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 };
Value futility_margin(Depth d) { return Value(150 * d / ONE_PLY); }
return Reductions[PvNode][i][std::min(d / ONE_PLY, 63)][std::min(mn, 63)] * ONE_PLY;
}
+ // History and stats update bonus, based on depth
+ Value stat_bonus(Depth depth) {
+ int d = depth / ONE_PLY ;
+ return Value(d * d + 2 * d - 2);
+ }
+
// Skill structure is used to implement strength limit
struct Skill {
Skill(int l) : level(l) {}
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];
for (Thread* th : Threads)
{
- th->history.clear();
th->counterMoves.clear();
- th->fromTo.clear();
+ th->history.clear();
th->counterMoveHistory.clear();
th->resetCalls = true;
}
&& 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;
Piece moved_piece;
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))
+ {
+ Value penalty = -stat_bonus(depth + ONE_PLY);
+ 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 piecesCount = pos.count<ALL_PIECES>(WHITE) + pos.count<ALL_PIECES>(BLACK);
+ int piecesCount = pos.count<ALL_PIECES>();
if ( piecesCount <= TB::Cardinality
&& (piecesCount < TB::Cardinality || depth >= TB::ProbeDepth)
// 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)
&& (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)
- : - 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)
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;
+ const bool cm_ok = is_ok((ss-1)->currentMove);
+ const bool fm_ok = is_ok((ss-2)->currentMove);
+ const bool f2_ok = is_ok((ss-4)->currentMove);
MovePicker mp(pos, ttMove, depth, ss);
value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
moveCountPruning = depth < 16 * ONE_PLY
&& moveCount >= FutilityMoveCounts[improving][depth / ONE_PLY];
- // Step 12. Extend checks
+ // Step 12. Extensions
+ // Extend checks
if ( givesCheck
&& !moveCountPruning
&& pos.see_ge(move, VALUE_ZERO))
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 ( !captureOrPromotion
&& !givesCheck
- && !pos.advanced_pawn_push(move))
+ && (!pos.advanced_pawn_push(move) || pos.non_pawn_material() >= 5000))
{
// Move count based pruning
if (moveCountPruning)
// 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)] < VALUE_ZERO) || !cm_ok)
+ && ((fmh[moved_piece][to_sq(move)] < VALUE_ZERO) || !fm_ok)
+ && ((fm2[moved_piece][to_sq(move)] < VALUE_ZERO) || !f2_ok || (cm_ok && fm_ok)))
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)];
&& !pos.see_ge(make_move(to_sq(move), from_sq(move)), VALUE_ZERO))
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)
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));
+ && cm_ok)
+ 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 :
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);
-
- 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) {
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);
}
}
projects / stockfish / blobdiff