char *PrMove(const int move) {
static char MvStr[6];
int ff = FilesBrd[FROMSQ(move)];
int rf = RanksBrd[FROMSQ(move)];
int ft = FilesBrd[TOSQ(move)];
int rt = RanksBrd[TOSQ(move)];
int promoted = PROMOTED(move);
if (promoted) {
char pchar = 'q';
if (IsKn(promoted)) {
pchar = 'n';
}
else if (IsRQ(promoted) && !IsBQ(promoted)) {
pchar = 'r';
}
else if (!IsRQ(promoted) && IsBQ(promoted)) {
pchar = 'b';
}
sprintf(MvStr, "%c%c%c%c%c", ('a' + ff), ('1' + rf), ('a' + ft), ('1' + rt), pchar);
}
else {
sprintf(MvStr, "%c%c%c%c", ('a' + ff), ('1' + rf), ('a' + ft), ('1' + rt));
}
return MvStr;
}
static void addcapturemove(const S_BOARD *pos,int move, S_MOVELIST *list)
{
ASSERT(sqonboard(FROMSQ(move)));
ASSERT(sqonboard(TOSQ(move)));
ASSERT(piecevalid(CAPTURED(move)));
list->moves[list->count].move = move;
list->moves[list->count].score = MvvLvaScores[CAPTURED(move)][pos->pieces[FROMSQ(move)]]+1000000;
list->count++;
}
static void AddCaptureMove(const CHESS_BOARD *pos, int move, MOVELIST *list) {
ASSERT(SqOnBoard(FROMSQ(move)));
ASSERT(SqOnBoard(TOSQ(move)));
ASSERT(PieceValid(CAPTURED(move)));
ASSERT(CheckBoard(pos));
list->moves[list->count].move = move;
list->moves[list->count].score = MvvLvaScores[CAPTURED(move)][pos->pieces[FROMSQ(move)]] + 1000000;
list->count++;
}
void SortCaptures (int ply)
/***************************************************************************
*
* Actually no sorting is done. Just scores are assigned to the captures.
* When we need a move, we will select the highest score move from the
* list, place it at the top and try it. This move might give us a cut
* in which case, there is no reason to sort.
*
***************************************************************************/
{
leaf *p;
int temp, f, t;
for (p = TreePtr[ply]; p < TreePtr[ply+1]; p++)
{
f = Value[cboard[FROMSQ(p->move)]];
t = Value[cboard[TOSQ(p->move)]];
if (f < t)
p->score = t - f;
else
{
temp = SwapOff (p->move);
p->score = (temp < 0 ? -INFINITY : temp);
}
}
}
static void addenpassantmove(const S_BOARD *pos,int move, S_MOVELIST *list)
{
ASSERT(sqonboard(FROMSQ(move)));
ASSERT(sqonboard(TOSQ(move)));
list->moves[list->count].move = move;
list->moves[list->count].score = 105+1000000;
list->count++;
}
static void AddQuietMove(const CHESS_BOARD *pos, int move, MOVELIST *list) {
ASSERT(SqOnBoard(FROMSQ(move)));
ASSERT(SqOnBoard(TOSQ(move)));
ASSERT(CheckBoard(pos));
ASSERT(pos->ply >= 0 && pos->ply < MAXDEPTH);
list->moves[list->count].move = move;
if (pos->searchKillers[0][pos->ply] == move) {
list->moves[list->count].score = 900000;
}
else if (pos->searchKillers[1][pos->ply] == move) {
list->moves[list->count].score = 800000;
}
else {
list->moves[list->count].score = pos->searchHistory[pos->pieces[FROMSQ(move)]][TOSQ(move)];
}
list->count++;
}
static void AddEnPassantMove(const CHESS_BOARD *pos, int move, MOVELIST *list) {
ASSERT(SqOnBoard(FROMSQ(move)));
ASSERT(SqOnBoard(TOSQ(move)));
ASSERT(CheckBoard(pos));
ASSERT((RanksBrd[TOSQ(move)] == RANK_6 && pos->side == WHITE) || (RanksBrd[TOSQ(move)] == RANK_3 && pos->side == BLACK));
list->moves[list->count].move = move;
list->moves[list->count].score = 105 + 1000000;
list->count++;
}
/*
* Extracts a command from the engine input buffer.
*
* The command is removed from the buffer.
* If the command is a move, the move is made.
*/
void NextEngineCmd( void )
{
char engineinput[BUF_SIZE]="";
char enginemovestr[BUF_SIZE]="";
leaf* enginemove;
if ( strlen( engineinputbuf ) > 0 ) {
if ( GetNextLine( engineinputbuf, engineinput ) > 0 ) {
dbg_printf("< ENGINE: %s\n", engineinput);
if ( strncmp( engineinput, "move", 4 ) == 0 ) {
/* Input from engine is a move */
sscanf( engineinput, "move %s", enginemovestr );
enginemove = ValidateMove( enginemovestr );
if ( enginemove == (leaf *) NULL ) {
dbg_printf( "Bad move from engine\n" );
} else {
dbg_printf( "Engine move: <%s> (%d,%d)\n", enginemovestr,
(enginemove!=NULL ? enginemove->move : -1),
(enginemove!=NULL ? enginemove->score : -1) );
SANMove (enginemove->move, 1);
MakeMove( board.side, &(enginemove->move) );
strcpy (Game[GameCnt].SANmv, SANmv);
if ( !(flags & XBOARD) ) {
//ShowBoard();
dbg_printf("USER <: My move is : %s\n", SANmv);
//printf( "\nMy move is : %s\n", SANmv );
printf( "\n<%i:%i>\n", FROMSQ(enginemove->move), TOSQ(enginemove->move) );
fflush( stdout );
} else {
dbg_printf("USER <: %d. ... %s\n", GameCnt/2 + 1, enginemovestr );
printf ("%d. ... %s\n", GameCnt/2 + 1, enginemovestr );
fflush( stdout );
dbg_printf("USER <: My move is : %s\n", enginemovestr);
printf( "My move is : %s\n", enginemovestr );
fflush( stdout );
}
RealGameCnt = GameCnt;
showprompt = 1;
/* Check if the color must be changed, e.g. after a go command. */
if ( changeColor ) {
RealGameCnt = GameCnt;
RealSide = board.side;
}
}
} else {
dbg_printf( "USER <: %s\n",engineinput );
printf( "%s", engineinput );
if ( flags & XBOARD ) {
fflush( stdout );
}
}
}
}
}
static void AddQuietMove(const S_BOARD *pos, int move, S_MOVELIST *list) {
list->moves[list->count].move = move;
if(pos->searchKillers[0][pos->ply] == move) {
list->moves[list->count].score = 900000;
} else if(pos->searchKillers[1][pos->ply] == move) {
list->moves[list->count].score = 800000;
} else {
list->moves[list->count].score = pos->searchHistory[pos->pieces[FROMSQ(move)]][TOSQ(move)];
}
list->count++;
}
static void addquietmove(const S_BOARD *pos,int move, S_MOVELIST *list)
{
ASSERT(sqonboard(FROMSQ(move)));
ASSERT(sqonboard(TOSQ(move)));
list->moves[list->count].move = move;
if(pos->searchkillers[0][pos->ply]==move)
{
list->moves[list->count].score = 900000;
}
else if(pos->searchkillers[1][pos->ply] == move)
{
list->moves[list->count].score = 800000;
}
else
{
list->moves[list->count].score = pos->searchhistory[pos->pieces[FROMSQ(move)]][TOSQ(move)];
}
list->count++;
}
void SortRoot (void)
/*****************************************************************************
*
* Sort the moves at the root. The heuristic is simple. Try captures/
* promotions first. Other moves are ordered based on their swapoff values.
*
*****************************************************************************/
{
leaf *p;
int f, t ;
int side, xside;
BitBoard enemyP;
side = board.side;
xside = 1^side;
enemyP = board.b[xside][pawn];
for (p = TreePtr[1]; p < TreePtr[2]; p++)
{
f = Value[cboard[FROMSQ(p->move)]];
if (cboard[TOSQ(p->move)] != 0 || (p->move & PROMOTION))
{
t = Value[cboard[TOSQ(p->move)]];
if (f < t)
p->score = -1000 + t - f;
else
p->score = -1000 + SwapOff (p->move);
}
else
p->score = -3000 + SwapOff (p->move);
p->score += taxicab[FROMSQ(p->move)][D5] - taxicab[TOSQ(p->move)][E4];
if ( f == ValueP ) {
/* Look at pushing Passed pawns first */
if ( (enemyP & PassedPawnMask[side][TOSQ(p->move)]) == NULLBITBOARD )
p->score +=50;
}
}
}
int ParseMove(char *ptrChar, CHESS_BOARD *pos) {
ASSERT(CheckBoard(pos));
if (ptrChar[1] > '8' || ptrChar[1] < '1') return NOMOVE;
if (ptrChar[3] > '8' || ptrChar[3] < '1') return NOMOVE;
if (ptrChar[0] > 'h' || ptrChar[0] < 'a') return NOMOVE;
if (ptrChar[2] > 'h' || ptrChar[2] < 'a') return NOMOVE;
int from = FR2SQ(ptrChar[0] - 'a', ptrChar[1] - '1');
int to = FR2SQ(ptrChar[2] - 'a', ptrChar[3] - '1');
ASSERT(SqOnBoard(from) && SqOnBoard(to));
MOVELIST list[1];
GenerateAllMoves(pos, list);
int MoveNum = 0;
int Move = 0;
int PromPce = EMPTY;
for (MoveNum = 0; MoveNum < list->count; ++MoveNum) {
Move = list->moves[MoveNum].move;
if (FROMSQ(Move) == from && TOSQ(Move) == to) {
PromPce = PROMOTED(Move);
if (PromPce != EMPTY) {
if (IsRQ(PromPce) && !IsBQ(PromPce) && ptrChar[4] == 'r') {
return Move;
}
else if (!IsRQ(PromPce) && IsBQ(PromPce) && ptrChar[4] == 'b') {
return Move;
}
else if (IsRQ(PromPce) && IsBQ(PromPce) && ptrChar[4] == 'q') {
return Move;
}
else if (IsKn(PromPce) && ptrChar[4] == 'n') {
return Move;
}
continue;
}
return Move;
}
}
return NOMOVE;
}
inline const char *printMove(const unsigned move) {
static char result[6];
const unsigned from = FROMSQ(move);
const unsigned to = TOSQ(move);
ASSERT(squareOnBoard(to));
if (move & MFLAGDROP) {
result[0] = pieceChar[PROMOTED(move) % 6];
result[1] = '@';
result[2] = 'a' + fileBoard[to];
result[3] = '1' + rankBoard[to];
result[4] = 0;
} else {
ASSERT(squareOnBoard(from));
result[0] = 'a' + fileBoard[from];
result[1] = '1' + rankBoard[from];
result[2] = 'a' + fileBoard[to];
result[3] = '1' + rankBoard[to];
result[4] = PROMOTED(move) ? "__nbrq__nbrq_"[PROMOTED(move)] : 0;
result[5] = 0;
}
return result;
}
int MoveListOk(const S_MOVELIST *list, const S_BOARD *pos) {
if(list->count < 0 || list->count >= MAXPOSITIONMOVES) {
return FALSE;
}
int MoveNum;
int from = 0;
int to = 0;
for(MoveNum = 0; MoveNum < list->count; ++MoveNum) {
to = TOSQ(list->moves[MoveNum].move);
from = FROMSQ(list->moves[MoveNum].move);
if(!SqOnBoard(to) || !SqOnBoard(from)) {
return FALSE;
}
if(!PieceValid(pos->pieces[from])) {
PrintBoard(pos);
return FALSE;
}
}
return TRUE;
}
void SortMoves (int ply)
/*****************************************************************************
*
* Sort criteria is as follows.
* 1. The move from the hash table
* 2. Captures as above.
* 3. Killers.
* 4. History.
* 5. Moves to the centre.
*
*****************************************************************************/
{
leaf *p;
int f, t, m, tovalue;
int side, xside;
BitBoard enemyP;
side = board.side;
xside = 1^side;
enemyP = board.b[xside][pawn];
for (p = TreePtr[ply]; p < TreePtr[ply+1]; p++)
{
p->score = -INFINITY;
f = FROMSQ (p->move);
t = TOSQ (p->move);
m = p->move & MOVEMASK;
/* Hash table move (highest score) */
if (m == Hashmv[ply])
p->score += HASHSORTSCORE;
else if (cboard[t] != 0 || p->move & PROMOTION)
{
/* ***** SRW My Interpretation of this code *************
* Captures normally in other places but..... *
* *
* On capture we generally prefer to capture with the *
* with the lowest value piece so to chose between *
* pieces we should subtract the piece value .... but *
* *
* The original code was looking at some captures *
* last, especially where the piece was worth more *
* than the piece captured - KP v K in endgame.epd *
* *
* So code modified to prefer any capture by adding *
* ValueK *
****************************************************** */
tovalue = (Value[cboard[t]] + Value[PROMOTEPIECE (p->move)]);
p->score += tovalue + ValueK - Value[cboard[f]];
}
/* Killers */
else if (m == killer1[ply] || m == killer2[ply])
p->score += KILLERSORTSCORE;
else if (ply > 2 && (m == killer1[ply-2] || m == killer2[ply-2]))
p->score += KILLERSORTSCORE;
p->score += history[side][(p->move & 0x0FFF)] + taxicab[f][D5] - taxicab[t][E4];
if ( cboard[f] == pawn ) {
/* Look at pushing Passed pawns first */
if ( (enemyP & PassedPawnMask[side][t]) == NULLBITBOARD )
p->score +=50;
}
}
}
int PhasePick (leaf **p1, int ply)
/***************************************************************************
*
* A phase style routine which returns the next move to the search.
* Hash move is first returned. If it doesn't fail high, captures are
* generated, sorted and tried. If no fail high still occur, the rest of
* the moves are generated and tried.
* The idea behind all this is to save time generating moves which might
* not be needed.
* CAVEAT: To implement this, the way that genmoves & friends are called
* have to be modified. In particular, TreePtr[ply+1] = TreePtr[ply] must
* be set before the calls can be made.
* If the board ever gets corrupted during the search, then there is a bug
* in IsLegalMove() which has to be fixed.
*
***************************************************************************/
{
static leaf* p[MAXPLYDEPTH];
leaf *p2;
int mv;
int side;
side = board.side;
switch (pickphase[ply])
{
case PICKHASH:
TreePtr[ply+1] = TreePtr[ply];
pickphase[ply] = PICKGEN1;
if (Hashmv[ply] && IsLegalMove (Hashmv[ply]))
{
TreePtr[ply+1]->move = Hashmv[ply];
*p1 = TreePtr[ply+1]++;
return (true);
}
case PICKGEN1:
pickphase[ply] = PICKCAPT;
p[ply] = TreePtr[ply+1];
GenCaptures (ply);
for (p2 = p[ply]; p2 < TreePtr[ply+1]; p2++)
p2->score = SwapOff(p2->move) * WEIGHT +
Value[cboard[TOSQ(p2->move)]];
case PICKCAPT:
while (p[ply] < TreePtr[ply+1])
{
pick (p[ply], ply);
if ((p[ply]->move & MOVEMASK) == Hashmv[ply])
{
p[ply]++;
continue;
}
*p1 = p[ply]++;
return (true);
}
case PICKKILL1:
pickphase[ply] = PICKKILL2;
if (killer1[ply] && killer1[ply] != Hashmv[ply] &&
IsLegalMove (killer1[ply]))
{
TreePtr[ply+1]->move = killer1[ply];
*p1 = TreePtr[ply+1];
TreePtr[ply+1]++;
return (true);
}
case PICKKILL2:
pickphase[ply] = PICKGEN2;
if (killer2[ply] && killer2[ply] != Hashmv[ply] &&
IsLegalMove (killer2[ply]))
{
TreePtr[ply+1]->move = killer2[ply];
*p1 = TreePtr[ply+1];
TreePtr[ply+1]++;
return (true);
}
case PICKGEN2:
pickphase[ply] = PICKREST;
p[ply] = TreePtr[ply+1];
GenNonCaptures (ply);
for (p2 = p[ply]; p2 < TreePtr[ply+1]; p2++)
{
p2->score = history[side][(p2->move & 0x0FFF)] +
taxicab[FROMSQ(p2->move)][D5] - taxicab[TOSQ(p2->move)][E4];
if (p2->move & CASTLING)
p2->score += CASTLINGSCORE;
}
case PICKREST:
while (p[ply] < TreePtr[ply+1])
{
pick (p[ply], ply);
mv = p[ply]->move & MOVEMASK;
if (mv == Hashmv[ply] || mv == killer1[ply] ||
mv == killer2[ply])
{
p[ply]++;
continue;
}
*p1 = p[ply]++;
return (true);
}
}
return (false);
}
int Search (int ply, int depth, int alpha, int beta, int nodetype)
/**************************************************************************
*
* The basic algorithm for this search routine came from Anthony
* Marsland. It is a PVS (Principal Variation Search) algorithm.
* The fail-soft alpha-beta technique is also used for improved
* pruning.
*
**************************************************************************/
{
int best, score, nullscore, savealpha;
int side, xside;
int rc, t0, t1, firstmove;
int fcut, fdel, donull, savenode, nullthreatdone, extend;
leaf *p, *pbest;
int g0, g1;
int upperbound;
/* Check if this position is a known draw */
if (EvaluateDraw ())
return (DRAWSCORE);
if (GameCnt >= Game50+3 && Repeat())
{
RepeatCnt++;
return (DRAWSCORE);
}
side = board.side;
xside = 1^side;
donull = true;
/*************************************************************************
*
* Perform some basic search extensions.
* 1. One reply extensions.
* 2. If in check, extend (maximum of Idepth-1).
* 3. If there is a threat to the King, extend (not beyond 2*Idepth)
* 4. If recapture to same square and not beyond Idepth+2
* 5. If pawn move to 7th rank at the leaf node, extend.
*
*************************************************************************/
extend = false;
InChk[ply] = SqAtakd (board.king[side], xside);
if (InChk[ply])
{
TreePtr[ply+1] = TreePtr[ply];
GenCheckEscapes (ply);
if (TreePtr[ply] == TreePtr[ply+1])
return (-MATE+ply-2);
if (TreePtr[ply]+1 == TreePtr[ply+1])
{
depth += DEPTH;
extend = true;
OneRepCnt++;
}
}
/*
We've already found a mate at the next ply. If we aren't being mated by
a shorter line, so just return the current material value.
*/
if (rootscore + ply >= MATE)
return (MATERIAL);
g0 = Game[GameCnt].move;
g1 = GameCnt > 0 ? Game[GameCnt-1].move : 0;
t0 = TOSQ(g0);
t1 = TOSQ(g1);
ChkCnt[ply+1] = ChkCnt[ply];
ThrtCnt[ply+1] = ThrtCnt[ply];
KingThrt[white][ply] = MateScan (white);
KingThrt[black][ply] = MateScan (black);
if (InChk[ply] && /* ChkCnt[ply] < Idepth-1*/ ply <= 2*Idepth/DEPTH)
{
ChkExtCnt++;
ChkCnt[ply+1]++;
depth += DEPTH;
extend = true;
}
else if (!KingThrt[side][ply-1] && KingThrt[side][ply] && ply <= 2*Idepth/DEPTH)
{
KingExtCnt++;
extend = true;
depth += DEPTH;
extend = true;
donull = false;
}
/* Promotion extension */
else if (g0 & PROMOTION)
{
PawnExtCnt++;
depth += DEPTH;
extend = true;
}
/* Recapture extension */
else if ((g0 & CAPTURE) && (board.material[computer] -
board.material[1^computer] == RootMaterial))
{
RcpExtCnt++;
depth += DEPTH;
extend = true;
}
/* 6th or 7th rank extension */
else if (depth <= DEPTH && cboard[t0] == pawn && (RANK(t0) == rank7[xside] || RANK(t0) == rank6[xside]))
{
PawnExtCnt++;
depth += DEPTH;
extend = true;
}
/****************************************************************************
*
* The following extension is to handle cases when the opposing side is
* delaying the mate by useless interposing moves.
*
****************************************************************************/
if (ply > 2 && InChk[ply-1] && cboard[t0] != king && t0 != t1 &&
!SqAtakd (t0, xside))
{
HorzExtCnt++;
depth += DEPTH;
extend = true;
}
/***************************************************************************
*
* This is a new code to perform search reductiion. We introduce some
* form of selectivity here.
*
**************************************************************************/
if (depth <= 0)
return (Quiesce (ply, alpha, beta));
/****************************************************************************
*
* Probe the transposition table for a score and a move.
* If the score is an upperbound, then we can use it to improve the value
* of beta. If a lowerbound, we improve alpha. If it is an exact score,
* if we now get a cut-off due to the new alpha/beta, return the score.
*
***************************************************************************/
Hashmv[ply] = 0;
upperbound = INFINITY;
if (flags & USEHASH)
{
rc = TTGet (side, depth, ply, alpha, beta, &score, &g1);
if (rc)
{
Hashmv[ply] = g1 & MOVEMASK;
switch (rc)
{
case POORDRAFT : break;
case EXACTSCORE : return (score);
case UPPERBOUND : beta = MIN (beta, score);
upperbound = score;
donull = false;
break;
case LOWERBOUND : /*alpha = MAX (alpha, score);*/
alpha = score;
break;
case QUIESCENT : Hashmv[ply] = 0;
break;
default : break;
}
if (alpha >= beta)
return (score);
}
}
/*****************************************************************************
*
* Perform the null move here. There are certain cases when null move
* is not done.
* 1. When the previous move is a null move.
* 2. At the frontier (depth == 1)
* 3. At a PV node.
* 4. If side to move is in check.
* 5. If the material score + pawn value is still below beta.
* 6. If we are being mated at next ply.
* 7. If hash table indicate the real score is below beta (UPPERBOUND).
* 8. If side to move has less than or equal to a bishop in value.
* 9. If Idepth <= 3. This allows us to find mate-in 2 problems quickly.
* 10. We are looking for a null threat.
*
*****************************************************************************/
if (ply > 4 && InChk[ply-2] && InChk[ply-4])
donull = false;
if (flags & USENULL && g0 != NULLMOVE && depth > DEPTH && nodetype != PV &&
!InChk[ply] && MATERIAL+ValueP > beta && beta > -MATE+ply && donull &&
board.pmaterial[side] > ValueB && !threatply)
{
TreePtr[ply+1] = TreePtr[ply];
MakeNullMove (side);
nullscore = -Search (ply+1, depth-DEPTH-R, -beta, -beta+1, nodetype);
UnmakeNullMove (xside);
if (nullscore >= beta)
{
NullCutCnt++;
return (nullscore);
}
if ( depth-DEPTH-R >= 1 && MATERIAL > beta && nullscore <= -MATE+256)
{
depth += DEPTH;
extend = true;
}
}
if (InChk[ply] && TreePtr[ply]+1 < TreePtr[ply+1])
SortMoves (ply);
pickphase[ply] = PICKHASH;
GETNEXTMOVE;
/*************************************************************************
*
* Razoring + Futility.
* At depth 3, if there is no extensions and we are really bad, decrease
* the search depth by 1.
* At depth 2, if there is no extensions and we are quite bad, then we
* prune all non checking moves and capturing moves that don't bring us up
* back to alpha.
* Caveat: Skip all this if we are in the ending.
*
*************************************************************************/
fcut = false;
fdel = MAX (ValueQ, maxposnscore[side]);
if (!extend && nodetype != PV && depth == 3*DEPTH && FUTSCORE <= alpha)
{
depth = 2*DEPTH;
RazrCutCnt++;
}
fdel = MAX (ValueR, maxposnscore[side]);
fcut = (!extend && nodetype != PV && depth == 2*DEPTH && FUTSCORE <= alpha);
if (!fcut)
{
fdel = MAX (3*ValueP, maxposnscore[side]);
fcut = (nodetype != PV && depth == DEPTH && FUTSCORE <= alpha);
}
MakeMove (side, &p->move);
NodeCnt++;
g0 = g1 = 0;
while ((g0 = SqAtakd (board.king[side], xside)) > 0 ||
(fcut && FUTSCORE < alpha && !SqAtakd (board.king[xside], side) &&
!MateScan (xside)))
{
if (g0 == 0) g1++;
UnmakeMove (xside, &p->move);
if (GETNEXTMOVE == false)
return (g1 ? Evaluate(alpha,beta) : DRAWSCORE);
MakeMove (side, &p->move);
NodeCnt++;
}
firstmove = true;
pbest = p;
best = -INFINITY;
savealpha = alpha;
nullthreatdone = false;
nullscore = INFINITY;
savenode = nodetype;
if (nodetype != PV)
nodetype = (nodetype == CUT) ? ALL : CUT;
while (1)
{
/* We have already made the move before the loop. */
if (firstmove)
{
firstmove = false;
score = -Search (ply+1, depth-DEPTH, -beta, -alpha, nodetype);
}
/* Zero window search for rest of moves */
else
{
if (GETNEXTMOVE == false)
break;
#ifdef THREATEXT
/****************************************************************************
*
* This section needs to be explained. We are doing a null threat search
* and the previous ply was the null move. Inhibit any move which captures
* the fail-high moving piece. Also inhibit any move by the piece which is
* captured by the fail-high move. Both these moves cannot be executed in
* the actual threat, so.....
* Also 3 plies later, inhibit moves out of the target square of the PV/fail
* high move as this is also not possible.
*
****************************************************************************/
if (threatply+1 == ply)
{
if ((TOSQ(p->move) == FROMSQ(threatmv)) ||
(FROMSQ(p->move) == TOSQ(threatmv)))
continue;
}
if (threatply && threatply+3 == ply && FROMSQ(p->move)==TOSQ(threatmv))
continue;
#endif
MakeMove (side, &p->move);
NodeCnt++;
if (SqAtakd (board.king[side], xside))
{
UnmakeMove (xside, &p->move);
continue;
}
/*****************************************************************************
*
* Futility pruning. The idea is that at the frontier node (depth == 1),
* if the side on the move is materially bad, then if the move doesn't win
* back material or the move isn't a check or doesn't threatened the king,
* then there is no point in searching this move. So skip it.
* Caveat: However if the node is a PV, we skip this test.
*
*****************************************************************************/
if (fcut && FUTSCORE <= alpha && !SqAtakd (board.king[xside], side) &&
!MateScan (xside))
{
UnmakeMove (xside, &p->move);
FutlCutCnt++;
NodeCnt--;
continue;
}
NodeCnt++;
if (nodetype == PV)
nodetype = CUT;
alpha = MAX (best, alpha); /* fail-soft condition */
score = -Search (ply+1, depth-DEPTH, -alpha-1, -alpha, nodetype);
if (score > best)
{
if (savenode == PV)
nodetype = PV;
if (alpha < score && score < beta)
{
score = -Search (ply+1, depth-DEPTH, -beta, -score, nodetype);
}
if (nodetype == PV && score <= alpha &&
Game[GameCnt+1].move == NULLMOVE)
{
score = -Search (ply+1, depth-DEPTH, -alpha, INFINITY, nodetype);
}
}
}
UnmakeMove (xside, &p->move);
/* Perform threat extensions code */
#ifdef THREATEXT
if ((score >= beta || nodetype == PV) && !InChk[ply] && g0 != NULLMOVE &&
!threatply && depth == 4 && ThrtCnt[ply] < 1)
{
if (!nullthreatdone)
{
threatply = ply;
threatmv = p->move;
MakeNullMove (side);
nullscore = -Search(ply+1, depth-1-R, -alpha+THREATMARGIN,
-alpha+THREATMARGIN+1, nodetype);
UnmakeNullMove (xside);
nullthreatdone = true;
threatply = 0;
}
if (nullscore <= alpha-THREATMARGIN)
{
ThrtExtCnt++;
ThrtCnt[ply+1]++;
MakeMove (side, &p->move);
score = -Search (ply+1, depth, -beta, -alpha, nodetype);
UnmakeMove (xside, &p->move);
ThrtCnt[ply+1]--;
}
}
#endif
if (score > best)
{
best = score;
pbest = p;
if (best >= beta)
goto done;
}
if (flags & TIMEOUT)
{
best = (ply & 1 ? rootscore : -rootscore);
return (best);
}
if (SearchDepth == 0 && (NodeCnt & TIMECHECK) == 0)
{
GetElapsed ();
if ((et >= SearchTime && (rootscore == -INFINITY-1 ||
ply1score > lastrootscore - 25 || flags & SOLVE)) ||
et >= maxtime)
SET (flags, TIMEOUT);
}
/* The following line should be explained as I occasionally forget too :) */
/* This code means that if at this ply, a mating move has been found, */
/* then we can skip the rest of the moves! */
if (MATE+1 == best+ply)
goto done;
}
/*****************************************************************************
*
* Out of main search loop.
*
*****************************************************************************/
done:
/*
if (upperbound < best)
printf ("Inconsistencies %d %d\n", upperbound, best);
*/
/* Save the best move inside the transposition table */
if (flags & USEHASH)
TTPut (side, depth, ply, savealpha, beta, best, pbest->move);
/* Update history */
if (best > savealpha)
history[side][pbest->move & 0x0FFF] += HISTSCORE(depth/DEPTH);
/* Don't store captures as killers as they are tried before killers */
if (!(pbest->move & (CAPTURE | PROMOTION)) && best > savealpha)
{
if (killer1[ply] == 0)
killer1[ply] = pbest->move & MOVEMASK;
else if ((pbest->move & MOVEMASK) != killer1[ply])
killer2[ply] = pbest->move & MOVEMASK;
}
return (best);
}
int Quiesce (uint8_t ply, int alpha, int beta)
/**************************************************************************
*
* Our quiescent search. This quiescent search is able to recognize
* mates.
*
**************************************************************************/
{
uint8_t side, xside;
int best, delta, score, savealpha;
leaf *p, *pbest;
if (EvaluateDraw ())
return (DRAWSCORE);
side = board.side;
xside = 1^side;
InChk[ply] = SqAtakd (board.king[side], xside);
best = Evaluate (alpha, beta);
if (best >= beta && !InChk[ply])
return (best);
TreePtr[ply+1] = TreePtr[ply];
if (InChk[ply])
{
GenCheckEscapes (ply);
if (TreePtr[ply] == TreePtr[ply+1])
return (-MATE+ply-2);
if (best >= beta)
return (best);
SortMoves (ply);
}
else
{
GenCaptures (ply);
if (TreePtr[ply] == TreePtr[ply+1])
return (best);
SortCaptures (ply);
}
savealpha = alpha;
pbest = NULL;
alpha = MAX(best, alpha);
delta = MAX (alpha - 150 - best, 0);
for (p = TreePtr[ply]; p < TreePtr[ply+1]; p++)
{
pick (p, ply);
/* We are in check or capture cannot bring score near alpha, give up */
if (!InChk[ply] && SwapOff (p->move) < delta)
continue;
/* If capture cannot bring score near alpha, give up */
if (p->score == -INFINITY)
continue;
#ifdef THREATEXT
/* See search.c for an explanation of the code below */
if (threatply+1 == ply)
{
if ((TOSQ(p->move) == FROMSQ(threatmv)) ||
(FROMSQ(p->move) == TOSQ(threatmv)))
continue;
}
if (threatply && threatply+3 == ply && FROMSQ(p->move) == TOSQ(threatmv))
continue;
#endif
MakeMove (side, &p->move);
QuiesCnt++;
if (SqAtakd (board.king[side], xside))
{
UnmakeMove (xside, &p->move);
continue;
}
score = -Quiesce (ply+1, -beta, -alpha);
UnmakeMove (xside, &p->move);
if (score > best)
{
best = score;
pbest = p;
if (best >= beta)
goto done;
alpha = MAX (alpha, best);
}
}
done:
if (flags & USEHASH && pbest != NULL)
TTPut (side, 0, ply, savealpha, beta, best, pbest->move);
return (best);
}
int SwapOff (int move)
/****************************************************************************
*
* A Static Exchange Evaluator (or SEE for short).
* First determine the target square. Create a bitboard of all squares
* attacking the target square for both sides. Using these 2 bitboards,
* we take turn making captures from smallest piece to largest piece.
* When a sliding piece makes a capture, we check behind it to see if
* another attacker piece has been exposed. If so, add this to the bitboard
* as well. When performing the "captures", we stop if one side is ahead
* and doesn't need to capture, a form of pseudo-minimaxing.
*
****************************************************************************/
{
int f, t, sq, piece, lastval;
int side, xside;
int swaplist[MAXPLYDEPTH], n;
BitBoard b, c, *d, *e, r;
f = FROMSQ (move);
t = TOSQ (move);
side = ((board.friends[white] & BitPosArray[f]) ? white : black);
xside = 1^side;
/* Squares attacking t for side and xside */
b = AttackTo (t, side);
c = AttackTo (t, xside);
CLEARBIT(b, f);
if (xray[cboard[f]])
AddXrayPiece (t, f, side, &b, &c);
d = board.b[side];
e = board.b[xside];
if (move & PROMOTION)
{
swaplist[0] = Value[PROMOTEPIECE (move)] - ValueP;
lastval = -Value[PROMOTEPIECE (move)];
}
else
{
swaplist[0] = (move & ENPASSANT ? ValueP : Value[cboard[t]]);
lastval = -Value[cboard[f]];
}
n = 1;
while (1)
{
if (c == NULLBITBOARD)
break;
for (piece = pawn; piece <= king; piece++)
{
r = c & e[piece];
if (r)
{
sq = leadz (r);
CLEARBIT (c, sq);
if (xray[piece])
AddXrayPiece (t, sq, xside, &c, &b);
swaplist[n] = swaplist[n-1] + lastval;
n++;
lastval = Value[piece];
break;
}
}
if (b == NULLBITBOARD)
break;
for (piece = pawn; piece <= king; piece++)
{
r = b & d[piece];
if (r)
{
sq = leadz (r);
CLEARBIT (b, sq);
if (xray[piece])
AddXrayPiece (t, sq, side, &b, &c);
swaplist[n] = swaplist[n-1] + lastval;
n++;
lastval = -Value[piece];
break;
}
}
}
/****************************************************************************
*
* At this stage, we have the swap scores in a list. We just need to
* mini-max the scores from the bottom up to the top of the list.
*
****************************************************************************/
--n;
while (n)
{
if (n & 1)
{
if (swaplist[n] <= swaplist[n-1])
swaplist[n-1] = swaplist[n];
}
else
{
if (swaplist[n] >= swaplist[n-1])
swaplist[n-1] = swaplist[n];
}
--n;
}
return (swaplist[0]);
}
static void AddCaptureMove(const S_BOARD *pos, int move, S_MOVELIST *list) {
list->moves[list->count].move = move;
list->moves[list->count].score = MvvLvaScores[CAPTURED(move)][pos->pieces[FROMSQ(move)]] + 1000000;
list->count++;
}
