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trapmoves.d
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trapmoves.d
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import position;
struct CaptureInfo
{
Piece victim;
ulong victim_bit;
int length;
ulong trap_bit;
Step first_step;
}
class TrapGenerator
{
static const int MAX_CAPTURES = 80;
int num_captures;
CaptureInfo[MAX_CAPTURES] captures;
private Position pos;
private Side side;
void clear()
{
if (pos !is null)
{
pos = null;
}
num_captures = 0;
}
void add_capture(Piece piece, ulong vbit, int steps, ulong tbit, ulong frombit, ulong tobit, bool ispush=false)
in
{
assert (tbit & TRAPS, "trap_bit not a trap");
assert (popcount(tbit) == 1, "more than one trap in trap_bit");
}
body
{
debug (static_captures)
{
Stdout.format("cap {} at {} in {} steps {} trap step from {} to {} is push {}",
".RCDHMErcdhme"[piece], ix_to_alg(bitindex(vbit)), steps,
ix_to_alg(bitindex(tbit)), ix_to_alg(bitindex(frombit)),
ix_to_alg(bitindex(tobit)), ispush).newline;
}
captures[num_captures].victim = piece;
captures[num_captures].victim_bit = vbit;
captures[num_captures].length = steps;
captures[num_captures].trap_bit = tbit;
captures[num_captures].first_step.set(frombit, tobit, ispush);
num_captures++;
}
void add_capture(Piece piece, ulong vbit, int steps, ulong tbit, Step* step)
in
{
assert (tbit & TRAPS, "trap_bit not a trap");
assert (popcount(tbit) == 1, "more than one trap in trap_bit");
}
body
{
debug (static_captures)
{
Stdout.format("cap {} at {} in {} steps {} trap using step {} to {} is push {}",
".RCDHMErcdhme"[piece], ix_to_alg(bitindex(vbit)),
steps, ix_to_alg(bitindex(tbit)),
ix_to_alg(bitindex(step.frombit)),
ix_to_alg(bitindex(step.tobit)), step.push).newline;
}
captures[num_captures].victim = piece;
captures[num_captures].victim_bit = vbit;
captures[num_captures].length = steps;
captures[num_captures].trap_bit = tbit;
captures[num_captures].first_step = *step;
num_captures++;
}
private void gen_0n(ulong tbit)
{
// There are no enemy pieces neighboring the trap
int enemyoffset = -6;
int pieceoffset = 0;
if (side == Side.BLACK)
{
enemyoffset = 6;
pieceoffset = 6;
}
ulong t_neighbors = neighbors_of(tbit);
if (tbit & pos.bitBoards[Piece.EMPTY])
{
// The Trap is empty
ulong ncheckbits = t_neighbors;
while (ncheckbits)
{
ulong nbit = ncheckbits & -ncheckbits;
ncheckbits ^= nbit;
bitix nix = bitindex(nbit);
if (nbit & pos.placement[side] & ~pos.frozen)
{
// neighbor has an unfrozen friendly piece
ulong possibles = neighbors_of(nbit) & pos.placement[side^1];
while (possibles)
{
ulong pbit = possibles & -possibles;
possibles ^= pbit;
bitix pix = bitindex(pbit);
if (pos.pieces[nix] > pos.pieces[pix] + enemyoffset)
{
ulong tobits = neighbors_of(nbit) & ~tbit & ~pbit & pos.bitBoards[Piece.EMPTY];
bool tobits_handled = false;
if (pos.strongest[side][nix] > pos.pieces[pix] + enemyoffset)
{
ulong pospushers = neighbors_of(nbit) & pos.placement[side];
while (pospushers)
{
ulong push = pospushers & -pospushers;
bitix pushix = bitindex(push);
if (pos.pieces[pushix] > pos.pieces[pix] + enemyoffset
&& (pos.pieces[pushix] >= pos.strongest[side^1][pushix] + enemyoffset
|| (neighbors_of(push) & pos.placement[side] & ~nbit)))
{
break;
}
pospushers ^= push;
}
if (pospushers)
{
if (tobits)
{
// There should only be one bit in tobits set
assert (tobits == (tobits & -tobits));
add_capture(pos.pieces[pix], pbit, 4, tbit, nbit, tobits);
tobits_handled = true;
}
if (!(t_neighbors & ~nbit & pos.placement[side]))
{
add_capture(pos.pieces[pix], pbit, 4, tbit, nbit, tbit);
}
}
}
if (!tobits_handled)
{
while (tobits)
{
ulong tobit = tobits & -tobits;
tobits ^= tobit;
bitix toix = bitindex(tobit);
if (pos.pieces[nix] >= (pos.strongest[side^1][toix] + enemyoffset)
|| (neighbors_of(tobit) & pos.placement[side] & ~nbit))
{
add_capture(pos.pieces[pix], pbit, 4, tbit, nbit, tobit);
break;
}
}
}
if ((t_neighbors & pos.bitBoards[Piece.EMPTY])
&& (t_neighbors & ~nbit & pos.placement[side]))
{
add_capture(pos.pieces[pix], pbit, 4, tbit, nbit, tbit);
}
}
}
ulong lastbit = 1UL << pos.lastfrom;
if ((side == pos.side) && (neighbors_of(nbit) & lastbit))
{
possibles = neighbors_of(lastbit) & pos.placement[side^1];
while (possibles)
{
ulong pbit = possibles & -possibles;
possibles ^= pbit;
bitix pix = bitindex(pbit);
if (pos.lastpiece <= pos.pieces[pix] + enemyoffset
|| pos.pieces[nix] <= pos.pieces[pix] + enemyoffset)
continue;
ulong tobits = neighbors_of(nbit) & pos.bitBoards[Piece.EMPTY]
& ~tbit & ~lastbit;
while (tobits)
{
ulong tobit = tobits & -tobits;
bitix toix = bitindex(tobit);
if ((tobit == tbit) && (t_neighbors & pos.placement[side] & ~nbit)
&& (t_neighbors & pos.bitBoards[Piece.EMPTY]))
break;
if (pos.pieces[nix] >= pos.strongest[side^1][toix] + enemyoffset)
break;
tobits ^= tobit;
}
if (tobits)
{
add_capture(pos.pieces[pix], pbit, 5, tbit, pbit, lastbit);
}
}
}
} else if (nbit & pos.bitBoards[Piece.EMPTY])
{
// the neighbor is empty
ulong possibles = neighbors_of(nbit) & pos.placement[side^1];
while (possibles)
{
ulong pbit = possibles & -possibles;
possibles ^= pbit;
bitix pix = bitindex(pbit);
if ((side == pos.side) && (nbit == (1UL << pos.lastfrom))
&& (pos.lastpiece > pos.pieces[pix] + enemyoffset))
{
// can pull piece closer to trap
ulong finishers = neighbors_of(nbit) & pos.placement[side] & ~pos.frozen;
while (finishers)
{
ulong fbit = finishers & -finishers;
finishers ^= fbit;
bitix fix = bitindex(fbit);
if (pos.pieces[fix] > pos.pieces[pix] + enemyoffset)
{
// can finish trap
add_capture(pos.pieces[pix], pbit, 3, tbit, pbit, nbit);
break;
}
}
}
ulong pneighbors = neighbors_of(pbit) & pos.placement[side] & ~pos.frozen;
while (pneighbors)
{
ulong pnbit = pneighbors & -pneighbors;
pneighbors ^= pnbit;
bitix pnix = bitindex(pnbit);
if (pos.pieces[pnix] > pos.pieces[pix] + enemyoffset)
{
ulong p_neighbors = neighbors_of(pbit);
bool safe_push = pos.pieces[pnix] >= pos.strongest[side^1][pix] + enemyoffset
|| (p_neighbors & pos.placement[side] & ~pnbit);
if (!safe_push && (p_neighbors & TRAPS)
&& !(neighbors_of(p_neighbors & TRAPS) & pos.placement[side^1] & ~pbit))
{
// after pushing pnbit may freeze but possibly the freezer will be trapped
safe_push = true;
ulong posfreezers = p_neighbors & pos.placement[side^1] & ~TRAPS;
while (posfreezers)
{
ulong pfbit = posfreezers & -posfreezers;
posfreezers ^= pfbit;
bitix pfix = bitindex(pfbit);
if (pos.pieces[pnix] < pos.pieces[pfix] + enemyoffset)
{
safe_push = false;
break;
}
}
}
if (safe_push)
{
// This piece won't be frozen and can finish trap
add_capture(pos.pieces[pix], pbit, 4, tbit, pbit, nbit, true);
break;
} else if (pos.strongest[side][nix] > pos.pieces[pix] + enemyoffset)
{
// possibly another neighbor of nix can finish the trap
bool finished = false;
ulong finishers = neighbors_of(nbit) & pos.placement[side] & ~pos.frozen;
while (finishers)
{
ulong fbit = finishers & -finishers;
finishers ^= fbit;
bitix fix = bitindex(fbit);
if (!(neighbors_of(fbit) & pos.placement[side] & ~pnbit)
&& pos.pieces[fix] < pos.strongest[side^1][fix] + enemyoffset)
continue;
if (pos.pieces[fix] > pos.pieces[pix] + enemyoffset)
{
// can finish trap
add_capture(pos.pieces[pix], pbit, 4, tbit, pbit, nbit, true);
break;
}
}
if (finished)
break;
}
}
}
}
// maybe there's a friendly that can pull a piece to the trap
possibles = neighbors_of(nbit) & pos.placement[side] & ~pos.frozen
& ~pos.bitBoards[Piece.WRABBIT + pieceoffset]
& neighbors_of(pos.placement[side^1]);
while (possibles)
{
ulong pbit = possibles & -possibles;
possibles ^= pbit;
bitix pix = bitindex(pbit);
Piece ppiece = pos.pieces[pix];
if ((nbit & ~neighbors_of(pos.placement[side] & ~pbit))
&& (ppiece < pos.strongest[side^1][nix] + enemyoffset))
continue;
ulong pvictims = neighbors_of(pbit) & pos.placement[side^1];
ulong victims;
while (pvictims)
{
ulong vbit = pvictims & -pvictims;
pvictims ^= vbit;
if (ppiece > pos.pieces[bitindex(vbit)] + enemyoffset)
victims |= vbit;
}
if (!victims)
continue;
ulong ptos = neighbors_of(pbit) & pos.bitBoards[Piece.EMPTY];
ulong tobits;
while (ptos)
{
ulong tobit = ptos & -ptos;
ptos ^= tobit;
if ((tobit & ~neighbors_of(pos.placement[side] & ~pbit))
&& (TRAPS
|| ppiece < pos.strongest[side^1][bitindex(tobit)] + enemyoffset))
continue;
if ((tobit & nbit)
&& !((t_neighbors & pos.bitBoards[Piece.EMPTY] & ~nbit)
&& (t_neighbors & pos.placement[side])))
{
// can't pull through the trap can we flip on nbit
ulong pflips = neighbors_of(nbit) & pos.bitBoards[Piece.EMPTY];
while (pflips)
{
ulong pfbit = pflips & - pflips;
if (ppiece >= pos.strongest[side^1][bitindex(pfbit)] + enemyoffset)
break;
pflips ^= pfbit;
}
if (!pflips)
continue;
}
ulong vbits = victims;
while (vbits)
{
ulong vbit = vbits & -vbits;
vbits ^= vbit;
bitix vix = bitindex(vbit);
add_capture(pos.pieces[vix], vbit, 6, tbit, pbit, tobit);
}
}
}
ulong enn = neighbors_of(nbit) & pos.bitBoards[Piece.EMPTY] & ~t_neighbors;
while (enn)
{
ulong ennbit = enn & -enn;
enn ^= ennbit;
bitix ennix = bitindex(ennbit);
ulong enn_neighbors = neighbors_of(ennbit);
ulong oneighbors = enn_neighbors & pos.placement[side^1];
while (oneighbors)
{
ulong onbit = oneighbors & - oneighbors;
oneighbors ^= onbit;
bitix onix = bitindex(onbit);
if ((side == pos.side) && (ennbit == (1UL << pos.lastfrom))
&& (pos.lastpiece > pos.pieces[onix] + enemyoffset))
{
// can pull piece closer to trap
ulong finishers = neighbors_of(ennbit) & pos.placement[side] & ~pos.frozen;
while (finishers)
{
ulong fbit = finishers & -finishers;
finishers ^= fbit;
bitix fix = bitindex(fbit);
if (pos.pieces[fix] > pos.pieces[onix] + enemyoffset
&& (pos.pieces[fix] > pos.strongest[side^1][ennix] + enemyoffset
|| (neighbors_of(ennbit) & pos.placement[side] & ~fbit)))
{
// can finish trap
add_capture(pos.pieces[onix], onbit, 5, tbit, onbit, ennbit);
break;
}
}
}
if (pos.strongest[side][onix] > pos.pieces[onix] + enemyoffset)
{
ulong onn = neighbors_of(onbit) & pos.placement[side];
if (!(onbit & TRAPS)
|| popcount(onn) > 1)
{
onn &= ~pos.frozen;
while (onn)
{
ulong pusher = onn & -onn;
onn ^= pusher;
bitix pushix = bitindex(pusher);
if (pos.pieces[pushix] > pos.pieces[onix] + enemyoffset
&& pos.pieces[pushix] >= pos.strongest[side^1][onix] + enemyoffset
&& pos.pieces[pushix] >= pos.strongest[side^1][ennix] + enemyoffset
&& pos.pieces[pushix] >= pos.strongest[side^1][nix] + enemyoffset)
{
add_capture(pos.pieces[onix], onbit, 6, tbit, onbit, ennbit, true);
break;
}
}
}
}
}
}
}
}
} else {
// no enemy pieces neighboring the trap and it's not empty so
// it seems there must be a friendly piece sitting on the trap
assert (tbit & pos.placement[side]);
bitix tix = bitindex(tbit);
ulong lastbit = 1UL << pos.lastfrom;
if ((side == pos.side) && (t_neighbors & lastbit)
&& (t_neighbors & pos.bitBoards[Piece.EMPTY]))
{
ulong possibles = neighbors_of(lastbit) & pos.placement[side^1];
while (possibles)
{
ulong pbit = possibles & -possibles;
possibles ^= pbit;
bitix pix = bitindex(pbit);
if ((pos.lastpiece > pos.pieces[pix] + enemyoffset)
&& (pos.pieces[tix] > pos.pieces[pix] + enemyoffset)
&& (neighbors_of(tbit) & pos.bitBoards[Piece.EMPTY]
& ~lastbit))
{
add_capture(pos.pieces[pix], pbit, 3, tbit, pbit, lastbit);
}
}
}
int ft_pop = popcount(t_neighbors & pos.placement[side]);
if (ft_pop < 3)
{
// see if something can be pushed toward the trap that the
// trap piece can then pull onto the trap
ulong possibles = neighbors_of(t_neighbors
& pos.bitBoards[Piece.EMPTY]) & pos.placement[side^1]
& neighbors_of(pos.placement[side] & ~pos.frozen
& ~pos.bitBoards[Piece.WRABBIT + (side * 6)]);
while (possibles)
{
ulong pbit = possibles & -possibles;
possibles ^= pbit;
bitix pix = bitindex(pbit);
if (pos.strongest[side][pix] > pos.pieces[pix] + enemyoffset
&& pos.pieces[tix] > pos.pieces[pix] + enemyoffset)
{
ulong tobits = neighbors_of(pbit) & t_neighbors
& pos.bitBoards[Piece.EMPTY];
ulong pushers = neighbors_of(pbit) & pos.placement[side]
& ~pos.frozen & ~pos.bitBoards[Piece.WRABBIT + (side * 6)];
if (ft_pop == 1)
pushers &= ~t_neighbors;
while (pushers)
{
ulong atbit = pushers & -pushers;
pushers ^= atbit;
bitix atix = bitindex(atbit);
if (pos.pieces[atix] > pos.pieces[pix] + enemyoffset)
{
while (tobits)
{
ulong tobit = tobits & -tobits;
tobits ^= tobit;
add_capture(pos.pieces[pix], pbit, 4, tbit, pbit, tobit, true);
}
break;
}
}
}
}
}
if (ft_pop == 1)
{
ulong atbit = t_neighbors & pos.placement[side];
bitix atix = bitindex(atbit);
Piece at_piece = pos.pieces[atix];
// the piece on the trap will be captured if the neighbor moves
ulong at_neighbors = neighbors_of(atbit);
ulong possibles = at_neighbors & pos.placement[side^1];
while (possibles)
{
ulong pbit = possibles & -possibles;
possibles ^= pbit;
bitix pix = bitindex(pbit);
if (at_piece > pos.pieces[pix] + enemyoffset)
{
bool can_finish = true;
if (at_piece < pos.strongest[side^1][pix] + enemyoffset
&& !(neighbors_of(pbit) & pos.placement[side] & ~atbit))
{
can_finish = false;
ulong finishers = neighbors_of(neighbors_of(pbit) & t_neighbors
& pos.bitBoards[Piece.EMPTY]) & pos.placement[side] & ~tbit
& ~pos.bitBoards[Piece.WRABBIT + (side * 6)] & ~pos.frozen;
while (finishers)
{
ulong fbit = finishers & -finishers;
finishers ^= fbit;
Piece fpiece = pos.pieces[bitindex(fbit)];
if (fpiece > pos.pieces[pix] + enemyoffset)
{
can_finish = true;
break;
}
}
}
if (can_finish)
{
ulong ptobit = neighbors_of(pbit) & t_neighbors & pos.bitBoards[Piece.EMPTY];
if (ptobit)
{
add_capture(pos.pieces[pix], pbit, 4, tbit, pbit, ptobit, true);
}
}
ulong tobits = at_neighbors & pos.bitBoards[Piece.EMPTY];
while (tobits)
{
ulong tobit = tobits & -tobits;
tobits ^= tobit;
bitix toix = bitindex(tobit);
if (at_piece < pos.strongest[side^1][toix] + enemyoffset
&& !(neighbors_of(tobit) & pos.placement[side] & ~atbit))
{
ulong finishers = neighbors_of(atbit) & pos.placement[side] & ~tbit
& ~pos.bitBoards[Piece.WRABBIT + (side * 6)] & ~pos.frozen;
while (finishers)
{
ulong fbit = finishers & -finishers;
bitix fix = bitindex(fbit);
if (pos.pieces[fix] > pos.pieces[pix] + enemyoffset
&& (pos.pieces[fix] >= pos.strongest[side^1][fix] + enemyoffset
|| (neighbors_of(fbit) & pos.placement[side] & ~atbit)))
break;
finishers ^= fbit;
}
if (!finishers)
continue;
}
add_capture(pos.pieces[pix], pbit, 4, tbit, atbit, tobit);
}
}
}
}
else if (ft_pop < 4)
{
Piece t_piece = pos.pieces[tix];
ulong ft_neighbors = t_neighbors & pos.placement[side]
& ~pos.bitBoards[Piece.WRABBIT + (side * 6)];
while (ft_neighbors)
{
ulong atbit = ft_neighbors & -ft_neighbors;
ft_neighbors ^= atbit;
bitix atix = bitindex(atbit);
Piece at_piece = pos.pieces[atix];
ulong at_neighbors = neighbors_of(atbit);
ulong possibles = at_neighbors & pos.placement[side^1];
while (possibles)
{
ulong pbit = possibles & -possibles;
possibles ^= pbit;
bitix pix = bitindex(pbit);
if (at_piece > pos.pieces[pix] + enemyoffset
&& t_piece > pos.pieces[pix] + enemyoffset)
{
ulong empties = at_neighbors & pos.bitBoards[Piece.EMPTY];
while (empties)
{
ulong tobit = empties & -empties;
empties ^= tobit;
add_capture(pos.pieces[pix], pbit, 4, tbit, atbit, tobit);
}
ulong ptobit = neighbors_of(pbit) & t_neighbors & pos.bitBoards[Piece.EMPTY];
if (ptobit)
{
add_capture(pos.pieces[pix], pbit, 4, tbit, pbit, ptobit, true);
}
}
}
}
}
}
}
// 1 enemy neighboring the trap and enemy on the trap
private void gen_1n_et(ulong tbit, bitix tix, ulong t_neighbors,
ulong pbit, bitix pix, ulong lastbit,
int enemyoffset, int pieceoffset)
{
ulong pneighbors = neighbors_of(pbit);
if ((side == pos.side) && (pneighbors & lastbit)
&& (pos.lastpiece > pos.pieces[pix] + enemyoffset))
{
add_capture(pos.pieces[tix], tbit, 1, tbit, pbit, lastbit);
}
while (pneighbors)
{
ulong pnbit = pneighbors & -pneighbors;
pneighbors ^= pnbit;
bitix pnix = bitindex(pnbit);
if (pnbit & pos.placement[side])
{
if (pnbit & ~pos.frozen)
{
if (pos.pieces[pnix] > pos.pieces[pix] + enemyoffset)
{
ulong pushtos = neighbors_of(pbit) & pos.bitBoards[Piece.EMPTY];
while (pushtos)
{
ulong tobit = pushtos & -pushtos;
pushtos ^= tobit;
add_capture(pos.pieces[tix], tbit, 2, tbit, pbit, tobit, true);
}
ulong pulltos = neighbors_of(pnbit) & pos.bitBoards[Piece.EMPTY];
while (pulltos)
{
ulong tobit = pulltos & -pulltos;
pulltos ^= tobit;
add_capture(pos.pieces[tix], tbit, 2, tbit, pnbit, tobit);
}
ulong clear = neighbors_of(pbit) & pos.placement[side] & ~pnbit;
while (clear)
{
ulong cbit = clear & -clear;
clear ^= cbit;
ulong pobits = neighbors_of(cbit) & ~pbit;
ulong ebits = pobits & pos.bitBoards[Piece.EMPTY];
if (cbit & pos.bitBoards[Piece.WRABBIT + pieceoffset])
{
ulong backward = (side == Side.WHITE) ? cbit >> 8 : cbit << 8;
pobits &= ~backward;
}
if (cbit & ~pos.frozen)
{
bitix cix = bitindex(cbit);
bool canfreeze = popcount(neighbors_of(cbit) & pos.placement[side]) == 1
&& pos.pieces[cix] < pos.strongest[side^1][cix] + enemyoffset;
while (pobits)
{
ulong pobit = pobits & -pobits;
pobits ^= pobit;
if (pobit & pos.bitBoards[Piece.EMPTY])
{
add_capture(pos.pieces[tix], tbit, 3, tbit, cbit, pobit);
}
else if (pobit & pos.placement[side] && !canfreeze)
{
ulong aways = neighbors_of(pobit) & pos.bitBoards[Piece.EMPTY];
if (pobit & pos.bitBoards[Piece.WRABBIT + pieceoffset])
{
ulong backward = (side == Side.WHITE) ? pobit >> 8 : pobit << 8;
aways &= ~backward;
}
while (aways)
{
ulong abit = aways & -aways;
aways ^= abit;
add_capture(pos.pieces[tix], tbit, 4, tbit, pobit, abit);
}
}
else if (pobit & pos.placement[side^1])
{
bitix opix = bitindex(pobit);
if (pos.pieces[cix] > pos.pieces[opix] + enemyoffset)
{
ulong tobits = neighbors_of(pobit)
& pos.bitBoards[Piece.EMPTY] & ~t_neighbors;
while (tobits)
{
ulong tobit = tobits & -tobits;
tobits ^= tobit;
add_capture(pos.pieces[tix], tbit, 4, tbit, pobit, tobit, true);
}
}
}
}
}
else if (ebits != (ebits & -ebits))
{
// clear is frozen and has more than one empty space around it
pobits &= ebits;
if (pobits == (pobits & -pobits))
ebits ^= pobits;
while (ebits)
{
ulong empty = ebits & -ebits;
ebits ^= empty;
ulong forward = (side == Side.WHITE) ? empty << 8 : empty >> 8;
ulong unfreezers = neighbors_of(empty) & pos.placement[side]
& ~pos.frozen & ~(pos.bitBoards[Piece.WRABBIT + pieceoffset]
& forward);
while (unfreezers)
{
ulong unbit = unfreezers & -unfreezers;
unfreezers ^= unbit;
add_capture(pos.pieces[tix], tbit, 4, tbit, unbit, empty);
}
}
}
}
bool pn_safe = false;
clear = neighbors_of(pnbit) & pos.placement[side];
if (pos.pieces[pnix] >= pos.strongest[side^1][pnix] + enemyoffset
|| (clear != (clear & -clear)))
{
pn_safe = true;
while (clear)
{
ulong cbit = clear & -clear;
clear ^= cbit;
bitix cix = bitindex(cbit);
ulong posouts = neighbors_of(cbit) & ~pnbit;
if (cbit & pos.bitBoards[Piece.WRABBIT + pieceoffset])
{
ulong backward = (side == Side.WHITE) ? cbit >> 8 : cbit << 8;
posouts &= ~backward;
}
while (posouts)
{
ulong pobit = posouts & -posouts;
posouts ^= pobit;
if (pobit & pos.bitBoards[Piece.EMPTY])
{
add_capture(pos.pieces[tix], tbit, 3, tbit, cbit, pobit);
}
else if (pobit & pos.placement[side])
{
ulong empties = neighbors_of(pobit) & pos.bitBoards[Piece.EMPTY];
if (pobit & pos.bitBoards[Piece.WRABBIT + pieceoffset])
{
ulong backward = (side == Side.WHITE) ? pobit >> 8 : pobit << 8;
empties &= ~backward;
}
while (empties)
{
ulong tobit = empties & -empties;
empties ^= tobit;
add_capture(pos.pieces[tix], tbit, 4, tbit, pobit, tobit);
}
} else {
// pobit must be opponent peice
assert (pobit & pos.placement[side^1]);
bitix poix = bitindex(pobit);
if (pos.pieces[cix] > pos.pieces[poix] + enemyoffset)
{
ulong tobits = neighbors_of(pobit)
& pos.bitBoards[Piece.EMPTY] & ~t_neighbors;
if (pos.pieces[pnix] < pos.pieces[poix] + enemyoffset
&& !(neighbors_of(pnbit) & pos.placement[side] & ~cbit))
tobits &= ~neighbors_of(pnbit);
while (tobits)
{
ulong tobit = tobits & -tobits;
tobits ^= tobit;
add_capture(pos.pieces[tix], tbit, 4, tbit, pobit, tobit, true);
}
}
}
}
}
}
// can we pull an opponent away from p so pn can push it
clear = neighbors_of(pbit) & pos.placement[side^1] & ~tbit;
while (clear)
{
ulong cbit = clear & -clear;
clear ^= cbit;
bitix cix = bitindex(cbit);
ulong c_neighbors = neighbors_of(cbit);
if ((c_neighbors & lastbit) && (lastbit & ~t_neighbors)
&& pos.lastpiece > pos.pieces[cix] + enemyoffset
&& ((lastbit & ~neighbors_of(pnbit))
|| pos.pieces[pnix] >= pos.pieces[cix] + enemyoffset
|| (neighbors_of(pnbit) & pos.placement[side])))
{
add_capture(pos.pieces[tix], tbit, 3, tbit, cbit, lastbit);
}
ulong pullers = c_neighbors & ~t_neighbors & ~pos.frozen
& pos.placement[side] & neighbors_of(pos.bitBoards[Piece.EMPTY])
& ~pos.bitBoards[Piece.WRABBIT + pieceoffset];
if (!pn_safe)
pullers &= ~neighbors_of(pnbit);
while (pullers)
{
ulong pullbit = pullers & -pullers;
pullers ^= pullbit;
bitix pullix = bitindex(pullbit);
if ((pullbit & neighbors_of(pnbit))
&& pos.pieces[pnix] < pos.pieces[cix] + enemyoffset
&& !(neighbors_of(pnbit) & pos.placement[side] & ~pullbit))
continue;
if (pos.pieces[pullix] > pos.pieces[cix] + enemyoffset)
{
ulong tobits = neighbors_of(pullbit) & pos.bitBoards[Piece.EMPTY];
while (tobits)
{
ulong tobit = tobits & -tobits;
tobits ^= tobit;
add_capture(pos.pieces[tix], tbit, 4, tbit, pullbit, tobit);
}
}
}
}
// can we pull an opponent away from pn so it has space to pull
clear = neighbors_of(pnbit) & pos.placement[side^1] & ~pbit;
while (clear)
{
ulong cbit = clear & -clear;
clear ^= cbit;
bitix cix = bitindex(cbit);
ulong c_neighbors = neighbors_of(cbit);
if ((c_neighbors & lastbit)
&& pos.lastpiece > pos.pieces[cix] + enemyoffset)
{
add_capture(pos.pieces[tix], tbit, 3, tbit, cbit, lastbit);
}
if ((cbit & TRAPS)
&& (neighbors_of(neighbors_of(cbit) & pos.placement[side^1])
& lastbit))
{
ulong holder = neighbors_of(cbit) & pos.placement[side^1];
if (holder == (holder & -holder))
{
assert (neighbors_of(holder) & lastbit);
Piece hpiece = pos.pieces[bitindex(holder)];
if (pos.lastpiece > hpiece + enemyoffset)
{
add_capture(pos.pieces[tix], tbit, 3, tbit, holder, lastbit);
}
}
}
ulong pullers = c_neighbors & ~pnbit & ~pos.frozen
& pos.placement[side] & neighbors_of(pos.bitBoards[Piece.EMPTY])
& ~pos.bitBoards[Piece.WRABBIT + pieceoffset];
while (pullers)
{
ulong pullbit = pullers & -pullers;
pullers ^= pullbit;
bitix pullix = bitindex(pullbit);
if (pos.pieces[pullix] > pos.pieces[cix] + enemyoffset)
{
ulong tobits = neighbors_of(pullbit) & pos.bitBoards[Piece.EMPTY];
while (tobits)
{
ulong tobit = tobits & -tobits;
tobits ^= tobit;
add_capture(pos.pieces[tix], tbit, 4, tbit, pullbit, tobit);
}
}
}
}
}
// can this piece move out of the way and have another piece do the push/pull
ulong finishers = neighbors_of(pnbit);
if ((finishers & pos.bitBoards[Piece.EMPTY])
&& (finishers & pos.placement[side] & ~pos.frozen))
{
finishers &= pos.placement[side] & ~pos.frozen;
while (finishers)
{
ulong fbit = finishers & -finishers;
finishers ^= fbit;
bitix fix = bitindex(fbit);
if ((pos.pieces[fix] > pos.pieces[pix] + enemyoffset)
&& ((neighbors_of(fbit) & pos.placement[side] & ~pnbit)
|| ((fbit & ~TRAPS)
&& (pos.pieces[fix] >= pos.strongest[side^1][fix] + enemyoffset))))
{
// finisher can push pix and won't be frozen or safe in pn moves away
ulong tobits = neighbors_of(pnbit) & pos.bitBoards[Piece.EMPTY];
if (pos.pieces[pnix] == Piece.WRABBIT + pieceoffset)
{
if (side == Side.WHITE)
{
tobits &= ~((pnbit & NOT_RANK_1) >> 8);
} else {
tobits &= ~((pnbit & NOT_RANK_8) << 8);
}
}
bool real_finish = false;
while (tobits)
{
ulong tobit = tobits & -tobits;
tobits ^= tobit;
if ((tobit & ~TRAPS)
|| (neighbors_of(pnbit) & pos.placement[side] & ~fbit)
|| (neighbors_of(tobit) & pos.placement[side] & ~pnbit & ~fbit)
|| (pos.pieces[fix] >= pos.strongest[side^1][pnix] + enemyoffset))
{
// pn square will be safe for finisher after pn piece moves away
real_finish = true;
add_capture(pos.pieces[tix], tbit, 4, tbit, pnbit, tobit);
}
}
if (real_finish)
{
break;
}
}
}
}
} else if (pos.pieces[pnix] > pos.pieces[pix] + enemyoffset)
{
assert(pnbit & pos.frozen);
// pn is frozen can we unfreeze in two steps or less
ulong pn_neighbors = neighbors_of(pnbit) & ~pbit;
while (pn_neighbors)
{
ulong pnnbit = pn_neighbors & -pn_neighbors;
pn_neighbors ^= pnnbit;
if (pnnbit & pos.bitBoards[Piece.EMPTY])
{
ulong pnn_neighbors = neighbors_of(pnnbit) & ~pos.placement[side^1] & ~pnbit;
while (pnn_neighbors)
{
ulong pnnnbit = pnn_neighbors & -pnn_neighbors;
pnn_neighbors ^= pnnnbit;
bitix pnnnix = bitindex(pnnnbit);
if ((pnnnbit & pos.bitBoards[Piece.EMPTY])
&& ((neighbors_of(pbit) & pos.bitBoards[Piece.EMPTY])
|| (neighbors_of(pnbit) & pos.bitBoards[Piece.EMPTY] & ~pnnbit)))
{
ulong unfreezers = neighbors_of(pnnnbit) & pos.placement[side] & ~pos.frozen;
while (unfreezers)
{
ulong unbit = unfreezers & -unfreezers;
unfreezers ^= unbit;
bitix unix = bitindex(unbit);
if ((pos.placement[side] & neighbors_of(pnnnbit) & ~unbit)
|| ((pnnnbit & ~TRAPS)
&& (pos.pieces[unix] >= pos.strongest[side^1][pnnnix] + enemyoffset)))
{
if (pos.pieces[unix] == Piece.WRABBIT + pieceoffset)
{
// can it really make the two steps to pnn
ulong rsteps;
if (side == Side.WHITE)
{
rsteps = (unbit & ~B_FILE) << 2;
rsteps |= (unbit & ~G_FILE) >> 2;
rsteps |= (unbit & NOT_RANK_8 & NOT_A_FILE) << 9;
rsteps |= (unbit & NOT_RANK_8 & NOT_H_FILE) << 7;
rsteps |= (unbit & ~RANK_7) << 16;
} else {
rsteps = (unbit & ~B_FILE) << 2;
rsteps |= (unbit & ~G_FILE) >> 2;
rsteps |= (unbit & NOT_RANK_1 & NOT_A_FILE) >> 7;
rsteps |= (unbit & NOT_RANK_1 & NOT_H_FILE) >> 9;
rsteps |= (unbit & ~RANK_2) >> 16;