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) 2015-2017 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ Copyright (C) 2015-2018 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
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
- // razor_margin[0] is unused as long as depth >= ONE_PLY in search
- const int razor_margin[] = { 0, 570, 603, 554 };
+ const int razor_margin = 600;
Value futility_margin(Depth d) { return Value(150 * d / ONE_PLY); }
// Futility and reductions lookup tables, initialized at startup
Move best = MOVE_NONE;
};
- Value DrawValue[COLOR_NB];
-
template <NodeType NT>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning);
Time.availableNodes = 0;
TT.clear();
-
- for (Thread* th : Threads)
- th->clear();
-
- Threads.main()->callsCnt = 0;
- Threads.main()->previousScore = VALUE_INFINITE;
- Threads.main()->previousTimeReduction = 1;
+ Threads.clear();
}
TT.new_search();
int contempt = Options["Contempt"] * PawnValueEg / 100; // From centipawns
- DrawValue[ us] = VALUE_DRAW - Value(contempt);
- DrawValue[~us] = VALUE_DRAW + Value(contempt);
+
+ Eval::Contempt = (us == WHITE ? make_score(contempt, contempt / 2)
+ : -make_score(contempt, contempt / 2));
if (rootMoves.empty())
{
mainThread->bestMoveChanges = 0;
}
- size_t multiPV = Options["MultiPV"];
+ multiPV = Options["MultiPV"];
Skill skill(Options["Skill Level"]);
// When playing with strength handicap enable MultiPV search that we will
int improvingFactor = std::max(229, std::min(715, 357 + 119 * F[0] - 6 * F[1]));
Color us = rootPos.side_to_move();
- bool thinkHard = DrawValue[us] == bestValue
+ bool thinkHard = bestValue == VALUE_DRAW
&& Limits.time[us] - Time.elapsed() > Limits.time[~us]
&& ::pv_is_draw(rootPos);
Key posKey;
Move ttMove, move, excludedMove, bestMove;
Depth extension, newDepth;
- Value bestValue, value, ttValue, eval;
+ Value bestValue, value, ttValue, eval, maxValue;
bool ttHit, inCheck, givesCheck, singularExtensionNode, improving;
bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture, pvExact;
Piece movedPiece;
moveCount = captureCount = quietCount = ss->moveCount = 0;
ss->statScore = 0;
bestValue = -VALUE_INFINITE;
+ maxValue = VALUE_INFINITE;
// Check for the available remaining time
if (thisThread == Threads.main())
{
// Step 2. Check for aborted search and immediate draw
if (Threads.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()];
+ return ss->ply >= MAX_PLY && !inCheck ? evaluate(pos) : VALUE_DRAW;
// Step 3. Mate distance pruning. Even if we mate at the next move our score
// would be at best mate_in(ss->ply+1), but if alpha is already bigger because
// search to overwrite a previous full search TT value, so we use a different
// position key in case of an excluded move.
excludedMove = ss->excludedMove;
- posKey = pos.key() ^ Key(excludedMove);
+ posKey = pos.key() ^ Key(excludedMove << 16); // isn't a very good hash
tte = TT.probe(posKey, ttHit);
ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
ttMove = rootNode ? thisThread->rootMoves[thisThread->PVIdx].pv[0]
&& !pos.can_castle(ANY_CASTLING))
{
TB::ProbeState err;
- TB::WDLScore v = Tablebases::probe_wdl(pos, &err);
+ TB::WDLScore wdl = Tablebases::probe_wdl(pos, &err);
if (err != TB::ProbeState::FAIL)
{
int drawScore = TB::UseRule50 ? 1 : 0;
- value = v < -drawScore ? -VALUE_MATE + MAX_PLY + ss->ply + 1
- : v > drawScore ? VALUE_MATE - MAX_PLY - ss->ply - 1
- : VALUE_DRAW + 2 * v * drawScore;
+ value = wdl < -drawScore ? -VALUE_MATE + MAX_PLY + ss->ply + 1
+ : wdl > drawScore ? VALUE_MATE - MAX_PLY - ss->ply - 1
+ : VALUE_DRAW + 2 * wdl * drawScore;
- tte->save(posKey, value_to_tt(value, ss->ply), BOUND_EXACT,
- std::min(DEPTH_MAX - ONE_PLY, depth + 6 * ONE_PLY),
- MOVE_NONE, VALUE_NONE, TT.generation());
+ Bound b = wdl < -drawScore ? BOUND_UPPER
+ : wdl > drawScore ? BOUND_LOWER : BOUND_EXACT;
- return value;
+ if ( b == BOUND_EXACT
+ || (b == BOUND_LOWER ? value >= beta : value <= alpha))
+ {
+ tte->save(posKey, value_to_tt(value, ss->ply), b,
+ std::min(DEPTH_MAX - ONE_PLY, depth + 6 * ONE_PLY),
+ MOVE_NONE, VALUE_NONE, TT.generation());
+
+ return value;
+ }
+
+ if (PvNode)
+ {
+ if (b == BOUND_LOWER)
+ bestValue = value, alpha = std::max(alpha, bestValue);
+ else
+ maxValue = value;
+ }
}
}
}
// Step 6. Razoring (skipped when in check)
if ( !PvNode
&& depth < 4 * ONE_PLY
- && eval + razor_margin[depth / ONE_PLY] <= alpha)
+ && eval + razor_margin <= alpha)
{
if (depth <= ONE_PLY)
return qsearch<NonPV, false>(pos, ss, alpha, alpha+1);
- Value ralpha = alpha - razor_margin[depth / ONE_PLY];
+ Value ralpha = alpha - razor_margin;
Value v = qsearch<NonPV, false>(pos, ss, ralpha, ralpha+1);
if (v <= ralpha)
return v;
// Step 8. Null move search with verification search (is omitted in PV nodes)
if ( !PvNode
&& eval >= beta
- && ss->staticEval >= beta - 36 * depth / ONE_PLY + 225)
+ && ss->staticEval >= beta - 36 * depth / ONE_PLY + 225
+ && (ss->ply >= thisThread->nmp_ply || ss->ply % 2 != thisThread->nmp_odd))
{
assert(eval - beta >= 0);
if (nullValue >= VALUE_MATE_IN_MAX_PLY)
nullValue = beta;
- if (depth < 12 * ONE_PLY && abs(beta) < VALUE_KNOWN_WIN)
+ if (abs(beta) < VALUE_KNOWN_WIN && (depth < 12 * ONE_PLY || thisThread->nmp_ply))
return nullValue;
// Do verification search at high depths
+ // disable null move pruning for side to move for the first part of the remaining search tree
+ thisThread->nmp_ply = ss->ply + 3 * (depth-R) / 4;
+ thisThread->nmp_odd = ss->ply % 2;
+
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);
+ thisThread->nmp_odd = thisThread->nmp_ply = 0;
+
if (v >= beta)
return nullValue;
}
if (move == excludedMove)
continue;
- // At root obey the "searchmoves" option and skip moves not listed in Root
- // Move List. As a consequence any illegal move is also skipped. In MultiPV
- // mode we also skip PV moves which have been already searched.
- if (rootNode && !std::count(thisThread->rootMoves.begin() + thisThread->PVIdx,
- thisThread->rootMoves.end(), move))
- continue;
+ if (rootNode)
+ {
+ // At root obey the "searchmoves" option and skip moves not listed in Root
+ // Move List. As a consequence any illegal move is also skipped.
+ if (!std::count(thisThread->rootMoves.begin() + thisThread->PVIdx,
+ thisThread->rootMoves.end(), move))
+ continue;
+
+ // In MultiPV mode we not only skip PV moves which have already been searched,
+ // but also any other move except we have reached the last PV line.
+ if ( thisThread->PVIdx + 1 < thisThread->multiPV
+ && move != ttMove)
+ continue;
+ }
ss->moveCount = ++moveCount;
if (!moveCount)
bestValue = excludedMove ? alpha
- : inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()];
+ : inCheck ? mated_in(ss->ply) : VALUE_DRAW;
else if (bestMove)
{
// Quiet best move: update move sorting heuristics
&& is_ok((ss-1)->currentMove))
update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth));
+ if (PvNode)
+ bestValue = std::min(bestValue, maxValue);
+
if (!excludedMove)
tte->save(posKey, value_to_tt(bestValue, ss->ply),
bestValue >= beta ? BOUND_LOWER :
// Check for an instant draw or if the maximum ply has been reached
if (pos.is_draw(ss->ply) || ss->ply >= MAX_PLY)
- return ss->ply >= MAX_PLY && !InCheck ? evaluate(pos)
- : DrawValue[pos.side_to_move()];
+ return ss->ply >= MAX_PLY && !InCheck ? evaluate(pos) : VALUE_DRAW;
assert(0 <= ss->ply && ss->ply < MAX_PLY);
// Don't search moves with negative SEE values
if ( (!InCheck || evasionPrunable)
- && type_of(move) != PROMOTION
&& !pos.see_ge(move))
continue;
if (Threads.ponder)
return;
- if ( (Limits.use_time_management() && elapsed > Time.maximum())
+ if ( (Limits.use_time_management() && elapsed > Time.maximum() - 10)
|| (Limits.movetime && elapsed >= Limits.movetime)
|| (Limits.nodes && Threads.nodes_searched() >= (uint64_t)Limits.nodes))
Threads.stop = true;
int elapsed = Time.elapsed() + 1;
const RootMoves& rootMoves = pos.this_thread()->rootMoves;
size_t PVIdx = pos.this_thread()->PVIdx;
- size_t multiPV = std::min((size_t)Options["MultiPV"], rootMoves.size());
+ size_t multiPV = pos.this_thread()->multiPV;
uint64_t nodesSearched = Threads.nodes_searched();
uint64_t tbHits = Threads.tb_hits() + (TB::RootInTB ? rootMoves.size() : 0);
TB::Score = TB::Score > VALUE_DRAW ? VALUE_MATE - MAX_PLY - 1
: TB::Score < VALUE_DRAW ? -VALUE_MATE + MAX_PLY + 1
: VALUE_DRAW;
+
+ // Since root_probe() and root_probe_wdl() dirty the root move scores,
+ // we reset them to -VALUE_INFINITE
+ for (RootMove& rm : rootMoves)
+ rm.score = -VALUE_INFINITE;
}
projects / stockfish / blobdiff