/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2013 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
#include "book.h"
#include "evaluate.h"
-#include "history.h"
#include "movegen.h"
#include "movepick.h"
#include "notation.h"
volatile SignalsType Signals;
LimitsType Limits;
std::vector<RootMove> RootMoves;
- Position RootPosition;
+ Position RootPos;
Color RootColor;
Time::point SearchTime;
StateStackPtr SetupStates;
// Different node types, used as template parameter
enum NodeType { Root, PV, NonPV, SplitPointRoot, SplitPointPV, SplitPointNonPV };
- // Lookup table to check if a Piece is a slider and its access function
- const bool Slidings[18] = { 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1 };
- inline bool piece_is_slider(Piece p) { return Slidings[p]; }
-
// Dynamic razoring margin based on depth
inline Value razor_margin(Depth d) { return Value(512 + 16 * int(d)); }
return (Depth) Reductions[PvNode][std::min(int(d) / ONE_PLY, 63)][std::min(mn, 63)];
}
- size_t MultiPV, UCIMultiPV, PVIdx;
+ size_t PVSize, PVIdx;
TimeManager TimeMgr;
int BestMoveChanges;
- int SkillLevel;
- Move skillBest;
- bool SkillLevelEnabled, Chess960;
Value DrawValue[COLOR_NB];
- History H;
+ History Hist;
+ Gains Gain;
+ Refutations Refutation;
template <NodeType NT>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth);
- template <NodeType NT>
+ template <NodeType NT, bool InCheck>
Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth);
void id_loop(Position& pos);
- bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta);
- bool connected_moves(const Position& pos, Move m1, Move m2);
Value value_to_tt(Value v, int ply);
Value value_from_tt(Value v, int ply);
- bool connected_threat(const Position& pos, Move m, Move threat);
- Move do_skill_level();
+ bool check_is_dangerous(const Position& pos, Move move, Value futilityBase, Value beta);
+ bool allows(const Position& pos, Move first, Move second);
+ bool refutes(const Position& pos, Move first, Move second);
string uci_pv(const Position& pos, int depth, Value alpha, Value beta);
+ struct Skill {
+ Skill(int l) : level(l), best(MOVE_NONE) {}
+ ~Skill() {
+ if (enabled()) // Swap best PV line with the sub-optimal one
+ std::swap(RootMoves[0], *std::find(RootMoves.begin(),
+ RootMoves.end(), best ? best : pick_move()));
+ }
+
+ bool enabled() const { return level < 20; }
+ bool time_to_pick(int depth) const { return depth == 1 + level; }
+ Move pick_move();
+
+ int level;
+ Move best;
+ };
+
} // namespace
// Init futility move count array
for (d = 0; d < 32; d++)
- FutilityMoveCounts[d] = int(3.001 + 0.25 * pow(double(d), 2.0));
+ FutilityMoveCounts[d] = int(3.001 + 0.3 * pow(double(d), 1.8));
}
/// Search::think() is the external interface to Stockfish's search, and is
/// called by the main thread when the program receives the UCI 'go' command. It
-/// searches from RootPosition and at the end prints the "bestmove" to output.
+/// searches from RootPos and at the end prints the "bestmove" to output.
void Search::think() {
static PolyglotBook book; // Defined static to initialize the PRNG only once
- Position& pos = RootPosition;
- Chess960 = pos.is_chess960();
- RootColor = pos.side_to_move();
- TimeMgr.init(Limits, pos.startpos_ply_counter(), pos.side_to_move());
- TT.new_search();
- H.clear();
+ RootColor = RootPos.side_to_move();
+ TimeMgr.init(Limits, RootPos.game_ply(), RootColor);
if (RootMoves.empty())
{
+ RootMoves.push_back(MOVE_NONE);
sync_cout << "info depth 0 score "
- << score_to_uci(pos.in_check() ? -VALUE_MATE : VALUE_DRAW) << sync_endl;
+ << score_to_uci(RootPos.checkers() ? -VALUE_MATE : VALUE_DRAW)
+ << sync_endl;
- RootMoves.push_back(MOVE_NONE);
goto finalize;
}
- if (Options["Contempt Factor"] && !Options["UCI_AnalyseMode"])
+ if (Options["OwnBook"] && !Limits.infinite && !Limits.mate)
{
- int cf = Options["Contempt Factor"] * PawnValueMg / 100; // In centipawns
- cf = cf * MaterialTable::game_phase(pos) / PHASE_MIDGAME; // Scale down with phase
- DrawValue[ RootColor] = VALUE_DRAW - Value(cf);
- DrawValue[~RootColor] = VALUE_DRAW + Value(cf);
- }
- else
- DrawValue[WHITE] = DrawValue[BLACK] = VALUE_DRAW;
-
- if (Options["OwnBook"] && !Limits.infinite)
- {
- Move bookMove = book.probe(pos, Options["Book File"], Options["Best Book Move"]);
+ Move bookMove = book.probe(RootPos, Options["Book File"], Options["Best Book Move"]);
if (bookMove && std::count(RootMoves.begin(), RootMoves.end(), bookMove))
{
}
}
- UCIMultiPV = Options["MultiPV"];
- SkillLevel = Options["Skill Level"];
-
- // Do we have to play with skill handicap? In this case enable MultiPV that
- // we will use behind the scenes to retrieve a set of possible moves.
- SkillLevelEnabled = (SkillLevel < 20);
- skillBest = MOVE_NONE;
- MultiPV = (SkillLevelEnabled ? std::max(UCIMultiPV, (size_t)4) : UCIMultiPV);
+ if (Options["Contempt Factor"] && !Options["UCI_AnalyseMode"])
+ {
+ int cf = Options["Contempt Factor"] * PawnValueMg / 100; // From centipawns
+ cf = cf * Material::game_phase(RootPos) / PHASE_MIDGAME; // Scale down with phase
+ DrawValue[ RootColor] = VALUE_DRAW - Value(cf);
+ DrawValue[~RootColor] = VALUE_DRAW + Value(cf);
+ }
+ else
+ DrawValue[WHITE] = DrawValue[BLACK] = VALUE_DRAW;
if (Options["Use Search Log"])
{
Log log(Options["Search Log Filename"]);
- log << "\nSearching: " << pos.to_fen()
+ log << "\nSearching: " << RootPos.fen()
<< "\ninfinite: " << Limits.infinite
<< " ponder: " << Limits.ponder
- << " time: " << Limits.time[pos.side_to_move()]
- << " increment: " << Limits.inc[pos.side_to_move()]
+ << " time: " << Limits.time[RootColor]
+ << " increment: " << Limits.inc[RootColor]
<< " moves to go: " << Limits.movestogo
<< std::endl;
}
- Threads.wake_up();
+ // Reset the threads, still sleeping: will be wake up at split time
+ for (size_t i = 0; i < Threads.size(); i++)
+ Threads[i]->maxPly = 0;
+
+ Threads.sleepWhileIdle = Options["Use Sleeping Threads"];
// Set best timer interval to avoid lagging under time pressure. Timer is
// used to check for remaining available thinking time.
- if (Limits.use_time_management())
- Threads.set_timer(std::min(100, std::max(TimeMgr.available_time() / 16, TimerResolution)));
- else if (Limits.nodes)
- Threads.set_timer(2 * TimerResolution);
- else
- Threads.set_timer(100);
+ Threads.timer->msec =
+ Limits.use_time_management() ? std::min(100, std::max(TimeMgr.available_time() / 16, TimerResolution)) :
+ Limits.nodes ? 2 * TimerResolution
+ : 100;
- // We're ready to start searching. Call the iterative deepening loop function
- id_loop(pos);
+ Threads.timer->notify_one(); // Wake up the recurring timer
- Threads.set_timer(0); // Stop timer
- Threads.sleep();
+ id_loop(RootPos); // Let's start searching !
- // When using skills swap best PV line with the sub-optimal one
- if (SkillLevelEnabled)
- {
- if (skillBest == MOVE_NONE) // Still unassigned ?
- skillBest = do_skill_level();
-
- std::swap(RootMoves[0], *std::find(RootMoves.begin(), RootMoves.end(), skillBest));
- }
+ Threads.timer->msec = 0; // Stop the timer
+ Threads.sleepWhileIdle = true; // Send idle threads to sleep
if (Options["Use Search Log"])
{
Time::point elapsed = Time::now() - SearchTime + 1;
Log log(Options["Search Log Filename"]);
- log << "Nodes: " << pos.nodes_searched()
- << "\nNodes/second: " << pos.nodes_searched() * 1000 / elapsed
- << "\nBest move: " << move_to_san(pos, RootMoves[0].pv[0]);
+ log << "Nodes: " << RootPos.nodes_searched()
+ << "\nNodes/second: " << RootPos.nodes_searched() * 1000 / elapsed
+ << "\nBest move: " << move_to_san(RootPos, RootMoves[0].pv[0]);
StateInfo st;
- pos.do_move(RootMoves[0].pv[0], st);
- log << "\nPonder move: " << move_to_san(pos, RootMoves[0].pv[1]) << std::endl;
- pos.undo_move(RootMoves[0].pv[0]);
+ RootPos.do_move(RootMoves[0].pv[0], st);
+ log << "\nPonder move: " << move_to_san(RootPos, RootMoves[0].pv[1]) << std::endl;
+ RootPos.undo_move(RootMoves[0].pv[0]);
}
finalize:
+ // When search is stopped this info is not printed
+ sync_cout << "info nodes " << RootPos.nodes_searched()
+ << " time " << Time::now() - SearchTime + 1 << sync_endl;
+
// When we reach max depth we arrive here even without Signals.stop is raised,
- // but if we are pondering or in infinite search, we shouldn't print the best
- // move before we are told to do so.
+ // but if we are pondering or in infinite search, according to UCI protocol,
+ // we shouldn't print the best move before the GUI sends a "stop" or "ponderhit"
+ // command. We simply wait here until GUI sends one of those commands (that
+ // raise Signals.stop).
if (!Signals.stop && (Limits.ponder || Limits.infinite))
- pos.this_thread()->wait_for_stop_or_ponderhit();
+ {
+ Signals.stopOnPonderhit = true;
+ RootPos.this_thread()->wait_for(Signals.stop);
+ }
// Best move could be MOVE_NONE when searching on a stalemate position
- sync_cout << "bestmove " << move_to_uci(RootMoves[0].pv[0], Chess960)
- << " ponder " << move_to_uci(RootMoves[0].pv[1], Chess960) << sync_endl;
+ sync_cout << "bestmove " << move_to_uci(RootMoves[0].pv[0], RootPos.is_chess960())
+ << " ponder " << move_to_uci(RootMoves[0].pv[1], RootPos.is_chess960())
+ << sync_endl;
}
Stack ss[MAX_PLY_PLUS_2];
int depth, prevBestMoveChanges;
Value bestValue, alpha, beta, delta;
- bool bestMoveNeverChanged = true;
memset(ss, 0, 4 * sizeof(Stack));
depth = BestMoveChanges = 0;
bestValue = delta = -VALUE_INFINITE;
ss->currentMove = MOVE_NULL; // Hack to skip update gains
+ TT.new_search();
+ Hist.clear();
+ Gain.clear();
+ Refutation.clear();
+
+ PVSize = Options["MultiPV"];
+ Skill skill(Options["Skill Level"]);
+
+ // Do we have to play with skill handicap? In this case enable MultiPV search
+ // that we will use behind the scenes to retrieve a set of possible moves.
+ if (skill.enabled() && PVSize < 4)
+ PVSize = 4;
+
+ PVSize = std::min(PVSize, RootMoves.size());
// Iterative deepening loop until requested to stop or target depth reached
while (++depth <= MAX_PLY && !Signals.stop && (!Limits.depth || depth <= Limits.depth))
for (size_t i = 0; i < RootMoves.size(); i++)
RootMoves[i].prevScore = RootMoves[i].score;
- prevBestMoveChanges = BestMoveChanges;
+ prevBestMoveChanges = BestMoveChanges; // Only sensible when PVSize == 1
BestMoveChanges = 0;
// MultiPV loop. We perform a full root search for each PV line
- for (PVIdx = 0; PVIdx < std::min(MultiPV, RootMoves.size()); PVIdx++)
+ for (PVIdx = 0; PVIdx < PVSize; PVIdx++)
{
// Set aspiration window default width
if (depth >= 5 && abs(RootMoves[PVIdx].prevScore) < VALUE_KNOWN_WIN)
// we want to keep the same order for all the moves but the new
// PV that goes to the front. Note that in case of MultiPV search
// the already searched PV lines are preserved.
- sort<RootMove>(RootMoves.begin() + PVIdx, RootMoves.end());
+ std::stable_sort(RootMoves.begin() + PVIdx, RootMoves.end());
// Write PV back to transposition table in case the relevant
// entries have been overwritten during the search.
return;
// In case of failing high/low increase aspiration window and
- // research, otherwise sort multi-PV lines and exit the loop.
+ // research, otherwise exit the loop.
if (bestValue > alpha && bestValue < beta)
- {
- sort<RootMove>(RootMoves.begin(), RootMoves.begin() + PVIdx);
- sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
break;
- }
// Give some update (without cluttering the UI) before to research
if (Time::now() - SearchTime > 3000)
assert(alpha >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
}
+
+ // Sort the PV lines searched so far and update the GUI
+ std::stable_sort(RootMoves.begin(), RootMoves.begin() + PVIdx + 1);
+
+ if (PVIdx + 1 == PVSize || Time::now() - SearchTime > 3000)
+ sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
}
- // Skills: Do we need to pick now the best move ?
- if (SkillLevelEnabled && depth == 1 + SkillLevel)
- skillBest = do_skill_level();
+ // Do we need to pick now the sub-optimal best move ?
+ if (skill.enabled() && skill.time_to_pick(depth))
+ skill.pick_move();
if (Options["Use Search Log"])
{
<< std::endl;
}
- // Filter out startup noise when monitoring best move stability
- if (depth > 2 && BestMoveChanges)
- bestMoveNeverChanged = false;
+ // Do we have found a "mate in x"?
+ if ( Limits.mate
+ && bestValue >= VALUE_MATE_IN_MAX_PLY
+ && VALUE_MATE - bestValue <= 2 * Limits.mate)
+ Signals.stop = true;
// Do we have time for the next iteration? Can we stop searching now?
if (Limits.use_time_management() && !Signals.stopOnPonderhit)
bool stop = false; // Local variable, not the volatile Signals.stop
// Take in account some extra time if the best move has changed
- if (depth > 4 && depth < 50)
+ if (depth > 4 && depth < 50 && PVSize == 1)
TimeMgr.pv_instability(BestMoveChanges, prevBestMoveChanges);
// Stop search if most of available time is already consumed. We
// Stop search early if one move seems to be much better than others
if ( depth >= 12
&& !stop
- && ( (bestMoveNeverChanged && pos.captured_piece_type())
- || Time::now() - SearchTime > (TimeMgr.available_time() * 40) / 100))
+ && 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+1)->excludedMove = RootMoves[0].pv[0];
Move movesSearched[64];
StateInfo st;
const TTEntry *tte;
- SplitPoint* sp;
+ SplitPoint* splitPoint;
Key posKey;
Move ttMove, move, excludedMove, bestMove, threatMove;
Depth ext, newDepth;
// Step 1. Initialize node
Thread* thisThread = pos.this_thread();
moveCount = playedMoveCount = 0;
- inCheck = pos.in_check();
+ inCheck = pos.checkers();
if (SpNode)
{
- sp = ss->sp;
- bestMove = sp->bestMove;
- threatMove = sp->threatMove;
- bestValue = sp->bestValue;
+ splitPoint = ss->splitPoint;
+ bestMove = splitPoint->bestMove;
+ threatMove = splitPoint->threatMove;
+ bestValue = splitPoint->bestValue;
tte = NULL;
ttMove = excludedMove = MOVE_NONE;
ttValue = VALUE_NONE;
- assert(sp->bestValue > -VALUE_INFINITE && sp->moveCount > 0);
+ assert(splitPoint->bestValue > -VALUE_INFINITE && splitPoint->moveCount > 0);
goto split_point_start;
}
bestValue = -VALUE_INFINITE;
ss->currentMove = threatMove = (ss+1)->excludedMove = bestMove = MOVE_NONE;
ss->ply = (ss-1)->ply + 1;
+ ss->futilityMoveCount = 0;
(ss+1)->skipNullMove = false; (ss+1)->reduction = DEPTH_ZERO;
(ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
if (!RootNode)
{
// Step 2. Check for aborted search and immediate draw
- if (Signals.stop || pos.is_draw<false>() || ss->ply > MAX_PLY)
+ if (Signals.stop || pos.is_draw() || ss->ply > MAX_PLY)
return DrawValue[pos.side_to_move()];
// Step 3. Mate distance pruning. Even if we mate at the next move our score
// smooth experience in analysis mode. We don't probe at Root nodes otherwise
// we should also update RootMoveList to avoid bogus output.
if ( !RootNode
- && tte && tte->depth() >= depth
+ && tte
+ && tte->depth() >= depth
+ && ttValue != VALUE_NONE // Only in case of TT access race
&& ( PvNode ? tte->type() == BOUND_EXACT
: ttValue >= beta ? (tte->type() & BOUND_LOWER)
: (tte->type() & BOUND_UPPER)))
{
- assert(ttValue != VALUE_NONE); // Due to depth > DEPTH_NONE
-
TT.refresh(tte);
ss->currentMove = ttMove; // Can be MOVE_NONE
else if (tte)
{
- assert(tte->static_value() != VALUE_NONE);
- assert(ttValue != VALUE_NONE || tte->type() == BOUND_NONE);
-
- ss->staticEval = eval = tte->static_value();
- ss->evalMargin = tte->static_value_margin();
+ // Never assume anything on values stored in TT
+ if ( (ss->staticEval = eval = tte->eval_value()) == VALUE_NONE
+ ||(ss->evalMargin = tte->eval_margin()) == VALUE_NONE)
+ eval = ss->staticEval = evaluate(pos, ss->evalMargin);
// Can ttValue be used as a better position evaluation?
- if ( ((tte->type() & BOUND_LOWER) && ttValue > eval)
- || ((tte->type() & BOUND_UPPER) && ttValue < eval))
- eval = ttValue;
+ if (ttValue != VALUE_NONE)
+ if ( ((tte->type() & BOUND_LOWER) && ttValue > eval)
+ || ((tte->type() & BOUND_UPPER) && ttValue < eval))
+ eval = ttValue;
}
else
{
&& type_of(move) == NORMAL)
{
Square to = to_sq(move);
- H.update_gain(pos.piece_on(to), to, -(ss-1)->staticEval - ss->staticEval);
+ Gain.update(pos.piece_on(to), to, -(ss-1)->staticEval - ss->staticEval);
}
// Step 6. Razoring (is omitted in PV nodes)
&& !pos.pawn_on_7th(pos.side_to_move()))
{
Value rbeta = beta - razor_margin(depth);
- Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO);
+ 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 did slightly weaker in tests.
&& !ss->skipNullMove
&& depth < 4 * ONE_PLY
&& !inCheck
- && eval - FutilityMargins[depth][0] >= beta
+ && eval - futility_margin(depth, (ss-1)->futilityMoveCount) >= beta
&& abs(beta) < VALUE_MATE_IN_MAX_PLY
+ && abs(eval) < VALUE_KNOWN_WIN
&& pos.non_pawn_material(pos.side_to_move()))
- return eval - FutilityMargins[depth][0];
+ return eval - futility_margin(depth, (ss-1)->futilityMoveCount);
// Step 8. Null move search with verification search (is omitted in PV nodes)
if ( !PvNode
if (eval - PawnValueMg > beta)
R += ONE_PLY;
- pos.do_null_move<true>(st);
+ pos.do_null_move(st);
(ss+1)->skipNullMove = true;
- nullValue = depth-R < ONE_PLY ? -qsearch<NonPV>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
+ nullValue = depth-R < ONE_PLY ? -qsearch<NonPV, false>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
: - search<NonPV>(pos, ss+1, -beta, -alpha, depth-R);
(ss+1)->skipNullMove = false;
- pos.do_null_move<false>(st);
+ pos.undo_null_move();
if (nullValue >= beta)
{
if (nullValue >= VALUE_MATE_IN_MAX_PLY)
nullValue = beta;
- if (depth < 6 * ONE_PLY)
+ if (depth < 12 * ONE_PLY)
return nullValue;
// Do verification search at high depths
if ( depth < 5 * ONE_PLY
&& (ss-1)->reduction
&& threatMove != MOVE_NONE
- && connected_moves(pos, (ss-1)->currentMove, threatMove))
+ && allows(pos, (ss-1)->currentMove, threatMove))
return beta - 1;
}
}
assert((ss-1)->currentMove != MOVE_NONE);
assert((ss-1)->currentMove != MOVE_NULL);
- MovePicker mp(pos, ttMove, H, pos.captured_piece_type());
+ MovePicker mp(pos, ttMove, Hist, pos.captured_piece_type());
CheckInfo ci(pos);
while ((move = mp.next_move<false>()) != MOVE_NONE)
&& ttMove == MOVE_NONE
&& (PvNode || (!inCheck && ss->staticEval + Value(256) >= beta)))
{
- Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
+ Depth d = depth - 2 * ONE_PLY - (PvNode ? DEPTH_ZERO : depth / 4);
ss->skipNullMove = true;
search<PvNode ? PV : NonPV>(pos, ss, alpha, beta, d);
split_point_start: // At split points actual search starts from here
- MovePicker mp(pos, ttMove, depth, H, ss, PvNode ? -VALUE_INFINITE : beta);
+ MovePicker mp(pos, ttMove, depth, Hist, Refutation, ss, PvNode ? -VALUE_INFINITE : beta);
CheckInfo ci(pos);
value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
singularExtensionNode = !RootNode
if (!pos.pl_move_is_legal(move, ci.pinned))
continue;
- moveCount = ++sp->moveCount;
- sp->mutex.unlock();
+ moveCount = ++splitPoint->moveCount;
+ splitPoint->mutex.unlock();
}
else
moveCount++;
{
Signals.firstRootMove = (moveCount == 1);
- if (thisThread == Threads.main_thread() && Time::now() - SearchTime > 2000)
+ if (thisThread == Threads.main_thread() && Time::now() - SearchTime > 3000)
sync_cout << "info depth " << depth / ONE_PLY
- << " currmove " << move_to_uci(move, Chess960)
+ << " currmove " << move_to_uci(move, pos.is_chess960())
<< " currmovenumber " << moveCount + PVIdx << sync_endl;
}
ss->excludedMove = MOVE_NONE;
if (value < rBeta)
- ext = rBeta >= beta ? ONE_PLY + ONE_PLY / 2 : ONE_PLY;
+ ext = ONE_PLY;
}
// Update current move (this must be done after singular extension search)
&& !captureOrPromotion
&& !inCheck
&& !dangerous
- && move != ttMove
- && (bestValue > VALUE_MATED_IN_MAX_PLY || ( bestValue == -VALUE_INFINITE
- && alpha > VALUE_MATED_IN_MAX_PLY)))
+ /* && move != ttMove Already implicit in the next condition */
+ && bestValue > VALUE_MATED_IN_MAX_PLY)
{
// Move count based pruning
if ( depth < 16 * ONE_PLY
&& moveCount >= FutilityMoveCounts[depth]
- && (!threatMove || !connected_threat(pos, move, threatMove)))
+ && (!threatMove || !refutes(pos, move, threatMove)))
{
if (SpNode)
- sp->mutex.lock();
+ splitPoint->mutex.lock();
continue;
}
// but fixing this made program slightly weaker.
Depth predictedDepth = newDepth - reduction<PvNode>(depth, moveCount);
futilityValue = ss->staticEval + ss->evalMargin + futility_margin(predictedDepth, moveCount)
- + H.gain(pos.piece_moved(move), to_sq(move));
+ + Gain[pos.piece_moved(move)][to_sq(move)];
if (futilityValue < beta)
{
- if (SpNode)
- sp->mutex.lock();
+ bestValue = std::max(bestValue, futilityValue);
+ if (SpNode)
+ {
+ splitPoint->mutex.lock();
+ if (bestValue > splitPoint->bestValue)
+ splitPoint->bestValue = bestValue;
+ }
continue;
}
// Prune moves with negative SEE at low depths
- if ( predictedDepth < 2 * ONE_PLY
+ if ( predictedDepth < 4 * ONE_PLY
&& pos.see_sign(move) < 0)
{
if (SpNode)
- sp->mutex.lock();
+ splitPoint->mutex.lock();
continue;
}
+
+ // We have not pruned the move that will be searched, but remember how
+ // far in the move list we are to be more aggressive in the child node.
+ ss->futilityMoveCount = moveCount;
}
+ else
+ ss->futilityMoveCount = 0;
// Check for legality only before to do the move
- if (!pos.pl_move_is_legal(move, ci.pinned))
+ if (!RootNode && !SpNode && !pos.pl_move_is_legal(move, ci.pinned))
{
moveCount--;
continue;
}
- pvMove = PvNode ? moveCount == 1 : false;
+ pvMove = PvNode && moveCount == 1;
ss->currentMove = move;
if (!SpNode && !captureOrPromotion && playedMoveCount < 64)
movesSearched[playedMoveCount++] = move;
&& !pvMove
&& !captureOrPromotion
&& !dangerous
- && ss->killers[0] != move
- && ss->killers[1] != move)
+ && move != ttMove
+ && move != ss->killers[0]
+ && move != ss->killers[1])
{
ss->reduction = reduction<PvNode>(depth, moveCount);
Depth d = std::max(newDepth - ss->reduction, ONE_PLY);
- alpha = SpNode ? sp->alpha : alpha;
+ if (SpNode)
+ alpha = splitPoint->alpha;
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d);
// Step 16. Full depth search, when LMR is skipped or fails high
if (doFullDepthSearch)
{
- alpha = SpNode ? sp->alpha : alpha;
- value = newDepth < ONE_PLY ? -qsearch<NonPV>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
+ if (SpNode)
+ alpha = splitPoint->alpha;
+
+ 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)
: - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth);
}
// high, in the latter case search only if value < beta, otherwise let the
// parent node to fail low with value <= alpha and to try another move.
if (PvNode && (pvMove || (value > alpha && (RootNode || value < beta))))
- value = newDepth < ONE_PLY ? -qsearch<PV>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
+ 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)
: - search<PV>(pos, ss+1, -beta, -alpha, newDepth);
-
// Step 17. Undo move
pos.undo_move(move);
// Step 18. Check for new best move
if (SpNode)
{
- sp->mutex.lock();
- bestValue = sp->bestValue;
- alpha = sp->alpha;
+ splitPoint->mutex.lock();
+ bestValue = splitPoint->bestValue;
+ alpha = splitPoint->alpha;
}
// Finished searching the move. If Signals.stop is true, the search
// ran out of time. In this case, the return value of the search cannot
// be trusted, and we don't update the best move and/or PV.
if (Signals.stop || thisThread->cutoff_occurred())
- return bestValue;
+ return value; // To avoid returning VALUE_INFINITE
if (RootNode)
{
// We record how often the best move has been changed in each
// iteration. This information is used for time management: When
// the best move changes frequently, we allocate some more time.
- if (!pvMove && MultiPV == 1)
+ if (!pvMove)
BestMoveChanges++;
}
else
if (value > bestValue)
{
- bestValue = value;
- if (SpNode) sp->bestValue = value;
+ bestValue = SpNode ? splitPoint->bestValue = value : value;
if (value > alpha)
{
- bestMove = move;
- if (SpNode) sp->bestMove = move;
+ bestMove = SpNode ? splitPoint->bestMove = move : move;
- if (PvNode && value < beta)
- {
- alpha = value; // Update alpha here! Always alpha < beta
- if (SpNode) sp->alpha = value;
- }
- else // Fail high
+ if (PvNode && value < beta) // Update alpha! Always alpha < beta
+ alpha = SpNode ? splitPoint->alpha = value : value;
+ else
{
- if (SpNode) sp->cutoff = true;
+ assert(value >= beta); // Fail high
+
+ if (SpNode)
+ splitPoint->cutoff = true;
+
break;
}
}
// Step 19. Check for splitting the search
if ( !SpNode
- && depth >= Threads.min_split_depth()
- && bestValue < beta
- && Threads.available_slave_exists(thisThread))
+ && depth >= Threads.minimumSplitDepth
+ && Threads.available_slave(thisThread)
+ && thisThread->splitPointsSize < MAX_SPLITPOINTS_PER_THREAD)
{
- bestValue = Threads.split<FakeSplit>(pos, ss, alpha, beta, bestValue, &bestMove,
- depth, threatMove, moveCount, mp, NT);
- break;
+ assert(bestValue < beta);
+
+ thisThread->split<FakeSplit>(pos, ss, alpha, beta, &bestValue, &bestMove,
+ depth, threatMove, moveCount, &mp, NT);
+ if (bestValue >= beta)
+ break;
}
}
// Increase history value of the cut-off move
Value bonus = Value(int(depth) * int(depth));
- H.add(pos.piece_moved(bestMove), to_sq(bestMove), bonus);
+ Hist.update(pos.piece_moved(bestMove), to_sq(bestMove), bonus);
+ if (is_ok((ss-1)->currentMove))
+ {
+ Square prevSq = to_sq((ss-1)->currentMove);
+ Refutation.update(pos.piece_on(prevSq), prevSq, bestMove);
+ }
// Decrease history of all the other played non-capture moves
for (int i = 0; i < playedMoveCount - 1; i++)
{
Move m = movesSearched[i];
- H.add(pos.piece_moved(m), to_sq(m), -bonus);
+ Hist.update(pos.piece_moved(m), to_sq(m), -bonus);
}
}
}
// search function when the remaining depth is zero (or, to be more precise,
// less than ONE_PLY).
- template <NodeType NT>
+ template <NodeType NT, bool InCheck>
Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
const bool PvNode = (NT == PV);
assert(NT == PV || NT == NonPV);
+ assert(InCheck == !!pos.checkers());
assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE);
assert(PvNode || (alpha == beta - 1));
assert(depth <= DEPTH_ZERO);
const TTEntry* tte;
Key posKey;
Move ttMove, move, bestMove;
- Value bestValue, value, ttValue, futilityValue, futilityBase;
- bool inCheck, givesCheck, enoughMaterial, evasionPrunable;
+ Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha;
+ bool givesCheck, enoughMaterial, evasionPrunable;
Depth ttDepth;
- inCheck = pos.in_check();
+ // To flag BOUND_EXACT a node with eval above alpha and no available moves
+ if (PvNode)
+ oldAlpha = alpha;
+
ss->currentMove = bestMove = MOVE_NONE;
ss->ply = (ss-1)->ply + 1;
// Check for an instant draw or maximum ply reached
- if (pos.is_draw<true>() || ss->ply > MAX_PLY)
+ if (pos.is_draw() || ss->ply > MAX_PLY)
return DrawValue[pos.side_to_move()];
+ // Decide whether or not to include checks, this fixes also the type of
+ // TT entry depth that we are going to use. Note that in qsearch we use
+ // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
+ ttDepth = InCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS
+ : DEPTH_QS_NO_CHECKS;
+
// Transposition table lookup. At PV nodes, we don't use the TT for
// pruning, but only for move ordering.
posKey = pos.key();
ttMove = tte ? tte->move() : MOVE_NONE;
ttValue = tte ? value_from_tt(tte->value(),ss->ply) : VALUE_NONE;
- // Decide whether or not to include checks, this fixes also the type of
- // TT entry depth that we are going to use. Note that in qsearch we use
- // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
- ttDepth = inCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS
- : DEPTH_QS_NO_CHECKS;
- if ( tte && tte->depth() >= ttDepth
+ if ( tte
+ && tte->depth() >= ttDepth
+ && ttValue != VALUE_NONE // Only in case of TT access race
&& ( PvNode ? tte->type() == BOUND_EXACT
: ttValue >= beta ? (tte->type() & BOUND_LOWER)
: (tte->type() & BOUND_UPPER)))
{
- assert(ttValue != VALUE_NONE); // Due to ttDepth > DEPTH_NONE
-
ss->currentMove = ttMove; // Can be MOVE_NONE
return ttValue;
}
// Evaluate the position statically
- if (inCheck)
+ if (InCheck)
{
ss->staticEval = ss->evalMargin = VALUE_NONE;
bestValue = futilityBase = -VALUE_INFINITE;
{
if (tte)
{
- assert(tte->static_value() != VALUE_NONE);
-
- ss->staticEval = bestValue = tte->static_value();
- ss->evalMargin = tte->static_value_margin();
+ // Never assume anything on values stored in TT
+ if ( (ss->staticEval = bestValue = tte->eval_value()) == VALUE_NONE
+ ||(ss->evalMargin = tte->eval_margin()) == VALUE_NONE)
+ ss->staticEval = bestValue = evaluate(pos, ss->evalMargin);
}
else
ss->staticEval = bestValue = evaluate(pos, ss->evalMargin);
// to search the moves. Because the depth is <= 0 here, only captures,
// queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
// be generated.
- MovePicker mp(pos, ttMove, depth, H, to_sq((ss-1)->currentMove));
+ MovePicker mp(pos, ttMove, depth, Hist, to_sq((ss-1)->currentMove));
CheckInfo ci(pos);
// Loop through the moves until no moves remain or a beta cutoff occurs
// Futility pruning
if ( !PvNode
- && !inCheck
+ && !InCheck
&& !givesCheck
&& move != ttMove
&& enoughMaterial
if (futilityValue < beta)
{
- if (futilityValue > bestValue)
- bestValue = futilityValue;
-
+ bestValue = std::max(bestValue, futilityValue);
continue;
}
- // Prune moves with negative or equal SEE
+ // Prune moves with negative or equal SEE and also moves with positive
+ // SEE where capturing piece loses a tempo and SEE < beta - futilityBase.
if ( futilityBase < beta
&& depth < DEPTH_ZERO
- && pos.see(move) <= 0)
+ && pos.see(move, beta - futilityBase) <= 0)
+ {
+ bestValue = std::max(bestValue, futilityBase);
continue;
+ }
}
// Detect non-capture evasions that are candidate to be pruned
evasionPrunable = !PvNode
- && inCheck
+ && InCheck
&& bestValue > VALUE_MATED_IN_MAX_PLY
&& !pos.is_capture(move)
&& !pos.can_castle(pos.side_to_move());
// Don't search moves with negative SEE values
if ( !PvNode
- && (!inCheck || evasionPrunable)
+ && (!InCheck || evasionPrunable)
&& move != ttMove
&& type_of(move) != PROMOTION
&& pos.see_sign(move) < 0)
// Don't search useless checks
if ( !PvNode
- && !inCheck
+ && !InCheck
&& givesCheck
&& move != ttMove
&& !pos.is_capture_or_promotion(move)
// Make and search the move
pos.do_move(move, st, ci, givesCheck);
- value = -qsearch<NT>(pos, ss+1, -beta, -alpha, depth - ONE_PLY);
+ value = givesCheck ? -qsearch<NT, true>(pos, ss+1, -beta, -alpha, depth - ONE_PLY)
+ : -qsearch<NT, false>(pos, ss+1, -beta, -alpha, depth - ONE_PLY);
pos.undo_move(move);
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
// All legal moves have been searched. A special case: If we're in check
// and no legal moves were found, it is checkmate.
- if (inCheck && bestValue == -VALUE_INFINITE)
+ if (InCheck && bestValue == -VALUE_INFINITE)
return mated_in(ss->ply); // Plies to mate from the root
TT.store(posKey, value_to_tt(bestValue, ss->ply),
- PvNode && bestMove != MOVE_NONE ? BOUND_EXACT : BOUND_UPPER,
+ PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER,
ttDepth, bestMove, ss->staticEval, ss->evalMargin);
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
}
- // check_is_dangerous() tests if a checking move can be pruned in qsearch().
- // bestValue is updated only when returning false because in that case move
- // will be pruned.
+ // value_to_tt() adjusts a mate score from "plies to mate from the root" to
+ // "plies to mate from the current position". Non-mate scores are unchanged.
+ // The function is called before storing a value to the transposition table.
+
+ Value value_to_tt(Value v, int ply) {
+
+ assert(v != VALUE_NONE);
+
+ return v >= VALUE_MATE_IN_MAX_PLY ? v + ply
+ : v <= VALUE_MATED_IN_MAX_PLY ? v - ply : v;
+ }
+
+
+ // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score
+ // from the transposition table (where refers to the plies to mate/be mated
+ // from current position) to "plies to mate/be mated from the root".
+
+ Value value_from_tt(Value v, int ply) {
+
+ return v == VALUE_NONE ? VALUE_NONE
+ : v >= VALUE_MATE_IN_MAX_PLY ? v - ply
+ : v <= VALUE_MATED_IN_MAX_PLY ? v + ply : v;
+ }
+
- bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta)
+ // check_is_dangerous() tests if a checking move can be pruned in qsearch()
+
+ bool check_is_dangerous(const Position& pos, Move move, Value futilityBase, Value beta)
{
- Bitboard b, occ, oldAtt, newAtt, kingAtt;
- Square from, to, ksq;
- Piece pc;
- Color them;
-
- from = from_sq(move);
- to = to_sq(move);
- them = ~pos.side_to_move();
- ksq = pos.king_square(them);
- kingAtt = pos.attacks_from<KING>(ksq);
- pc = pos.piece_moved(move);
-
- occ = pos.pieces() ^ from ^ ksq;
- oldAtt = pos.attacks_from(pc, from, occ);
- newAtt = pos.attacks_from(pc, to, occ);
-
- // Rule 1. Checks which give opponent's king at most one escape square are dangerous
- b = kingAtt & ~pos.pieces(them) & ~newAtt & ~(1ULL << to);
-
- if (!more_than_one(b))
+ Piece pc = pos.piece_moved(move);
+ Square from = from_sq(move);
+ Square to = to_sq(move);
+ Color them = ~pos.side_to_move();
+ Square ksq = pos.king_square(them);
+ Bitboard enemies = pos.pieces(them);
+ Bitboard kingAtt = pos.attacks_from<KING>(ksq);
+ Bitboard occ = pos.pieces() ^ from ^ ksq;
+ Bitboard oldAtt = pos.attacks_from(pc, from, occ);
+ Bitboard newAtt = pos.attacks_from(pc, to, occ);
+
+ // Checks which give opponent's king at most one escape square are dangerous
+ if (!more_than_one(kingAtt & ~(enemies | newAtt | to)))
return true;
- // Rule 2. Queen contact check is very dangerous
+ // Queen contact check is very dangerous
if (type_of(pc) == QUEEN && (kingAtt & to))
return true;
- // Rule 3. Creating new double threats with checks
- b = pos.pieces(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
+ // Creating new double threats with checks is dangerous
+ Bitboard b = (enemies ^ ksq) & newAtt & ~oldAtt;
while (b)
{
// Note that here we generate illegal "double move"!
}
- // connected_moves() tests whether two moves are 'connected' in the sense
- // that the first move somehow made the second move possible (for instance
- // if the moving piece is the same in both moves). The first move is assumed
- // to be the move that was made to reach the current position, while the
- // second move is assumed to be a move from the current position.
-
- bool connected_moves(const Position& pos, Move m1, Move m2) {
+ // allows() tests whether the 'first' move at previous ply somehow makes the
+ // 'second' move possible, for instance if the moving piece is the same in
+ // both moves. Normally the second move is the threat (the best move returned
+ // from a null search that fails low).
- Square f1, t1, f2, t2;
- Piece p1, p2;
- Square ksq;
+ bool allows(const Position& pos, Move first, Move second) {
- assert(is_ok(m1));
- assert(is_ok(m2));
+ assert(is_ok(first));
+ assert(is_ok(second));
+ assert(color_of(pos.piece_on(from_sq(second))) == ~pos.side_to_move());
+ assert(color_of(pos.piece_on(to_sq(first))) == ~pos.side_to_move());
- // Case 1: The moving piece is the same in both moves
- f2 = from_sq(m2);
- t1 = to_sq(m1);
- if (f2 == t1)
- return true;
+ Square m1from = from_sq(first);
+ Square m2from = from_sq(second);
+ Square m1to = to_sq(first);
+ Square m2to = to_sq(second);
- // Case 2: The destination square for m2 was vacated by m1
- t2 = to_sq(m2);
- f1 = from_sq(m1);
- if (t2 == f1)
+ // The piece is the same or second's destination was vacated by the first move
+ if (m1to == m2from || m2to == m1from)
return true;
- // Case 3: Moving through the vacated square
- p2 = pos.piece_on(f2);
- if (piece_is_slider(p2) && (between_bb(f2, t2) & f1))
+ // Second one moves through the square vacated by first one
+ if (between_bb(m2from, m2to) & m1from)
return true;
- // Case 4: The destination square for m2 is defended by the moving piece in m1
- p1 = pos.piece_on(t1);
- if (pos.attacks_from(p1, t1) & t2)
+ // Second's destination is defended by the first move's piece
+ Bitboard m1att = pos.attacks_from(pos.piece_on(m1to), m1to, pos.pieces() ^ m2from);
+ if (m1att & m2to)
return true;
- // Case 5: Discovered check, checking piece is the piece moved in m1
- ksq = pos.king_square(pos.side_to_move());
- if ( piece_is_slider(p1)
- && (between_bb(t1, ksq) & f2)
- && (pos.attacks_from(p1, t1, pos.pieces() ^ f2) & ksq))
+ // Second move gives a discovered check through the first's checking piece
+ if (m1att & pos.king_square(pos.side_to_move()))
+ {
+ assert(between_bb(m1to, pos.king_square(pos.side_to_move())) & m2from);
return true;
+ }
return false;
}
- // value_to_tt() adjusts a mate score from "plies to mate from the root" to
- // "plies to mate from the current position". Non-mate scores are unchanged.
- // The function is called before storing a value to the transposition table.
-
- Value value_to_tt(Value v, int ply) {
-
- assert(v != VALUE_NONE);
-
- return v >= VALUE_MATE_IN_MAX_PLY ? v + ply
- : v <= VALUE_MATED_IN_MAX_PLY ? v - ply : v;
- }
-
-
- // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score
- // from the transposition table (where refers to the plies to mate/be mated
- // from current position) to "plies to mate/be mated from the root".
+ // refutes() tests whether a 'first' move is able to defend against a 'second'
+ // opponent's move. In this case will not be pruned. Normally the second move
+ // is the threat (the best move returned from a null search that fails low).
- Value value_from_tt(Value v, int ply) {
-
- return v == VALUE_NONE ? VALUE_NONE
- : v >= VALUE_MATE_IN_MAX_PLY ? v - ply
- : v <= VALUE_MATED_IN_MAX_PLY ? v + ply : v;
- }
+ bool refutes(const Position& pos, Move first, Move second) {
+ assert(is_ok(first));
+ assert(is_ok(second));
- // connected_threat() tests whether it is safe to forward prune a move or if
- // is somehow connected to the threat move returned by null search.
+ Square m1from = from_sq(first);
+ Square m2from = from_sq(second);
+ Square m1to = to_sq(first);
+ Square m2to = to_sq(second);
- bool connected_threat(const Position& pos, Move m, Move threat) {
-
- assert(is_ok(m));
- assert(is_ok(threat));
- assert(!pos.is_capture_or_promotion(m));
- assert(!pos.is_passed_pawn_push(m));
+ // Don't prune moves of the threatened piece
+ if (m1from == m2to)
+ return true;
- Square mfrom, mto, tfrom, tto;
+ // If the threatened piece has value less than or equal to the value of the
+ // threat piece, don't prune moves which defend it.
+ if ( pos.is_capture(second)
+ && ( PieceValue[MG][pos.piece_on(m2from)] >= PieceValue[MG][pos.piece_on(m2to)]
+ || type_of(pos.piece_on(m2from)) == KING))
+ {
+ // Update occupancy as if the piece and the threat are moving
+ Bitboard occ = pos.pieces() ^ m1from ^ m1to ^ m2from;
+ Piece piece = pos.piece_on(m1from);
- mfrom = from_sq(m);
- mto = to_sq(m);
- tfrom = from_sq(threat);
- tto = to_sq(threat);
+ // The moved piece attacks the square 'tto' ?
+ if (pos.attacks_from(piece, m1to, occ) & m2to)
+ return true;
- // Case 1: Don't prune moves which move the threatened piece
- if (mfrom == tto)
- return true;
+ // Scan for possible X-ray attackers behind the moved piece
+ Bitboard xray = (attacks_bb< ROOK>(m2to, occ) & pos.pieces(color_of(piece), QUEEN, ROOK))
+ | (attacks_bb<BISHOP>(m2to, occ) & pos.pieces(color_of(piece), QUEEN, BISHOP));
- // Case 2: If the threatened piece has value less than or equal to the
- // value of the threatening piece, don't prune moves which defend it.
- if ( pos.is_capture(threat)
- && ( PieceValue[MG][pos.piece_on(tfrom)] >= PieceValue[MG][pos.piece_on(tto)]
- || type_of(pos.piece_on(tfrom)) == KING)
- && pos.move_attacks_square(m, tto))
- return true;
+ // Verify attackers are triggered by our move and not already existing
+ if (xray && (xray ^ (xray & pos.attacks_from<QUEEN>(m2to))))
+ return true;
+ }
- // Case 3: If the moving piece in the threatened move is a slider, don't
- // prune safe moves which block its ray.
- if ( piece_is_slider(pos.piece_on(tfrom))
- && (between_bb(tfrom, tto) & mto)
- && pos.see_sign(m) >= 0)
+ // Don't prune safe moves which block the threat path
+ if ((between_bb(m2from, m2to) & m1to) && pos.see_sign(first) >= 0)
return true;
return false;
// When playing with strength handicap choose best move among the MultiPV set
- // using a statistical rule dependent on SkillLevel. Idea by Heinz van Saanen.
-
- Move do_skill_level() {
+ // using a statistical rule dependent on 'level'. Idea by Heinz van Saanen.
- assert(MultiPV > 1);
+ Move Skill::pick_move() {
static RKISS rk;
rk.rand<unsigned>();
// RootMoves are already sorted by score in descending order
- size_t size = std::min(MultiPV, RootMoves.size());
- int variance = std::min(RootMoves[0].score - RootMoves[size - 1].score, PawnValueMg);
- int weakness = 120 - 2 * SkillLevel;
+ int variance = std::min(RootMoves[0].score - RootMoves[PVSize - 1].score, PawnValueMg);
+ int weakness = 120 - 2 * level;
int max_s = -VALUE_INFINITE;
- Move best = MOVE_NONE;
+ best = MOVE_NONE;
// Choose best move. For each move score we add two terms both dependent on
// weakness, one deterministic and bigger for weaker moves, and one random,
// then we choose the move with the resulting highest score.
- for (size_t i = 0; i < size; i++)
+ for (size_t i = 0; i < PVSize; i++)
{
int s = RootMoves[i].score;
std::stringstream s;
Time::point elaspsed = Time::now() - SearchTime + 1;
+ size_t uciPVSize = std::min((size_t)Options["MultiPV"], RootMoves.size());
int selDepth = 0;
for (size_t i = 0; i < Threads.size(); i++)
- if (Threads[i].maxPly > selDepth)
- selDepth = Threads[i].maxPly;
+ if (Threads[i]->maxPly > selDepth)
+ selDepth = Threads[i]->maxPly;
- for (size_t i = 0; i < std::min(UCIMultiPV, RootMoves.size()); i++)
+ for (size_t i = 0; i < uciPVSize; i++)
{
bool updated = (i <= PVIdx);
if (depth == 1 && !updated)
continue;
- int d = (updated ? depth : depth - 1);
- Value v = (updated ? RootMoves[i].score : RootMoves[i].prevScore);
+ int d = updated ? depth : depth - 1;
+ Value v = updated ? RootMoves[i].score : RootMoves[i].prevScore;
- if (s.rdbuf()->in_avail())
+ if (s.rdbuf()->in_avail()) // Not at first line
s << "\n";
s << "info depth " << d
<< " pv";
for (size_t j = 0; RootMoves[i].pv[j] != MOVE_NONE; j++)
- s << " " << move_to_uci(RootMoves[i].pv[j], Chess960);
+ s << " " << move_to_uci(RootMoves[i].pv[j], pos.is_chess960());
}
return s.str();
StateInfo state[MAX_PLY_PLUS_2], *st = state;
TTEntry* tte;
- int ply = 1;
+ int ply = 0;
Move m = pv[0];
- assert(m != MOVE_NONE && pos.is_pseudo_legal(m));
-
pv.clear();
- pv.push_back(m);
- pos.do_move(m, *st++);
-
- while ( (tte = TT.probe(pos.key())) != NULL
- && (m = tte->move()) != MOVE_NONE // Local copy, TT entry could change
- && pos.is_pseudo_legal(m)
- && pos.pl_move_is_legal(m, pos.pinned_pieces())
- && ply < MAX_PLY
- && (!pos.is_draw<false>() || ply < 2))
- {
+
+ do {
pv.push_back(m);
- pos.do_move(m, *st++);
- ply++;
- }
- pv.push_back(MOVE_NONE);
- do pos.undo_move(pv[--ply]); while (ply);
+ assert(MoveList<LEGAL>(pos).contains(pv[ply]));
+
+ pos.do_move(pv[ply++], *st++);
+ tte = TT.probe(pos.key());
+
+ } while ( tte
+ && pos.is_pseudo_legal(m = tte->move()) // Local copy, TT could change
+ && pos.pl_move_is_legal(m, pos.pinned_pieces())
+ && ply < MAX_PLY
+ && (!pos.is_draw() || ply < 2));
+
+ pv.push_back(MOVE_NONE); // Must be zero-terminating
+
+ while (ply) pos.undo_move(pv[--ply]);
}
StateInfo state[MAX_PLY_PLUS_2], *st = state;
TTEntry* tte;
- Key k;
- Value v, m = VALUE_NONE;
int ply = 0;
- assert(pv[ply] != MOVE_NONE && pos.is_pseudo_legal(pv[ply]));
-
do {
- k = pos.key();
- tte = TT.probe(k);
+ tte = TT.probe(pos.key());
- // Don't overwrite existing correct entries
- if (!tte || tte->move() != pv[ply])
- {
- v = (pos.in_check() ? VALUE_NONE : evaluate(pos, m));
- TT.store(k, VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[ply], v, m);
- }
- pos.do_move(pv[ply], *st++);
+ if (!tte || tte->move() != pv[ply]) // Don't overwrite correct entries
+ TT.store(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[ply], VALUE_NONE, VALUE_NONE);
+
+ assert(MoveList<LEGAL>(pos).contains(pv[ply]));
- } while (pv[++ply] != MOVE_NONE);
+ pos.do_move(pv[ply++], *st++);
- do pos.undo_move(pv[--ply]); while (ply);
+ } while (pv[ply] != MOVE_NONE);
+
+ while (ply) pos.undo_move(pv[--ply]);
}
void Thread::idle_loop() {
- // Pointer 'sp_master', if non-NULL, points to the active SplitPoint
- // object for which the thread is the master.
- const SplitPoint* sp_master = splitPointsCnt ? curSplitPoint : NULL;
+ // Pointer 'this_sp' is not null only if we are called from split(), and not
+ // at the thread creation. So it means we are the split point's master.
+ SplitPoint* this_sp = splitPointsSize ? activeSplitPoint : NULL;
- assert(!sp_master || (sp_master->master == this && is_searching));
+ assert(!this_sp || (this_sp->masterThread == this && searching));
- // If this thread is the master of a split point and all slaves have
- // finished their work at this split point, return from the idle loop.
- while (!sp_master || sp_master->slavesMask)
+ while (true)
{
- // If we are not searching, wait for a condition to be signaled
- // instead of wasting CPU time polling for work.
- while ( do_sleep
- || do_exit
- || (!is_searching && Threads.use_sleeping_threads()))
+ // If we are not searching, wait for a condition to be signaled instead of
+ // wasting CPU time polling for work.
+ while ((!searching && Threads.sleepWhileIdle) || exit)
{
- if (do_exit)
+ if (exit)
{
- assert(!sp_master);
+ assert(!this_sp);
return;
}
- // Grab the lock to avoid races with Thread::wake_up()
+ // Grab the lock to avoid races with Thread::notify_one()
mutex.lock();
- // If we are master and all slaves have finished don't go to sleep
- if (sp_master && !sp_master->slavesMask)
+ // If we are master and all slaves have finished then exit idle_loop
+ if (this_sp && !this_sp->slavesMask)
{
mutex.unlock();
break;
// Do sleep after retesting sleep conditions under lock protection, in
// particular we need to avoid a deadlock in case a master thread has,
- // in the meanwhile, allocated us and sent the wake_up() call before we
- // had the chance to grab the lock.
- if (do_sleep || !is_searching)
+ // in the meanwhile, allocated us and sent the notify_one() call before
+ // we had the chance to grab the lock.
+ if (!searching && !exit)
sleepCondition.wait(mutex);
mutex.unlock();
}
// If this thread has been assigned work, launch a search
- if (is_searching)
+ if (searching)
{
- assert(!do_sleep && !do_exit);
+ assert(!exit);
Threads.mutex.lock();
- assert(is_searching);
- SplitPoint* sp = curSplitPoint;
+ assert(searching);
+ SplitPoint* sp = activeSplitPoint;
Threads.mutex.unlock();
Position pos(*sp->pos, this);
memcpy(ss, sp->ss - 1, 4 * sizeof(Stack));
- (ss+1)->sp = sp;
+ (ss+1)->splitPoint = sp;
sp->mutex.lock();
- assert(sp->activePositions[idx] == NULL);
+ assert(activePosition == NULL);
- sp->activePositions[idx] = &pos;
+ activePosition = &pos;
- if (sp->nodeType == Root)
+ switch (sp->nodeType) {
+ case Root:
search<SplitPointRoot>(pos, ss+1, sp->alpha, sp->beta, sp->depth);
- else if (sp->nodeType == PV)
+ break;
+ case PV:
search<SplitPointPV>(pos, ss+1, sp->alpha, sp->beta, sp->depth);
- else if (sp->nodeType == NonPV)
+ break;
+ case NonPV:
search<SplitPointNonPV>(pos, ss+1, sp->alpha, sp->beta, sp->depth);
- else
+ break;
+ default:
assert(false);
+ }
- assert(is_searching);
+ assert(searching);
- is_searching = false;
- sp->activePositions[idx] = NULL;
+ searching = false;
+ activePosition = NULL;
sp->slavesMask &= ~(1ULL << idx);
sp->nodes += pos.nodes_searched();
- // Wake up master thread so to allow it to return from the idle loop in
- // case we are the last slave of the split point.
- if ( Threads.use_sleeping_threads()
- && this != sp->master
+ // Wake up master thread so to allow it to return from the idle loop
+ // in case we are the last slave of the split point.
+ if ( Threads.sleepWhileIdle
+ && this != sp->masterThread
&& !sp->slavesMask)
{
- assert(!sp->master->is_searching);
- sp->master->wake_up();
+ assert(!sp->masterThread->searching);
+ sp->masterThread->notify_one();
}
// After releasing the lock we cannot access anymore any SplitPoint
// unsafe because if we are exiting there is a chance are already freed.
sp->mutex.unlock();
}
+
+ // If this thread is the master of a split point and all slaves have finished
+ // their work at this split point, return from the idle loop.
+ if (this_sp && !this_sp->slavesMask)
+ {
+ this_sp->mutex.lock();
+ bool finished = !this_sp->slavesMask; // Retest under lock protection
+ this_sp->mutex.unlock();
+ if (finished)
+ return;
+ }
}
}
{
Threads.mutex.lock();
- nodes = RootPosition.nodes_searched();
+ nodes = RootPos.nodes_searched();
// Loop across all split points and sum accumulated SplitPoint nodes plus
- // all the currently active slaves positions.
+ // all the currently active positions nodes.
for (size_t i = 0; i < Threads.size(); i++)
- for (int j = 0; j < Threads[i].splitPointsCnt; j++)
+ for (int j = 0; j < Threads[i]->splitPointsSize; j++)
{
- SplitPoint& sp = Threads[i].splitPoints[j];
+ SplitPoint& sp = Threads[i]->splitPoints[j];
sp.mutex.lock();
Bitboard sm = sp.slavesMask;
while (sm)
{
- Position* pos = sp.activePositions[pop_lsb(&sm)];
- nodes += pos ? pos->nodes_searched() : 0;
+ Position* pos = Threads[pop_lsb(&sm)]->activePosition;
+ if (pos)
+ nodes += pos->nodes_searched();
}
sp.mutex.unlock();