/*
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) 2008-2014 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
#include <cassert>
#include <cmath>
#include <cstring>
-#include <iomanip>
#include <iostream>
#include <sstream>
-#include "book.h"
#include "evaluate.h"
-#include "history.h"
#include "movegen.h"
#include "movepick.h"
+#include "notation.h"
+#include "rkiss.h"
#include "search.h"
#include "timeman.h"
#include "thread.h"
#include "tt.h"
-#include "ucioption.h"
+#include "uci.h"
namespace Search {
volatile SignalsType Signals;
LimitsType Limits;
std::vector<RootMove> RootMoves;
- Position RootPosition;
- Time SearchTime;
+ Position RootPos;
+ Time::point SearchTime;
+ StateStackPtr SetupStates;
}
using std::string;
-using std::cout;
-using std::endl;
using Eval::evaluate;
using namespace Search;
-// For some reason argument-dependent lookup (ADL) doesn't work for Android's
-// STLPort, so explicitly qualify following functions.
-using std::count;
-using std::find;
-
namespace {
- // Set to true to force running with one thread. Used for debugging
- const bool FakeSplit = false;
-
// 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]; }
-
- // Maximum depth for razoring
- const Depth RazorDepth = 4 * ONE_PLY;
+ enum NodeType { Root, PV, NonPV };
// Dynamic razoring margin based on depth
- inline Value razor_margin(Depth d) { return Value(512 + 16 * int(d)); }
-
- // Maximum depth for use of dynamic threat detection when null move fails low
- const Depth ThreatDepth = 5 * ONE_PLY;
-
- // Minimum depth for use of internal iterative deepening
- const Depth IIDDepth[] = { 8 * ONE_PLY, 5 * ONE_PLY };
-
- // At Non-PV nodes we do an internal iterative deepening search
- // when the static evaluation is bigger then beta - IIDMargin.
- const Value IIDMargin = Value(256);
-
- // Minimum depth for use of singular extension
- const Depth SingularExtensionDepth[] = { 8 * ONE_PLY, 6 * ONE_PLY };
-
- // Futility margin for quiescence search
- const Value FutilityMarginQS = Value(128);
+ inline Value razor_margin(Depth d) { return Value(512 + 32 * d); }
// Futility lookup tables (initialized at startup) and their access functions
- Value FutilityMargins[16][64]; // [depth][moveNumber]
- int FutilityMoveCounts[32]; // [depth]
-
- inline Value futility_margin(Depth d, int mn) {
-
- return d < 7 * ONE_PLY ? FutilityMargins[std::max(int(d), 1)][std::min(mn, 63)]
- : 2 * VALUE_INFINITE;
- }
+ int FutilityMoveCounts[2][32]; // [improving][depth]
- inline int futility_move_count(Depth d) {
-
- return d < 16 * ONE_PLY ? FutilityMoveCounts[d] : MAX_MOVES;
+ inline Value futility_margin(Depth d) {
+ return Value(200 * d);
}
// Reduction lookup tables (initialized at startup) and their access function
- int8_t Reductions[2][64][64]; // [pv][depth][moveNumber]
-
- template <bool PvNode> inline Depth reduction(Depth d, int mn) {
+ int8_t Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber]
- return (Depth) Reductions[PvNode][std::min(int(d) / ONE_PLY, 63)][std::min(mn, 63)];
+ template <bool PvNode> inline Depth reduction(bool i, Depth d, int mn) {
+ return (Depth) Reductions[PvNode][i][std::min(int(d), 63)][std::min(mn, 63)];
}
- // Easy move margin. An easy move candidate must be at least this much better
- // than the second best move.
- const Value EasyMoveMargin = Value(0x150);
-
- // This is the minimum interval in msec between two check_time() calls
- const int TimerResolution = 5;
-
-
- size_t MultiPV, UCIMultiPV, PVIdx;
+ size_t PVIdx;
TimeManager TimeMgr;
- int BestMoveChanges;
- int SkillLevel;
- bool SkillLevelEnabled, Chess960;
- History H;
-
+ double BestMoveChanges;
+ Value DrawValue[COLOR_NB];
+ HistoryStats History;
+ GainsStats Gains;
+ MovesStats Countermoves, Followupmoves;
- template <NodeType NT>
- Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth);
+ template <NodeType NT, bool SpNode>
+ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode);
- 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 can_return_tt(const TTEntry* tte, Depth depth, Value ttValue, Value beta);
- bool connected_threat(const Position& pos, Move m, Move threat);
- Value refine_eval(const TTEntry* tte, Value ttValue, Value defaultEval);
- Move do_skill_level();
- string score_to_uci(Value v, Value alpha = -VALUE_INFINITE, Value beta = VALUE_INFINITE);
- void pv_info_to_log(Position& pos, int depth, Value score, int time, Move pv[]);
- void pv_info_to_uci(const Position& pos, int depth, Value alpha, Value beta);
-
- // MovePickerExt class template extends MovePicker and allows to choose at
- // compile time the proper moves source according to the type of node. In the
- // default case we simply create and use a standard MovePicker object.
- template<bool SpNode> struct MovePickerExt : public MovePicker {
-
- MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, Stack* ss, Value b)
- : MovePicker(p, ttm, d, h, ss, b) {}
- };
-
- // In case of a SpNode we use split point's shared MovePicker object as moves source
- template<> struct MovePickerExt<true> : public MovePicker {
-
- MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, Stack* ss, Value b)
- : MovePicker(p, ttm, d, h, ss, b), mp(ss->sp->mp) {}
-
- Move next_move() { return mp->next_move(); }
- MovePicker* mp;
- };
-
- // is_dangerous() checks whether a move belongs to some classes of known
- // 'dangerous' moves so that we avoid to prune it.
- FORCE_INLINE bool is_dangerous(const Position& pos, Move m, bool captureOrPromotion) {
-
- // Test for a pawn pushed to 7th or a passed pawn move
- if (type_of(pos.piece_moved(m)) == PAWN)
- {
- Color c = pos.side_to_move();
- if ( relative_rank(c, to_sq(m)) == RANK_7
- || pos.pawn_is_passed(c, to_sq(m)))
- return true;
+ void update_stats(const 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 {
+ Skill(int l, size_t rootSize) : level(l),
+ candidates(l < 20 ? std::min(4, (int)rootSize) : 0),
+ best(MOVE_NONE) {}
+ ~Skill() {
+ if (candidates) // Swap best PV line with the sub-optimal one
+ std::swap(RootMoves[0], *std::find(RootMoves.begin(),
+ RootMoves.end(), best ? best : pick_move()));
}
- // Test for a capture that triggers a pawn endgame
- if ( captureOrPromotion
- && type_of(pos.piece_on(to_sq(m))) != PAWN
- && type_of(m) == NORMAL
- && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
- - PieceValueMidgame[pos.piece_on(to_sq(m))] == VALUE_ZERO))
- return true;
+ size_t candidates_size() const { return candidates; }
+ bool time_to_pick(int depth) const { return depth == 1 + level; }
+ Move pick_move();
- return false;
- }
+ int level;
+ size_t candidates;
+ Move best;
+ };
} // namespace
int mc; // moveCount
// Init reductions array
- for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
+ for (hd = 1; hd < 64; ++hd) for (mc = 1; mc < 64; ++mc)
{
- double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
+ double pvRed = 0.00 + log(double(hd)) * log(double(mc)) / 3.00;
double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
- Reductions[1][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0);
- Reductions[0][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0);
- }
- // Init futility margins array
- for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++)
- FutilityMargins[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45);
+ Reductions[1][1][hd][mc] = int8_t( pvRed >= 1.0 ? pvRed + 0.5: 0);
+ Reductions[0][1][hd][mc] = int8_t(nonPVRed >= 1.0 ? nonPVRed + 0.5: 0);
+
+ Reductions[1][0][hd][mc] = Reductions[1][1][hd][mc];
+ Reductions[0][0][hd][mc] = Reductions[0][1][hd][mc];
+
+ if (Reductions[0][0][hd][mc] >= 2)
+ Reductions[0][0][hd][mc] += 1;
+ }
// Init futility move count array
- for (d = 0; d < 32; d++)
- FutilityMoveCounts[d] = int(3.001 + 0.25 * pow(d, 2.0));
+ for (d = 0; d < 32; ++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));
+ }
}
/// Search::perft() is our utility to verify move generation. All the leaf nodes
/// up to the given depth are generated and counted and the sum returned.
-
-int64_t Search::perft(Position& pos, Depth depth) {
+template<bool Root>
+uint64_t Search::perft(Position& pos, Depth depth) {
StateInfo st;
- int64_t cnt = 0;
-
- MoveList<LEGAL> ml(pos);
-
- // At the last ply just return the number of moves (leaf nodes)
- if (depth == ONE_PLY)
- return ml.size();
-
+ uint64_t cnt, nodes = 0;
CheckInfo ci(pos);
- for ( ; !ml.end(); ++ml)
+ const bool leaf = (depth == 2 * ONE_PLY);
+
+ for (MoveList<LEGAL> it(pos); *it; ++it)
{
- pos.do_move(ml.move(), st, ci, pos.move_gives_check(ml.move(), ci));
- cnt += perft(pos, depth - ONE_PLY);
- pos.undo_move(ml.move());
+ if (Root && depth <= ONE_PLY)
+ cnt = 1, nodes++;
+ else
+ {
+ pos.do_move(*it, st, ci, pos.gives_check(*it, ci));
+ cnt = leaf ? MoveList<LEGAL>(pos).size() : perft<false>(pos, depth - ONE_PLY);
+ nodes += cnt;
+ pos.undo_move(*it);
+ }
+ if (Root)
+ sync_cout << move_to_uci(*it, pos.is_chess960()) << ": " << cnt << sync_endl;
}
- return cnt;
+ return nodes;
}
+template uint64_t Search::perft<true>(Position& pos, Depth depth);
+
/// 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 Book book; // Defined static to initialize the PRNG only once
+ TimeMgr.init(Limits, RootPos.game_ply(), RootPos.side_to_move());
- Position& pos = RootPosition;
- Chess960 = pos.is_chess960();
- Eval::RootColor = pos.side_to_move();
- TimeMgr.init(Limits, pos.startpos_ply_counter(), pos.side_to_move());
- TT.new_search();
- H.clear();
+ int cf = Options["Contempt"] * PawnValueEg / 100; // From centipawns
+ DrawValue[ RootPos.side_to_move()] = VALUE_DRAW - Value(cf);
+ DrawValue[~RootPos.side_to_move()] = VALUE_DRAW + Value(cf);
if (RootMoves.empty())
{
- cout << "info depth 0 score "
- << score_to_uci(pos.in_check() ? -VALUE_MATE : VALUE_DRAW) << endl;
-
RootMoves.push_back(MOVE_NONE);
- goto finalize;
- }
+ sync_cout << "info depth 0 score "
+ << score_to_uci(RootPos.checkers() ? -VALUE_MATE : VALUE_DRAW)
+ << sync_endl;
- if (Options["OwnBook"] && !Limits.infinite)
- {
- Move bookMove = book.probe(pos, Options["Book File"], Options["Best Book Move"]);
-
- if (bookMove && count(RootMoves.begin(), RootMoves.end(), bookMove))
- {
- std::swap(RootMoves[0], *find(RootMoves.begin(), RootMoves.end(), bookMove));
- goto finalize;
- }
+ goto finalize;
}
- 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);
- MultiPV = (SkillLevelEnabled ? std::max(UCIMultiPV, (size_t)4) : UCIMultiPV);
+ // Reset the threads, still sleeping: will wake up at split time
+ for (size_t i = 0; i < Threads.size(); ++i)
+ Threads[i]->maxPly = 0;
- if (Options["Use Search Log"])
- {
- Log log(Options["Search Log Filename"]);
- log << "\nSearching: " << pos.to_fen()
- << "\ninfinite: " << Limits.infinite
- << " ponder: " << Limits.ponder
- << " time: " << Limits.time[pos.side_to_move()]
- << " increment: " << Limits.inc[pos.side_to_move()]
- << " moves to go: " << Limits.movestogo
- << endl;
- }
+ Threads.timer->run = true;
+ Threads.timer->notify_one(); // Wake up the recurring timer
- Threads.wake_up();
+ id_loop(RootPos); // Let's start searching !
- // 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
- Threads.set_timer(100);
+ Threads.timer->run = false; // Stop the timer
- // We're ready to start searching. Call the iterative deepening loop function
- id_loop(pos);
+finalize:
- Threads.set_timer(0); // Stop timer
- Threads.sleep();
+ // When search is stopped this info is not printed
+ sync_cout << "info nodes " << RootPos.nodes_searched()
+ << " time " << Time::now() - SearchTime + 1 << sync_endl;
- if (Options["Use Search Log"])
+ // When we reach the maximum depth, we can arrive here without a raise of
+ // Signals.stop. However, if we are pondering or in an infinite search,
+ // the UCI protocol states that we shouldn't print the best move before the
+ // GUI sends a "stop" or "ponderhit" command. We therefore simply wait here
+ // until the GUI sends one of those commands (which also raises Signals.stop).
+ if (!Signals.stop && (Limits.ponder || Limits.infinite))
{
- int e = SearchTime.elapsed();
-
- Log log(Options["Search Log Filename"]);
- log << "Nodes: " << pos.nodes_searched()
- << "\nNodes/second: " << (e > 0 ? pos.nodes_searched() * 1000 / e : 0)
- << "\nBest move: " << move_to_san(pos, 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]) << endl;
- pos.undo_move(RootMoves[0].pv[0]);
+ Signals.stopOnPonderhit = true;
+ RootPos.this_thread()->wait_for(Signals.stop);
}
-finalize:
-
- // 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.
- if (!Signals.stop && (Limits.ponder || Limits.infinite))
- pos.this_thread()->wait_for_stop_or_ponderhit();
-
// Best move could be MOVE_NONE when searching on a stalemate position
- cout << "bestmove " << move_to_uci(RootMoves[0].pv[0], Chess960)
- << " ponder " << move_to_uci(RootMoves[0].pv[1], Chess960) << 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;
}
void id_loop(Position& pos) {
- Stack ss[MAX_PLY_PLUS_2];
- int depth, prevBestMoveChanges;
+ Stack stack[MAX_PLY_PLUS_6], *ss = stack+2; // To allow referencing (ss-2)
+ int depth;
Value bestValue, alpha, beta, delta;
- bool bestMoveNeverChanged = true;
- Move skillBest = MOVE_NONE;
- memset(ss, 0, 4 * sizeof(Stack));
- depth = BestMoveChanges = 0;
- bestValue = delta = -VALUE_INFINITE;
- ss->currentMove = MOVE_NULL; // Hack to skip update gains
+ std::memset(ss-2, 0, 5 * sizeof(Stack));
+
+ depth = 0;
+ BestMoveChanges = 0;
+ bestValue = delta = alpha = -VALUE_INFINITE;
+ beta = VALUE_INFINITE;
+
+ TT.new_search();
+ History.clear();
+ Gains.clear();
+ Countermoves.clear();
+ Followupmoves.clear();
+
+ size_t multiPV = Options["MultiPV"];
+ Skill skill(Options["Skill Level"], RootMoves.size());
+
+ // 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.
+ multiPV = std::max(multiPV, skill.candidates_size());
// Iterative deepening loop until requested to stop or target depth reached
- while (!Signals.stop && ++depth <= MAX_PLY && (!Limits.depth || depth <= Limits.depth))
+ while (++depth <= MAX_PLY && !Signals.stop && (!Limits.depth || depth <= Limits.depth))
{
- // Save last iteration's scores before first PV line is searched and all
- // the move scores but the (new) PV are set to -VALUE_INFINITE.
- for (size_t i = 0; i < RootMoves.size(); i++)
- RootMoves[i].prevScore = RootMoves[i].score;
+ // Age out PV variability metric
+ BestMoveChanges *= 0.5;
- prevBestMoveChanges = BestMoveChanges;
- BestMoveChanges = 0;
+ // Save the last iteration's scores before first PV line is searched and
+ // all the move scores except the (new) PV are set to -VALUE_INFINITE.
+ for (size_t i = 0; i < RootMoves.size(); ++i)
+ RootMoves[i].prevScore = RootMoves[i].score;
// 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 < std::min(multiPV, RootMoves.size()) && !Signals.stop; ++PVIdx)
{
- // Set aspiration window default width
- if (depth >= 5 && abs(RootMoves[PVIdx].prevScore) < VALUE_KNOWN_WIN)
+ // Reset aspiration window starting size
+ if (depth >= 5)
{
delta = Value(16);
- alpha = RootMoves[PVIdx].prevScore - delta;
- beta = RootMoves[PVIdx].prevScore + delta;
+ alpha = std::max(RootMoves[PVIdx].prevScore - delta,-VALUE_INFINITE);
+ beta = std::min(RootMoves[PVIdx].prevScore + delta, VALUE_INFINITE);
}
- else
+
+ // Start with a small aspiration window and, in the case of a fail
+ // high/low, re-search with a bigger window until we're not failing
+ // high/low anymore.
+ while (true)
{
- alpha = -VALUE_INFINITE;
- beta = VALUE_INFINITE;
- }
+ bestValue = search<Root, false>(pos, ss, alpha, beta, depth * ONE_PLY, false);
- // Start with a small aspiration window and, in case of fail high/low,
- // research with bigger window until not failing high/low anymore.
- do {
- // Search starts from ss+1 to allow referencing (ss-1). This is
- // needed by update gains and ss copy when splitting at Root.
- bestValue = search<Root>(pos, ss+1, alpha, beta, depth * ONE_PLY);
-
- // Bring to front the best move. It is critical that sorting is
- // done with a stable algorithm because all the values but the first
- // and eventually the new best one are set to -VALUE_INFINITE and
- // 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());
-
- // In case we have found an exact score and we are going to leave
- // the fail high/low loop then reorder the PV moves, otherwise
- // leave the last PV move in its position so to be searched again.
- // Of course this is needed only in MultiPV search.
- if (PVIdx && bestValue > alpha && bestValue < beta)
- sort<RootMove>(RootMoves.begin(), RootMoves.begin() + PVIdx);
+ // Bring the best move to the front. It is critical that sorting
+ // is done with a stable algorithm because all the values but the
+ // first and eventually the new best one are set to -VALUE_INFINITE
+ // and we want to keep the same order for all the moves except the
+ // new PV that goes to the front. Note that in case of MultiPV
+ // search the already searched PV lines are preserved.
+ 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.
- for (size_t i = 0; i <= PVIdx; i++)
+ for (size_t i = 0; i <= PVIdx; ++i)
RootMoves[i].insert_pv_in_tt(pos);
- // If search has been stopped exit the aspiration window loop.
- // Sorting and writing PV back to TT is safe becuase RootMoves
- // is still valid, although refers to previous iteration.
+ // If search has been stopped break immediately. Sorting and
+ // writing PV back to TT is safe because RootMoves is still
+ // valid, although it refers to previous iteration.
if (Signals.stop)
break;
- // Send full PV info to GUI if we are going to leave the loop or
- // if we have a fail high/low and we are deep in the search.
- if ((bestValue > alpha && bestValue < beta) || SearchTime.elapsed() > 2000)
- pv_info_to_uci(pos, depth, alpha, beta);
+ // When failing high/low give some update (without cluttering
+ // the UI) before a re-search.
+ if ( (bestValue <= alpha || bestValue >= beta)
+ && Time::now() - SearchTime > 3000)
+ sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
- // In case of failing high/low increase aspiration window and
- // research, otherwise exit the fail high/low loop.
- if (bestValue >= beta)
- {
- beta += delta;
- delta += delta / 2;
- }
- else if (bestValue <= alpha)
+ // In case of failing low/high increase aspiration window and
+ // re-search, otherwise exit the loop.
+ if (bestValue <= alpha)
{
+ alpha = std::max(bestValue - delta, -VALUE_INFINITE);
+
Signals.failedLowAtRoot = true;
Signals.stopOnPonderhit = false;
-
- alpha -= delta;
- delta += delta / 2;
}
+ else if (bestValue >= beta)
+ beta = std::min(bestValue + delta, VALUE_INFINITE);
+
else
break;
+ delta += 3 * delta / 8;
+
assert(alpha >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
+ }
- } while (abs(bestValue) < VALUE_KNOWN_WIN);
- }
+ // Sort the PV lines searched so far and update the GUI
+ std::stable_sort(RootMoves.begin(), RootMoves.begin() + PVIdx + 1);
- // Skills: Do we need to pick now the best move ?
- if (SkillLevelEnabled && depth == 1 + SkillLevel)
- skillBest = do_skill_level();
+ if (PVIdx + 1 == std::min(multiPV, RootMoves.size()) || Time::now() - SearchTime > 3000)
+ sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
+ }
- if (!Signals.stop && Options["Use Search Log"])
- pv_info_to_log(pos, depth, bestValue, SearchTime.elapsed(), &RootMoves[0].pv[0]);
+ // If skill levels are enabled and time is up, pick a sub-optimal best move
+ if (skill.candidates_size() && skill.time_to_pick(depth))
+ skill.pick_move();
- // Filter out startup noise when monitoring best move stability
- if (depth > 2 && BestMoveChanges)
- bestMoveNeverChanged = false;
+ // Have we 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 (!Signals.stop && !Signals.stopOnPonderhit && Limits.use_time_management())
+ if (Limits.use_time_management() && !Signals.stop && !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)
- TimeMgr.pv_instability(BestMoveChanges, prevBestMoveChanges);
-
- // Stop search if most of available time is already consumed. We
- // probably don't have enough time to search the first move at the
- // next iteration anyway.
- if (SearchTime.elapsed() > (TimeMgr.available_time() * 62) / 100)
- stop = true;
-
- // Stop search early if one move seems to be much better than others
- if ( depth >= 12
- && !stop
- && ( (bestMoveNeverChanged && pos.captured_piece_type())
- || SearchTime.elapsed() > (TimeMgr.available_time() * 40) / 100))
- {
- Value rBeta = bestValue - EasyMoveMargin;
- (ss+1)->excludedMove = RootMoves[0].pv[0];
- (ss+1)->skipNullMove = true;
- Value v = search<NonPV>(pos, ss+1, rBeta - 1, rBeta, (depth - 3) * ONE_PLY);
- (ss+1)->skipNullMove = false;
- (ss+1)->excludedMove = MOVE_NONE;
-
- if (v < rBeta)
- stop = true;
- }
-
- if (stop)
+ // Take some extra time if the best move has changed
+ if (depth > 4 && multiPV == 1)
+ TimeMgr.pv_instability(BestMoveChanges);
+
+ // Stop the search if only one legal move is available or all
+ // of the available time has been used.
+ if ( RootMoves.size() == 1
+ || Time::now() - SearchTime > TimeMgr.available_time())
{
// If we are allowed to ponder do not stop the search now but
- // keep pondering until GUI sends "ponderhit" or "stop".
+ // keep pondering until the GUI sends "ponderhit" or "stop".
if (Limits.ponder)
Signals.stopOnPonderhit = true;
else
}
}
}
-
- // 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], *find(RootMoves.begin(), RootMoves.end(), skillBest));
- }
}
// search<>() is the main search function for both PV and non-PV nodes and for
// normal and SplitPoint nodes. When called just after a split point the search
// is simpler because we have already probed the hash table, done a null move
- // search, and searched the first move before splitting, we don't have to repeat
- // all this work again. We also don't need to store anything to the hash table
- // here: This is taken care of after we return from the split point.
+ // search, and searched the first move before splitting, so we don't have to
+ // repeat all this work again. We also don't need to store anything to the hash
+ // table here: This is taken care of after we return from the split point.
- template <NodeType NT>
- Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
+ template <NodeType NT, bool SpNode>
+ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) {
- const bool PvNode = (NT == PV || NT == Root || NT == SplitPointPV || NT == SplitPointRoot);
- const bool SpNode = (NT == SplitPointPV || NT == SplitPointNonPV || NT == SplitPointRoot);
- const bool RootNode = (NT == Root || NT == SplitPointRoot);
+ const bool RootNode = NT == Root;
+ const bool PvNode = NT == PV || NT == Root;
- assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE);
- assert((alpha == beta - 1) || PvNode);
+ assert(-VALUE_INFINITE <= alpha && alpha < beta && beta <= VALUE_INFINITE);
+ assert(PvNode || (alpha == beta - 1));
assert(depth > DEPTH_ZERO);
- Move movesSearched[64];
+ Move quietsSearched[64];
StateInfo st;
const TTEntry *tte;
+ SplitPoint* splitPoint;
Key posKey;
- Move ttMove, move, excludedMove, bestMove, threatMove;
- Depth ext, newDepth;
- Bound bt;
- Value bestValue, value, oldAlpha, ttValue;
- Value refinedValue, nullValue, futilityBase, futilityValue;
- bool isPvMove, inCheck, singularExtensionNode, givesCheck;
+ Move ttMove, move, excludedMove, bestMove;
+ Depth ext, newDepth, predictedDepth;
+ Value bestValue, value, ttValue, eval, nullValue, futilityValue;
+ bool inCheck, givesCheck, pvMove, singularExtensionNode, improving;
bool captureOrPromotion, dangerous, doFullDepthSearch;
- int moveCount = 0, playedMoveCount = 0;
- Thread* thisThread = pos.this_thread();
- SplitPoint* sp = NULL;
-
- refinedValue = bestValue = value = -VALUE_INFINITE;
- oldAlpha = alpha;
- inCheck = pos.in_check();
- ss->ply = (ss-1)->ply + 1;
-
- // Used to send selDepth info to GUI
- if (PvNode && thisThread->maxPly < ss->ply)
- thisThread->maxPly = ss->ply;
+ int moveCount, quietCount;
// Step 1. Initialize node
+ Thread* thisThread = pos.this_thread();
+ inCheck = pos.checkers();
+
if (SpNode)
{
+ splitPoint = ss->splitPoint;
+ bestMove = splitPoint->bestMove;
+ bestValue = splitPoint->bestValue;
tte = NULL;
ttMove = excludedMove = MOVE_NONE;
- ttValue = VALUE_ZERO;
- sp = ss->sp;
- bestMove = sp->bestMove;
- threatMove = sp->threatMove;
- bestValue = sp->bestValue;
- moveCount = sp->moveCount; // Lock must be held here
+ ttValue = VALUE_NONE;
- assert(bestValue > -VALUE_INFINITE && moveCount > 0);
-
- goto split_point_start;
- }
- else
- {
- ss->currentMove = threatMove = (ss+1)->excludedMove = bestMove = MOVE_NONE;
- (ss+1)->skipNullMove = false; (ss+1)->reduction = DEPTH_ZERO;
- (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
+ assert(splitPoint->bestValue > -VALUE_INFINITE && splitPoint->moveCount > 0);
+ goto moves_loop;
}
- // Step 2. Check for aborted search and immediate draw
- // Enforce node limit here. FIXME: This only works with 1 search thread.
- if (Limits.nodes && pos.nodes_searched() >= Limits.nodes)
- Signals.stop = true;
+ moveCount = quietCount = 0;
+ bestValue = -VALUE_INFINITE;
+ 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;
- if (( Signals.stop
- || pos.is_draw<false>()
- || ss->ply > MAX_PLY) && !RootNode)
- return VALUE_DRAW;
+ // Used to send selDepth info to GUI
+ if (PvNode && thisThread->maxPly < ss->ply)
+ thisThread->maxPly = ss->ply;
- // 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
- // a shorter mate was found upward in the tree then there is no need to search
- // further, we will never beat current alpha. Same logic but with reversed signs
- // applies also in the opposite condition of being mated instead of giving mate,
- // in this case return a fail-high score.
if (!RootNode)
{
+ // Step 2. Check for aborted search and immediate draw
+ if (Signals.stop || pos.is_draw() || ss->ply > MAX_PLY)
+ return ss->ply > MAX_PLY && !inCheck ? evaluate(pos) : DrawValue[pos.side_to_move()];
+
+ // 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
+ // a shorter mate was found upward in the tree then there is no need to search
+ // because we will never beat the current alpha. Same logic but with reversed
+ // signs applies also in the opposite condition of being mated instead of giving
+ // mate. In this case return a fail-high score.
alpha = std::max(mated_in(ss->ply), alpha);
beta = std::min(mate_in(ss->ply+1), beta);
if (alpha >= beta)
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;
- ttValue = tte ? value_from_tt(tte->value(), ss->ply) : VALUE_ZERO;
+ 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, while at non-PV nodes we check for
- // a fail high/low. Biggest advantage at probing at PV nodes is to have a
+ // At PV nodes we check for exact scores, whilst at non-PV nodes we check for
+ // a fail high/low. The biggest advantage to probing at PV nodes is to have a
// 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 && (PvNode ? tte->depth() >= depth && tte->type() == BOUND_EXACT
- : can_return_tt(tte, depth, ttValue, beta)))
+ if ( !RootNode
+ && tte
+ && tte->depth() >= depth
+ && ttValue != VALUE_NONE // Only in case of TT access race
+ && ( PvNode ? tte->bound() == BOUND_EXACT
+ : ttValue >= beta ? (tte->bound() & BOUND_LOWER)
+ : (tte->bound() & BOUND_UPPER)))
{
- TT.refresh(tte);
ss->currentMove = ttMove; // Can be MOVE_NONE
- if ( ttValue >= beta
- && ttMove
- && !pos.is_capture_or_promotion(ttMove)
- && ttMove != ss->killers[0])
- {
- ss->killers[1] = ss->killers[0];
- ss->killers[0] = ttMove;
- }
+ // 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);
+
return ttValue;
}
// Step 5. Evaluate the position statically and update parent's gain statistics
if (inCheck)
- ss->eval = ss->evalMargin = VALUE_NONE;
- else if (tte)
{
- assert(tte->static_value() != VALUE_NONE);
+ ss->staticEval = eval = VALUE_NONE;
+ goto moves_loop;
+ }
- ss->eval = tte->static_value();
- ss->evalMargin = tte->static_value_margin();
- refinedValue = refine_eval(tte, ttValue, ss->eval);
+ else if (tte)
+ {
+ // Never assume anything on values stored in TT
+ if ((ss->staticEval = eval = tte->eval_value()) == VALUE_NONE)
+ eval = ss->staticEval = evaluate(pos);
+
+ // Can ttValue be used as a better position evaluation?
+ if (ttValue != VALUE_NONE)
+ if (tte->bound() & (ttValue > eval ? BOUND_LOWER : BOUND_UPPER))
+ eval = ttValue;
}
else
{
- refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
- TT.store(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
+ eval = ss->staticEval =
+ (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) : -(ss-1)->staticEval + 2 * Eval::Tempo;
+
+ TT.store(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, ss->staticEval);
}
- // Update gain for the parent non-capture move given the static position
- // evaluation before and after the move.
- if ( (move = (ss-1)->currentMove) != MOVE_NULL
- && (ss-1)->eval != VALUE_NONE
- && ss->eval != VALUE_NONE
- && !pos.captured_piece_type()
+ if ( !pos.captured_piece_type()
+ && ss->staticEval != VALUE_NONE
+ && (ss-1)->staticEval != VALUE_NONE
+ && (move = (ss-1)->currentMove) != MOVE_NULL
+ && move != MOVE_NONE
&& type_of(move) == NORMAL)
{
Square to = to_sq(move);
- H.update_gain(pos.piece_on(to), to, -(ss-1)->eval - ss->eval);
+ Gains.update(pos.piece_on(to), to, -(ss-1)->staticEval - ss->staticEval);
}
- // Step 6. Razoring (is omitted in PV nodes)
+ // Step 6. Razoring (skipped when in check)
if ( !PvNode
- && depth < RazorDepth
- && !inCheck
- && refinedValue + razor_margin(depth) < beta
+ && depth < 4 * ONE_PLY
+ && 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>(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.
+ if ( depth <= ONE_PLY
+ && eval + razor_margin(3 * ONE_PLY) <= alpha)
+ return qsearch<NonPV, false>(pos, ss, alpha, beta, DEPTH_ZERO);
+
+ Value ralpha = alpha - razor_margin(depth);
+ Value v = qsearch<NonPV, false>(pos, ss, ralpha, ralpha+1, DEPTH_ZERO);
+ if (v <= ralpha)
return v;
}
- // Step 7. Static null move pruning (is omitted in PV nodes)
- // We're betting that the opponent doesn't have a move that will reduce
- // the score by more than futility_margin(depth) if we do a null move.
+ // Step 7. Futility pruning: child node (skipped when in check)
if ( !PvNode
&& !ss->skipNullMove
- && depth < RazorDepth
- && !inCheck
- && refinedValue - futility_margin(depth, 0) >= beta
- && abs(beta) < VALUE_MATE_IN_MAX_PLY
+ && depth < 7 * ONE_PLY
+ && eval - futility_margin(depth) >= beta
+ && eval < VALUE_KNOWN_WIN // Do not return unproven wins
&& pos.non_pawn_material(pos.side_to_move()))
- return refinedValue - futility_margin(depth, 0);
+ return eval - futility_margin(depth);
// Step 8. Null move search with verification search (is omitted in PV nodes)
if ( !PvNode
&& !ss->skipNullMove
- && depth > ONE_PLY
- && !inCheck
- && refinedValue >= beta
- && abs(beta) < VALUE_MATE_IN_MAX_PLY
+ && depth >= 2 * ONE_PLY
+ && eval >= beta
&& pos.non_pawn_material(pos.side_to_move()))
{
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 (refinedValue - PawnValueMidgame > beta)
- R += ONE_PLY;
+ // Null move dynamic reduction based on depth and value
+ Depth R = (3 + depth / 4 + std::min(int(eval - beta) / PawnValueMg, 3)) * 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)
- : - search<NonPV>(pos, ss+1, -beta, -alpha, depth-R);
+ nullValue = depth-R < ONE_PLY ? -qsearch<NonPV, false>(pos, ss+1, -beta, -beta+1, DEPTH_ZERO)
+ : - search<NonPV, false>(pos, ss+1, -beta, -beta+1, depth-R, !cutNode);
(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 && abs(beta) < VALUE_KNOWN_WIN)
return nullValue;
// Do verification search at high depths
ss->skipNullMove = true;
- Value v = search<NonPV>(pos, ss, alpha, beta, depth-R);
+ Value v = depth-R < ONE_PLY ? qsearch<NonPV, false>(pos, ss, beta-1, beta, DEPTH_ZERO)
+ : search<NonPV, false>(pos, ss, beta-1, beta, depth-R, false);
ss->skipNullMove = false;
if (v >= beta)
return nullValue;
}
- else
- {
- // The null move failed low, which means that we may be faced with
- // some kind of threat. If the previous move was reduced, check if
- // the move that refuted the null move was somehow connected to the
- // move which was reduced. If a connection is found, return a fail
- // low score (which will cause the reduced move to fail high in the
- // parent node, which will trigger a re-search with full depth).
- threatMove = (ss+1)->currentMove;
-
- if ( depth < ThreatDepth
- && (ss-1)->reduction
- && threatMove != MOVE_NONE
- && connected_moves(pos, (ss-1)->currentMove, threatMove))
- return beta - 1;
- }
}
- // Step 9. ProbCut (is omitted in PV nodes)
+ // Step 9. ProbCut (skipped when in check)
// If we have a very good capture (i.e. SEE > seeValues[captured_piece_type])
// and a reduced search returns a value much above beta, we can (almost) safely
// prune the previous move.
if ( !PvNode
- && depth >= RazorDepth + ONE_PLY
- && !inCheck
+ && depth >= 5 * ONE_PLY
&& !ss->skipNullMove
- && excludedMove == MOVE_NONE
&& abs(beta) < VALUE_MATE_IN_MAX_PLY)
{
- Value rbeta = beta + 200;
- Depth rdepth = depth - ONE_PLY - 3 * ONE_PLY;
+ Value rbeta = std::min(beta + 200, VALUE_INFINITE);
+ Depth rdepth = depth - 4 * ONE_PLY;
assert(rdepth >= ONE_PLY);
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, History, pos.captured_piece_type());
CheckInfo ci(pos);
- while ((move = mp.next_move()) != MOVE_NONE)
- if (pos.pl_move_is_legal(move, ci.pinned))
+ while ((move = mp.next_move<false>()) != MOVE_NONE)
+ if (pos.legal(move, ci.pinned))
{
ss->currentMove = move;
- pos.do_move(move, st, ci, pos.move_gives_check(move, ci));
- value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, rdepth);
+ pos.do_move(move, st, ci, pos.gives_check(move, ci));
+ value = -search<NonPV, false>(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode);
pos.undo_move(move);
if (value >= rbeta)
return value;
}
}
- // Step 10. Internal iterative deepening
- if ( depth >= IIDDepth[PvNode]
- && ttMove == MOVE_NONE
- && (PvNode || (!inCheck && ss->eval + IIDMargin >= beta)))
+ // Step 10. Internal iterative deepening (skipped when in check)
+ if ( depth >= (PvNode ? 5 * ONE_PLY : 8 * ONE_PLY)
+ && !ttMove
+ && (PvNode || ss->staticEval + 256 >= beta))
{
- Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
-
+ Depth d = 2 * (depth - 2 * ONE_PLY) - (PvNode ? DEPTH_ZERO : depth / 2);
ss->skipNullMove = true;
- search<PvNode ? PV : NonPV>(pos, ss, alpha, beta, d);
+ search<PvNode ? PV : NonPV, false>(pos, ss, alpha, beta, d / 2, true);
ss->skipNullMove = false;
tte = TT.probe(posKey);
ttMove = tte ? tte->move() : MOVE_NONE;
}
-split_point_start: // At split points actual search starts from here
+moves_loop: // When in check and at SpNode search starts from here
+
+ Square prevMoveSq = to_sq((ss-1)->currentMove);
+ Move countermoves[] = { Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq].first,
+ Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq].second };
- MovePickerExt<SpNode> mp(pos, ttMove, depth, H, ss, PvNode ? -VALUE_INFINITE : beta);
+ 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);
- futilityBase = ss->eval + ss->evalMargin;
+ value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
+ improving = ss->staticEval >= (ss-2)->staticEval
+ || ss->staticEval == VALUE_NONE
+ ||(ss-2)->staticEval == VALUE_NONE;
+
singularExtensionNode = !RootNode
&& !SpNode
- && depth >= SingularExtensionDepth[PvNode]
+ && depth >= 8 * ONE_PLY
&& ttMove != MOVE_NONE
+ /* && ttValue != VALUE_NONE Already implicit in the next condition */
+ && abs(ttValue) < VALUE_KNOWN_WIN
&& !excludedMove // Recursive singular search is not allowed
- && (tte->type() & BOUND_LOWER)
+ && (tte->bound() & BOUND_LOWER)
&& tte->depth() >= depth - 3 * ONE_PLY;
// Step 11. Loop through moves
// Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs
- while ( bestValue < beta
- && (move = mp.next_move()) != MOVE_NONE
- && !thisThread->cutoff_occurred()
- && !Signals.stop)
+ while ((move = mp.next_move<SpNode>()) != MOVE_NONE)
{
assert(is_ok(move));
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
+ // 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 && !count(RootMoves.begin() + PVIdx, RootMoves.end(), move))
- continue;
-
- // At PV and SpNode nodes we want all moves to be legal since the beginning
- if ((PvNode || SpNode) && !pos.pl_move_is_legal(move, ci.pinned))
+ if (RootNode && !std::count(RootMoves.begin() + PVIdx, RootMoves.end(), move))
continue;
if (SpNode)
{
- moveCount = ++sp->moveCount;
- lock_release(sp->lock);
+ // Shared counter cannot be decremented later if the move turns out to be illegal
+ if (!pos.legal(move, ci.pinned))
+ continue;
+
+ moveCount = ++splitPoint->moveCount;
+ splitPoint->mutex.unlock();
}
else
- moveCount++;
+ ++moveCount;
if (RootNode)
{
Signals.firstRootMove = (moveCount == 1);
- if (thisThread == Threads.main_thread() && SearchTime.elapsed() > 2000)
- cout << "info depth " << depth / ONE_PLY
- << " currmove " << move_to_uci(move, Chess960)
- << " currmovenumber " << moveCount + PVIdx << endl;
+ if (thisThread == Threads.main() && Time::now() - SearchTime > 3000)
+ sync_cout << "info depth " << depth
+ << " currmove " << move_to_uci(move, pos.is_chess960())
+ << " currmovenumber " << moveCount + PVIdx << sync_endl;
}
- isPvMove = (PvNode && moveCount <= 1);
- captureOrPromotion = pos.is_capture_or_promotion(move);
- givesCheck = pos.move_gives_check(move, ci);
- dangerous = givesCheck || is_dangerous(pos, move, captureOrPromotion);
ext = DEPTH_ZERO;
+ captureOrPromotion = pos.capture_or_promotion(move);
- // Step 12. Extend checks and, in PV nodes, also dangerous moves
- if (PvNode && dangerous)
- ext = ONE_PLY;
+ givesCheck = type_of(move) == NORMAL && !ci.dcCandidates
+ ? ci.checkSq[type_of(pos.piece_on(from_sq(move)))] & to_sq(move)
+ : pos.gives_check(move, ci);
+
+ dangerous = givesCheck
+ || type_of(move) != NORMAL
+ || pos.advanced_pawn_push(move);
- else if (givesCheck && pos.see_sign(move) >= 0)
- ext = ONE_PLY / 2;
+ // Step 12. Extend checks
+ if (givesCheck && pos.see_sign(move) >= VALUE_ZERO)
+ ext = ONE_PLY;
// 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, if result is lower than ttValue minus
- // a margin then we extend ttMove.
+ // on all the other moves but the ttMove and if the result is lower than
+ // ttValue minus a margin then we extend the ttMove.
if ( singularExtensionNode
- && !ext
&& move == ttMove
- && pos.pl_move_is_legal(move, ci.pinned))
+ && !ext
+ && pos.legal(move, ci.pinned))
{
- if (abs(ttValue) < VALUE_KNOWN_WIN)
- {
- Value rBeta = ttValue - int(depth);
- ss->excludedMove = move;
- ss->skipNullMove = true;
- value = search<NonPV>(pos, ss, rBeta - 1, rBeta, depth / 2);
- ss->skipNullMove = false;
- ss->excludedMove = MOVE_NONE;
- if (value < rBeta)
- ext = ONE_PLY;
- }
+ Value rBeta = ttValue - int(2 * depth);
+ ss->excludedMove = move;
+ ss->skipNullMove = true;
+ value = search<NonPV, false>(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode);
+ ss->skipNullMove = false;
+ ss->excludedMove = MOVE_NONE;
+
+ if (value < rBeta)
+ ext = ONE_PLY;
}
- // Update current move (this must be done after singular extension search)
+ // Update the current move (this must be done after singular extension search)
newDepth = depth - ONE_PLY + ext;
- // Step 13. Futility pruning (is omitted in PV nodes)
+ // Step 13. Pruning at shallow depth (exclude PV nodes)
if ( !PvNode
&& !captureOrPromotion
&& !inCheck
&& !dangerous
- && move != ttMove
- && type_of(move) != CASTLE
- && (bestValue > VALUE_MATED_IN_MAX_PLY || bestValue == -VALUE_INFINITE))
+ /* && move != ttMove Already implicit in the next condition */
+ && bestValue > VALUE_MATED_IN_MAX_PLY)
{
// Move count based pruning
- if ( moveCount >= futility_move_count(depth)
- && (!threatMove || !connected_threat(pos, move, threatMove)))
+ if ( depth < 16 * ONE_PLY
+ && moveCount >= FutilityMoveCounts[improving][depth])
{
if (SpNode)
- lock_grab(sp->lock);
+ splitPoint->mutex.lock();
continue;
}
- // Value based pruning
- // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
- // but fixing this made program slightly weaker.
- Depth predictedDepth = newDepth - reduction<PvNode>(depth, moveCount);
- futilityValue = futilityBase + futility_margin(predictedDepth, moveCount)
- + H.gain(pos.piece_moved(move), to_sq(move));
+ predictedDepth = newDepth - reduction<PvNode>(improving, depth, moveCount);
- if (futilityValue < beta)
+ // Futility pruning: parent node
+ if (predictedDepth < 7 * ONE_PLY)
{
- if (SpNode)
- lock_grab(sp->lock);
-
- continue;
+ futilityValue = ss->staticEval + futility_margin(predictedDepth)
+ + 128 + Gains[pos.moved_piece(move)][to_sq(move)];
+
+ if (futilityValue <= alpha)
+ {
+ 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
- && pos.see_sign(move) < 0)
+ if (predictedDepth < 4 * ONE_PLY && pos.see_sign(move) < VALUE_ZERO)
{
if (SpNode)
- lock_grab(sp->lock);
+ splitPoint->mutex.lock();
continue;
}
}
- // Check for legality only before to do the move
- if (!pos.pl_move_is_legal(move, ci.pinned))
+ // Speculative prefetch as early as possible
+ prefetch((char*)TT.first_entry(pos.key_after(move)));
+
+ // Check for legality just before making the move
+ if (!RootNode && !SpNode && !pos.legal(move, ci.pinned))
{
moveCount--;
continue;
}
+ pvMove = PvNode && moveCount == 1;
ss->currentMove = move;
- if (!SpNode && !captureOrPromotion && playedMoveCount < 64)
- movesSearched[playedMoveCount++] = move;
+ if (!SpNode && !captureOrPromotion && quietCount < 64)
+ quietsSearched[quietCount++] = move;
// Step 14. Make the move
pos.do_move(move, st, ci, givesCheck);
- // Step 15. Reduced depth search (LMR). If the move fails high will be
+ // Step 15. Reduced depth search (LMR). If the move fails high it will be
// re-searched at full depth.
- if ( depth > 3 * ONE_PLY
- && !isPvMove
+ if ( depth >= 3 * ONE_PLY
+ && !pvMove
&& !captureOrPromotion
- && !dangerous
- && type_of(move) != CASTLE
- && ss->killers[0] != move
- && ss->killers[1] != move)
+ && move != ttMove
+ && move != ss->killers[0]
+ && move != ss->killers[1])
{
- ss->reduction = reduction<PvNode>(depth, moveCount);
+ ss->reduction = reduction<PvNode>(improving, depth, moveCount);
+
+ if ( (!PvNode && cutNode)
+ || History[pos.piece_on(to_sq(move))][to_sq(move)] < 0)
+ ss->reduction += ONE_PLY;
+
+ if (move == countermoves[0] || move == countermoves[1])
+ ss->reduction = std::max(DEPTH_ZERO, ss->reduction - ONE_PLY);
+
+ // Decrease reduction for moves that escape a capture
+ if ( ss->reduction
+ && type_of(move) == NORMAL
+ && type_of(pos.piece_on(to_sq(move))) != PAWN
+ && pos.see(make_move(to_sq(move), from_sq(move))) < 0)
+ ss->reduction = std::max(DEPTH_ZERO, ss->reduction - ONE_PLY);
+
Depth d = std::max(newDepth - ss->reduction, ONE_PLY);
- alpha = SpNode ? sp->alpha : alpha;
+ if (SpNode)
+ alpha = splitPoint->alpha;
+
+ value = -search<NonPV, false>(pos, ss+1, -(alpha+1), -alpha, d, true);
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d);
+ // Re-search at intermediate depth if reduction is very high
+ if (value > alpha && ss->reduction >= 4 * ONE_PLY)
+ {
+ Depth d2 = std::max(newDepth - 2 * ONE_PLY, ONE_PLY);
+ value = -search<NonPV, false>(pos, ss+1, -(alpha+1), -alpha, d2, true);
+ }
doFullDepthSearch = (value > alpha && ss->reduction != DEPTH_ZERO);
ss->reduction = DEPTH_ZERO;
}
else
- doFullDepthSearch = !isPvMove;
+ doFullDepthSearch = !pvMove;
// 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)
- : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth);
- }
+ if (SpNode)
+ alpha = splitPoint->alpha;
- // Only for PV nodes do a full PV search on the first move or after a fail
- // 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 && (isPvMove || (value > alpha && (RootNode || value < beta))))
- value = newDepth < ONE_PLY ? -qsearch<PV>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
- : - search<PV>(pos, ss+1, -beta, -alpha, newDepth);
+ 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, false>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode);
+ }
+ // For PV nodes only, do a full PV search on the first move or after a fail
+ // high (in the latter case search only if value < beta), otherwise let the
+ // parent node fail low with value <= alpha and to try another move.
+ if (PvNode && (pvMove || (value > alpha && (RootNode || value < beta))))
+ 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, false>(pos, ss+1, -beta, -alpha, newDepth, false);
// Step 17. Undo move
pos.undo_move(move);
// Step 18. Check for new best move
if (SpNode)
{
- lock_grab(sp->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
- // was aborted because the user interrupted the search or because we
- // 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 (RootNode && !Signals.stop)
+ // Finished searching the move. If a stop or a cutoff occurred, the return
+ // value of the search cannot be trusted, and we return immediately without
+ // updating best move, PV and TT.
+ if (Signals.stop || thisThread->cutoff_occurred())
+ return VALUE_ZERO;
+
+ if (RootNode)
{
- RootMove& rm = *find(RootMoves.begin(), RootMoves.end(), move);
+ RootMove& rm = *std::find(RootMoves.begin(), RootMoves.end(), move);
// PV move or new best move ?
- if (isPvMove || value > alpha)
+ if (pvMove || value > alpha)
{
rm.score = value;
rm.extract_pv_from_tt(pos);
// 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 (!isPvMove && MultiPV == 1)
- BestMoveChanges++;
+ if (!pvMove)
+ ++BestMoveChanges;
}
else
- // All other moves but the PV are set to the lowest value, this
- // is not a problem when sorting becuase sort is stable and move
- // position in the list is preserved, just the PV is pushed up.
+ // All other moves but the PV are set to the lowest value: this is
+ // not a problem when sorting because the sort is stable and the
+ // move position in the list is preserved - just the PV is pushed up.
rm.score = -VALUE_INFINITE;
-
}
if (value > bestValue)
{
- bestValue = value;
- bestMove = move;
-
- if ( PvNode
- && value > alpha
- && value < beta) // We want always alpha < beta
- alpha = value;
+ bestValue = SpNode ? splitPoint->bestValue = value : value;
- if (SpNode && !thisThread->cutoff_occurred())
+ if (value > alpha)
{
- sp->bestValue = value;
- sp->bestMove = move;
- sp->alpha = alpha;
+ bestMove = SpNode ? splitPoint->bestMove = move : move;
- if (value >= beta)
- sp->cutoff = true;
+ if (PvNode && value < beta) // Update alpha! Always alpha < beta
+ alpha = SpNode ? splitPoint->alpha = value : value;
+ else
+ {
+ assert(value >= beta); // Fail high
+
+ if (SpNode)
+ splitPoint->cutoff = true;
+
+ break;
+ }
}
}
- // Step 19. Check for split
+ // Step 19. Check for splitting the search
if ( !SpNode
- && depth >= Threads.min_split_depth()
- && bestValue < beta
- && Threads.available_slave_exists(thisThread)
- && !Signals.stop
- && !thisThread->cutoff_occurred())
- bestValue = Threads.split<FakeSplit>(pos, ss, alpha, beta, bestValue, &bestMove,
- depth, threatMove, moveCount, &mp, NT);
- }
+ && Threads.size() >= 2
+ && depth >= Threads.minimumSplitDepth
+ && ( !thisThread->activeSplitPoint
+ || !thisThread->activeSplitPoint->allSlavesSearching)
+ && thisThread->splitPointsSize < MAX_SPLITPOINTS_PER_THREAD)
+ {
+ assert(bestValue > -VALUE_INFINITE && bestValue < beta);
- // Step 20. Check for mate and stalemate
- // All legal moves have been searched and if there are no legal moves, it
- // must be mate or stalemate. Note that we can have a false positive in
- // case of Signals.stop or thread.cutoff_occurred() are set, but this is
- // harmless because return value is discarded anyhow in the parent nodes.
- // If we are in a singular extension search then return a fail low score.
- if (!moveCount)
- return excludedMove ? oldAlpha : inCheck ? mated_in(ss->ply) : VALUE_DRAW;
+ thisThread->split(pos, ss, alpha, beta, &bestValue, &bestMove,
+ depth, moveCount, &mp, NT, cutNode);
- // If we have pruned all the moves without searching return a fail-low score
- if (bestValue == -VALUE_INFINITE)
- {
- assert(!playedMoveCount);
+ if (Signals.stop || thisThread->cutoff_occurred())
+ return VALUE_ZERO;
- bestValue = oldAlpha;
+ if (bestValue >= beta)
+ break;
+ }
}
- // Step 21. Update tables
- // Update transposition table entry, killers and history
- if (!SpNode && !Signals.stop && !thisThread->cutoff_occurred())
- {
- move = bestValue <= oldAlpha ? MOVE_NONE : bestMove;
- bt = bestValue <= oldAlpha ? BOUND_UPPER
- : bestValue >= beta ? BOUND_LOWER : BOUND_EXACT;
+ if (SpNode)
+ return bestValue;
- TT.store(posKey, value_to_tt(bestValue, ss->ply), bt, depth, move, ss->eval, ss->evalMargin);
+ // Following condition would detect a stop or a cutoff set only after move
+ // loop has been completed. But in this case bestValue is valid because we
+ // have fully searched our subtree, and we can anyhow save the result in TT.
+ /*
+ if (Signals.stop || thisThread->cutoff_occurred())
+ return VALUE_DRAW;
+ */
- // Update killers and history for non capture cut-off moves
- if ( bestValue >= beta
- && !pos.is_capture_or_promotion(move)
- && !inCheck)
- {
- if (move != ss->killers[0])
- {
- ss->killers[1] = ss->killers[0];
- ss->killers[0] = move;
- }
+ // Step 20. Check for mate and stalemate
+ // All legal moves have been searched and if there are no legal moves, it
+ // must be mate or stalemate. If we are in a singular extension search then
+ // return a fail low score.
+ if (!moveCount)
+ bestValue = excludedMove ? alpha
+ : inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()];
- // Increase history value of the cut-off move
- Value bonus = Value(int(depth) * int(depth));
- H.add(pos.piece_moved(move), to_sq(move), bonus);
+ // Quiet best move: update killers, history, countermoves and followupmoves
+ else if (bestValue >= beta && !pos.capture_or_promotion(bestMove) && !inCheck)
+ update_stats(pos, ss, bestMove, depth, quietsSearched, quietCount - 1);
- // 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);
- }
- }
- }
+ TT.store(posKey, value_to_tt(bestValue, ss->ply),
+ bestValue >= beta ? BOUND_LOWER :
+ PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER,
+ depth, bestMove, ss->staticEval);
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
// 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);
+ const bool PvNode = NT == PV;
assert(NT == PV || NT == NonPV);
+ assert(InCheck == !!pos.checkers());
assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE);
- assert((alpha == beta - 1) || PvNode);
+ assert(PvNode || (alpha == beta - 1));
assert(depth <= DEPTH_ZERO);
StateInfo st;
- Move ttMove, move, bestMove;
- Value ttValue, bestValue, value, evalMargin, futilityValue, futilityBase;
- bool inCheck, enoughMaterial, givesCheck, evasionPrunable;
const TTEntry* tte;
+ Key posKey;
+ Move ttMove, move, bestMove;
+ Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha;
+ bool givesCheck, evasionPrunable;
Depth ttDepth;
- Bound bt;
- Value oldAlpha = alpha;
+
+ // 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)
- return VALUE_DRAW;
+ // Check for an instant draw or if the maximum ply has been reached
+ if (pos.is_draw() || ss->ply > MAX_PLY)
+ return ss->ply > MAX_PLY && !InCheck ? evaluate(pos) : DrawValue[pos.side_to_move()];
- // Decide whether or not to include checks, this fixes also the type of
+ // 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.
- inCheck = pos.in_check();
- 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.
- tte = TT.probe(pos.key());
- ttMove = (tte ? tte->move() : MOVE_NONE);
- ttValue = tte ? value_from_tt(tte->value(),ss->ply) : VALUE_ZERO;
+ ttDepth = InCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS
+ : DEPTH_QS_NO_CHECKS;
- if (!PvNode && tte && can_return_tt(tte, ttDepth, ttValue, beta))
+ // Transposition table lookup
+ posKey = pos.key();
+ tte = TT.probe(posKey);
+ ttMove = tte ? tte->move() : MOVE_NONE;
+ ttValue = tte ? value_from_tt(tte->value(),ss->ply) : VALUE_NONE;
+
+ if ( tte
+ && tte->depth() >= ttDepth
+ && ttValue != VALUE_NONE // Only in case of TT access race
+ && ( PvNode ? tte->bound() == BOUND_EXACT
+ : ttValue >= beta ? (tte->bound() & BOUND_LOWER)
+ : (tte->bound() & BOUND_UPPER)))
{
ss->currentMove = ttMove; // Can be MOVE_NONE
return ttValue;
}
// Evaluate the position statically
- if (inCheck)
+ if (InCheck)
{
+ ss->staticEval = VALUE_NONE;
bestValue = futilityBase = -VALUE_INFINITE;
- ss->eval = evalMargin = VALUE_NONE;
- enoughMaterial = false;
}
else
{
if (tte)
{
- assert(tte->static_value() != VALUE_NONE);
-
- evalMargin = tte->static_value_margin();
- ss->eval = bestValue = tte->static_value();
+ // Never assume anything on values stored in TT
+ if ((ss->staticEval = bestValue = tte->eval_value()) == VALUE_NONE)
+ ss->staticEval = bestValue = evaluate(pos);
+
+ // Can ttValue be used as a better position evaluation?
+ if (ttValue != VALUE_NONE)
+ if (tte->bound() & (ttValue > bestValue ? BOUND_LOWER : BOUND_UPPER))
+ bestValue = ttValue;
}
else
- ss->eval = bestValue = evaluate(pos, evalMargin);
+ ss->staticEval = bestValue =
+ (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) : -(ss-1)->staticEval + 2 * Eval::Tempo;
// Stand pat. Return immediately if static value is at least beta
if (bestValue >= beta)
{
if (!tte)
- TT.store(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
+ TT.store(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER,
+ DEPTH_NONE, MOVE_NONE, ss->staticEval);
return bestValue;
}
if (PvNode && bestValue > alpha)
alpha = bestValue;
- futilityBase = ss->eval + evalMargin + FutilityMarginQS;
- enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
+ futilityBase = bestValue + 128;
}
// Initialize a MovePicker object for the current position, and prepare
// 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, History, to_sq((ss-1)->currentMove));
CheckInfo ci(pos);
// Loop through the moves until no moves remain or a beta cutoff occurs
- while ( bestValue < beta
- && (move = mp.next_move()) != MOVE_NONE)
+ while ((move = mp.next_move<false>()) != MOVE_NONE)
{
assert(is_ok(move));
- givesCheck = pos.move_gives_check(move, ci);
+ givesCheck = type_of(move) == NORMAL && !ci.dcCandidates
+ ? ci.checkSq[type_of(pos.piece_on(from_sq(move)))] & to_sq(move)
+ : pos.gives_check(move, ci);
// Futility pruning
if ( !PvNode
- && !inCheck
+ && !InCheck
&& !givesCheck
&& move != ttMove
- && enoughMaterial
- && type_of(move) != PROMOTION
- && !pos.is_passed_pawn_push(move))
+ && futilityBase > -VALUE_KNOWN_WIN
+ && !pos.advanced_pawn_push(move))
{
- futilityValue = futilityBase
- + PieceValueEndgame[pos.piece_on(to_sq(move))]
- + (type_of(move) == ENPASSANT ? PawnValueEndgame : VALUE_ZERO);
+ assert(type_of(move) != ENPASSANT); // Due to !pos.advanced_pawn_push
+
+ futilityValue = futilityBase + PieceValue[EG][pos.piece_on(to_sq(move))];
if (futilityValue < beta)
{
- if (futilityValue > bestValue)
- bestValue = futilityValue;
-
+ bestValue = std::max(bestValue, futilityValue);
continue;
}
- // Prune moves with negative or equal SEE
- if ( futilityBase < beta
- && depth < DEPTH_ZERO
- && pos.see(move) <= 0)
+ if (futilityBase < beta && pos.see(move) <= VALUE_ZERO)
+ {
+ bestValue = std::max(bestValue, futilityBase);
continue;
+ }
}
- // Detect non-capture evasions that are candidate to be pruned
- evasionPrunable = !PvNode
- && inCheck
+ // Detect non-capture evasions that are candidates to be pruned
+ evasionPrunable = InCheck
&& bestValue > VALUE_MATED_IN_MAX_PLY
- && !pos.is_capture(move)
+ && !pos.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)
+ && pos.see_sign(move) < VALUE_ZERO)
continue;
- // Don't search useless checks
- if ( !PvNode
- && !inCheck
- && givesCheck
- && move != ttMove
- && !pos.is_capture_or_promotion(move)
- && ss->eval + PawnValueMidgame / 4 < beta
- && !check_is_dangerous(pos, move, futilityBase, beta))
- continue;
+ // Speculative prefetch as early as possible
+ prefetch((char*)TT.first_entry(pos.key_after(move)));
- // Check for legality only before to do the move
- if (!pos.pl_move_is_legal(move, ci.pinned))
+ // Check for legality just before making the move
+ if (!pos.legal(move, ci.pinned))
continue;
ss->currentMove = 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);
- // New best move?
+ // Check for new best move
if (value > bestValue)
{
bestValue = value;
- bestMove = move;
- if ( PvNode
- && value > alpha
- && value < beta) // We want always alpha < beta
- alpha = value;
+ if (value > alpha)
+ {
+ if (PvNode && value < beta) // Update alpha here! Always alpha < beta
+ {
+ alpha = value;
+ bestMove = move;
+ }
+ else // Fail high
+ {
+ TT.store(posKey, value_to_tt(value, ss->ply), BOUND_LOWER,
+ ttDepth, move, ss->staticEval);
+
+ return value;
+ }
+ }
}
}
// 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
- // Update transposition table
- move = bestValue <= oldAlpha ? MOVE_NONE : bestMove;
- bt = bestValue <= oldAlpha ? BOUND_UPPER
- : bestValue >= beta ? BOUND_LOWER : BOUND_EXACT;
-
- TT.store(pos.key(), value_to_tt(bestValue, ss->ply), bt, ttDepth, move, ss->eval, evalMargin);
+ TT.store(posKey, value_to_tt(bestValue, ss->ply),
+ PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER,
+ ttDepth, bestMove, ss->staticEval);
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.
-
- bool check_is_dangerous(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))
- return true;
-
- // Rule 2. 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);
- while (b)
- {
- // Note that here we generate illegal "double move"!
- if (futilityBase + PieceValueEndgame[pos.piece_on(pop_lsb(&b))] >= beta)
- return true;
- }
-
- return false;
- }
-
-
- // 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) {
-
- Square f1, t1, f2, t2;
- Piece p1, p2;
- Square ksq;
-
- assert(is_ok(m1));
- assert(is_ok(m2));
-
- // Case 1: The moving piece is the same in both moves
- f2 = from_sq(m2);
- t1 = to_sq(m1);
- if (f2 == t1)
- return true;
-
- // Case 2: The destination square for m2 was vacated by m1
- t2 = to_sq(m2);
- f1 = from_sq(m1);
- if (t2 == f1)
- return true;
-
- // Case 3: Moving through the vacated square
- p2 = pos.piece_on(f2);
- if (piece_is_slider(p2) && (between_bb(f2, t2) & f1))
- 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)
- 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))
- 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.
+ // The function is called before storing a value in the transposition table.
Value value_to_tt(Value v, int ply) {
- if (v >= VALUE_MATE_IN_MAX_PLY)
- return v + ply;
-
- if (v <= VALUE_MATED_IN_MAX_PLY)
- return v - ply;
+ assert(v != VALUE_NONE);
- return v;
+ 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 the transposition table (which 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) {
- if (v >= VALUE_MATE_IN_MAX_PLY)
- return v - ply;
-
- if (v <= VALUE_MATED_IN_MAX_PLY)
- return v + ply;
-
- return v;
+ return v == VALUE_NONE ? VALUE_NONE
+ : v >= VALUE_MATE_IN_MAX_PLY ? v - ply
+ : v <= VALUE_MATED_IN_MAX_PLY ? v + ply : v;
}
- // 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.
-
- 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));
-
- Square mfrom, mto, tfrom, tto;
-
- mfrom = from_sq(m);
- mto = to_sq(m);
- tfrom = from_sq(threat);
- tto = to_sq(threat);
-
- // Case 1: Don't prune moves which move the threatened piece
- if (mfrom == tto)
- return true;
-
- // 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)
- && ( PieceValueMidgame[pos.piece_on(tfrom)] >= PieceValueMidgame[pos.piece_on(tto)]
- || type_of(pos.piece_on(tfrom)) == KING)
- && pos.move_attacks_square(m, tto))
- 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)
- return true;
-
- return false;
- }
-
+ // update_stats() updates killers, history, countermoves and followupmoves stats after a fail-high
+ // of a quiet move.
- // can_return_tt() returns true if a transposition table score can be used to
- // cut-off at a given point in search.
+ void update_stats(const Position& pos, Stack* ss, Move move, Depth depth, Move* quiets, int quietsCnt) {
- bool can_return_tt(const TTEntry* tte, Depth depth, Value v, Value beta) {
-
- return ( tte->depth() >= depth
- || v >= std::max(VALUE_MATE_IN_MAX_PLY, beta)
- || v < std::min(VALUE_MATED_IN_MAX_PLY, beta))
-
- && ( ((tte->type() & BOUND_LOWER) && v >= beta)
- || ((tte->type() & BOUND_UPPER) && v < beta));
- }
-
-
- // refine_eval() returns the transposition table score if possible, otherwise
- // falls back on static position evaluation.
-
- Value refine_eval(const TTEntry* tte, Value v, Value defaultEval) {
-
- assert(tte);
-
- if ( ((tte->type() & BOUND_LOWER) && v >= defaultEval)
- || ((tte->type() & BOUND_UPPER) && v < defaultEval))
- return v;
-
- return defaultEval;
- }
-
-
- // score_to_uci() converts a value to a string suitable for use with the UCI
- // protocol specifications:
- //
- // cp <x> The score from the engine's point of view in centipawns.
- // mate <y> Mate in y moves, not plies. If the engine is getting mated
- // use negative values for y.
-
- string score_to_uci(Value v, Value alpha, Value beta) {
-
- std::stringstream s;
-
- if (abs(v) < VALUE_MATE_IN_MAX_PLY)
- s << "cp " << v * 100 / int(PawnValueMidgame);
- else
- s << "mate " << (v > 0 ? VALUE_MATE - v + 1 : -VALUE_MATE - v) / 2;
-
- s << (v >= beta ? " lowerbound" : v <= alpha ? " upperbound" : "");
-
- return s.str();
- }
-
-
- // pv_info_to_uci() sends search info to GUI. UCI protocol requires to send all
- // the PV lines also if are still to be searched and so refer to the previous
- // search score.
-
- void pv_info_to_uci(const Position& pos, int depth, Value alpha, Value beta) {
-
- int t = SearchTime.elapsed();
- int selDepth = 0;
-
- for (int i = 0; i < Threads.size(); i++)
- if (Threads[i].maxPly > selDepth)
- selDepth = Threads[i].maxPly;
-
- for (size_t i = 0; i < std::min(UCIMultiPV, RootMoves.size()); i++)
+ if (ss->killers[0] != move)
{
- bool updated = (i <= PVIdx);
-
- if (depth == 1 && !updated)
- continue;
-
- int d = (updated ? depth : depth - 1);
- Value v = (updated ? RootMoves[i].score : RootMoves[i].prevScore);
- std::stringstream s;
-
- for (int j = 0; RootMoves[i].pv[j] != MOVE_NONE; j++)
- s << " " << move_to_uci(RootMoves[i].pv[j], Chess960);
-
- cout << "info depth " << d
- << " seldepth " << selDepth
- << " score " << (i == PVIdx ? score_to_uci(v, alpha, beta) : score_to_uci(v))
- << " nodes " << pos.nodes_searched()
- << " nps " << (t > 0 ? pos.nodes_searched() * 1000 / t : 0)
- << " time " << t
- << " multipv " << i + 1
- << " pv" << s.str() << endl;
+ ss->killers[1] = ss->killers[0];
+ ss->killers[0] = move;
}
- }
-
-
- // pv_info_to_log() writes human-readable search information to the log file
- // (which is created when the UCI parameter "Use Search Log" is "true"). It
- // uses the two below helpers to pretty format time and score respectively.
-
- string time_to_string(int millisecs) {
-
- const int MSecMinute = 1000 * 60;
- const int MSecHour = 1000 * 60 * 60;
-
- int hours = millisecs / MSecHour;
- int minutes = (millisecs % MSecHour) / MSecMinute;
- int seconds = ((millisecs % MSecHour) % MSecMinute) / 1000;
-
- std::stringstream s;
-
- if (hours)
- s << hours << ':';
-
- s << std::setfill('0') << std::setw(2) << minutes << ':'
- << std::setw(2) << seconds;
- return s.str();
- }
-
- string score_to_string(Value v) {
-
- std::stringstream s;
-
- if (v >= VALUE_MATE_IN_MAX_PLY)
- s << "#" << (VALUE_MATE - v + 1) / 2;
- else if (v <= VALUE_MATED_IN_MAX_PLY)
- s << "-#" << (VALUE_MATE + v) / 2;
- else
- s << std::setprecision(2) << std::fixed << std::showpos
- << float(v) / PawnValueMidgame;
- return s.str();
- }
-
- void pv_info_to_log(Position& pos, int depth, Value value, int time, Move pv[]) {
-
- const int64_t K = 1000;
- const int64_t M = 1000000;
-
- StateInfo state[MAX_PLY_PLUS_2], *st = state;
- Move* m = pv;
- string san, padding;
- size_t length;
- std::stringstream s;
-
- s << std::setw(2) << depth
- << std::setw(8) << score_to_string(value)
- << std::setw(8) << time_to_string(time);
-
- if (pos.nodes_searched() < M)
- s << std::setw(8) << pos.nodes_searched() / 1 << " ";
-
- else if (pos.nodes_searched() < K * M)
- s << std::setw(7) << pos.nodes_searched() / K << "K ";
-
- else
- s << std::setw(7) << pos.nodes_searched() / M << "M ";
-
- padding = string(s.str().length(), ' ');
- length = padding.length();
-
- while (*m != MOVE_NONE)
+ // Increase history value of the cut-off move and decrease all the other
+ // played quiet moves.
+ Value bonus = Value(4 * int(depth) * int(depth));
+ History.update(pos.moved_piece(move), to_sq(move), bonus);
+ for (int i = 0; i < quietsCnt; ++i)
{
- san = move_to_san(pos, *m);
-
- if (length + san.length() > 80)
- {
- s << "\n" + padding;
- length = padding.length();
- }
-
- s << san << ' ';
- length += san.length() + 1;
-
- pos.do_move(*m++, *st++);
+ Move m = quiets[i];
+ History.update(pos.moved_piece(m), to_sq(m), -bonus);
}
- while (m != pv)
- pos.undo_move(*--m);
+ if (is_ok((ss-1)->currentMove))
+ {
+ Square prevMoveSq = to_sq((ss-1)->currentMove);
+ Countermoves.update(pos.piece_on(prevMoveSq), prevMoveSq, move);
+ }
- Log l(Options["Search Log Filename"]);
- l << s.str() << endl;
+ 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 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() {
+ // When playing with a strength handicap, choose best move among the first 'candidates'
+ // RootMoves using a statistical rule dependent on 'level'. Idea by Heinz van Saanen.
- assert(MultiPV > 1);
+ Move Skill::pick_move() {
static RKISS rk;
// PRNG sequence should be not deterministic
- for (int i = Time::current_time().msec() % 50; i > 0; i--)
+ for (int i = Time::now() % 50; i > 0; --i)
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, PawnValueMidgame);
- int weakness = 120 - 2 * SkillLevel;
+ int variance = std::min(RootMoves[0].score - RootMoves[candidates - 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,
+ // 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 < candidates; ++i)
{
int s = RootMoves[i].score;
// Don't allow crazy blunders even at very low skills
- if (i > 0 && RootMoves[i-1].score > s + EasyMoveMargin)
+ if (i > 0 && RootMoves[i - 1].score > s + 2 * PawnValueMg)
break;
// This is our magic formula
return best;
}
+
+ // uci_pv() formats PV information according to the UCI protocol. UCI
+ // requires that all (if any) unsearched PV lines are sent using a previous
+ // search score.
+
+ string uci_pv(const Position& pos, int depth, Value alpha, Value beta) {
+
+ std::stringstream ss;
+ Time::point elapsed = 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;
+
+ 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;
+
+ if (ss.rdbuf()->in_avail()) // Not at first line
+ ss << "\n";
+
+ ss << "info depth " << d
+ << " seldepth " << selDepth
+ << " score " << (i == PVIdx ? score_to_uci(v, alpha, beta) : score_to_uci(v))
+ << " nodes " << pos.nodes_searched()
+ << " nps " << pos.nodes_searched() * 1000 / elapsed
+ << " time " << elapsed
+ << " multipv " << i + 1
+ << " pv";
+
+ for (size_t j = 0; RootMoves[i].pv[j] != MOVE_NONE; ++j)
+ ss << " " << move_to_uci(RootMoves[i].pv[j], pos.is_chess960());
+ }
+
+ return ss.str();
+ }
+
} // namespace
/// RootMove::extract_pv_from_tt() builds a PV by adding moves from the TT table.
-/// We consider also failing high nodes and not only BOUND_EXACT nodes so to
-/// allow to always have a ponder move even when we fail high at root, and a
-/// long PV to print that is important for position analysis.
+/// We also consider both failing high nodes and BOUND_EXACT nodes here to
+/// ensure that we have a ponder move even when we fail high at root. This
+/// results in a long PV to print that is important for position analysis.
void RootMove::extract_pv_from_tt(Position& pos) {
- StateInfo state[MAX_PLY_PLUS_2], *st = state;
- TTEntry* tte;
- int ply = 1;
- Move m = pv[0];
-
- assert(m != MOVE_NONE && pos.is_pseudo_legal(m));
+ StateInfo state[MAX_PLY_PLUS_6], *st = state;
+ const TTEntry* tte;
+ int ply = 1; // At root ply is 1...
+ Move m = pv[0]; // ...instead pv[] array starts from 0
+ Value expectedScore = score;
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 - 1]));
+
+ pos.do_move(pv[ply++ - 1], *st++);
+ tte = TT.probe(pos.key());
+ expectedScore = -expectedScore;
+
+ } while ( tte
+ && expectedScore == value_from_tt(tte->value(), ply)
+ && pos.pseudo_legal(m = tte->move()) // Local copy, TT could change
+ && pos.legal(m, pos.pinned_pieces(pos.side_to_move()))
+ && ply < MAX_PLY
+ && (!pos.is_draw() || ply <= 2));
+
+ pv.push_back(MOVE_NONE); // Must be zero-terminating
+
+ while (--ply) pos.undo_move(pv[ply - 1]);
}
void RootMove::insert_pv_in_tt(Position& pos) {
- 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]));
+ StateInfo state[MAX_PLY_PLUS_6], *st = state;
+ const TTEntry* tte;
+ int idx = 0; // Ply starts from 1, we need to start from 0
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[idx]) // Don't overwrite correct entries
+ TT.store(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[idx], VALUE_NONE);
- } while (pv[++ply] != MOVE_NONE);
+ assert(MoveList<LEGAL>(pos).contains(pv[idx]));
- do pos.undo_move(pv[--ply]); while (ply);
-}
+ pos.do_move(pv[idx++], *st++);
+ } while (pv[idx] != MOVE_NONE);
-/// Thread::idle_loop() is where the thread is parked when it has no work to do.
-/// The parameter 'master_sp', if non-NULL, is a pointer to an active SplitPoint
-/// object for which the thread is the master.
+ while (idx) pos.undo_move(pv[--idx]);
+}
-void Thread::idle_loop(SplitPoint* sp_master) {
- // 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)
- {
- // 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 (do_exit)
- {
- assert(!sp_master);
- return;
- }
-
- // Grab the lock to avoid races with Thread::wake_up()
- lock_grab(sleepLock);
+/// Thread::idle_loop() is where the thread is parked when it has no work to do
- // If we are master and all slaves have finished don't go to sleep
- if (sp_master && !sp_master->slavesMask)
- {
- lock_release(sleepLock);
- break;
- }
+void Thread::idle_loop() {
- // 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)
- cond_wait(sleepCond, sleepLock);
+ // Pointer 'this_sp' is not null only if we are called from split(), and not
+ // at the thread creation. This means we are the split point's master.
+ SplitPoint* this_sp = splitPointsSize ? activeSplitPoint : NULL;
- lock_release(sleepLock);
- }
+ assert(!this_sp || (this_sp->masterThread == this && searching));
+ while (!exit)
+ {
// If this thread has been assigned work, launch a search
- if (is_searching)
+ while (searching)
{
- assert(!do_sleep && !do_exit);
-
- lock_grab(Threads.splitLock);
+ Threads.mutex.lock();
- assert(is_searching);
- SplitPoint* sp = curSplitPoint;
+ assert(activeSplitPoint);
+ SplitPoint* sp = activeSplitPoint;
- lock_release(Threads.splitLock);
+ Threads.mutex.unlock();
- Stack ss[MAX_PLY_PLUS_2];
+ Stack stack[MAX_PLY_PLUS_6], *ss = stack+2; // To allow referencing (ss-2)
Position pos(*sp->pos, this);
- memcpy(ss, sp->ss - 1, 4 * sizeof(Stack));
- (ss+1)->sp = sp;
+ std::memcpy(ss-2, sp->ss-2, 5 * sizeof(Stack));
+ ss->splitPoint = sp;
+
+ sp->mutex.lock();
+
+ assert(activePosition == NULL);
+
+ activePosition = &pos;
- lock_grab(sp->lock);
+ if (sp->nodeType == NonPV)
+ search<NonPV, true>(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode);
- if (sp->nodeType == Root)
- search<SplitPointRoot>(pos, ss+1, sp->alpha, sp->beta, sp->depth);
else if (sp->nodeType == PV)
- search<SplitPointPV>(pos, ss+1, sp->alpha, sp->beta, sp->depth);
- else if (sp->nodeType == NonPV)
- search<SplitPointNonPV>(pos, ss+1, sp->alpha, sp->beta, sp->depth);
+ search<PV, true>(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode);
+
+ else if (sp->nodeType == Root)
+ search<Root, true>(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode);
+
else
assert(false);
- assert(is_searching);
+ assert(searching);
- is_searching = false;
- sp->slavesMask &= ~(1ULL << idx);
+ searching = false;
+ activePosition = NULL;
+ sp->slavesMask.reset(idx);
+ sp->allSlavesSearching = false;
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
- && !sp->master->is_searching)
- sp->master->wake_up();
-
- // After releasing the lock we cannot access anymore any SplitPoint
- // related data in a safe way becuase it could have been released under
- // our feet by the sp master. Also accessing other Thread objects is
- // unsafe because if we are exiting there is a chance are already freed.
- lock_release(sp->lock);
+ // Wake up the master thread so to allow it to return from the idle
+ // loop in case we are the last slave of the split point.
+ if ( this != sp->masterThread
+ && sp->slavesMask.none())
+ {
+ assert(!sp->masterThread->searching);
+ sp->masterThread->notify_one();
+ }
+
+ // After releasing the lock we can't access any SplitPoint related data
+ // in a safe way because it could have been released under our feet by
+ // the sp master.
+ sp->mutex.unlock();
+
+ // Try to late join to another split point if none of its slaves has
+ // already finished.
+ if (Threads.size() > 2)
+ for (size_t i = 0; i < Threads.size(); ++i)
+ {
+ const int size = Threads[i]->splitPointsSize; // Local copy
+ sp = size ? &Threads[i]->splitPoints[size - 1] : NULL;
+
+ if ( sp
+ && sp->allSlavesSearching
+ && available_to(Threads[i]))
+ {
+ // Recheck the conditions under lock protection
+ Threads.mutex.lock();
+ sp->mutex.lock();
+
+ if ( sp->allSlavesSearching
+ && available_to(Threads[i]))
+ {
+ sp->slavesMask.set(idx);
+ activeSplitPoint = sp;
+ searching = true;
+ }
+
+ sp->mutex.unlock();
+ Threads.mutex.unlock();
+
+ break; // Just a single attempt
+ }
+ }
+ }
+
+ // Grab the lock to avoid races with Thread::notify_one()
+ mutex.lock();
+
+ // If we are master and all slaves have finished then exit idle_loop
+ if (this_sp && this_sp->slavesMask.none())
+ {
+ assert(!searching);
+ mutex.unlock();
+ break;
}
+
+ // If we are not searching, wait for a condition to be signaled instead of
+ // wasting CPU time polling for work.
+ if (!searching && !exit)
+ sleepCondition.wait(mutex);
+
+ mutex.unlock();
}
}
/// check_time() is called by the timer thread when the timer triggers. It is
-/// used to print debug info and, more important, to detect when we are out of
-/// available time and so stop the search.
+/// used to print debug info and, more importantly, to detect when we are out of
+/// available time and thus stop the search.
void check_time() {
- static Time lastInfoTime = Time::current_time();
+ static Time::point lastInfoTime = Time::now();
+ int64_t nodes = 0; // Workaround silly 'uninitialized' gcc warning
- if (lastInfoTime.elapsed() >= 1000)
+ if (Time::now() - lastInfoTime >= 1000)
{
- lastInfoTime.restart();
+ lastInfoTime = Time::now();
dbg_print();
}
if (Limits.ponder)
return;
- int e = SearchTime.elapsed();
+ if (Limits.nodes)
+ {
+ Threads.mutex.lock();
+
+ nodes = RootPos.nodes_searched();
+
+ // Loop across all split points and sum accumulated SplitPoint nodes plus
+ // all the currently active positions nodes.
+ for (size_t i = 0; i < Threads.size(); ++i)
+ for (int j = 0; j < Threads[i]->splitPointsSize; ++j)
+ {
+ SplitPoint& sp = Threads[i]->splitPoints[j];
+
+ sp.mutex.lock();
+
+ nodes += sp.nodes;
+
+ for (size_t idx = 0; idx < Threads.size(); ++idx)
+ if (sp.slavesMask.test(idx) && Threads[idx]->activePosition)
+ nodes += Threads[idx]->activePosition->nodes_searched();
+
+ sp.mutex.unlock();
+ }
+
+ Threads.mutex.unlock();
+ }
+
+ Time::point elapsed = Time::now() - SearchTime;
bool stillAtFirstMove = Signals.firstRootMove
&& !Signals.failedLowAtRoot
- && e > TimeMgr.available_time();
+ && elapsed > TimeMgr.available_time() * 75 / 100;
- bool noMoreTime = e > TimeMgr.maximum_time() - 2 * TimerResolution
+ bool noMoreTime = elapsed > TimeMgr.maximum_time() - 2 * TimerThread::Resolution
|| stillAtFirstMove;
if ( (Limits.use_time_management() && noMoreTime)
- || (Limits.movetime && e >= Limits.movetime))
+ || (Limits.movetime && elapsed >= Limits.movetime)
+ || (Limits.nodes && nodes >= Limits.nodes))
Signals.stop = true;
}
projects / stockfish / blobdiff