/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
#include <iostream>
#include <sstream>
-#include "book.h"
#include "evaluate.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 {
LimitsType Limits;
std::vector<RootMove> RootMoves;
Position RootPos;
- Color RootColor;
Time::point SearchTime;
StateStackPtr SetupStates;
}
namespace {
- // Set to true to force running with one thread. Used for debugging
- const bool FakeSplit = false;
-
- // This is the minimum interval in msec between two check_time() calls
- const int TimerResolution = 5;
-
// Different node types, used as template parameter
- enum NodeType { Root, PV, NonPV, SplitPointRoot, SplitPointPV, SplitPointNonPV };
+ enum NodeType { Root, PV, NonPV };
// Dynamic razoring margin based on depth
- inline Value razor_margin(Depth d) { return Value(512 + 16 * int(d)); }
+ 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[2][32]; // [improving][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;
+ inline Value futility_margin(Depth d) {
+ return Value(200 * d);
}
// Reduction lookup tables (initialized at startup) and their access function
int8_t Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber]
template <bool PvNode> inline Depth reduction(bool i, Depth d, int mn) {
-
- return (Depth) Reductions[PvNode][i][std::min(int(d) / ONE_PLY, 63)][std::min(mn, 63)];
+ return (Depth) Reductions[PvNode][i][std::min(int(d), 63)][std::min(mn, 63)];
}
- size_t PVSize, PVIdx;
+ size_t PVIdx;
TimeManager TimeMgr;
- float BestMoveChanges;
+ double BestMoveChanges;
Value DrawValue[COLOR_NB];
HistoryStats History;
GainsStats Gains;
- CountermovesStats Countermoves;
+ MovesStats Countermoves, Followupmoves;
- template <NodeType NT>
+ template <NodeType NT, bool SpNode>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode);
template <NodeType NT, bool InCheck>
void id_loop(Position& pos);
Value value_to_tt(Value v, int ply);
Value value_from_tt(Value v, int ply);
- bool allows(const Position& pos, Move first, Move second);
- bool refutes(const Position& pos, Move first, Move second);
+ 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) : level(l), best(MOVE_NONE) {}
+ Skill(int l, size_t rootSize) : level(l),
+ candidates(l < 20 ? std::min(4, (int)rootSize) : 0),
+ best(MOVE_NONE) {}
~Skill() {
- if (enabled()) // Swap best PV line with the sub-optimal one
+ 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()));
}
- bool enabled() const { return level < 20; }
+ size_t candidates_size() const { return candidates; }
bool time_to_pick(int depth) const { return depth == 1 + level; }
Move pick_move();
int level;
+ size_t candidates;
Move best;
};
void Search::init() {
- int d; // depth (ONE_PLY == 2)
- int hd; // half depth (ONE_PLY == 1)
- int mc; // moveCount
-
// Init reductions array
- for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
- {
- double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
- double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
- Reductions[1][1][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0);
- Reductions[0][1][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0);
+ for (int d = 1; d < 64; ++d)
+ for (int mc = 1; mc < 64; ++mc)
+ {
+ double pvRed = 0.00 + log(double(d)) * log(double(mc)) / 3.00;
+ double nonPVRed = 0.33 + log(double(d)) * log(double(mc)) / 2.25;
- Reductions[1][0][hd][mc] = Reductions[1][1][hd][mc];
- Reductions[0][0][hd][mc] = Reductions[0][1][hd][mc];
+ Reductions[1][1][d][mc] = int8_t( pvRed >= 1.0 ? pvRed + 0.5: 0);
+ Reductions[0][1][d][mc] = int8_t(nonPVRed >= 1.0 ? nonPVRed + 0.5: 0);
- if (Reductions[0][0][hd][mc] > 2 * ONE_PLY)
- Reductions[0][0][hd][mc] += ONE_PLY;
- }
+ Reductions[1][0][d][mc] = Reductions[1][1][d][mc];
+ Reductions[0][0][d][mc] = Reductions[0][1][d][mc];
- // 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);
+ // Increase reduction when eval is not improving
+ if (Reductions[0][0][d][mc] >= 2)
+ Reductions[0][0][d][mc] += 1;
+ }
// Init futility move count array
- for (d = 0; d < 32; d++)
+ for (int d = 0; d < 32; ++d)
{
- FutilityMoveCounts[0][d] = int(3 + 0.3 * pow(double(d ), 1.8)) * 3/4 + (2 < d && d < 5);
- FutilityMoveCounts[1][d] = int(3 + 0.3 * pow(double(d + 0.98), 1.8));
+ 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.
-
-static size_t perft(Position& pos, Depth depth) {
+template<bool Root>
+uint64_t Search::perft(Position& pos, Depth depth) {
StateInfo st;
- size_t cnt = 0;
+ uint64_t cnt, nodes = 0;
CheckInfo ci(pos);
- const bool leaf = depth == 2 * ONE_PLY;
+ const bool leaf = (depth == 2 * ONE_PLY);
for (MoveList<LEGAL> it(pos); *it; ++it)
{
- pos.do_move(*it, st, ci, pos.move_gives_check(*it, ci));
- cnt += leaf ? MoveList<LEGAL>(pos).size() : ::perft(pos, depth - ONE_PLY);
- pos.undo_move(*it);
+ 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 << UCI::format_move(*it, pos.is_chess960()) << ": " << cnt << sync_endl;
}
- return cnt;
+ return nodes;
}
-size_t Search::perft(Position& pos, Depth depth) {
- return depth > ONE_PLY ? ::perft(pos, depth) : MoveList<LEGAL>(pos).size();
-}
+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
void Search::think() {
- static PolyglotBook book; // Defined static to initialize the PRNG only once
+ TimeMgr.init(Limits, RootPos.game_ply(), RootPos.side_to_move());
- RootColor = RootPos.side_to_move();
- TimeMgr.init(Limits, RootPos.game_ply(), RootColor);
+ 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())
{
RootMoves.push_back(MOVE_NONE);
sync_cout << "info depth 0 score "
- << score_to_uci(RootPos.checkers() ? -VALUE_MATE : VALUE_DRAW)
+ << UCI::format_value(RootPos.checkers() ? -VALUE_MATE : VALUE_DRAW)
<< sync_endl;
goto finalize;
}
- if (Options["OwnBook"] && !Limits.infinite && !Limits.mate)
- {
- Move bookMove = book.probe(RootPos, Options["Book File"], Options["Best Book Move"]);
-
- if (bookMove && std::count(RootMoves.begin(), RootMoves.end(), bookMove))
- {
- std::swap(RootMoves[0], *std::find(RootMoves.begin(), RootMoves.end(), bookMove));
- goto finalize;
- }
- }
-
- 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["Write Search Log"])
- {
- Log log(Options["Search Log Filename"]);
- log << "\nSearching: " << RootPos.fen()
- << "\ninfinite: " << Limits.infinite
- << " ponder: " << Limits.ponder
- << " time: " << Limits.time[RootColor]
- << " increment: " << Limits.inc[RootColor]
- << " moves to go: " << Limits.movestogo
- << std::endl;
- }
-
- // Reset the threads, still sleeping: will be wake up at split time
+ // Reset the threads, still sleeping: will wake up at split time
for (size_t i = 0; i < Threads.size(); ++i)
Threads[i]->maxPly = 0;
- Threads.sleepWhileIdle = Options["Idle Threads Sleep"];
-
- // Set best timer interval to avoid lagging under time pressure. Timer is
- // used to check for remaining available thinking time.
- Threads.timer->msec =
- Limits.use_time_management() ? std::min(100, std::max(TimeMgr.available_time() / 16, TimerResolution)) :
- Limits.nodes ? 2 * TimerResolution
- : 100;
-
+ Threads.timer->run = true;
Threads.timer->notify_one(); // Wake up the recurring timer
id_loop(RootPos); // Let's start searching !
- Threads.timer->msec = 0; // Stop the timer
- Threads.sleepWhileIdle = true; // Send idle threads to sleep
-
- if (Options["Write Search Log"])
- {
- Time::point elapsed = Time::now() - SearchTime + 1;
-
- Log log(Options["Search Log Filename"]);
- log << "Nodes: " << RootPos.nodes_searched()
- << "\nNodes/second: " << RootPos.nodes_searched() * 1000 / elapsed
- << "\nBest move: " << move_to_san(RootPos, RootMoves[0].pv[0]);
-
- StateInfo st;
- 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]);
- }
+ Threads.timer->run = false; // Stop the timer
finalize:
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, 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).
+ // 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))
{
Signals.stopOnPonderhit = true;
}
// Best move could be MOVE_NONE when searching on a stalemate position
- 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_cout << "bestmove " << UCI::format_move(RootMoves[0].pv[0], RootPos.is_chess960())
+ << " ponder " << UCI::format_move(RootMoves[0].pv[1], RootPos.is_chess960())
<< sync_endl;
}
void id_loop(Position& pos) {
- Stack stack[MAX_PLY_PLUS_6], *ss = stack+2; // To allow referencing (ss-2)
+ Stack stack[MAX_PLY+4], *ss = stack+2; // To allow referencing (ss-2) and (ss+2)
int depth;
Value bestValue, alpha, beta, delta;
std::memset(ss-2, 0, 5 * sizeof(Stack));
- (ss-1)->currentMove = MOVE_NULL; // Hack to skip update gains
depth = 0;
BestMoveChanges = 0;
History.clear();
Gains.clear();
Countermoves.clear();
+ Followupmoves.clear();
- PVSize = Options["MultiPV"];
- Skill skill(Options["Skill Level"]);
+ 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.
- if (skill.enabled() && PVSize < 4)
- PVSize = 4;
-
- PVSize = std::min(PVSize, RootMoves.size());
+ multiPV = std::max(multiPV, skill.candidates_size());
// Iterative deepening loop until requested to stop or target depth reached
- while (++depth <= MAX_PLY && !Signals.stop && (!Limits.depth || depth <= Limits.depth))
+ while (++depth < MAX_PLY && !Signals.stop && (!Limits.depth || depth <= Limits.depth))
{
// Age out PV variability metric
- BestMoveChanges *= 0.8f;
+ BestMoveChanges *= 0.5;
- // 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.
+ // 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 < PVSize; PVIdx++)
+ for (PVIdx = 0; PVIdx < std::min(multiPV, RootMoves.size()) && !Signals.stop; ++PVIdx)
{
// Reset aspiration window starting size
if (depth >= 5)
beta = std::min(RootMoves[PVIdx].prevScore + delta, VALUE_INFINITE);
}
- // Start with a small aspiration window and, in case of fail high/low,
- // research with bigger window until not failing high/low anymore.
+ // 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)
{
- bestValue = search<Root>(pos, ss, alpha, beta, depth * ONE_PLY, false);
-
- // 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.
+ bestValue = search<Root, false>(pos, ss, alpha, beta, depth * ONE_PLY, false);
+
+ // 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
for (size_t i = 0; i <= PVIdx; ++i)
RootMoves[i].insert_pv_in_tt(pos);
- // If search has been stopped return immediately. 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)
- return;
+ break;
// When failing high/low give some update (without cluttering
- // the UI) before to research.
+ // 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 low/high increase aspiration window and
- // research, otherwise exit the loop.
+ // re-search, otherwise exit the loop.
if (bestValue <= alpha)
{
+ beta = (alpha + beta) / 2;
alpha = std::max(bestValue - delta, -VALUE_INFINITE);
Signals.failedLowAtRoot = true;
Signals.stopOnPonderhit = false;
}
else if (bestValue >= beta)
+ {
+ alpha = (alpha + beta) / 2;
beta = std::min(bestValue + delta, VALUE_INFINITE);
-
+ }
else
break;
// 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)
+ if ( !Signals.stop
+ && ( PVIdx + 1 == std::min(multiPV, RootMoves.size())
+ || Time::now() - SearchTime > 3000))
sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
}
- // Do we need to pick now the sub-optimal best move ?
- if (skill.enabled() && skill.time_to_pick(depth))
+ // 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();
- if (Options["Write Search Log"])
- {
- RootMove& rm = RootMoves[0];
- if (skill.best != MOVE_NONE)
- rm = *std::find(RootMoves.begin(), RootMoves.end(), skill.best);
-
- Log log(Options["Search Log Filename"]);
- log << pretty_pv(pos, depth, rm.score, Time::now() - SearchTime, &rm.pv[0])
- << std::endl;
- }
-
- // Do we have found a "mate in x"?
+ // 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 (Limits.use_time_management() && !Signals.stopOnPonderhit)
+ 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 && PVSize == 1)
+ // Take some extra time if the best move has changed
+ if (depth > 4 && multiPV == 1)
TimeMgr.pv_instability(BestMoveChanges);
- // 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 (Time::now() - SearchTime > (TimeMgr.available_time() * 62) / 100)
- stop = true;
-
- // Stop search early if one move seems to be much better than others
- if ( depth >= 12
- && !stop
- && PVSize == 1
- && bestValue > VALUE_MATED_IN_MAX_PLY
- && ( RootMoves.size() == 1
- || Time::now() - SearchTime > (TimeMgr.available_time() * 20) / 100))
- {
- Value rBeta = bestValue - 2 * PawnValueMg;
- ss->excludedMove = RootMoves[0].pv[0];
- ss->skipNullMove = true;
- Value v = search<NonPV>(pos, ss, rBeta - 1, rBeta, (depth - 3) * ONE_PLY, true);
- ss->skipNullMove = false;
- ss->excludedMove = MOVE_NONE;
-
- if (v < rBeta)
- stop = true;
- }
-
- if (stop)
+ // 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
// 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>
+ 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(-VALUE_INFINITE <= alpha && alpha < beta && beta <= VALUE_INFINITE);
assert(PvNode || (alpha == beta - 1));
assert(depth > DEPTH_ZERO);
const TTEntry *tte;
SplitPoint* splitPoint;
Key posKey;
- Move ttMove, move, excludedMove, bestMove, threatMove;
- Depth ext, newDepth;
- Value bestValue, value, ttValue;
- Value eval, nullValue, futilityValue;
- bool inCheck, givesCheck, pvMove, singularExtensionNode, improving;
+ Move ttMove, move, excludedMove, bestMove;
+ Depth ext, newDepth, predictedDepth;
+ Value bestValue, value, ttValue, eval, nullValue, futilityValue;
+ bool inCheck, givesCheck, singularExtensionNode, improving;
bool captureOrPromotion, dangerous, doFullDepthSearch;
int moveCount, quietCount;
{
splitPoint = ss->splitPoint;
bestMove = splitPoint->bestMove;
- threatMove = splitPoint->threatMove;
bestValue = splitPoint->bestValue;
tte = NULL;
ttMove = excludedMove = MOVE_NONE;
moveCount = quietCount = 0;
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;
// Used to send selDepth info to GUI
if (PvNode && thisThread->maxPly < ss->ply)
if (!RootNode)
{
// Step 2. Check for aborted search and immediate draw
- if (Signals.stop || pos.is_draw() || ss->ply > MAX_PLY)
- return DrawValue[pos.side_to_move()];
+ 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
- // 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.
+ // 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)
return alpha;
}
+ assert(0 <= ss->ply && ss->ply < MAX_PLY);
+
+ ss->currentMove = ss->ttMove = (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;
+
// Step 4. Transposition table lookup
// We don't want the score of a partial search to overwrite a previous full search
// TT value, so we use a different position key in case of an excluded move.
excludedMove = ss->excludedMove;
posKey = excludedMove ? pos.exclusion_key() : pos.key();
tte = TT.probe(posKey);
- ttMove = RootNode ? RootMoves[PVIdx].pv[0] : tte ? tte->move() : MOVE_NONE;
+ ss->ttMove = ttMove = RootNode ? RootMoves[PVIdx].pv[0] : tte ? tte->move() : MOVE_NONE;
ttValue = tte ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
- // At PV nodes we check for exact scores, 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
: 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->staticEval = ss->evalMargin = eval = VALUE_NONE;
+ ss->staticEval = eval = VALUE_NONE;
goto moves_loop;
}
else if (tte)
{
// 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);
+ 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() & BOUND_LOWER) && ttValue > eval)
- || ((tte->bound() & BOUND_UPPER) && ttValue < eval))
+ if (tte->bound() & (ttValue > eval ? BOUND_LOWER : BOUND_UPPER))
eval = ttValue;
}
else
{
- eval = ss->staticEval = evaluate(pos, ss->evalMargin);
- TT.store(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE,
- ss->staticEval, 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 ( !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);
// Step 6. Razoring (skipped when in check)
if ( !PvNode
&& depth < 4 * ONE_PLY
- && eval + razor_margin(depth) < beta
+ && eval + razor_margin(depth) <= alpha
&& ttMove == MOVE_NONE
- && abs(beta) < VALUE_MATE_IN_MAX_PLY
&& !pos.pawn_on_7th(pos.side_to_move()))
{
- Value rbeta = beta - razor_margin(depth);
- Value v = qsearch<NonPV, false>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO);
- if (v < rbeta)
- // Logically we should return (v + razor_margin(depth)), but
- // surprisingly this 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 (skipped when in check)
- // 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 < 4 * ONE_PLY
- && eval - futility_margin(depth, (ss-1)->futilityMoveCount) >= beta
- && abs(beta) < VALUE_MATE_IN_MAX_PLY
- && abs(eval) < VALUE_KNOWN_WIN
+ && 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 eval - futility_margin(depth, (ss-1)->futilityMoveCount);
+ return eval - futility_margin(depth);
// Step 8. Null move search with verification search (is omitted in PV nodes)
if ( !PvNode
&& !ss->skipNullMove
&& depth >= 2 * ONE_PLY
&& eval >= beta
- && abs(beta) < VALUE_MATE_IN_MAX_PLY
&& 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 (eval - PawnValueMg > 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(st);
(ss+1)->skipNullMove = true;
- nullValue = depth-R < ONE_PLY ? -qsearch<NonPV, false>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
- : - search<NonPV>(pos, ss+1, -beta, -alpha, depth-R, !cutNode);
+ nullValue = depth-R < ONE_PLY ? -qsearch<NonPV, false>(pos, ss+1, -beta, -beta+1, DEPTH_ZERO)
+ : - search<NonPV, false>(pos, ss+1, -beta, -beta+1, depth-R, !cutNode);
(ss+1)->skipNullMove = false;
pos.undo_null_move();
if (nullValue >= VALUE_MATE_IN_MAX_PLY)
nullValue = beta;
- if (depth < 12 * 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, false);
+ 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 < 5 * ONE_PLY
- && (ss-1)->reduction
- && threatMove != MOVE_NONE
- && allows(pos, (ss-1)->currentMove, threatMove))
- return alpha;
- }
}
// Step 9. ProbCut (skipped when in check)
&& !ss->skipNullMove
&& 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);
CheckInfo ci(pos);
while ((move = mp.next_move<false>()) != MOVE_NONE)
- if (pos.pl_move_is_legal(move, ci.pinned))
+ 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, !cutNode);
+ 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 (skipped when in check)
- if ( depth >= (PvNode ? 5 * ONE_PLY : 8 * ONE_PLY)
- && ttMove == MOVE_NONE
- && (PvNode || ss->staticEval + Value(256) >= beta))
+ if ( depth >= (PvNode ? 5 * ONE_PLY : 8 * ONE_PLY)
+ && !ttMove
+ && (PvNode || ss->staticEval + 256 >= beta))
{
- Depth d = depth - 2 * ONE_PLY - (PvNode ? DEPTH_ZERO : depth / 4);
-
+ Depth d = 2 * (depth - 2 * ONE_PLY) - (PvNode ? DEPTH_ZERO : depth / 2);
ss->skipNullMove = true;
- search<PvNode ? PV : NonPV>(pos, ss, alpha, beta, d, true);
+ search<PvNode ? PV : NonPV, false>(pos, ss, alpha, beta, d / 2, true);
ss->skipNullMove = false;
tte = TT.probe(posKey);
Move countermoves[] = { Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq].first,
Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq].second };
- MovePicker mp(pos, ttMove, depth, History, countermoves, ss);
+ Square prevOwnMoveSq = to_sq((ss-2)->currentMove);
+ Move followupmoves[] = { Followupmoves[pos.piece_on(prevOwnMoveSq)][prevOwnMoveSq].first,
+ Followupmoves[pos.piece_on(prevOwnMoveSq)][prevOwnMoveSq].second };
+
+ MovePicker mp(pos, ttMove, depth, History, countermoves, followupmoves, ss);
CheckInfo ci(pos);
value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
improving = ss->staticEval >= (ss-2)->staticEval
&& !SpNode
&& 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->bound() & BOUND_LOWER)
&& tte->depth() >= depth - 3 * ONE_PLY;
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 && !std::count(RootMoves.begin() + PVIdx, RootMoves.end(), move))
continue;
if (SpNode)
{
- // Shared counter cannot be decremented later if move turns out to be illegal
- if (!pos.pl_move_is_legal(move, ci.pinned))
+ // 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() && Time::now() - SearchTime > 3000)
- sync_cout << "info depth " << depth / ONE_PLY
- << " currmove " << move_to_uci(move, pos.is_chess960())
+ sync_cout << "info depth " << depth
+ << " currmove " << UCI::format_move(move, pos.is_chess960())
<< " currmovenumber " << moveCount + PVIdx << sync_endl;
}
ext = DEPTH_ZERO;
- captureOrPromotion = pos.is_capture_or_promotion(move);
- givesCheck = pos.move_gives_check(move, ci);
+ captureOrPromotion = pos.capture_or_promotion(move);
+
+ 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
- || pos.is_passed_pawn_push(move)
- || type_of(move) == CASTLE;
+ || type_of(move) != NORMAL
+ || pos.advanced_pawn_push(move);
- // Step 12. Extend checks and, in PV nodes, also dangerous moves
- if (PvNode && dangerous)
+ // Step 12. Extend checks
+ if (givesCheck && pos.see_sign(move) >= VALUE_ZERO)
ext = ONE_PLY;
- else if (givesCheck && pos.see_sign(move) >= 0)
- ext = inCheck || ss->staticEval <= alpha ? ONE_PLY : ONE_PLY / 2;
-
// 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
&& move == ttMove
&& !ext
- && pos.pl_move_is_legal(move, ci.pinned)
- && abs(ttValue) < VALUE_KNOWN_WIN)
+ && pos.legal(move, ci.pinned))
{
- assert(ttValue != VALUE_NONE);
-
- Value rBeta = ttValue - int(depth);
+ Value rBeta = ttValue - int(2 * depth);
ss->excludedMove = move;
ss->skipNullMove = true;
- value = search<NonPV>(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode);
+ value = search<NonPV, false>(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode);
ss->skipNullMove = false;
ss->excludedMove = MOVE_NONE;
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 Already implicit in the next condition */
&& bestValue > VALUE_MATED_IN_MAX_PLY)
{
// Move count based pruning
if ( depth < 16 * ONE_PLY
- && moveCount >= FutilityMoveCounts[improving][depth]
- && (!threatMove || !refutes(pos, move, threatMove)))
+ && moveCount >= FutilityMoveCounts[improving][depth])
{
if (SpNode)
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>(improving, depth, moveCount);
- futilityValue = ss->staticEval + ss->evalMargin + futility_margin(predictedDepth, moveCount)
- + Gains[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)
{
- bestValue = std::max(bestValue, futilityValue);
+ futilityValue = ss->staticEval + futility_margin(predictedDepth)
+ + 128 + Gains[pos.moved_piece(move)][to_sq(move)];
- if (SpNode)
+ if (futilityValue <= alpha)
{
- splitPoint->mutex.lock();
- if (bestValue > splitPoint->bestValue)
- splitPoint->bestValue = bestValue;
+ bestValue = std::max(bestValue, futilityValue);
+
+ if (SpNode)
+ {
+ splitPoint->mutex.lock();
+ if (bestValue > splitPoint->bestValue)
+ splitPoint->bestValue = bestValue;
+ }
+ continue;
}
- continue;
}
// Prune moves with negative SEE at low depths
- if ( predictedDepth < 4 * ONE_PLY
- && pos.see_sign(move) < 0)
+ if (predictedDepth < 4 * ONE_PLY && pos.see_sign(move) < VALUE_ZERO)
{
if (SpNode)
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 (!RootNode && !SpNode && !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 && 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
- && !pvMove
+ && moveCount > 1
&& !captureOrPromotion
- && move != ttMove
&& move != ss->killers[0]
&& move != ss->killers[1])
{
ss->reduction = reduction<PvNode>(improving, depth, moveCount);
- if (!PvNode && cutNode)
+ 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);
+ 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);
if (SpNode)
alpha = splitPoint->alpha;
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);
+ value = -search<NonPV, false>(pos, ss+1, -(alpha+1), -alpha, d, true);
+
+ // 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 = !pvMove;
+ doFullDepthSearch = !PvNode || moveCount > 1;
// Step 16. Full depth search, when LMR is skipped or fails high
if (doFullDepthSearch)
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, !cutNode);
+ 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);
}
- // 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 && (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>(pos, ss+1, -beta, -alpha, newDepth, false);
+ // 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 && (moveCount == 1 || (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);
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.
+ // 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; // To avoid returning VALUE_INFINITE
+ return VALUE_ZERO;
if (RootNode)
{
RootMove& rm = *std::find(RootMoves.begin(), RootMoves.end(), move);
// PV move or new best move ?
- if (pvMove || value > alpha)
+ if (moveCount == 1 || 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 (!pvMove)
- BestMoveChanges++;
+ if (moveCount > 1)
+ ++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;
}
// Step 19. Check for splitting the search
if ( !SpNode
+ && Threads.size() >= 2
&& depth >= Threads.minimumSplitDepth
- && Threads.available_slave(thisThread)
+ && ( !thisThread->activeSplitPoint
+ || !thisThread->activeSplitPoint->allSlavesSearching)
&& thisThread->splitPointsSize < MAX_SPLITPOINTS_PER_THREAD)
{
- assert(bestValue < beta);
+ assert(bestValue > -VALUE_INFINITE && bestValue < beta);
+
+ thisThread->split(pos, ss, alpha, beta, &bestValue, &bestMove,
+ depth, moveCount, &mp, NT, cutNode);
+
+ if (Signals.stop || thisThread->cutoff_occurred())
+ return VALUE_ZERO;
- thisThread->split<FakeSplit>(pos, ss, alpha, beta, &bestValue, &bestMove,
- depth, threatMove, moveCount, &mp, NT, cutNode);
if (bestValue >= beta)
break;
}
if (SpNode)
return bestValue;
+ // 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;
+ */
+
// 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.
- // A split node has at least one move, the one tried before to be splitted.
+ // must be mate or stalemate. If we are in a singular extension search then
+ // return a fail low score.
if (!moveCount)
- return excludedMove ? alpha
- : inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()];
+ bestValue = excludedMove ? alpha
+ : inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()];
- // If we have pruned all the moves without searching return a fail-low score
- if (bestValue == -VALUE_INFINITE)
- bestValue = alpha;
+ // 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);
TT.store(posKey, value_to_tt(bestValue, ss->ply),
bestValue >= beta ? BOUND_LOWER :
PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER,
- depth, bestMove, ss->staticEval, ss->evalMargin);
-
- // Quiet best move: update killers, history and countermoves
- if ( bestValue >= beta
- && !pos.is_capture_or_promotion(bestMove)
- && !inCheck)
- {
- if (ss->killers[0] != bestMove)
- {
- ss->killers[1] = ss->killers[0];
- ss->killers[0] = bestMove;
- }
-
- // Increase history value of the cut-off move and decrease all the other
- // played non-capture moves.
- Value bonus = Value(int(depth) * int(depth));
- History.update(pos.piece_moved(bestMove), to_sq(bestMove), bonus);
- for (int i = 0; i < quietCount - 1; ++i)
- {
- Move m = quietsSearched[i];
- History.update(pos.piece_moved(m), to_sq(m), -bonus);
- }
-
- if (is_ok((ss-1)->currentMove))
- Countermoves.update(pos.piece_on(prevMoveSq), prevMoveSq, bestMove);
- }
+ depth, bestMove, ss->staticEval);
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
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());
ss->currentMove = bestMove = MOVE_NONE;
ss->ply = (ss-1)->ply + 1;
- // Check for an instant draw or maximum ply reached
- if (pos.is_draw() || ss->ply > MAX_PLY)
- return DrawValue[pos.side_to_move()];
+ // 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
+ assert(0 <= ss->ply && ss->ply < MAX_PLY);
+
+ // 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
// Evaluate the position statically
if (InCheck)
{
- ss->staticEval = ss->evalMargin = VALUE_NONE;
+ ss->staticEval = VALUE_NONE;
bestValue = futilityBase = -VALUE_INFINITE;
}
else
if (tte)
{
// 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);
+ 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->staticEval = bestValue = evaluate(pos, ss->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->staticEval, ss->evalMargin);
+ DEPTH_NONE, MOVE_NONE, ss->staticEval);
return bestValue;
}
if (PvNode && bestValue > alpha)
alpha = bestValue;
- futilityBase = ss->staticEval + ss->evalMargin + Value(128);
+ futilityBase = bestValue + 128;
}
// Initialize a MovePicker object for the current position, and prepare
{
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
&& !givesCheck
- && move != ttMove
- && type_of(move) != PROMOTION
&& futilityBase > -VALUE_KNOWN_WIN
- && !pos.is_passed_pawn_push(move))
+ && !pos.advanced_pawn_push(move))
{
- futilityValue = futilityBase
- + PieceValue[EG][pos.piece_on(to_sq(move))]
- + (type_of(move) == ENPASSANT ? PawnValueEg : 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)
{
continue;
}
- // 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
- && pos.see(move, beta - futilityBase) <= 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
+ // 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)
- && move != ttMove
&& type_of(move) != PROMOTION
- && pos.see_sign(move) < 0)
+ && pos.see_sign(move) < VALUE_ZERO)
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 (!pos.legal(move, ci.pinned))
continue;
ss->currentMove = move;
else // Fail high
{
TT.store(posKey, value_to_tt(value, ss->ply), BOUND_LOWER,
- ttDepth, move, ss->staticEval, ss->evalMargin);
+ ttDepth, move, ss->staticEval);
return value;
}
TT.store(posKey, value_to_tt(bestValue, ss->ply),
PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER,
- ttDepth, bestMove, ss->staticEval, ss->evalMargin);
+ ttDepth, bestMove, ss->staticEval);
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
// 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) {
// 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) {
}
- // 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).
-
- bool allows(const Position& pos, Move first, Move second) {
-
- assert(is_ok(first));
- assert(is_ok(second));
- assert(color_of(pos.piece_on(from_sq(second))) == ~pos.side_to_move());
- assert(type_of(first) == CASTLE || color_of(pos.piece_on(to_sq(first))) == ~pos.side_to_move());
-
- Square m1from = from_sq(first);
- Square m2from = from_sq(second);
- Square m1to = to_sq(first);
- Square m2to = to_sq(second);
-
- // The piece is the same or second's destination was vacated by the first move
- // We exclude the trivial case where a sliding piece does in two moves what
- // it could do in one move: eg. Ra1a2, Ra2a3.
- if ( m2to == m1from
- || (m1to == m2from && !squares_aligned(m1from, m2from, m2to)))
- return true;
-
- // Second one moves through the square vacated by first one
- if (between_bb(m2from, m2to) & m1from)
- return true;
+ // update_stats() updates killers, history, countermoves and followupmoves stats after a fail-high
+ // of a quiet move.
- // 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;
+ void update_stats(const Position& pos, Stack* ss, Move move, Depth depth, Move* quiets, int quietsCnt) {
- // Second move gives a discovered check through the first's checking piece
- if (m1att & pos.king_square(pos.side_to_move()))
+ if (ss->killers[0] != move)
{
- assert(between_bb(m1to, pos.king_square(pos.side_to_move())) & m2from);
- return true;
+ ss->killers[1] = ss->killers[0];
+ ss->killers[0] = move;
}
- return false;
- }
-
-
- // 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).
-
- bool refutes(const Position& pos, Move first, Move second) {
-
- assert(is_ok(first));
- assert(is_ok(second));
-
- Square m1from = from_sq(first);
- Square m2from = from_sq(second);
- Square m1to = to_sq(first);
- Square m2to = to_sq(second);
-
- // Don't prune moves of the threatened piece
- if (m1from == m2to)
- return true;
-
- // 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))
+ // 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)
{
- // Update occupancy as if the piece and the threat are moving
- Bitboard occ = pos.pieces() ^ m1from ^ m1to ^ m2from;
- Piece pc = pos.piece_on(m1from);
-
- // The moved piece attacks the square 'tto' ?
- if (pos.attacks_from(pc, m1to, occ) & m2to)
- return true;
-
- // Scan for possible X-ray attackers behind the moved piece
- Bitboard xray = (attacks_bb< ROOK>(m2to, occ) & pos.pieces(color_of(pc), QUEEN, ROOK))
- | (attacks_bb<BISHOP>(m2to, occ) & pos.pieces(color_of(pc), QUEEN, BISHOP));
-
- // Verify attackers are triggered by our move and not already existing
- if (unlikely(xray) && (xray & ~pos.attacks_from<QUEEN>(m2to)))
- return true;
+ Move m = quiets[i];
+ History.update(pos.moved_piece(m), to_sq(m), -bonus);
}
- // Don't prune safe moves which block the threat path
- if ((between_bb(m2from, m2to) & m1to) && pos.see_sign(first) >= 0)
- return true;
+ if (is_ok((ss-1)->currentMove))
+ {
+ Square prevMoveSq = to_sq((ss-1)->currentMove);
+ Countermoves.update(pos.piece_on(prevMoveSq), prevMoveSq, move);
+ }
- return false;
+ 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 'level'. Idea by Heinz van Saanen.
+ // 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.
Move Skill::pick_move() {
static RKISS rk;
// PRNG sequence should be not deterministic
- for (int i = Time::now() % 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
- int variance = std::min(RootMoves[0].score - RootMoves[PVSize - 1].score, PawnValueMg);
+ int variance = std::min(RootMoves[0].score - RootMoves[candidates - 1].score, PawnValueMg);
int weakness = 120 - 2 * level;
int max_s = -VALUE_INFINITE;
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 < PVSize; ++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 + 2 * PawnValueMg)
+ if (i > 0 && RootMoves[i - 1].score > s + 2 * PawnValueMg)
break;
// This is our magic formula
}
- // uci_pv() formats PV information according to UCI protocol. UCI requires
- // to send all the PV lines also if are still to be searched and so refer to
- // the previous search score.
+ // 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 s;
+ std::stringstream ss;
Time::point elapsed = Time::now() - SearchTime + 1;
size_t uciPVSize = std::min((size_t)Options["MultiPV"], RootMoves.size());
int selDepth = 0;
int d = updated ? depth : depth - 1;
Value v = updated ? RootMoves[i].score : RootMoves[i].prevScore;
- if (s.rdbuf()->in_avail()) // Not at first line
- s << "\n";
+ if (ss.rdbuf()->in_avail()) // Not at first line
+ ss << "\n";
- s << "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";
+ ss << "info depth " << d
+ << " seldepth " << selDepth
+ << " multipv " << i + 1
+ << " score " << (i == PVIdx ? UCI::format_value(v, alpha, beta) : UCI::format_value(v))
+ << " nodes " << pos.nodes_searched()
+ << " nps " << pos.nodes_searched() * 1000 / elapsed
+ << " time " << elapsed
+ << " pv";
- for (size_t j = 0; RootMoves[i].pv[j] != MOVE_NONE; j++)
- s << " " << move_to_uci(RootMoves[i].pv[j], pos.is_chess960());
+ for (size_t j = 0; RootMoves[i].pv[j] != MOVE_NONE; ++j)
+ ss << " " << UCI::format_move(RootMoves[i].pv[j], pos.is_chess960());
}
- return s.str();
+ 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_6], *st = state;
+ StateInfo state[MAX_PLY], *st = state;
const TTEntry* tte;
- int ply = 0;
- Move m = pv[0];
+ int ply = 1; // At root ply is 1...
+ Move m = pv[0]; // ...instead pv[] array starts from 0
+ Value expectedScore = score;
pv.clear();
do {
pv.push_back(m);
- assert(MoveList<LEGAL>(pos).contains(pv[ply]));
+ assert(MoveList<LEGAL>(pos).contains(pv[ply - 1]));
- pos.do_move(pv[ply++], *st++);
+ pos.do_move(pv[ply++ - 1], *st++);
tte = TT.probe(pos.key());
+ expectedScore = -expectedScore;
} while ( tte
- && pos.is_pseudo_legal(m = tte->move()) // Local copy, TT could change
- && pos.pl_move_is_legal(m, pos.pinned_pieces())
+ && 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));
+ && (!pos.is_draw() || ply <= 2));
pv.push_back(MOVE_NONE); // Must be zero-terminating
- while (ply) pos.undo_move(pv[--ply]);
+ while (--ply) pos.undo_move(pv[ply - 1]);
}
void RootMove::insert_pv_in_tt(Position& pos) {
- StateInfo state[MAX_PLY_PLUS_6], *st = state;
+ StateInfo state[MAX_PLY], *st = state;
const TTEntry* tte;
- int ply = 0;
+ int idx = 0; // Ply starts from 1, we need to start from 0
do {
tte = TT.probe(pos.key());
- 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);
+ 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);
- assert(MoveList<LEGAL>(pos).contains(pv[ply]));
+ assert(MoveList<LEGAL>(pos).contains(pv[idx]));
- pos.do_move(pv[ply++], *st++);
+ pos.do_move(pv[idx++], *st++);
- } while (pv[ply] != MOVE_NONE);
+ } while (pv[idx] != MOVE_NONE);
- while (ply) pos.undo_move(pv[--ply]);
+ while (idx) pos.undo_move(pv[--idx]);
}
void Thread::idle_loop() {
// 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.
+ // at the thread creation. This means we are the split point's master.
SplitPoint* this_sp = splitPointsSize ? activeSplitPoint : NULL;
assert(!this_sp || (this_sp->masterThread == this && searching));
- while (true)
+ while (!exit)
{
- // 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 (exit)
- {
- assert(!this_sp);
- return;
- }
-
- // 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)
- {
- 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 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 (searching)
+ while (searching)
{
- assert(!exit);
-
Threads.mutex.lock();
- assert(searching);
assert(activeSplitPoint);
SplitPoint* sp = activeSplitPoint;
Threads.mutex.unlock();
- Stack stack[MAX_PLY_PLUS_6], *ss = stack+2; // To allow referencing (ss-2)
+ Stack stack[MAX_PLY+4], *ss = stack+2; // To allow referencing (ss-2) and (ss+2)
Position pos(*sp->pos, this);
std::memcpy(ss-2, sp->ss-2, 5 * sizeof(Stack));
activePosition = &pos;
- switch (sp->nodeType) {
- case Root:
- search<SplitPointRoot>(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode);
- break;
- case PV:
- search<SplitPointPV>(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode);
- break;
- case NonPV:
- search<SplitPointNonPV>(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode);
- break;
- default:
+ if (sp->nodeType == NonPV)
+ search<NonPV, true>(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode);
+
+ else if (sp->nodeType == PV)
+ 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(searching);
searching = false;
activePosition = NULL;
- sp->slavesMask &= ~(1ULL << idx);
+ 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.sleepWhileIdle
- && this != sp->masterThread
- && !sp->slavesMask)
+ // 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 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.
+ // 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
+ }
+ }
}
- // 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)
+ // 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())
{
- this_sp->mutex.lock();
- bool finished = !this_sp->slavesMask; // Retest under lock protection
- this_sp->mutex.unlock();
- if (finished)
- return;
+ 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::point lastInfoTime = Time::now();
- int64_t nodes = 0; // Workaround silly 'uninitialized' gcc warning
+ Time::point elapsed = Time::now() - SearchTime;
if (Time::now() - lastInfoTime >= 1000)
{
dbg_print();
}
- if (Limits.ponder)
- return;
+ if (Limits.use_time_management() && !Limits.ponder)
+ {
+ bool stillAtFirstMove = Signals.firstRootMove
+ && !Signals.failedLowAtRoot
+ && elapsed > TimeMgr.available_time() * 75 / 100;
- if (Limits.nodes)
+ if ( stillAtFirstMove
+ || elapsed > TimeMgr.maximum_time() - 2 * TimerThread::Resolution)
+ Signals.stop = true;
+ }
+ else if (Limits.movetime && elapsed >= Limits.movetime)
+ Signals.stop = true;
+
+ else if (Limits.nodes)
{
Threads.mutex.lock();
- nodes = RootPos.nodes_searched();
+ int64_t 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++)
+ for (int j = 0; j < Threads[i]->splitPointsSize; ++j)
{
SplitPoint& sp = Threads[i]->splitPoints[j];
sp.mutex.lock();
nodes += sp.nodes;
- Bitboard sm = sp.slavesMask;
- while (sm)
- {
- Position* pos = Threads[pop_lsb(&sm)]->activePosition;
- if (pos)
- nodes += pos->nodes_searched();
- }
+
+ 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
- && elapsed > TimeMgr.available_time();
-
- bool noMoreTime = elapsed > TimeMgr.maximum_time() - 2 * TimerResolution
- || stillAtFirstMove;
-
- if ( (Limits.use_time_management() && noMoreTime)
- || (Limits.movetime && elapsed >= Limits.movetime)
- || (Limits.nodes && nodes >= Limits.nodes))
- Signals.stop = true;
+ if (nodes >= Limits.nodes)
+ Signals.stop = true;
+ }
}