = ptype[side][piece];
1594 u = first_direction(ptyp, &d, sq);
1596 ppos = (*nextpos[ptyp])[sq];
1597 pdir = (*nextdir[ptyp])[sq];
1602 if (color[u] == neutral || color[u] == xside)
1604 GenMakeMove(side, sq, u, &tempb, &tempc, false);
1605 ksq = (sq == sqking) ? u : sqking;
1606 threat = SqAttacked(ksq, xside, &dummy);
1607 GenUnmakeMove(side, sq, u, tempb, tempc, false);
1614 u = (color[u] == neutral)
1615 ? next_position(ptyp, &d, sq, u)
1616 : next_direction(ptyp, &d, sq);
1618 u = (color[u] == neutral) ? ppos[u] : pdir[u];
1625 * Couldn't find a move that prevents check.
1626 * Try to find a drop that prevents check.
1631 for (piece = king - 1; piece >= pawn; piece--)
1633 if (Captured[side][piece])
1635 for (u = 0; u < NO_SQUARES; u++)
1637 if (DropPossible(piece, side, u))
1640 f = NO_SQUARES + piece;
1645 GenMakeMove(side, f, u, &tempb, &tempc, false);
1646 threat = SqAttacked(sqking, xside, &dummy);
1647 GenUnmakeMove(side, f, u, tempb, tempc, false);
1655 * If the piece could be dropped at any square, it is
1656 * impossible for any other piece drop to prevent check.
1657 * Drops are restricted for pawns, lances, and knights.
1660 if (piece >= silver)