void GoRegionBoard::MergeAdjacentAndAddBlock(SgPoint move,
SgBlackWhite capturedColor)
{
SgVector<SgPoint> nb;
for (GoNbIterator it(Board(), move); it; ++it)
if (Board().IsEmpty(*it))
nb.PushBack(*it);
SgVectorOf<GoBlock> captures;
PreviousBlocksAt(nb, capturedColor, &captures);
SG_ASSERT(captures.NonEmpty());
SgPointSet captured;
{for (SgVectorIteratorOf<GoBlock> it(captures); it; ++it)
captured |= (*it)->Stones();
}
SgVectorOf<GoRegion> adj;
const int size = Board().Size();
RegionsAt(captured.Border(size), capturedColor, &adj);
SG_ASSERT(adj.NonEmpty());
GoRegion* r = MergeAll(adj, captured, capturedColor);
SG_UNUSED(r);
for (SgVectorIteratorOf<GoBlock> it(captures); it; ++it)
RemoveBlock(*it, true, false);
// don't remove from regions; already gone.
}
bool GoEyeUtil::IsSinglePointEye2(const GoBoard& board, SgPoint p,
SgBlackWhite color, SgVector<SgPoint>& eyes)
{
// Must be an empty point
if (! board.IsColor(p, SG_EMPTY))
return false;
// All adjacent neighbours must be friendly
SgBoardColor opp = SgOppBW(color);
for (SgNb4Iterator adj(p); adj; ++adj)
{
SgBoardColor adjColor = board.GetColor(*adj);
if (adjColor == opp || adjColor == SG_EMPTY)
return false;
}
// All diagonals (with up to one exception) must be friendly or an eye
int baddiags = 0;
int maxbaddiags = (board.Line(p) == 1 ? 0 : 1);
for (SgNb4DiagIterator it(p); it; ++it)
{
if (board.IsColor(*it, opp))
++baddiags;
if (board.IsColor(*it, SG_EMPTY) && ! eyes.Contains(*it))
{
// Assume this point is an eye and recurse
eyes.PushBack(p);
if (! IsSinglePointEye2(board, *it, color, eyes))
++baddiags;
eyes.PopBack();
}
if (baddiags > maxbaddiags)
return false;
}
return true;
}
SgVector<SgPoint> GoGtpCommandUtil::PointListArg(const GtpCommand& cmd,
std::size_t number,
const GoBoard& board)
{
SgVector<SgPoint> result;
for (size_t i = number; i < cmd.NuArg(); ++i)
result.PushBack(PointArg(cmd, i, board));
return result;
}
SgVector<SgPoint> GoGtpCommandUtil::GetHandicapStones(int size, int n)
{
SgVector<SgPoint> stones;
if (n == 0)
return stones;
// GTP locations are defined up to size 25, but SG_MAX_SIZE could be
// smaller
if (size > SG_MAX_SIZE || size > 25)
throw GtpFailure("no standard handicap locations defined");
int line1 = -1;
int line2 = -1;
int line3 = -1;
if (size >= 13)
{
line1 = 4;
line3 = size - 3;
}
else if (size >= 7)
{
line1 = 3;
line3 = size - 2;
}
if (size >= 9 && size % 2 != 0)
line2 = size / 2 + 1;
if (line1 < 0 || n == 1 || n > 9 || (n > 4 && line2 < 0))
throw GtpFailure("no standard handicap locations defined");
if (n >= 1)
stones.PushBack(Pt(line1, line1));
if (n >= 2)
stones.PushBack(Pt(line3, line3));
if (n >= 3)
stones.PushBack(Pt(line1, line3));
if (n >= 4)
stones.PushBack(Pt(line3, line1));
if (n >= 5 && n % 2 != 0)
{
stones.PushBack(Pt(line2, line2));
--n;
}
if (n >= 5)
stones.PushBack(Pt(line1, line2));
if (n >= 6)
stones.PushBack(Pt(line3, line2));
if (n >= 7)
stones.PushBack(Pt(line2, line1));
if (n >= 8)
stones.PushBack(Pt(line2, line3));
return stones;
}
void SgEvaluatedMovesArray::BestMoves(SgVector<SgPoint>& best, int nuMoves)
const
{
best.Clear();
while (--nuMoves >= 0)
{
int nextBest = SelectNextBest(best);
best.PushBack(nextBest);
}
}
void GoGtpCommandUtil::ParseMultiStoneArgument(GtpCommand& cmd,
const GoBoard& board,
SgBlackWhite& toPlay,
SgBlackWhite& defender,
SgVector<SgPoint>& crucial)
{
toPlay = GoGtpCommandUtil::BlackWhiteArg(cmd, 0);
SgDebug() << "Set " << SgBW(toPlay) << " to play\n";
SgPoint point = GoGtpCommandUtil::StoneArg(cmd, 1, board);
defender = board.GetColor(point);
SG_ASSERT(defender == SG_BLACK || defender == SG_WHITE);
crucial.PushBack(point);
for (size_t i = 2; i < cmd.NuArg(); ++i)
{
SgPoint p = GoGtpCommandUtil::StoneArg(cmd, i, board);
if (board.GetColor(p) != defender)
throw GtpFailure("Crucial stones must be same color");
else
crucial.PushBack(p);
}
}
void SgVectorUtil::Intersection(SgVector<int>* vector,
const SgVector<int>& vector2)
{
SgVector<int> newVector;
for (SgVectorIterator<int> it(*vector); it; ++it)
{
// @todo speed up by hash tags, if used in time-critical code
if (vector2.Contains(*it))
newVector.PushBack(*it);
}
newVector.SwapWith(vector);
}
void GoLadderUtil::FindLadderEscapeMoves(const GoBoard& bd, SgPoint prey,
SgVector<SgPoint>& escapeMoves)
{
SG_ASSERT(bd.NumLiberties(prey) == 1);
SG_ASSERT(escapeMoves.IsEmpty());
SgPoint p = bd.TheLiberty(prey);
SgVector<SgPoint> candidates;
candidates.PushBack(p);
if (IsLadderEscapeMove(bd, prey, p))
escapeMoves.PushBack(p);
for (GoAdjBlockIterator<GoBoard> it(bd, prey, 1); it; ++it)
{
// check if prey can escape by capturing *it on p.
SgPoint p = bd.TheLiberty(*it);
if (! candidates.Contains(p))
{
candidates.PushBack(p);
if (IsLadderEscapeMove(bd, prey, p))
escapeMoves.PushBack(p);
}
}
}
void GoRegion::GetDivideMiaiPairs(SgVector<SgMiaiPair>& pairs) const
{
SgVector<SgPoint> divPs;
for (SgVectorIteratorOf<GoBlock> it(Blocks()); it; ++it)
{
SgVector<SgPoint> libs, temp;
InsideLibs(*it, &libs);
SgMiaiPair p1;
SgPoint a = -1;
// only find miaipairs from libs (empty points)
for (SgVectorIterator<SgPoint> it2(libs); it2; ++it2)
{
if (IsSplitPt(*it2, Points()))
temp.PushBack(*it2);
}
temp.Sort();
divPs.PushBackList(temp);
for (SgVectorIterator<SgPoint> it2(temp); it2; ++it2)
{
if (a == -1)
a = (*it2);
else
{
if (SgPointUtil::AreAdjacent(a, *it2))
{
p1.first = a;
p1.second = *it2;
pairs.PushBack(p1);
}
a = *it2;
}
}
} // found miaipairs for each block
if (WRITEDEBUG)
{
SgDebug() << SgWritePointList(divPs, "divPs: ", true);
for (SgVectorIterator<SgMiaiPair> it(pairs); it; ++it)
{
SgDebug() << "Pair(1: " << SgWritePoint((*it).first)
<< " 2: " << SgWritePoint((*it).second) << ")\n";
}
}
}
void GoRegionBoard::FindNewNeighborRegions(SgPoint move,
BlackWhite moveColor)
{ // move was capture -> new region for each captured block.
SgVector<SgPoint> nb;
for (Nb4Iterator it(move); it; ++it)
if (Board().IsEmpty(*it))
nb.PushBack(*it);
SgVectorOf<GoBlock> captures;
PreviousBlocksAt(nb, OppBW(moveColor), &captures);
SG_ASSERT(captures.NonEmpty());
for (SgVectorIteratorOf<GoBlock> it(captures); it; ++it)
BlockToRegion(*it);
}
bool SgSearch::TrySpecialMove(SgMove move, SgVector<SgMove>& specialMoves,
const int depth,
const int alpha, const int beta,
int& loValue, int& hiValue,
SgSearchStack& stack,
bool& allExact,
bool& isCutoff)
{
if (specialMoves.Contains(move))
return false;
bool executed = TryMove(move, specialMoves,
depth, alpha, beta,
loValue, hiValue, stack,
allExact, isCutoff);
specialMoves.PushBack(move);
return executed;
}
void GoGame::InitHandicap(const GoRules& rules, SgNode* root)
{
// TODO: Use PlaceHandicap() in implementation of InitHandicap() to
// avoid redundancy
// Add handicap properties.
if (2 <= rules.Handicap())
{
SgPropInt* handicap =
new SgPropInt(SG_PROP_HANDICAP, rules.Handicap());
root->Add(handicap);
if (rules.JapaneseHandicap())
{
if (9 <= m_board.Size())
{
int h = rules.Handicap();
int half = (m_board.Size()+1) / 2;
SgVector<SgPoint> stones;
if ((4 < h) && (h % 2 != 0))
{
stones.PushBack(SgPointUtil::Pt(half, half));
--h;
}
if (13 <= m_board.Size())
{
AddHandicap(m_board.Size(), 4, 4, &h, &stones);
if (0 < h)
AddHandicap(m_board.Size(), half, 4, &h, &stones);
if (0 < h)
AddHandicap(m_board.Size(), 3, 3, &h, &stones);
if (0 < h)
AddHandicap(m_board.Size(), 7, 7, &h, &stones);
if (0 < h)
AddHandicap(m_board.Size(), half, 3, &h, &stones);
if (0 < h)
AddHandicap(m_board.Size(), half - (half - 4) / 2,
4, &h, &stones);
if (0 < h)
AddHandicap(m_board.Size(), half + (half - 4) / 2,
4, &h, &stones);
}
else
{
AddHandicap(m_board.Size(), 3, 3, &h, &stones);
if (0 < h)
AddHandicap(m_board.Size(), half, 3, &h, &stones);
if (0 < h)
AddHandicap(m_board.Size(), 4, 4, &h, &stones);
}
SgPropAddStone* addBlack =
new SgPropAddStone(SG_PROP_ADD_BLACK, stones);
root->Add(addBlack);
// White to play.
SgPropPlayer* player =
new SgPropPlayer(SG_PROP_PLAYER, SG_WHITE);
root->Add(player);
}
}
else
{
// Chinese handicap.
SgPropInt* chinese =
new SgPropInt(SG_PROP_CHINESE, rules.Handicap());
root->Add(chinese);
}
}
}
// improved by using recursive extension to find 2-conn paths.
bool GoRegion::Find2ConnForAllInterior(SgMiaiStrategy* miaiStrategy,
SgVector<SgPoint>& usedLibs) const
{
SgVector<SgMiaiPair> myStrategy;
const int size = m_bd.Size();
SgPointSet interior = AllInsideLibs();
if (interior.IsEmpty())
{
return true;
}
//if (GetFlag(GO_REGION_SINGLE_BLOCK_BOUNDARY))
{
SgPointSet testSet = interior;
SgPointSet originalLibs = testSet.Border(size) & Dep().Border(size)
& m_bd.AllEmpty() & Points();
SgPointSet updateLibs = originalLibs;
// now try to find miai-paths to remaining interior points recursively
bool changed = true;
while (changed)
{
changed = false;
if (testSet.IsEmpty())
{
SgVector<SgPoint> jlibs;
JointLibs(&jlibs);
SgVector<SgPoint> ips;
GetIPs(&ips);
SgVector<SgMiaiPair> updateStrg;
for (SgSetIterator it(interior); it; ++it)
{
SgPoint p = *it;
SgPointSet s1;
s1.Include(p);
SgPointSet rest = s1.Border(size) & updateLibs;
if (! rest.IsEmpty())
{
for (SgVectorIterator<SgMiaiPair> it2(myStrategy);
it2; ++it2)
{
SgMiaiPair x = *it2;
if ( SgPointUtil::AreAdjacent(p, x.first)
&& SgPointUtil::AreAdjacent(p, x.second)
)
{
if (ips.Contains(x.first))
{
updateLibs.Include(x.first);
usedLibs.Exclude(x.first);
SgPoint t = rest.PointOf();
x.first = t;
updateLibs.Exclude(t);
rest.Exclude(t);
usedLibs.Include(t);
}
if ( ips.Contains(x.second)
&& ! rest.IsEmpty()
)
{
updateLibs.Include(x.second);
usedLibs.Exclude(x.second);
SgPoint t = rest.PointOf();
x.second = t;
updateLibs.Exclude(t);
rest.Exclude(t);
usedLibs.Include(t);
}
updateStrg.Include(x);
}
}
}
}
miaiStrategy->SetStrategy(updateStrg);
/* */ return true; /* */
}
for (SgSetIterator it(interior); it; ++it)
{
SgMiaiPair miaiPair;
if (Find2BestLibs(*it, updateLibs, testSet, &miaiPair))
{
if (miaiPair.first == miaiPair.second)
{
SgDebug() <<"\nmiaipair are same: "
<< SgWritePoint(miaiPair.first)
<< SgWritePoint(miaiPair.second);
SgDebug() <<"\ncurrent region is:\n";
Points().Write(SgDebug(), size);
SG_ASSERT(false);
}
myStrategy.PushBack(miaiPair);
usedLibs.PushBack(miaiPair.first);
usedLibs.PushBack(miaiPair.second);
updateLibs.Exclude(miaiPair.first);
updateLibs.Exclude(miaiPair.second);
updateLibs.Include(*it);
testSet.Exclude(*it);
changed = true;
}
}
} // while loop for recursive finding
}
miaiStrategy->Clear();
return false;
}
int SgSearch::SearchEngine(int depth, int alpha, int beta,
SgSearchStack& stack, bool* isExactValue,
bool lastNullMove)
{
SG_ASSERT(stack.IsEmpty() || stack.Top() != SG_NULLMOVE);
SG_ASSERT(alpha < beta);
// Only place we check whether the search has been newly aborted. In all
// other places, just check whether search was aborted before.
// AR: what to return here?
// if - (SG_INFINITY-1), then will be positive on next level?
if (AbortSearch())
{
*isExactValue = false;
return alpha;
}
// Null move pruning
if ( m_useNullMove
&& depth > 0
&& ! lastNullMove
&& NullMovePrune(depth, DEPTH_UNIT * (1 + m_nullMoveDepth), beta)
)
{
*isExactValue = false;
return beta;
}
// ProbCut
if (m_probcut && m_probcut->IsEnabled())
{
int probCutValue;
if (m_probcut->ProbCut(*this, depth, alpha, beta, stack,
isExactValue, &probCutValue)
)
return probCutValue;
}
m_stat.IncNumNodes();
bool hasMove = false; // true if a move has been executed at this level
int loValue = -(SG_INFINITY - 1);
m_reachedDepthLimit = m_reachedDepthLimit || (depth <= 0);
// check whether position is solved from hash table.
SgSearchHashData data; // initialized to ! data.IsValid()
if (LookupHash(data))
{
if (data.IsExactValue()) // exact value: stop search
{
*isExactValue = true;
stack.Clear();
if (data.BestMove() != SG_NULLMOVE)
stack.Push(data.BestMove());
if (TraceIsOn())
m_tracer->TraceValue(data.Value(), GetToPlay(),
"exact-hash", true);
return data.Value();
}
}
bool allExact = true; // Do all moves have exact evaluation?
if (depth > 0 && ! EndOfGame())
{
// Check whether current position has already been encountered.
SgMove tryFirst = SG_NULLMOVE;
SgMove opponentBest = SG_NULLMOVE;
if (data.IsValid())
{
if (data.Depth() > 0)
{
tryFirst = data.BestMove();
SG_ASSERT(tryFirst != SG_NULLMOVE);
}
// If data returned from hash table is based on equal or deeper
// search than what we plan to do right now, just use that data.
// The hash table may have deeper data for the current position
// since the same number of moves may result in more 'depth'
// left if the 'delta' for the moves has been smaller, which
// will happen when most moves came from the cache.
if (depth <= data.Depth())
{
// Rely on value returned from hash table to be for the
// current position. In Go, it can happen that the move is
// not legal (ko recapture)
int delta = DEPTH_UNIT;
bool canExecute = CallExecute(tryFirst, &delta, depth);
if (canExecute)
CallTakeBack();
else
tryFirst = SG_NULLMOVE;
if (tryFirst != SG_NULLMOVE || data.IsExactValue())
{
// getting a deep enough hash hit or an exact value
// is as good as reaching the depth limit by search.
m_reachedDepthLimit = true;
// Update bounds with data from cache.
data.AdjustBounds(&alpha, &beta);
if (alpha >= beta)
{
*isExactValue = data.IsExactValue();
stack.Clear();
if (tryFirst != SG_NULLMOVE)
stack.Push(tryFirst);
if (TraceIsOn())
m_tracer->TraceValue(data.Value(), GetToPlay(),
"Hash hit", *isExactValue);
return data.Value();
}
}
}
int delta = DEPTH_UNIT;
if ( tryFirst != SG_NULLMOVE
&& CallExecute(tryFirst, &delta, depth)
)
{
bool childIsExact = true;
loValue = -SearchEngine(depth-delta, -beta, -alpha, stack,
&childIsExact);
if (TraceIsOn())
m_tracer->TraceComment("tryFirst");
CallTakeBack();
hasMove = true;
if (m_aborted)
{
if (TraceIsOn())
m_tracer->TraceComment("aborted");
*isExactValue = false;
return (1 < m_currentDepth) ? alpha : loValue;
}
if (stack.NonEmpty())
{
opponentBest = stack.Top();
SG_ASSERT(opponentBest != SG_NULLMOVE);
}
stack.Push(tryFirst);
if (! childIsExact)
allExact = false;
if (loValue >= beta)
{
if (TraceIsOn())
m_tracer->TraceValue(loValue, GetToPlay());
// store in hash table. Known to be exact only if
// solved for one player.
bool isExact = SgSearchValue::IsSolved(loValue);
StoreHash(depth, loValue, tryFirst,
false /*isUpperBound*/,
true /*isLowerBound*/, isExact);
*isExactValue = isExact;
if (TraceIsOn())
m_tracer->TraceValue(loValue, GetToPlay(),
"b-cut", isExact);
return loValue;
}
}
}
// 'hiValue' is equal to 'beta' for alpha-beta algorithm, and gets set
// to alpha+1 for Scout, except for the first move.
int hiValue =
(hasMove && m_useScout) ? max(loValue, alpha) + 1 : beta;
bool foundCutoff = false;
SgVector<SgMove> specialMoves;
// Don't execute 'tryFirst' again.
if (tryFirst != SG_NULLMOVE)
specialMoves.PushBack(tryFirst);
// Heuristic: "a good move for my opponent is a good move for me"
if ( ! foundCutoff
&& m_useOpponentBest
&& opponentBest != SG_NULLMOVE
&& TrySpecialMove(opponentBest, specialMoves,
depth, alpha, beta,
loValue, hiValue, stack,
allExact, foundCutoff)
)
hasMove = true;
if ( ! foundCutoff
&& m_useKillers
&& m_currentDepth <= MAX_KILLER_DEPTH
)
{
SgMove killer1 = m_killers[m_currentDepth].GetKiller1();
if ( killer1 != SG_NULLMOVE
&& TrySpecialMove(killer1, specialMoves,
depth, alpha, beta,
loValue, hiValue, stack,
allExact, foundCutoff)
)
hasMove = true;
SgMove killer2 = m_killers[m_currentDepth].GetKiller2();
if ( ! foundCutoff
&& killer2 != SG_NULLMOVE
&& TrySpecialMove(killer2, specialMoves,
depth, alpha, beta,
loValue, hiValue, stack,
allExact, foundCutoff)
)
hasMove = true;
}
// Generate the moves for this position.
SgVector<SgMove> moves;
if (! foundCutoff && ! m_aborted)
{
CallGenerate(&moves, depth);
// Iterate through all the moves to find the best move and
// correct value for this position.
for (SgVectorIterator<SgMove> it(moves); it && ! foundCutoff; ++it)
{
if (TryMove(*it, specialMoves,
depth, alpha, beta,
loValue, hiValue, stack,
allExact, foundCutoff)
)
hasMove = true;
if (! foundCutoff && m_aborted)
{
if (TraceIsOn())
m_tracer->TraceComment("ABORTED");
*isExactValue = false;
return (1 < m_currentDepth) ? alpha : loValue;
}
}
}
// Make sure the move added to the hash table really got generated.
#ifndef NDEBUG
if (hasMove && stack.NonEmpty() && ! m_aborted)
{
SgMove bestMove = stack.Top();
SG_ASSERT(bestMove != SG_NULLMOVE);
SG_ASSERT( specialMoves.Contains(bestMove)
|| moves.Contains(bestMove)
);
}
#endif
}
bool isSolved = ! m_aborted;
if (! m_aborted)
{
// Evaluate position if terminal node (either no moves generated, or
// none of the generated moves were legal).
bool solvedByEval = false;
if (! hasMove)
{
m_stat.IncNumEvals();
stack.Clear();
loValue = CallEvaluate(depth, &solvedByEval);
}
// Save data about current position in the hash table.
isSolved = solvedByEval
|| SgSearchValue::IsSolved(loValue)
|| (hasMove && allExact);
// || EndOfGame(); bug: cannot store exact score after two passes.
if ( m_hash
&& ! m_aborted
&& (isSolved || stack.NonEmpty())
)
{
SgMove bestMove = SG_NULLMOVE;
if (stack.NonEmpty())
{
bestMove = stack.Top();
SG_ASSERT(bestMove != SG_NULLMOVE);
}
SG_ASSERT(alpha <= beta);
StoreHash(depth, loValue, bestMove,
(loValue <= alpha) /* upper */,
(beta <= loValue) /* lower*/, isSolved);
}
}
// If aborted search and didn't find any values, just return alpha.
// Can't return best found so far, since may not have tried the optimal
// counter-move yet. However, return best value found so far on top
// level, since assuming hash move will have been tried first.
if (m_aborted && (1 < m_currentDepth || loValue < alpha))
loValue = alpha;
*isExactValue = isSolved;
if (TraceIsOn())
m_tracer->TraceValue(loValue, GetToPlay(), 0, isSolved);
SG_ASSERT(stack.IsEmpty() || stack.Top() != SG_NULLMOVE);
return loValue;
}
bool GoEyeUtil::NumberOfMoveToEye2(const GoBoard& board, SgBlackWhite color,
SgPoint p, int& nummoves)
{
nummoves = 0;
bool capturing = false;
SgVector<SgPoint> usedpoints;
usedpoints.PushBack(p);
SgPointSet counted;
// Can never turn own stone into an eye
if (board.IsColor(p, color))
return false;
// If opponent stone then it must be captured to make eye
if (board.IsColor(p, SgOppBW(color)))
{
capturing = true;
// If it is obviously safe then it can never be an eye
if (SinglePointSafe2(board, p)) // Quick, naive safety test
return false;
for (GoBoard::LibertyIterator libit(board, p); libit; ++libit)
counted.Include(*libit);
}
// Count immediate adjacencies
for (SgNb4Iterator nb(p); nb; ++nb)
{
SgPoint adj = *nb;
// Empty points must be filled
if (board.IsColor(adj, SG_EMPTY))
{
counted.Include(adj);
}
// If adjacent opponent then can never be an eye
else if (board.IsColor(adj, SgOppBW(color)))
{
if (capturing)
counted.Include(adj); // must capture and then fill
else
return false;
}
}
// Up to one diagonal can be ignored: estimate most costly
SgPoint toignore = SG_NULLPOINT;
int maxcost = 0;
int infcost = 1000;
if (board.Line(p) > 1)
{
for (SgNb4DiagIterator nbd(p); nbd; ++nbd)
{
SgPoint diag = *nbd;
int cost = 0;
if ( board.IsColor(diag, SG_EMPTY)
&& ! IsSinglePointEye2(board, diag, color, usedpoints))
{
cost = 1;
}
else if (board.IsColor(diag, SgOppBW(color)))
{
// quick safety test
if (SinglePointSafe2(board, diag))
cost = infcost;
else
cost = board.NumLiberties(diag);
}
if (cost > maxcost)
{
maxcost = cost;
toignore = diag;
}
}
}
// Now mark points that must be played to secure diagonals
for (SgNb4DiagIterator nbd(p); nbd; ++nbd)
{
SgPoint diag = *nbd;
if (diag == toignore)
continue;
// Empty points must be filled (unless they are eyes)
if ( board.IsColor(diag, SG_EMPTY)
&& ! IsSinglePointEye2(board, diag, color, usedpoints))
{
counted.Include(diag);
}
// Opponent stones on diagonals must be captured and filled
else if (board.IsColor(diag, SgOppBW(color)))
{
if (SinglePointSafe2(board, diag))
return false;
else
{
counted.Include(diag);
for (GoBoard::LibertyIterator libit(board, diag); libit;
++libit)
counted.Include(*libit);
}
}
}
nummoves = counted.Size();
return true;
}
/** Main ladder routine */
int GoLadder::Ladder(const GoBoard& bd, SgPoint prey, SgBlackWhite toPlay,
SgVector<SgPoint>* sequence, bool twoLibIsEscape)
{
GoModBoard modBoard(bd);
m_bd = &modBoard.Board();
InitMaxMoveNumber();
if (sequence)
sequence->Clear();
if (! m_bd->Occupied(prey))
return 0;
if (CheckMoveOverflow())
return GOOD_FOR_PREY;
int result = 0;
m_preyColor = m_bd->GetStone(prey);
m_hunterColor = SgOppBW(m_preyColor);
int numLib = m_bd->NumLiberties(prey);
if (2 < numLib)
result = GOOD_FOR_PREY;
else
{
GoBoard::LibertyIterator libit(*m_bd, prey);
SgPoint lib1 = *libit;
m_partOfPrey.Clear();
MarkStonesAsPrey(prey);
GoPointList adjBlk = GoBoardUtil::AdjacentStones(*m_bd, prey);
FilterAdjacent(adjBlk);
if (toPlay == m_preyColor)
{
if (numLib == 1)
result = PreyLadder(0, lib1, adjBlk, sequence);
else if (twoLibIsEscape) // prey to play, numLib >= 2
// For example, Explorer cannot treat this case as a ladder,
// it messes up the logic
result = GOOD_FOR_PREY;
else
{
// Prey to play, two liberties. This is usually good, but
// need to prove that there is some move that really
// escapes laddercapture.
// Try liberties of adjacent blocks with at most two
// liberties, try lib1 and lib2, and try moves one away
// from the two liberties.
// Good example with three blocks that test this case:
// (;GM[1]SZ[19]FF[3]
// AB[qa][pa][pb][pd][pc][qe][re][rd][rc][se]
// AW[pe][pf][qf][qd][qc][rb][qb][sa][sc][rf][rg][sg])
SgVector<SgPoint> movesToTry;
// Liberties of adj. blocks with at most two liberties.
adjBlk = GoBoardUtil::AdjacentStones(*m_bd, prey);
ReduceToBlocks(adjBlk);
for (GoPointList::Iterator iterAdj(adjBlk); iterAdj;
++iterAdj)
{
SgPoint block = *iterAdj;
SG_ASSERT(m_bd->IsColor(block, m_hunterColor));
SG_ASSERT(BlockIsAdjToPrey(block, 1));
if (m_bd->NumLiberties(block) <= 2)
for (GoBoard::LibertyIterator it(*m_bd, block); it;
++it)
movesToTry.PushBack(*it);
}
// Liberties of blocks.
++libit;
SgPoint lib2 = *libit;
movesToTry.PushBack(lib1);
movesToTry.PushBack(lib2);
// Moves one away from liberties.
SgVector<SgPoint> neighbors;
NeighborsOfColor(*m_bd, lib1, SG_EMPTY, &neighbors);
movesToTry.Concat(&neighbors);
NeighborsOfColor(*m_bd, lib2, SG_EMPTY, &neighbors);
movesToTry.Concat(&neighbors);
// Try whether any of these moves lead to escape.
for (SgVectorIterator<SgPoint> it(movesToTry); it; ++it)
{
if (PlayIfLegal(*m_bd, *it, m_preyColor))
{
if (Ladder(bd, prey, m_hunterColor, 0, twoLibIsEscape)
> 0)
{
if (sequence)
sequence->PushBack(*it);
result = GOOD_FOR_PREY;
}
m_bd->Undo();
}
if (result != 0)
break;
}
// If none of those moves worked, prey can't escape.
// This is a bit pessimistic, there may be other moves
// that do lead to escape (e.g. approach moves), but
// ladder algorithm doesn't know about those.
if (result == 0)
result = GOOD_FOR_HUNTER;
}
}
else
{
if (IsSnapback(prey))
result = GOOD_FOR_PREY;
else
{
++libit;
if (libit) // two liberties
result = HunterLadder(0, lib1, *libit, adjBlk, sequence);
else // one liberty
result = HunterLadder(0, lib1, adjBlk, sequence);
}
}
}
if (sequence)
sequence->Reverse(); // built as a stack, with first move at end.
return result;
}
/** Play prey move and update all the relevant information.
Extend the prey by playing at its only liberty, or capture a block
adjacent to the prey. */
int GoLadder::PlayPreyMove(int depth, SgPoint move, SgPoint lib1,
const GoPointList& adjBlk,
SgVector<SgPoint>* sequence)
{
int result = 0;
GoPointList newAdj(adjBlk);
SgVector<SgPoint> newLib;
SgVector<SgPoint> newStones;
SgVector<SgPoint> neighbors;
if (move == lib1)
{
NeighborsOfColor(*m_bd, move, m_preyColor, &neighbors);
for (SgVectorIterator<SgPoint> iter(neighbors); iter; ++iter)
{
SgPoint block = *iter;
if (! m_partOfPrey[block])
{
MarkStonesAsPrey(block, &newStones);
GoPointList temp =
GoBoardUtil::AdjacentStones(*m_bd, block);
newAdj.PushBackList(temp);
for (GoBoard::LibertyIterator it(*m_bd, block); it; ++it)
newLib.Include(*it);
}
}
m_partOfPrey.Include(move);
}
if (PlayIfLegal(*m_bd, move, m_preyColor))
{
if (move == lib1)
{
NeighborsOfColor(*m_bd, move, SG_EMPTY, &neighbors);
for (SgVectorIterator<SgPoint> iter(newLib); iter; ++iter)
{
SgPoint point = *iter;
// Test for Empty is necessary because newLib will include
// the move just played.
if (m_bd->IsEmpty(point))
neighbors.Include(point);
}
}
else
{
neighbors.PushBack(lib1);
}
if (m_bd->CapturingMove())
{ // Add the points at the captured stones that are adjacent to the
// prey to the liberties, at least if exactly one stone captured.
for (GoPointList::Iterator it(m_bd->CapturedStones()); it;
++it)
{
SgPoint stone = *it;
if (PointIsAdjToPrey(stone))
neighbors.Include(stone);
}
}
SG_ASSERT(! neighbors.IsEmpty());
lib1 = neighbors[0];
SG_ASSERT(m_bd->IsEmpty(lib1));
SgArrayList<SgPoint,4> temp =
NeighborsOfColor(*m_bd, move, m_hunterColor);
newAdj.PushBackList(temp);
FilterAdjacent(newAdj);
if (neighbors.Length() == 1)
result = HunterLadder(depth + 1, lib1, newAdj, sequence);
else if (neighbors.Length() == 2)
{
SgPoint lib2 = neighbors[1];
SG_ASSERT(m_bd->IsEmpty(lib2));
result = HunterLadder(depth + 1, lib1, lib2, newAdj, sequence);
}
else // 3 <= numLib
{
if (sequence)
sequence->Clear();
result = GOOD_FOR_PREY - (depth + 1);
}
if (sequence)
sequence->PushBack(move);
m_bd->Undo();
}
else
{
if (sequence)
sequence->Clear();
result = GOOD_FOR_HUNTER + depth;
}
m_partOfPrey.Exclude(move);
m_partOfPrey.Exclude(newStones);
return result;
}