Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
- Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ Copyright (C) 2015-2017 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
// Different node types, used as a template parameter
enum NodeType { NonPV, PV };
+ // Sizes and phases of the skip-blocks, used for distributing search depths across the threads
+ const int skipSize[] = { 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4 };
+ const int skipPhase[] = { 0, 1, 0, 1, 2, 3, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 6, 7 };
+
// Razoring and futility margin based on depth
- const int razor_margin[4] = { 483, 570, 603, 554 };
+ // razor_margin[0] is unused as long as depth >= ONE_PLY in search
+ const int razor_margin[] = { 0, 570, 603, 554 };
Value futility_margin(Depth d) { return Value(150 * d / ONE_PLY); }
// Futility and reductions lookup tables, initialized at startup
int FutilityMoveCounts[2][16]; // [improving][depth]
int Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber]
+ // Threshold used for countermoves based pruning
+ const int CounterMovePruneThreshold = 0;
+
template <bool PvNode> Depth reduction(bool i, Depth d, int mn) {
return Reductions[PvNode][i][std::min(d / ONE_PLY, 63)][std::min(mn, 63)] * ONE_PLY;
}
+ // History and stats update bonus, based on depth
+ int stat_bonus(Depth depth) {
+ int d = depth / ONE_PLY ;
+ return d > 17 ? 0 : d * d + 2 * d - 2;
+ }
+
// Skill structure is used to implement strength limit
struct Skill {
Skill(int l) : level(l) {}
Move best = MOVE_NONE;
};
- // EasyMoveManager structure is used to detect an 'easy move'. When the PV is
- // stable across multiple search iterations, we can quickly return the best move.
+ // EasyMoveManager structure is used to detect an 'easy move'. When the PV is stable
+ // across multiple search iterations, we can quickly return the best move.
struct EasyMoveManager {
void clear() {
Move pv[3];
};
- // Set of rows with half bits set to 1 and half to 0. It is used to allocate
- // the search depths across the threads.
- typedef std::vector<int> Row;
-
- const Row HalfDensity[] = {
- {0, 1},
- {1, 0},
- {0, 0, 1, 1},
- {0, 1, 1, 0},
- {1, 1, 0, 0},
- {1, 0, 0, 1},
- {0, 0, 0, 1, 1, 1},
- {0, 0, 1, 1, 1, 0},
- {0, 1, 1, 1, 0, 0},
- {1, 1, 1, 0, 0, 0},
- {1, 1, 0, 0, 0, 1},
- {1, 0, 0, 0, 1, 1},
- {0, 0, 0, 0, 1, 1, 1, 1},
- {0, 0, 0, 1, 1, 1, 1, 0},
- {0, 0, 1, 1, 1, 1, 0 ,0},
- {0, 1, 1, 1, 1, 0, 0 ,0},
- {1, 1, 1, 1, 0, 0, 0 ,0},
- {1, 1, 1, 0, 0, 0, 0 ,1},
- {1, 1, 0, 0, 0, 0, 1 ,1},
- {1, 0, 0, 0, 0, 1, 1 ,1},
- };
-
- Value bonus(Depth depth) { int d = depth / ONE_PLY ; return Value(d * d + 2 * d - 2); }
- Value penalty(Depth depth) { int d = depth / ONE_PLY ; return -Value(d * d + 4 * d + 1); }
-
- const size_t HalfDensitySize = std::extent<decltype(HalfDensity)>::value;
-
EasyMoveManager EasyMove;
Value DrawValue[COLOR_NB];
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning);
template <NodeType NT, bool InCheck>
- Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth);
+ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth = DEPTH_ZERO);
Value value_to_tt(Value v, int ply);
Value value_from_tt(Value v, int ply);
void update_pv(Move* pv, Move move, Move* childPv);
- void update_cm_stats(Stack* ss, Piece pc, Square s, Value bonus);
- void update_stats(const Position& pos, Stack* ss, Move move, Move* quiets, int quietsCnt, Value bonus);
+ void update_cm_stats(Stack* ss, Piece pc, Square s, int bonus);
+ void update_stats(const Position& pos, Stack* ss, Move move, Move* quiets, int quietsCnt, int bonus);
void check_time();
} // namespace
for (int d = 1; d < 64; ++d)
for (int mc = 1; mc < 64; ++mc)
{
- double r = log(d) * log(mc) / 2;
+ double r = log(d) * log(mc) / 1.95;
Reductions[NonPV][imp][d][mc] = int(std::round(r));
Reductions[PV][imp][d][mc] = std::max(Reductions[NonPV][imp][d][mc] - 1, 0);
for (int d = 0; d < 16; ++d)
{
- FutilityMoveCounts[0][d] = int(2.4 + 0.773 * pow(d + 0.00, 1.8));
- FutilityMoveCounts[1][d] = int(2.9 + 1.045 * pow(d + 0.49, 1.8));
+ FutilityMoveCounts[0][d] = int(2.4 + 0.74 * pow(d, 1.78));
+ FutilityMoveCounts[1][d] = int(5.0 + 1.00 * pow(d, 2.00));
}
}
for (Thread* th : Threads)
{
- th->history.clear();
th->counterMoves.clear();
- th->fromTo.clear();
+ th->history.clear();
th->counterMoveHistory.clear();
th->resetCalls = true;
+ CounterMoveStats& cm = th->counterMoveHistory[NO_PIECE][0];
+ int* t = &cm[NO_PIECE][0];
+ std::fill(t, t + sizeof(cm), CounterMovePruneThreshold - 1);
}
Threads.main()->previousScore = VALUE_INFINITE;
&& rootMoves[0].pv[0] != MOVE_NONE)
{
for (Thread* th : Threads)
- if ( th->completedDepth > bestThread->completedDepth
- && th->rootMoves[0].score > bestThread->rootMoves[0].score)
+ {
+ Depth depthDiff = th->completedDepth - bestThread->completedDepth;
+ Value scoreDiff = th->rootMoves[0].score - bestThread->rootMoves[0].score;
+
+ if (scoreDiff > 0 && depthDiff >= 0)
bestThread = th;
+ }
}
previousScore = bestThread->rootMoves[0].score;
}
-// Thread::search() is the main iterative deepening loop. It calls search()
-// repeatedly with increasing depth until the allocated thinking time has been
-// consumed, the user stops the search, or the maximum search depth is reached.
+/// Thread::search() is the main iterative deepening loop. It calls search()
+/// repeatedly with increasing depth until the allocated thinking time has been
+/// consumed, the user stops the search, or the maximum search depth is reached.
void Thread::search() {
MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr);
std::memset(ss-4, 0, 7 * sizeof(Stack));
+ for(int i = 4; i > 0; i--)
+ (ss-i)->counterMoves = &this->counterMoveHistory[NO_PIECE][0]; // Use as sentinel
bestValue = delta = alpha = -VALUE_INFINITE;
beta = VALUE_INFINITE;
&& !Signals.stop
&& (!Limits.depth || Threads.main()->rootDepth / ONE_PLY <= Limits.depth))
{
- // Set up the new depths for the helper threads skipping on average every
- // 2nd ply (using a half-density matrix).
- if (!mainThread)
+ // Distribute search depths across the threads
+ if (idx)
{
- const Row& row = HalfDensity[(idx - 1) % HalfDensitySize];
- if (row[(rootDepth / ONE_PLY + rootPos.game_ply()) % row.size()])
- continue;
+ int i = (idx - 1) % 20;
+ if (((rootDepth / ONE_PLY + rootPos.game_ply() + skipPhase[i]) / skipSize[i]) % 2)
+ continue;
}
// Age out PV variability metric
// search the already searched PV lines are preserved.
std::stable_sort(rootMoves.begin() + PVIdx, rootMoves.end());
- // If search has been stopped, break immediately. Sorting and
+ // If search has been stopped, we break immediately. Sorting and
// writing PV back to TT is safe because RootMoves is still
// valid, although it refers to the previous iteration.
if (Signals.stop)
bool doEasyMove = rootMoves[0].pv[0] == easyMove
&& mainThread->bestMoveChanges < 0.03
- && Time.elapsed() > Time.optimum() * 5 / 42;
+ && Time.elapsed() > Time.optimum() * 5 / 44;
if ( rootMoves.size() == 1
|| Time.elapsed() > Time.optimum() * unstablePvFactor * improvingFactor / 628
Key posKey;
Move ttMove, move, excludedMove, bestMove;
Depth extension, newDepth;
- Value bestValue, value, ttValue, eval, nullValue;
+ Value bestValue, value, ttValue, eval;
bool ttHit, inCheck, givesCheck, singularExtensionNode, improving;
- bool captureOrPromotion, doFullDepthSearch, moveCountPruning;
+ bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets;
Piece moved_piece;
int moveCount, quietCount;
// Step 1. Initialize node
Thread* thisThread = pos.this_thread();
inCheck = pos.checkers();
- moveCount = quietCount = ss->moveCount = 0;
- ss->history = VALUE_ZERO;
+ moveCount = quietCount = ss->moveCount = 0;
+ ss->history = 0;
bestValue = -VALUE_INFINITE;
ss->ply = (ss-1)->ply + 1;
if (thisThread->resetCalls.load(std::memory_order_relaxed))
{
thisThread->resetCalls = false;
+
// At low node count increase the checking rate to about 0.1% of nodes
// otherwise use a default value.
- thisThread->callsCnt = Limits.nodes ? std::min((int64_t)4096, Limits.nodes / 1024)
+ thisThread->callsCnt = Limits.nodes ? std::min(4096, int(Limits.nodes / 1024))
: 4096;
}
if (!rootNode)
{
// Step 2. Check for aborted search and immediate draw
- if (Signals.stop.load(std::memory_order_relaxed) || pos.is_draw() || ss->ply >= MAX_PLY)
+ if (Signals.stop.load(std::memory_order_relaxed) || pos.is_draw(ss->ply) || ss->ply >= MAX_PLY)
return ss->ply >= MAX_PLY && !inCheck ? evaluate(pos)
: DrawValue[pos.side_to_move()];
assert(0 <= ss->ply && ss->ply < MAX_PLY);
ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE;
- ss->counterMoves = nullptr;
+ ss->counterMoves = &thisThread->counterMoveHistory[NO_PIECE][0];
(ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
Square prevSq = to_sq((ss-1)->currentMove);
&& (ttValue >= beta ? (tte->bound() & BOUND_LOWER)
: (tte->bound() & BOUND_UPPER)))
{
- // If ttMove is quiet, update killers, history, counter move on TT hit
- if (ttValue >= beta && ttMove)
+ // If ttMove is quiet, update move sorting heuristics on TT hit
+ if (ttMove)
{
- if (!pos.capture_or_promotion(ttMove))
- update_stats(pos, ss, ttMove, nullptr, 0, bonus(depth));
+ if (ttValue >= beta)
+ {
+ if (!pos.capture_or_promotion(ttMove))
+ update_stats(pos, ss, ttMove, nullptr, 0, stat_bonus(depth));
- // Extra penalty for a quiet TT move in previous ply when it gets refuted
- if ((ss-1)->moveCount == 1 && !pos.captured_piece())
- update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, penalty(depth));
+ // Extra penalty for a quiet TT move in previous ply when it gets refuted
+ if ((ss-1)->moveCount == 1 && !pos.captured_piece())
+ update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY));
+ }
+ // Penalty for a quiet ttMove that fails low
+ else if (!pos.capture_or_promotion(ttMove))
+ {
+ int penalty = -stat_bonus(depth);
+ thisThread->history.update(pos.side_to_move(), ttMove, penalty);
+ update_cm_stats(ss, pos.moved_piece(ttMove), to_sq(ttMove), penalty);
+ }
}
return ttValue;
}
// Step 4a. Tablebase probe
if (!rootNode && TB::Cardinality)
{
- int piecesCnt = pos.count<ALL_PIECES>(WHITE) + pos.count<ALL_PIECES>(BLACK);
+ int piecesCount = pos.count<ALL_PIECES>();
- if ( piecesCnt <= TB::Cardinality
- && (piecesCnt < TB::Cardinality || depth >= TB::ProbeDepth)
+ if ( piecesCount <= TB::Cardinality
+ && (piecesCount < TB::Cardinality || depth >= TB::ProbeDepth)
&& pos.rule50_count() == 0
&& !pos.can_castle(ANY_CASTLING))
{
// Step 6. Razoring (skipped when in check)
if ( !PvNode
&& depth < 4 * ONE_PLY
- && ttMove == MOVE_NONE
&& eval + razor_margin[depth / ONE_PLY] <= alpha)
{
if (depth <= ONE_PLY)
- return qsearch<NonPV, false>(pos, ss, alpha, beta, DEPTH_ZERO);
+ return qsearch<NonPV, false>(pos, ss, alpha, alpha+1);
Value ralpha = alpha - razor_margin[depth / ONE_PLY];
- Value v = qsearch<NonPV, false>(pos, ss, ralpha, ralpha+1, DEPTH_ZERO);
+ Value v = qsearch<NonPV, false>(pos, ss, ralpha, ralpha+1);
if (v <= ralpha)
return v;
}
&& (ss->staticEval >= beta - 35 * (depth / ONE_PLY - 6) || depth >= 13 * ONE_PLY)
&& pos.non_pawn_material(pos.side_to_move()))
{
- ss->currentMove = MOVE_NULL;
- ss->counterMoves = nullptr;
assert(eval - beta >= 0);
// Null move dynamic reduction based on depth and value
Depth R = ((823 + 67 * depth / ONE_PLY) / 256 + std::min((eval - beta) / PawnValueMg, 3)) * ONE_PLY;
+ ss->currentMove = MOVE_NULL;
+ ss->counterMoves = &thisThread->counterMoveHistory[NO_PIECE][0];
+
pos.do_null_move(st);
- nullValue = depth-R < ONE_PLY ? -qsearch<NonPV, false>(pos, ss+1, -beta, -beta+1, DEPTH_ZERO)
- : - search<NonPV>(pos, ss+1, -beta, -beta+1, depth-R, !cutNode, true);
+ Value nullValue = depth-R < ONE_PLY ? -qsearch<NonPV, false>(pos, ss+1, -beta, -beta+1)
+ : - search<NonPV>(pos, ss+1, -beta, -beta+1, depth-R, !cutNode, true);
pos.undo_null_move();
if (nullValue >= beta)
return nullValue;
// Do verification search at high depths
- Value v = depth-R < ONE_PLY ? qsearch<NonPV, false>(pos, ss, beta-1, beta, DEPTH_ZERO)
+ Value v = depth-R < ONE_PLY ? qsearch<NonPV, false>(pos, ss, beta-1, beta)
: search<NonPV>(pos, ss, beta-1, beta, depth-R, false, true);
if (v >= beta)
Depth rdepth = depth - 4 * ONE_PLY;
assert(rdepth >= ONE_PLY);
- assert((ss-1)->currentMove != MOVE_NONE);
- assert((ss-1)->currentMove != MOVE_NULL);
+ assert(is_ok((ss-1)->currentMove));
MovePicker mp(pos, ttMove, rbeta - ss->staticEval);
{
ss->currentMove = move;
ss->counterMoves = &thisThread->counterMoveHistory[pos.moved_piece(move)][to_sq(move)];
+
pos.do_move(move, st);
value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode, false);
pos.undo_move(move);
moves_loop: // When in check search starts from here
- const CounterMoveStats* cmh = (ss-1)->counterMoves;
- const CounterMoveStats* fmh = (ss-2)->counterMoves;
- const CounterMoveStats* fmh2 = (ss-4)->counterMoves;
+ const CounterMoveStats& cmh = *(ss-1)->counterMoves;
+ const CounterMoveStats& fmh = *(ss-2)->counterMoves;
+ const CounterMoveStats& fm2 = *(ss-4)->counterMoves;
MovePicker mp(pos, ttMove, depth, ss);
value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
&& !excludedMove // Recursive singular search is not allowed
&& (tte->bound() & BOUND_LOWER)
&& tte->depth() >= depth - 3 * ONE_PLY;
+ skipQuiets = false;
// Step 11. Loop through moves
// Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs
- while ((move = mp.next_move()) != MOVE_NONE)
+ while ((move = mp.next_move(skipQuiets)) != MOVE_NONE)
{
assert(is_ok(move));
moveCountPruning = depth < 16 * ONE_PLY
&& moveCount >= FutilityMoveCounts[improving][depth / ONE_PLY];
- // Step 12. Extend checks
- if ( givesCheck
- && !moveCountPruning
- && pos.see_ge(move, VALUE_ZERO))
- extension = ONE_PLY;
+ // Step 12. Singular and Gives Check Extensions
// Singular extension search. If all moves but one fail low on a search of
// (alpha-s, beta-s), and just one fails high on (alpha, beta), then that move
// is singular and should be extended. To verify this we do a reduced search
// on all the other moves but the ttMove and if the result is lower than
- // ttValue minus a margin then we extend the ttMove.
+ // ttValue minus a margin then we will extend the ttMove.
if ( singularExtensionNode
&& move == ttMove
- && !extension
&& pos.legal(move))
{
Value rBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE);
if (value < rBeta)
extension = ONE_PLY;
}
+ else if ( givesCheck
+ && !moveCountPruning
+ && pos.see_ge(move))
+ extension = ONE_PLY;
- // Update the current move (this must be done after singular extension search)
+ // Calculate new depth for this move
newDepth = depth - ONE_PLY + extension;
// Step 13. Pruning at shallow depth
if ( !rootNode
+ && pos.non_pawn_material(pos.side_to_move())
&& bestValue > VALUE_MATED_IN_MAX_PLY)
{
if ( !captureOrPromotion
&& !givesCheck
- && !pos.advanced_pawn_push(move))
+ && (!pos.advanced_pawn_push(move) || pos.non_pawn_material() >= Value(5000)))
{
// Move count based pruning
if (moveCountPruning)
+ {
+ skipQuiets = true;
continue;
+ }
// Reduced depth of the next LMR search
int lmrDepth = std::max(newDepth - reduction<PvNode>(improving, depth, moveCount), DEPTH_ZERO) / ONE_PLY;
// Countermoves based pruning
if ( lmrDepth < 3
- && (!cmh || (*cmh )[moved_piece][to_sq(move)] < VALUE_ZERO)
- && (!fmh || (*fmh )[moved_piece][to_sq(move)] < VALUE_ZERO)
- && (!fmh2 || (*fmh2)[moved_piece][to_sq(move)] < VALUE_ZERO || (cmh && fmh)))
+ && (cmh[moved_piece][to_sq(move)] < CounterMovePruneThreshold)
+ && (fmh[moved_piece][to_sq(move)] < CounterMovePruneThreshold))
continue;
// Futility pruning: parent node
continue;
}
+ // Update the current move (this must be done after singular extension search)
ss->currentMove = move;
ss->counterMoves = &thisThread->counterMoveHistory[moved_piece][to_sq(move)];
// Decrease reduction for moves that escape a capture. Filter out
// castling moves, because they are coded as "king captures rook" and
// hence break make_move().
- else if ( type_of(move) == NORMAL
- && !pos.see_ge(make_move(to_sq(move), from_sq(move)), VALUE_ZERO))
+ else if ( type_of(move) == NORMAL
+ && !pos.see_ge(make_move(to_sq(move), from_sq(move))))
r -= 2 * ONE_PLY;
- ss->history = thisThread->history[moved_piece][to_sq(move)]
- + (cmh ? (*cmh )[moved_piece][to_sq(move)] : VALUE_ZERO)
- + (fmh ? (*fmh )[moved_piece][to_sq(move)] : VALUE_ZERO)
- + (fmh2 ? (*fmh2)[moved_piece][to_sq(move)] : VALUE_ZERO)
- + thisThread->fromTo.get(~pos.side_to_move(), move)
- - 8000; // Correction factor
+ ss->history = cmh[moved_piece][to_sq(move)]
+ + fmh[moved_piece][to_sq(move)]
+ + fm2[moved_piece][to_sq(move)]
+ + thisThread->history.get(~pos.side_to_move(), move)
+ - 4000; // Correction factor
// Decrease/increase reduction by comparing opponent's stat score
- if (ss->history > VALUE_ZERO && (ss-1)->history < VALUE_ZERO)
+ if (ss->history > 0 && (ss-1)->history < 0)
r -= ONE_PLY;
- else if (ss->history < VALUE_ZERO && (ss-1)->history > VALUE_ZERO)
+ else if (ss->history < 0 && (ss-1)->history > 0)
r += ONE_PLY;
// Decrease/increase reduction for moves with a good/bad history
// Step 16. Full depth search when LMR is skipped or fails high
if (doFullDepthSearch)
value = newDepth < ONE_PLY ?
- givesCheck ? -qsearch<NonPV, true>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
- : -qsearch<NonPV, false>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
+ givesCheck ? -qsearch<NonPV, true>(pos, ss+1, -(alpha+1), -alpha)
+ : -qsearch<NonPV, false>(pos, ss+1, -(alpha+1), -alpha)
: - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode, false);
// For PV nodes only, do a full PV search on the first move or after a fail
(ss+1)->pv[0] = MOVE_NONE;
value = newDepth < ONE_PLY ?
- givesCheck ? -qsearch<PV, true>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
- : -qsearch<PV, false>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
+ givesCheck ? -qsearch<PV, true>(pos, ss+1, -beta, -alpha)
+ : -qsearch<PV, false>(pos, ss+1, -beta, -alpha)
: - search<PV>(pos, ss+1, -beta, -alpha, newDepth, false, false);
}
if (value > alpha)
{
- // If there is an easy move for this position, clear it if unstable
- if ( PvNode
- && thisThread == Threads.main()
- && EasyMove.get(pos.key())
- && (move != EasyMove.get(pos.key()) || moveCount > 1))
- EasyMove.clear();
-
bestMove = move;
if (PvNode && !rootNode) // Update pv even in fail-high case
: inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()];
else if (bestMove)
{
-
- // Quiet best move: update killers, history and countermoves
+ // Quiet best move: update move sorting heuristics
if (!pos.capture_or_promotion(bestMove))
- update_stats(pos, ss, bestMove, quietsSearched, quietCount, bonus(depth));
+ update_stats(pos, ss, bestMove, quietsSearched, quietCount, stat_bonus(depth));
// Extra penalty for a quiet TT move in previous ply when it gets refuted
if ((ss-1)->moveCount == 1 && !pos.captured_piece())
- update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, penalty(depth));
+ update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY));
}
// Bonus for prior countermove that caused the fail low
else if ( depth >= 3 * ONE_PLY
&& !pos.captured_piece()
&& is_ok((ss-1)->currentMove))
- update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, bonus(depth));
+ update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth));
- tte->save(posKey, value_to_tt(bestValue, ss->ply),
- bestValue >= beta ? BOUND_LOWER :
- PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER,
- depth, bestMove, ss->staticEval, TT.generation());
+ if (!excludedMove)
+ tte->save(posKey, value_to_tt(bestValue, ss->ply),
+ bestValue >= beta ? BOUND_LOWER :
+ PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER,
+ depth, bestMove, ss->staticEval, TT.generation());
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
// qsearch() is the quiescence search function, which is called by the main
- // search function when the remaining depth is zero (or, to be more precise,
- // less than ONE_PLY).
+ // search function with depth zero, or recursively with depth less than ONE_PLY.
template <NodeType NT, bool InCheck>
Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
ss->ply = (ss-1)->ply + 1;
// Check for an instant draw or if the maximum ply has been reached
- if (pos.is_draw() || ss->ply >= MAX_PLY)
+ if (pos.is_draw(ss->ply) || ss->ply >= MAX_PLY)
return ss->ply >= MAX_PLY && !InCheck ? evaluate(pos)
: DrawValue[pos.side_to_move()];
// Detect non-capture evasions that are candidates to be pruned
evasionPrunable = InCheck
+ && depth != DEPTH_ZERO
&& bestValue > VALUE_MATED_IN_MAX_PLY
&& !pos.capture(move);
// Don't search moves with negative SEE values
if ( (!InCheck || evasionPrunable)
&& type_of(move) != PROMOTION
- && !pos.see_ge(move, VALUE_ZERO))
+ && !pos.see_ge(move))
continue;
// Speculative prefetch as early as possible
// update_cm_stats() updates countermove and follow-up move history
- void update_cm_stats(Stack* ss, Piece pc, Square s, Value bonus) {
-
- CounterMoveStats* cmh = (ss-1)->counterMoves;
- CounterMoveStats* fmh1 = (ss-2)->counterMoves;
- CounterMoveStats* fmh2 = (ss-4)->counterMoves;
-
- if (cmh)
- cmh->update(pc, s, bonus);
-
- if (fmh1)
- fmh1->update(pc, s, bonus);
+ void update_cm_stats(Stack* ss, Piece pc, Square s, int bonus) {
- if (fmh2)
- fmh2->update(pc, s, bonus);
+ for (int i : {1, 2, 4})
+ if (is_ok((ss-i)->currentMove))
+ (ss-i)->counterMoves->update(pc, s, bonus);
}
- // update_stats() updates killers, history, countermove and countermove plus
- // follow-up move history when a new quiet best move is found.
+ // update_stats() updates move sorting heuristics when a new quiet best move is found
void update_stats(const Position& pos, Stack* ss, Move move,
- Move* quiets, int quietsCnt, Value bonus) {
+ Move* quiets, int quietsCnt, int bonus) {
if (ss->killers[0] != move)
{
Color c = pos.side_to_move();
Thread* thisThread = pos.this_thread();
- thisThread->fromTo.update(c, move, bonus);
- thisThread->history.update(pos.moved_piece(move), to_sq(move), bonus);
+ thisThread->history.update(c, move, bonus);
update_cm_stats(ss, pos.moved_piece(move), to_sq(move), bonus);
- if ((ss-1)->counterMoves)
+ if (is_ok((ss-1)->currentMove))
{
Square prevSq = to_sq((ss-1)->currentMove);
thisThread->counterMoves.update(pos.piece_on(prevSq), prevSq, move);
// Decrease all the other played quiet moves
for (int i = 0; i < quietsCnt; ++i)
{
- thisThread->fromTo.update(c, quiets[i], -bonus);
- thisThread->history.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
+ thisThread->history.update(c, quiets[i], -bonus);
update_cm_stats(ss, pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
}
}
for (size_t i = 0; i < multiPV; ++i)
{
- bool updated = (i <= PVIdx);
+ bool updated = (i <= PVIdx && rootMoves[i].score != -VALUE_INFINITE);
if (depth == ONE_PLY && !updated)
continue;
projects / stockfish / blobdiff