/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, 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
std::vector<RootMove> RootMoves;
Position RootPos;
Color RootColor;
- Time::point SearchTime;
+ Time::point SearchTime, IterationTime;
StateStackPtr SetupStates;
}
using Eval::evaluate;
using namespace Search;
+// Fast wrapper for common case of pos.gives_check()
+#define FAST_GIVES_CHECK(pos, m, ci) \
+ ((type_of(m) == NORMAL && ci.dcCandidates == 0) \
+ ? (ci.checkSq[type_of(pos.piece_on(from_sq(m)))] & to_sq(m)) \
+ : pos.gives_check(m, ci))
+
namespace {
// Set to true to force running with one thread. Used for debugging
Value DrawValue[COLOR_NB];
HistoryStats History;
GainsStats Gains;
- CountermovesStats Countermoves;
+ MovesStats Countermoves, Followupmoves;
template <NodeType NT>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode);
void id_loop(Position& pos);
Value value_to_tt(Value v, int ply);
Value value_from_tt(Value v, int ply);
+ void update_stats(Position& pos, Stack* ss, Move move, Depth depth, Move* quiets, int quietsCnt);
string uci_pv(const Position& pos, int depth, Value alpha, Value beta);
struct Skill {
History.clear();
Gains.clear();
Countermoves.clear();
+ Followupmoves.clear();
PVSize = Options["MultiPV"];
Skill skill(Options["Skill Level"]);
sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
}
+ IterationTime = Time::now() - SearchTime;
+
// If skill levels are enabled and time is up, pick a sub-optimal best move
if (skill.enabled() && skill.time_to_pick(depth))
skill.pick_move();
if (depth > 4 && depth < 50 && PVSize == 1)
TimeMgr.pv_instability(BestMoveChanges);
- // Stop the search if most of the available time has been used. We
- // probably don't have enough time to search the first move at the
- // next iteration anyway.
- if (Time::now() - SearchTime > (TimeMgr.available_time() * 62) / 100)
+ // Stop the search if only one legal move is available or most
+ // of the available time has been used. We probably don't have
+ // enough time to search the first move at the next iteration anyway.
+ if ( RootMoves.size() == 1
+ || IterationTime > (TimeMgr.available_time() * 62) / 100)
stop = true;
- // Stop the search early if one move seems to be much better than others
- if ( depth >= 12
- && BestMoveChanges <= DBL_EPSILON
- && !stop
- && PVSize == 1
- && bestValue > VALUE_MATED_IN_MAX_PLY
- && ( RootMoves.size() == 1
- || Time::now() - SearchTime > (TimeMgr.available_time() * 20) / 100))
- {
- Value rBeta = bestValue - 2 * PawnValueMg;
- ss->excludedMove = RootMoves[0].pv[0];
- ss->skipNullMove = true;
- Value v = search<NonPV>(pos, ss, rBeta - 1, rBeta, (depth - 3) * ONE_PLY, true);
- ss->skipNullMove = false;
- ss->excludedMove = MOVE_NONE;
-
- if (v < rBeta)
- stop = true;
- }
-
if (stop)
{
// If we are allowed to ponder do not stop the search now but
moveCount = quietCount = 0;
bestValue = -VALUE_INFINITE;
- ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE;
+ ss->currentMove = ss->ttMove = (ss+1)->excludedMove = bestMove = MOVE_NONE;
ss->ply = (ss-1)->ply + 1;
(ss+1)->skipNullMove = false; (ss+1)->reduction = DEPTH_ZERO;
(ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
excludedMove = ss->excludedMove;
posKey = excludedMove ? pos.exclusion_key() : pos.key();
tte = TT.probe(posKey);
- ttMove = RootNode ? RootMoves[PVIdx].pv[0] : tte ? tte->move() : MOVE_NONE;
+ ss->ttMove = ttMove = RootNode ? RootMoves[PVIdx].pv[0] : tte ? tte->move() : MOVE_NONE;
ttValue = tte ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
// At PV nodes we check for exact scores, whilst at non-PV nodes we check for
TT.refresh(tte);
ss->currentMove = ttMove; // Can be MOVE_NONE
- // Update killers, history, and counter move on TT hit
- if ( ttValue >= beta
- && ttMove
- && !pos.capture_or_promotion(ttMove)
- && !inCheck)
- {
- if (ss->killers[0] != ttMove)
- {
- ss->killers[1] = ss->killers[0];
- ss->killers[0] = ttMove;
- }
-
- Value bonus = Value(int(depth) * int(depth));
- History.update(pos.moved_piece(ttMove), to_sq(ttMove), bonus);
+ // If ttMove is quiet, update killers, history, counter move and followup move on TT hit
+ if (ttValue >= beta && ttMove && !pos.capture_or_promotion(ttMove) && !inCheck)
+ update_stats(pos, ss, ttMove, depth, NULL, 0);
- if (is_ok((ss-1)->currentMove))
- {
- Square prevMoveSq = to_sq((ss-1)->currentMove);
- Countermoves.update(pos.piece_on(prevMoveSq), prevMoveSq, ttMove);
- }
- }
return ttValue;
}
// Step 6. Razoring (skipped when in check)
if ( !PvNode
&& depth < 4 * ONE_PLY
- && eval + razor_margin(depth) < beta
+ && eval + razor_margin(depth) <= alpha
&& ttMove == MOVE_NONE
&& abs(beta) < VALUE_MATE_IN_MAX_PLY
&& !pos.pawn_on_7th(pos.side_to_move()))
{
- Value rbeta = beta - razor_margin(depth);
- Value v = qsearch<NonPV, false>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO);
- if (v < rbeta)
- // Logically we should return (v + razor_margin(depth)), but
- // surprisingly this performed slightly weaker in tests.
+ Value ralpha = alpha - razor_margin(depth);
+ Value v = qsearch<NonPV, false>(pos, ss, ralpha, ralpha+1, DEPTH_ZERO);
+ if (v <= ralpha)
return v;
}
{
ss->currentMove = MOVE_NULL;
- // Null move dynamic reduction based on depth
- Depth R = 3 * ONE_PLY + depth / 4;
+ assert(eval - beta >= 0);
- // Null move dynamic reduction based on value
- if (eval - PawnValueMg > beta)
- R += ONE_PLY;
+ // Null move dynamic reduction based on depth and value
+ Depth R = 3 * ONE_PLY
+ + depth / 4
+ + int(eval - beta) / PawnValueMg * ONE_PLY;
pos.do_null_move(st);
(ss+1)->skipNullMove = true;
- nullValue = depth-R < ONE_PLY ? -qsearch<NonPV, false>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
- : - search<NonPV>(pos, ss+1, -beta, -alpha, depth-R, !cutNode);
+ 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);
(ss+1)->skipNullMove = false;
pos.undo_null_move();
- if (nullValue >= beta)
- {
- // Do not return unproven mate scores
- if (nullValue >= VALUE_MATE_IN_MAX_PLY)
- nullValue = beta;
-
- if (depth < 12 * ONE_PLY)
- return nullValue;
-
- // Do verification search at high depths
- ss->skipNullMove = true;
- Value v = search<NonPV>(pos, ss, alpha, beta, depth-R, false);
- ss->skipNullMove = false;
-
- if (v >= beta)
- return nullValue;
- }
+ if (nullValue >= beta) // Do not return unproven mate scores
+ return nullValue >= VALUE_MATE_IN_MAX_PLY ? beta : nullValue;
}
// Step 9. ProbCut (skipped when in check)
Move countermoves[] = { Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq].first,
Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq].second };
- MovePicker mp(pos, ttMove, depth, History, countermoves, ss);
+ Square prevOwnMoveSq = to_sq((ss-2)->currentMove);
+ Move followupmoves[] = { Followupmoves[pos.piece_on(prevOwnMoveSq)][prevOwnMoveSq].first,
+ Followupmoves[pos.piece_on(prevOwnMoveSq)][prevOwnMoveSq].second };
+
+ MovePicker mp(pos, ttMove, depth, History, countermoves, followupmoves, ss);
CheckInfo ci(pos);
value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
improving = ss->staticEval >= (ss-2)->staticEval
ext = DEPTH_ZERO;
captureOrPromotion = pos.capture_or_promotion(move);
- givesCheck = pos.gives_check(move, ci);
+ givesCheck = FAST_GIVES_CHECK(pos, move, ci);
dangerous = givesCheck
|| type_of(move) != NORMAL
|| pos.advanced_pawn_push(move);
PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER,
depth, bestMove, ss->staticEval);
- // Quiet best move: update killers, history and countermoves
- if ( bestValue >= beta
- && !pos.capture_or_promotion(bestMove)
- && !inCheck)
- {
- if (ss->killers[0] != bestMove)
- {
- ss->killers[1] = ss->killers[0];
- ss->killers[0] = bestMove;
- }
-
- // Increase history value of the cut-off move and decrease all the other
- // played non-capture moves.
- Value bonus = Value(int(depth) * int(depth));
- History.update(pos.moved_piece(bestMove), to_sq(bestMove), bonus);
- for (int i = 0; i < quietCount - 1; ++i)
- {
- Move m = quietsSearched[i];
- History.update(pos.moved_piece(m), to_sq(m), -bonus);
- }
-
- if (is_ok((ss-1)->currentMove))
- Countermoves.update(pos.piece_on(prevMoveSq), prevMoveSq, bestMove);
- }
+ // Quiet best move: update killers, history, countermoves and followupmoves
+ if (bestValue >= beta && !pos.capture_or_promotion(bestMove) && !inCheck)
+ update_stats(pos, ss, bestMove, depth, quietsSearched, quietCount - 1);
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
{
assert(is_ok(move));
- givesCheck = pos.gives_check(move, ci);
+ givesCheck = FAST_GIVES_CHECK(pos, move, ci);
// Futility pruning
if ( !PvNode
}
+ // update_stats() updates killers, history, countermoves and followupmoves stats after a fail-high
+ // of a quiet move.
+
+ void update_stats(Position& pos, Stack* ss, Move move, Depth depth, Move* quiets, int quietsCnt) {
+
+ if (ss->killers[0] != move)
+ {
+ ss->killers[1] = ss->killers[0];
+ ss->killers[0] = move;
+ }
+
+ // Increase history value of the cut-off move and decrease all the other
+ // played quiet moves.
+ Value bonus = Value(int(depth) * int(depth));
+ History.update(pos.moved_piece(move), to_sq(move), bonus);
+ for (int i = 0; i < quietsCnt; ++i)
+ {
+ Move m = quiets[i];
+ History.update(pos.moved_piece(m), to_sq(m), -bonus);
+ }
+
+ if (is_ok((ss-1)->currentMove))
+ {
+ Square prevMoveSq = to_sq((ss-1)->currentMove);
+ Countermoves.update(pos.piece_on(prevMoveSq), prevMoveSq, move);
+ }
+
+ if (is_ok((ss-2)->currentMove) && (ss-1)->currentMove == (ss-1)->ttMove)
+ {
+ Square prevOwnMoveSq = to_sq((ss-2)->currentMove);
+ Followupmoves.update(pos.piece_on(prevOwnMoveSq), prevOwnMoveSq, move);
+ }
+ }
+
+
// When playing with a strength handicap, choose best move among the MultiPV
// set using a statistical rule dependent on 'level'. Idea by Heinz van Saanen.
Time::point elapsed = Time::now() - SearchTime;
bool stillAtFirstMove = Signals.firstRootMove
&& !Signals.failedLowAtRoot
- && elapsed > TimeMgr.available_time();
+ && ( elapsed > TimeMgr.available_time()
+ || ( elapsed > (TimeMgr.available_time() * 62) / 100
+ && elapsed > IterationTime * 1.4));
bool noMoreTime = elapsed > TimeMgr.maximum_time() - 2 * TimerThread::Resolution
|| stillAtFirstMove;
projects / stockfish / blobdiff