/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2015 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 <algorithm>
#include <cassert>
#include <cmath>
-#include <cstring>
+#include <cstring> // For std::memset
#include <iostream>
#include <sstream>
#include "evaluate.h"
+#include "misc.h"
#include "movegen.h"
#include "movepick.h"
-#include "rkiss.h"
#include "search.h"
#include "timeman.h"
#include "thread.h"
#include "tt.h"
#include "uci.h"
+#include "syzygy/tbprobe.h"
namespace Search {
volatile SignalsType Signals;
LimitsType Limits;
- std::vector<RootMove> RootMoves;
+ RootMoveVector RootMoves;
Position RootPos;
- Time::point SearchTime;
StateStackPtr SetupStates;
}
+namespace Tablebases {
+
+ int Cardinality;
+ uint64_t Hits;
+ bool RootInTB;
+ bool UseRule50;
+ Depth ProbeDepth;
+ Value Score;
+}
+
+namespace TB = Tablebases;
+
using std::string;
using Eval::evaluate;
using namespace Search;
// Different node types, used as template parameter
enum NodeType { Root, PV, NonPV };
- // Dynamic razoring margin based on depth
- inline Value razor_margin(Depth d) { return Value(512 + 32 * d); }
+ // Razoring and futility margin based on depth
+ Value razor_margin(Depth d) { return Value(512 + 32 * d); }
+ Value futility_margin(Depth d) { return Value(200 * d); }
- // Futility lookup tables (initialized at startup) and their access functions
- int FutilityMoveCounts[2][32]; // [improving][depth]
+ // Futility and reductions lookup tables, initialized at startup
+ int FutilityMoveCounts[2][16]; // [improving][depth]
+ Depth Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber]
- inline Value futility_margin(Depth d) {
- return Value(200 * d);
+ template <bool PvNode> Depth reduction(bool i, Depth d, int mn) {
+ return Reductions[PvNode][i][std::min(d, 63 * ONE_PLY)][std::min(mn, 63)];
}
- // Reduction lookup tables (initialized at startup) and their access function
- int8_t Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber]
+ // Skill struct is used to implement strength limiting
+ struct Skill {
+ Skill(int l) : level(l) {}
+ bool enabled() const { return level < 20; }
+ bool time_to_pick(Depth depth) const { return depth / ONE_PLY == 1 + level; }
+ Move best_move(size_t multiPV) { return best ? best : pick_best(multiPV); }
+ Move pick_best(size_t multiPV);
- 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)];
- }
+ int level;
+ Move best = MOVE_NONE;
+ };
+
+ // EasyMoveManager struct is used to detect a so called 'easy move'; when PV is
+ // stable across multiple search iterations we can fast return the best move.
+ struct EasyMoveManager {
+
+ void clear() {
+ stableCnt = 0;
+ expectedPosKey = 0;
+ pv[0] = pv[1] = pv[2] = MOVE_NONE;
+ }
+
+ Move get(Key key) const {
+ return expectedPosKey == key ? pv[2] : MOVE_NONE;
+ }
+
+ void update(Position& pos, const std::vector<Move>& newPv) {
+
+ assert(newPv.size() >= 3);
+
+ // Keep track of how many times in a row 3rd ply remains stable
+ stableCnt = (newPv[2] == pv[2]) ? stableCnt + 1 : 0;
+
+ if (!std::equal(newPv.begin(), newPv.begin() + 3, pv))
+ {
+ std::copy(newPv.begin(), newPv.begin() + 3, pv);
+
+ StateInfo st[2];
+ pos.do_move(newPv[0], st[0], pos.gives_check(newPv[0], CheckInfo(pos)));
+ pos.do_move(newPv[1], st[1], pos.gives_check(newPv[1], CheckInfo(pos)));
+ expectedPosKey = pos.key();
+ pos.undo_move(newPv[1]);
+ pos.undo_move(newPv[0]);
+ }
+ }
+
+ int stableCnt;
+ Key expectedPosKey;
+ Move pv[3];
+ };
size_t PVIdx;
- TimeManager TimeMgr;
+ EasyMoveManager EasyMove;
double BestMoveChanges;
Value DrawValue[COLOR_NB];
HistoryStats History;
- GainsStats Gains;
- MovesStats Countermoves, Followupmoves;
+ CounterMovesHistoryStats CounterMovesHistory;
+ MovesStats Countermoves;
template <NodeType NT, bool SpNode>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode);
void id_loop(Position& pos);
Value value_to_tt(Value v, int ply);
Value value_from_tt(Value v, int ply);
+ void update_pv(Move* pv, Move move, Move* childPv);
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()));
- }
-
- 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;
- };
} // namespace
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 = 0.00 + log(double(hd)) * log(double(mc)) / 3.00;
- double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
+ const double K[][2] = {{ 0.83, 2.25 }, { 0.50, 3.00 }};
- 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);
+ for (int pv = 0; pv <= 1; ++pv)
+ for (int imp = 0; imp <= 1; ++imp)
+ for (int d = 1; d < 64; ++d)
+ for (int mc = 1; mc < 64; ++mc)
+ {
+ double r = K[pv][0] + log(d) * log(mc) / K[pv][1];
- Reductions[1][0][hd][mc] = Reductions[1][1][hd][mc];
- Reductions[0][0][hd][mc] = Reductions[0][1][hd][mc];
+ if (r >= 1.5)
+ Reductions[pv][imp][d][mc] = int(r) * ONE_PLY;
- if (Reductions[0][0][hd][mc] >= 2)
- Reductions[0][0][hd][mc] += 1;
- }
+ // Increase reduction when eval is not improving
+ if (!pv && !imp && Reductions[pv][imp][d][mc] >= 2 * ONE_PLY)
+ Reductions[pv][imp][d][mc] += ONE_PLY;
+ }
- // Init futility move count array
- for (d = 0; d < 32; ++d)
+ for (int d = 0; d < 16; ++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::reset() clears all search memory, to obtain reproducible search results
+
+void Search::reset () {
+
+ TT.clear();
+ History.clear();
+ CounterMovesHistory.clear();
+ Countermoves.clear();
+}
+
+
/// 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.
template<bool Root>
CheckInfo ci(pos);
const bool leaf = (depth == 2 * ONE_PLY);
- for (MoveList<LEGAL> it(pos); *it; ++it)
+ for (const auto& m : MoveList<LEGAL>(pos))
{
if (Root && depth <= ONE_PLY)
cnt = 1, nodes++;
else
{
- pos.do_move(*it, st, ci, pos.gives_check(*it, ci));
+ pos.do_move(m, st, pos.gives_check(m, ci));
cnt = leaf ? MoveList<LEGAL>(pos).size() : perft<false>(pos, depth - ONE_PLY);
nodes += cnt;
- pos.undo_move(*it);
+ pos.undo_move(m);
}
if (Root)
- sync_cout << UCI::format_move(*it, pos.is_chess960()) << ": " << cnt << sync_endl;
+ sync_cout << UCI::move(m, pos.is_chess960()) << ": " << cnt << sync_endl;
}
return nodes;
}
void Search::think() {
- TimeMgr.init(Limits, RootPos.game_ply(), RootPos.side_to_move());
+ Color us = RootPos.side_to_move();
+ Time.init(Limits, us, RootPos.game_ply(), now());
- 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);
+ int contempt = Options["Contempt"] * PawnValueEg / 100; // From centipawns
+ DrawValue[ us] = VALUE_DRAW - Value(contempt);
+ DrawValue[~us] = VALUE_DRAW + Value(contempt);
+
+ TB::Hits = 0;
+ TB::RootInTB = false;
+ TB::UseRule50 = Options["Syzygy50MoveRule"];
+ TB::ProbeDepth = Options["SyzygyProbeDepth"] * ONE_PLY;
+ TB::Cardinality = Options["SyzygyProbeLimit"];
+
+ // Skip TB probing when no TB found: !TBLargest -> !TB::Cardinality
+ if (TB::Cardinality > TB::MaxCardinality)
+ {
+ TB::Cardinality = TB::MaxCardinality;
+ TB::ProbeDepth = DEPTH_ZERO;
+ }
if (RootMoves.empty())
{
- RootMoves.push_back(MOVE_NONE);
+ RootMoves.push_back(RootMove(MOVE_NONE));
sync_cout << "info depth 0 score "
- << UCI::format_value(RootPos.checkers() ? -VALUE_MATE : VALUE_DRAW)
+ << UCI::value(RootPos.checkers() ? -VALUE_MATE : VALUE_DRAW)
<< sync_endl;
-
- goto finalize;
}
+ else
+ {
+ if (TB::Cardinality >= RootPos.count<ALL_PIECES>(WHITE)
+ + RootPos.count<ALL_PIECES>(BLACK))
+ {
+ // If the current root position is in the tablebases then RootMoves
+ // contains only moves that preserve the draw or win.
+ TB::RootInTB = Tablebases::root_probe(RootPos, RootMoves, TB::Score);
- // 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 (TB::RootInTB)
+ TB::Cardinality = 0; // Do not probe tablebases during the search
- Threads.timer->run = true;
- Threads.timer->notify_one(); // Wake up the recurring timer
+ else // If DTZ tables are missing, use WDL tables as a fallback
+ {
+ // Filter out moves that do not preserve a draw or win
+ TB::RootInTB = Tablebases::root_probe_wdl(RootPos, RootMoves, TB::Score);
- id_loop(RootPos); // Let's start searching !
+ // Only probe during search if winning
+ if (TB::Score <= VALUE_DRAW)
+ TB::Cardinality = 0;
+ }
+
+ if (TB::RootInTB)
+ {
+ TB::Hits = RootMoves.size();
+
+ if (!TB::UseRule50)
+ TB::Score = TB::Score > VALUE_DRAW ? VALUE_MATE - MAX_PLY - 1
+ : TB::Score < VALUE_DRAW ? -VALUE_MATE + MAX_PLY + 1
+ : VALUE_DRAW;
+ }
+ }
- Threads.timer->run = false; // Stop the timer
+ for (Thread* th : Threads)
+ {
+ th->maxPly = 0;
+ th->notify_one(); // Wake up all the threads
+ }
+
+ Threads.timer->run = true;
+ Threads.timer->notify_one(); // Start the recurring timer
-finalize:
+ id_loop(RootPos); // Let's start searching !
- // When search is stopped this info is not printed
- sync_cout << "info nodes " << RootPos.nodes_searched()
- << " time " << Time::now() - SearchTime + 1 << sync_endl;
+ Threads.timer->run = false;
+ }
+
+ // When playing in 'nodes as time' mode, subtract the searched nodes from
+ // the available ones before to exit.
+ if (Limits.npmsec)
+ Time.availableNodes += Limits.inc[us] - RootPos.nodes_searched();
// 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,
RootPos.this_thread()->wait_for(Signals.stop);
}
- // Best move could be MOVE_NONE when searching on a stalemate position
- 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;
+ sync_cout << "bestmove " << UCI::move(RootMoves[0].pv[0], RootPos.is_chess960());
+
+ if (RootMoves[0].pv.size() > 1 || RootMoves[0].extract_ponder_from_tt(RootPos))
+ std::cout << " ponder " << UCI::move(RootMoves[0].pv[1], RootPos.is_chess960());
+
+ std::cout << sync_endl;
}
void id_loop(Position& pos) {
Stack stack[MAX_PLY+4], *ss = stack+2; // To allow referencing (ss-2) and (ss+2)
- int depth;
+ Depth depth;
Value bestValue, alpha, beta, delta;
+ Move easyMove = EasyMove.get(pos.key());
+ EasyMove.clear();
+
std::memset(ss-2, 0, 5 * sizeof(Stack));
- depth = 0;
+ depth = DEPTH_ZERO;
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());
+ Skill skill(Options["Skill Level"]);
+
+ // When playing with strength handicap enable MultiPV search that we will
+ // use behind the scenes to retrieve a set of possible moves.
+ if (skill.enabled())
+ multiPV = std::max(multiPV, (size_t)4);
- // 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());
+ multiPV = std::min(multiPV, RootMoves.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 < DEPTH_MAX && !Signals.stop && (!Limits.depth || depth <= Limits.depth))
{
// Age out PV variability metric
BestMoveChanges *= 0.5;
// 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;
+ for (RootMove& rm : RootMoves)
+ rm.previousScore = rm.score;
// MultiPV loop. We perform a full root search for each PV line
- for (PVIdx = 0; PVIdx < std::min(multiPV, RootMoves.size()) && !Signals.stop; ++PVIdx)
+ for (PVIdx = 0; PVIdx < multiPV && !Signals.stop; ++PVIdx)
{
// Reset aspiration window starting size
- if (depth >= 5)
+ if (depth >= 5 * ONE_PLY)
{
delta = Value(16);
- alpha = std::max(RootMoves[PVIdx].prevScore - delta,-VALUE_INFINITE);
- beta = std::min(RootMoves[PVIdx].prevScore + delta, VALUE_INFINITE);
+ alpha = std::max(RootMoves[PVIdx].previousScore - delta,-VALUE_INFINITE);
+ beta = std::min(RootMoves[PVIdx].previousScore + delta, VALUE_INFINITE);
}
// Start with a small aspiration window and, in the case of a fail
// high/low anymore.
while (true)
{
- bestValue = search<Root, false>(pos, ss, alpha, beta, depth * ONE_PLY, false);
+ bestValue = search<Root, false>(pos, ss, alpha, beta, depth, 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
// 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;
+ if ( multiPV == 1
+ && (bestValue <= alpha || bestValue >= beta)
+ && Time.elapsed() > 3000)
+ sync_cout << UCI::pv(pos, depth, alpha, beta) << sync_endl;
// In case of failing low/high increase aspiration window and
// 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;
- delta += 3 * delta / 8;
+ delta += delta / 2;
assert(alpha >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
}
// Sort the PV lines searched so far and update the GUI
std::stable_sort(RootMoves.begin(), RootMoves.begin() + PVIdx + 1);
- if ( !Signals.stop
- && ( PVIdx + 1 == std::min(multiPV, RootMoves.size())
- || Time::now() - SearchTime > 3000))
- sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
+ if (Signals.stop)
+ sync_cout << "info nodes " << RootPos.nodes_searched()
+ << " time " << Time.elapsed() << sync_endl;
+
+ else if (PVIdx + 1 == multiPV || Time.elapsed() > 3000)
+ sync_cout << UCI::pv(pos, depth, alpha, beta) << sync_endl;
}
- // 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 skill level is enabled and time is up, pick a sub-optimal best move
+ if (skill.enabled() && skill.time_to_pick(depth))
+ skill.pick_best(multiPV);
// Have we found a "mate in x"?
if ( Limits.mate
Signals.stop = true;
// Do we have time for the next iteration? Can we stop searching now?
- if (Limits.use_time_management() && !Signals.stop && !Signals.stopOnPonderhit)
+ if (Limits.use_time_management())
{
- // 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 (!Signals.stop && !Signals.stopOnPonderhit)
{
- // If we are allowed to ponder do not stop the search now but
- // keep pondering until the GUI sends "ponderhit" or "stop".
- if (Limits.ponder)
- Signals.stopOnPonderhit = true;
- else
- Signals.stop = true;
+ // Take some extra time if the best move has changed
+ if (depth > 4 * ONE_PLY && multiPV == 1)
+ Time.pv_instability(BestMoveChanges);
+
+ // Stop the search if only one legal move is available or all
+ // of the available time has been used or we matched an easyMove
+ // from the previous search and just did a fast verification.
+ if ( RootMoves.size() == 1
+ || Time.elapsed() > Time.available()
+ || ( RootMoves[0].pv[0] == easyMove
+ && BestMoveChanges < 0.03
+ && Time.elapsed() > Time.available() / 10))
+ {
+ // If we are allowed to ponder do not stop the search now but
+ // keep pondering until the GUI sends "ponderhit" or "stop".
+ if (Limits.ponder)
+ Signals.stopOnPonderhit = true;
+ else
+ Signals.stop = true;
+ }
}
+
+ if (RootMoves[0].pv.size() >= 3)
+ EasyMove.update(pos, RootMoves[0].pv);
+ else
+ EasyMove.clear();
}
}
+
+ // Clear any candidate easy move that wasn't stable for the last search
+ // iterations; the second condition prevents consecutive fast moves.
+ if (EasyMove.stableCnt < 6 || Time.elapsed() < Time.available())
+ EasyMove.clear();
+
+ // If skill level is enabled, swap best PV line with the sub-optimal one
+ if (skill.enabled())
+ std::swap(RootMoves[0], *std::find(RootMoves.begin(),
+ RootMoves.end(), skill.best_move(multiPV)));
}
assert(PvNode || (alpha == beta - 1));
assert(depth > DEPTH_ZERO);
- Move quietsSearched[64];
+ Move pv[MAX_PLY+1], quietsSearched[64];
StateInfo st;
- const TTEntry *tte;
+ TTEntry* tte;
SplitPoint* splitPoint;
Key posKey;
Move ttMove, move, excludedMove, bestMove;
- Depth ext, newDepth, predictedDepth;
+ Depth extension, newDepth, predictedDepth;
Value bestValue, value, ttValue, eval, nullValue, futilityValue;
- bool inCheck, givesCheck, pvMove, singularExtensionNode, improving;
+ bool ttHit, inCheck, givesCheck, singularExtensionNode, improving;
bool captureOrPromotion, dangerous, doFullDepthSearch;
int moveCount, quietCount;
splitPoint = ss->splitPoint;
bestMove = splitPoint->bestMove;
bestValue = splitPoint->bestValue;
- tte = NULL;
+ tte = nullptr;
+ ttHit = false;
ttMove = excludedMove = MOVE_NONE;
ttValue = VALUE_NONE;
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+1)->skipEarlyPruning = false; (ss+1)->reduction = DEPTH_ZERO;
(ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
// Step 4. Transposition table lookup
// 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);
- ss->ttMove = ttMove = RootNode ? RootMoves[PVIdx].pv[0] : tte ? tte->move() : MOVE_NONE;
- ttValue = tte ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
-
- // At PV nodes we check for exact scores, whilst at non-PV nodes we check for
- // 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
+ tte = TT.probe(posKey, ttHit);
+ ss->ttMove = ttMove = RootNode ? RootMoves[PVIdx].pv[0] : ttHit ? tte->move() : MOVE_NONE;
+ ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
+
+ // At non-PV nodes we check for a fail high/low. We don't prune at PV nodes
+ if ( !PvNode
+ && ttHit
&& 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)))
+ && (ttValue >= beta ? (tte->bound() & BOUND_LOWER)
+ : (tte->bound() & BOUND_UPPER)))
{
ss->currentMove = ttMove; // Can be MOVE_NONE
- // If ttMove is quiet, update killers, history, counter move and followup move on TT hit
- if (ttValue >= beta && ttMove && !pos.capture_or_promotion(ttMove) && !inCheck)
- update_stats(pos, ss, ttMove, depth, NULL, 0);
+ // If ttMove is quiet, update killers, history, counter move on TT hit
+ if (ttValue >= beta && ttMove && !pos.capture_or_promotion(ttMove))
+ update_stats(pos, ss, ttMove, depth, nullptr, 0);
return ttValue;
}
- // Step 5. Evaluate the position statically and update parent's gain statistics
+ // Step 4a. Tablebase probe
+ if (!RootNode && TB::Cardinality)
+ {
+ int piecesCnt = pos.count<ALL_PIECES>(WHITE) + pos.count<ALL_PIECES>(BLACK);
+
+ if ( piecesCnt <= TB::Cardinality
+ && (piecesCnt < TB::Cardinality || depth >= TB::ProbeDepth)
+ && pos.rule50_count() == 0)
+ {
+ int found, v = Tablebases::probe_wdl(pos, &found);
+
+ if (found)
+ {
+ TB::Hits++;
+
+ int drawScore = TB::UseRule50 ? 1 : 0;
+
+ value = v < -drawScore ? -VALUE_MATE + MAX_PLY + ss->ply
+ : v > drawScore ? VALUE_MATE - MAX_PLY - ss->ply
+ : VALUE_DRAW + 2 * v * drawScore;
+
+ tte->save(posKey, value_to_tt(value, ss->ply), BOUND_EXACT,
+ std::min(DEPTH_MAX - ONE_PLY, depth + 6 * ONE_PLY),
+ MOVE_NONE, VALUE_NONE, TT.generation());
+
+ return value;
+ }
+ }
+ }
+
+ // Step 5. Evaluate the position statically
if (inCheck)
{
ss->staticEval = eval = VALUE_NONE;
goto moves_loop;
}
- else if (tte)
+ else if (ttHit)
{
// Never assume anything on values stored in TT
- if ((ss->staticEval = eval = tte->eval_value()) == VALUE_NONE)
+ if ((ss->staticEval = eval = tte->eval()) == VALUE_NONE)
eval = ss->staticEval = evaluate(pos);
// Can ttValue be used as a better position evaluation?
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);
+ tte->save(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, ss->staticEval, TT.generation());
}
- 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);
- Gains.update(pos.piece_on(to), to, -(ss-1)->staticEval - ss->staticEval);
- }
+ if (ss->skipEarlyPruning)
+ goto moves_loop;
// Step 6. Razoring (skipped when in check)
if ( !PvNode
}
// Step 7. Futility pruning: child node (skipped when in check)
- if ( !PvNode
- && !ss->skipNullMove
+ if ( !RootNode
&& depth < 7 * ONE_PLY
&& eval - futility_margin(depth) >= beta
&& eval < VALUE_KNOWN_WIN // Do not return unproven wins
// Step 8. Null move search with verification search (is omitted in PV nodes)
if ( !PvNode
- && !ss->skipNullMove
&& depth >= 2 * ONE_PLY
&& eval >= beta
&& pos.non_pawn_material(pos.side_to_move()))
assert(eval - beta >= 0);
// Null move dynamic reduction based on depth and value
- Depth R = (3 + depth / 4 + std::min(int(eval - beta) / PawnValueMg, 3)) * ONE_PLY;
+ Depth R = ((823 + 67 * depth) / 256 + std::min((eval - beta) / PawnValueMg, 3)) * ONE_PLY;
pos.do_null_move(st);
- (ss+1)->skipNullMove = true;
+ (ss+1)->skipEarlyPruning = true;
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;
+ (ss+1)->skipEarlyPruning = false;
pos.undo_null_move();
if (nullValue >= beta)
return nullValue;
// Do verification search at high depths
- ss->skipNullMove = true;
+ ss->skipEarlyPruning = true;
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;
+ ss->skipEarlyPruning = false;
if (v >= beta)
return nullValue;
// prune the previous move.
if ( !PvNode
&& depth >= 5 * ONE_PLY
- && !ss->skipNullMove
&& abs(beta) < VALUE_MATE_IN_MAX_PLY)
{
Value rbeta = std::min(beta + 200, VALUE_INFINITE);
assert((ss-1)->currentMove != MOVE_NONE);
assert((ss-1)->currentMove != MOVE_NULL);
- MovePicker mp(pos, ttMove, History, pos.captured_piece_type());
+ MovePicker mp(pos, ttMove, History, CounterMovesHistory, pos.captured_piece_type());
CheckInfo ci(pos);
while ((move = mp.next_move<false>()) != MOVE_NONE)
if (pos.legal(move, ci.pinned))
{
ss->currentMove = move;
- pos.do_move(move, st, ci, pos.gives_check(move, ci));
+ pos.do_move(move, st, pos.gives_check(move, ci));
value = -search<NonPV, false>(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode);
pos.undo_move(move);
if (value >= rbeta)
&& (PvNode || ss->staticEval + 256 >= beta))
{
Depth d = 2 * (depth - 2 * ONE_PLY) - (PvNode ? DEPTH_ZERO : depth / 2);
- ss->skipNullMove = true;
+ ss->skipEarlyPruning = true;
search<PvNode ? PV : NonPV, false>(pos, ss, alpha, beta, d / 2, true);
- ss->skipNullMove = false;
+ ss->skipEarlyPruning = false;
- tte = TT.probe(posKey);
- ttMove = tte ? tte->move() : MOVE_NONE;
+ tte = TT.probe(posKey, ttHit);
+ ttMove = ttHit ? tte->move() : MOVE_NONE;
}
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 };
-
- Square prevOwnMoveSq = to_sq((ss-2)->currentMove);
- Move followupmoves[] = { Followupmoves[pos.piece_on(prevOwnMoveSq)][prevOwnMoveSq].first,
- Followupmoves[pos.piece_on(prevOwnMoveSq)][prevOwnMoveSq].second };
+ Move countermove = Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq];
- MovePicker mp(pos, ttMove, depth, History, countermoves, followupmoves, ss);
+ MovePicker mp(pos, ttMove, depth, History, CounterMovesHistory, countermove, ss);
CheckInfo ci(pos);
value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
improving = ss->staticEval >= (ss-2)->staticEval
continue;
moveCount = ++splitPoint->moveCount;
- splitPoint->mutex.unlock();
+ splitPoint->spinlock.release();
}
else
++moveCount;
{
Signals.firstRootMove = (moveCount == 1);
- if (thisThread == Threads.main() && Time::now() - SearchTime > 3000)
- sync_cout << "info depth " << depth
- << " currmove " << UCI::format_move(move, pos.is_chess960())
+ if (thisThread == Threads.main() && Time.elapsed() > 3000)
+ sync_cout << "info depth " << depth / ONE_PLY
+ << " currmove " << UCI::move(move, pos.is_chess960())
<< " currmovenumber " << moveCount + PVIdx << sync_endl;
}
- ext = DEPTH_ZERO;
+ if (PvNode)
+ (ss+1)->pv = nullptr;
+
+ extension = DEPTH_ZERO;
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)
+ ? ci.checkSquares[type_of(pos.piece_on(from_sq(move)))] & to_sq(move)
: pos.gives_check(move, ci);
dangerous = givesCheck
// Step 12. Extend checks
if (givesCheck && pos.see_sign(move) >= VALUE_ZERO)
- ext = ONE_PLY;
+ extension = 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
// ttValue minus a margin then we extend the ttMove.
if ( singularExtensionNode
&& move == ttMove
- && !ext
+ && !extension
&& pos.legal(move, ci.pinned))
{
- Value rBeta = ttValue - int(2 * depth);
+ Value rBeta = ttValue - 2 * depth / ONE_PLY;
ss->excludedMove = move;
- ss->skipNullMove = true;
+ ss->skipEarlyPruning = true;
value = search<NonPV, false>(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode);
- ss->skipNullMove = false;
+ ss->skipEarlyPruning = false;
ss->excludedMove = MOVE_NONE;
if (value < rBeta)
- ext = ONE_PLY;
+ extension = ONE_PLY;
}
// Update the current move (this must be done after singular extension search)
- newDepth = depth - ONE_PLY + ext;
+ newDepth = depth - ONE_PLY + extension;
- // Step 13. Pruning at shallow depth (exclude PV nodes)
- if ( !PvNode
+ // Step 13. Pruning at shallow depth
+ if ( !RootNode
&& !captureOrPromotion
&& !inCheck
&& !dangerous
- /* && move != ttMove Already implicit in the next condition */
&& bestValue > VALUE_MATED_IN_MAX_PLY)
{
// Move count based pruning
&& moveCount >= FutilityMoveCounts[improving][depth])
{
if (SpNode)
- splitPoint->mutex.lock();
+ splitPoint->spinlock.acquire();
continue;
}
// Futility pruning: parent node
if (predictedDepth < 7 * ONE_PLY)
{
- futilityValue = ss->staticEval + futility_margin(predictedDepth)
- + 128 + Gains[pos.moved_piece(move)][to_sq(move)];
+ futilityValue = ss->staticEval + futility_margin(predictedDepth) + 256;
if (futilityValue <= alpha)
{
if (SpNode)
{
- splitPoint->mutex.lock();
+ splitPoint->spinlock.acquire();
if (bestValue > splitPoint->bestValue)
splitPoint->bestValue = bestValue;
}
if (predictedDepth < 4 * ONE_PLY && pos.see_sign(move) < VALUE_ZERO)
{
if (SpNode)
- splitPoint->mutex.lock();
+ splitPoint->spinlock.acquire();
continue;
}
}
// Speculative prefetch as early as possible
- prefetch((char*)TT.first_entry(pos.key_after(move)));
+ prefetch(TT.first_entry(pos.key_after(move)));
// Check for legality just before making the move
if (!RootNode && !SpNode && !pos.legal(move, ci.pinned))
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);
+ pos.do_move(move, st, givesCheck);
// 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)
- || History[pos.piece_on(to_sq(move))][to_sq(move)] < 0)
+ || ( History[pos.piece_on(to_sq(move))][to_sq(move)] < VALUE_ZERO
+ && CounterMovesHistory[pos.piece_on(prevMoveSq)][prevMoveSq]
+ [pos.piece_on(to_sq(move))][to_sq(move)] <= VALUE_ZERO))
ss->reduction += ONE_PLY;
- if (move == countermoves[0] || move == countermoves[1])
+ if ( move == countermove
+ || ( History[pos.piece_on(to_sq(move))][to_sq(move)] > VALUE_ZERO
+ && CounterMovesHistory[pos.piece_on(prevMoveSq)][prevMoveSq]
+ [pos.piece_on(to_sq(move))][to_sq(move)] > VALUE_ZERO))
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)
+ && pos.see(make_move(to_sq(move), from_sq(move))) < VALUE_ZERO)
ss->reduction = std::max(DEPTH_ZERO, ss->reduction - ONE_PLY);
Depth d = std::max(newDepth - ss->reduction, ONE_PLY);
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)
// 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))))
+ if (PvNode && (moveCount == 1 || (value > alpha && (RootNode || value < beta))))
+ {
+ (ss+1)->pv = pv;
+ (ss+1)->pv[0] = MOVE_NONE;
+
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)
{
- splitPoint->mutex.lock();
+ splitPoint->spinlock.acquire();
bestValue = splitPoint->bestValue;
alpha = splitPoint->alpha;
}
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);
+ rm.pv.resize(1);
+
+ assert((ss+1)->pv);
+
+ for (Move* m = (ss+1)->pv; *m != MOVE_NONE; ++m)
+ rm.pv.push_back(*m);
// 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)
+ if (moveCount > 1)
++BestMoveChanges;
}
else
if (value > alpha)
{
+ // If there is an easy move for this position, clear it if unstable
+ if ( PvNode
+ && EasyMove.get(pos.key())
+ && (move != EasyMove.get(pos.key()) || moveCount > 1))
+ EasyMove.clear();
+
bestMove = SpNode ? splitPoint->bestMove = move : move;
+ if (PvNode && !RootNode) // Update pv even in fail-high case
+ update_pv(SpNode ? splitPoint->ss->pv : ss->pv, move, (ss+1)->pv);
+
if (PvNode && value < beta) // Update alpha! Always alpha < beta
alpha = SpNode ? splitPoint->alpha = value : value;
else
}
}
+ if (!SpNode && !captureOrPromotion && move != bestMove && quietCount < 64)
+ quietsSearched[quietCount++] = move;
+
// Step 19. Check for splitting the search
if ( !SpNode
&& Threads.size() >= 2
&& depth >= Threads.minimumSplitDepth
&& ( !thisThread->activeSplitPoint
- || !thisThread->activeSplitPoint->allSlavesSearching)
+ || !thisThread->activeSplitPoint->allSlavesSearching
+ || ( Threads.size() > MAX_SLAVES_PER_SPLITPOINT
+ && thisThread->activeSplitPoint->slavesMask.count() == MAX_SLAVES_PER_SPLITPOINT))
&& thisThread->splitPointsSize < MAX_SPLITPOINTS_PER_THREAD)
{
assert(bestValue > -VALUE_INFINITE && bestValue < beta);
bestValue = excludedMove ? alpha
: inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()];
- // 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);
+ // Quiet best move: update killers, history and countermoves
+ else if (bestMove && !pos.capture_or_promotion(bestMove))
+ update_stats(pos, ss, bestMove, depth, quietsSearched, quietCount);
- TT.store(posKey, value_to_tt(bestValue, ss->ply),
- bestValue >= beta ? BOUND_LOWER :
- PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER,
- depth, bestMove, ss->staticEval);
+ tte->save(posKey, value_to_tt(bestValue, ss->ply),
+ bestValue >= beta ? BOUND_LOWER :
+ PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER,
+ depth, bestMove, ss->staticEval, TT.generation());
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
assert(PvNode || (alpha == beta - 1));
assert(depth <= DEPTH_ZERO);
+ Move pv[MAX_PLY+1];
StateInfo st;
- const TTEntry* tte;
+ TTEntry* tte;
Key posKey;
Move ttMove, move, bestMove;
Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha;
- bool givesCheck, evasionPrunable;
+ bool ttHit, givesCheck, evasionPrunable;
Depth ttDepth;
- // To flag BOUND_EXACT a node with eval above alpha and no available moves
if (PvNode)
- oldAlpha = alpha;
+ {
+ oldAlpha = alpha; // To flag BOUND_EXACT when eval above alpha and no available moves
+ (ss+1)->pv = pv;
+ ss->pv[0] = MOVE_NONE;
+ }
ss->currentMove = bestMove = MOVE_NONE;
ss->ply = (ss-1)->ply + 1;
// 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;
+ tte = TT.probe(posKey, ttHit);
+ ttMove = ttHit ? tte->move() : MOVE_NONE;
+ ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
- if ( tte
+ if ( !PvNode
+ && ttHit
&& 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)))
+ && (ttValue >= beta ? (tte->bound() & BOUND_LOWER)
+ : (tte->bound() & BOUND_UPPER)))
{
ss->currentMove = ttMove; // Can be MOVE_NONE
return ttValue;
}
else
{
- if (tte)
+ if (ttHit)
{
// Never assume anything on values stored in TT
- if ((ss->staticEval = bestValue = tte->eval_value()) == VALUE_NONE)
+ if ((ss->staticEval = bestValue = tte->eval()) == VALUE_NONE)
ss->staticEval = bestValue = evaluate(pos);
// Can ttValue be used as a better position evaluation?
// 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);
+ if (!ttHit)
+ tte->save(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER,
+ DEPTH_NONE, MOVE_NONE, ss->staticEval, TT.generation());
return bestValue;
}
// 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, History, to_sq((ss-1)->currentMove));
+ MovePicker mp(pos, ttMove, depth, History, CounterMovesHistory, to_sq((ss-1)->currentMove));
CheckInfo ci(pos);
// Loop through the moves until no moves remain or a beta cutoff occurs
assert(is_ok(move));
givesCheck = type_of(move) == NORMAL && !ci.dcCandidates
- ? ci.checkSq[type_of(pos.piece_on(from_sq(move)))] & to_sq(move)
+ ? ci.checkSquares[type_of(pos.piece_on(from_sq(move)))] & to_sq(move)
: pos.gives_check(move, ci);
// Futility pruning
- if ( !PvNode
- && !InCheck
+ if ( !InCheck
&& !givesCheck
- && move != ttMove
&& futilityBase > -VALUE_KNOWN_WIN
&& !pos.advanced_pawn_push(move))
{
futilityValue = futilityBase + PieceValue[EG][pos.piece_on(to_sq(move))];
- if (futilityValue < beta)
+ if (futilityValue <= alpha)
{
bestValue = std::max(bestValue, futilityValue);
continue;
}
- if (futilityBase < beta && pos.see(move) <= VALUE_ZERO)
+ if (futilityBase <= alpha && pos.see(move) <= VALUE_ZERO)
{
bestValue = std::max(bestValue, futilityBase);
continue;
// Detect non-capture evasions that are candidates to be pruned
evasionPrunable = InCheck
&& bestValue > VALUE_MATED_IN_MAX_PLY
- && !pos.capture(move)
- && !pos.can_castle(pos.side_to_move());
+ && !pos.capture(move);
// Don't search moves with negative SEE values
- if ( !PvNode
- && (!InCheck || evasionPrunable)
- && move != ttMove
+ if ( (!InCheck || evasionPrunable)
&& type_of(move) != PROMOTION
&& pos.see_sign(move) < VALUE_ZERO)
continue;
// Speculative prefetch as early as possible
- prefetch((char*)TT.first_entry(pos.key_after(move)));
+ prefetch(TT.first_entry(pos.key_after(move)));
// Check for legality just before making the move
if (!pos.legal(move, ci.pinned))
ss->currentMove = move;
// Make and search the move
- pos.do_move(move, st, ci, givesCheck);
+ pos.do_move(move, st, givesCheck);
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);
if (value > alpha)
{
+ if (PvNode) // Update pv even in fail-high case
+ update_pv(ss->pv, move, (ss+1)->pv);
+
if (PvNode && value < beta) // Update alpha here! Always alpha < beta
{
alpha = value;
}
else // Fail high
{
- TT.store(posKey, value_to_tt(value, ss->ply), BOUND_LOWER,
- ttDepth, move, ss->staticEval);
+ tte->save(posKey, value_to_tt(value, ss->ply), BOUND_LOWER,
+ ttDepth, move, ss->staticEval, TT.generation());
return value;
}
if (InCheck && bestValue == -VALUE_INFINITE)
return mated_in(ss->ply); // Plies to mate from the root
- TT.store(posKey, value_to_tt(bestValue, ss->ply),
- PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER,
- ttDepth, bestMove, ss->staticEval);
+ tte->save(posKey, value_to_tt(bestValue, ss->ply),
+ PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER,
+ ttDepth, bestMove, ss->staticEval, TT.generation());
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
}
- // update_stats() updates killers, history, countermoves and followupmoves stats after a fail-high
- // of a quiet move.
+ // update_pv() adds current move and appends child pv[]
+
+ void update_pv(Move* pv, Move move, Move* childPv) {
+
+ for (*pv++ = move; childPv && *childPv != MOVE_NONE; )
+ *pv++ = *childPv++;
+ *pv = MOVE_NONE;
+ }
+
+
+ // update_stats() updates killers, history, countermove history and
+ // countermoves stats for a quiet best move.
- void update_stats(const Position& pos, Stack* ss, Move move, Depth depth, Move* quiets, int quietsCnt) {
+ void update_stats(const Position& pos, Stack* ss, Move move,
+ Depth depth, Move* quiets, int quietsCnt) {
if (ss->killers[0] != move)
{
ss->killers[0] = move;
}
- // Increase history value of the cut-off move and decrease all the other
- // played quiet moves.
- Value bonus = Value(4 * int(depth) * int(depth));
+ Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY));
+
+ Square prevSq = to_sq((ss-1)->currentMove);
+ HistoryStats& cmh = CounterMovesHistory[pos.piece_on(prevSq)][prevSq];
+
History.update(pos.moved_piece(move), to_sq(move), bonus);
- for (int i = 0; i < quietsCnt; ++i)
+
+ if (is_ok((ss-1)->currentMove))
{
- Move m = quiets[i];
- History.update(pos.moved_piece(m), to_sq(m), -bonus);
+ Countermoves.update(pos.piece_on(prevSq), prevSq, move);
+ cmh.update(pos.moved_piece(move), to_sq(move), bonus);
}
- if (is_ok((ss-1)->currentMove))
+ // Decrease all the other played quiet moves
+ for (int i = 0; i < quietsCnt; ++i)
{
- Square prevMoveSq = to_sq((ss-1)->currentMove);
- Countermoves.update(pos.piece_on(prevMoveSq), prevMoveSq, move);
+ History.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
+
+ if (is_ok((ss-1)->currentMove))
+ cmh.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
}
+ // Extra penalty for TT move in previous ply when it gets refuted
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);
+ Square prevPrevSq = to_sq((ss-2)->currentMove);
+ HistoryStats& ttMoveCmh = CounterMovesHistory[pos.piece_on(prevPrevSq)][prevPrevSq];
+ ttMoveCmh.update(pos.piece_on(prevSq), prevSq, -bonus - 2 * depth / ONE_PLY - 1);
}
}
- // 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() {
+ // When playing with strength handicap, choose best move among a set of RootMoves
+ // using a statistical rule dependent on 'level'. Idea by Heinz van Saanen.
- static RKISS rk;
+ Move Skill::pick_best(size_t multiPV) {
- // PRNG sequence should be not deterministic
- for (int i = Time::now() % 50; i > 0; --i)
- rk.rand<unsigned>();
+ // PRNG sequence should be non-deterministic, so we seed it with the time at init
+ static PRNG rng(now());
// RootMoves are already sorted by score in descending order
- int variance = std::min(RootMoves[0].score - RootMoves[candidates - 1].score, PawnValueMg);
+ int variance = std::min(RootMoves[0].score - RootMoves[multiPV - 1].score, PawnValueMg);
int weakness = 120 - 2 * level;
- int max_s = -VALUE_INFINITE;
- best = MOVE_NONE;
+ int maxScore = -VALUE_INFINITE;
// 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 levels, and one random,
// then we choose the move with the resulting highest score.
- for (size_t i = 0; i < candidates; ++i)
+ for (size_t i = 0; i < multiPV; ++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)
- break;
-
// This is our magic formula
- s += ( weakness * int(RootMoves[0].score - s)
- + variance * (rk.rand<unsigned>() % weakness)) / 128;
+ int push = ( weakness * int(RootMoves[0].score - RootMoves[i].score)
+ + variance * (rng.rand<unsigned>() % weakness)) / 128;
- if (s > max_s)
+ if (RootMoves[i].score + push > maxScore)
{
- max_s = s;
+ maxScore = RootMoves[i].score + push;
best = RootMoves[i].pv[0];
}
}
return best;
}
+} // namespace
- // 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";
+/// 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.
- 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";
+string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) {
- for (size_t j = 0; RootMoves[i].pv[j] != MOVE_NONE; ++j)
- ss << " " << UCI::format_move(RootMoves[i].pv[j], pos.is_chess960());
- }
+ std::stringstream ss;
+ int elapsed = Time.elapsed() + 1;
+ size_t multiPV = std::min((size_t)Options["MultiPV"], RootMoves.size());
+ int selDepth = 0;
- return ss.str();
- }
+ for (Thread* th : Threads)
+ if (th->maxPly > selDepth)
+ selDepth = th->maxPly;
-} // namespace
+ for (size_t i = 0; i < multiPV; ++i)
+ {
+ bool updated = (i <= PVIdx);
+ if (depth == ONE_PLY && !updated)
+ continue;
-/// RootMove::extract_pv_from_tt() builds a PV by adding moves from the TT table.
-/// 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.
+ Depth d = updated ? depth : depth - ONE_PLY;
+ Value v = updated ? RootMoves[i].score : RootMoves[i].previousScore;
-void RootMove::extract_pv_from_tt(Position& pos) {
+ bool tb = TB::RootInTB && abs(v) < VALUE_MATE - MAX_PLY;
+ v = tb ? TB::Score : v;
- StateInfo state[MAX_PLY], *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;
+ if (ss.rdbuf()->in_avail()) // Not at first line
+ ss << "\n";
- pv.clear();
+ ss << "info"
+ << " depth " << d / ONE_PLY
+ << " seldepth " << selDepth
+ << " multipv " << i + 1
+ << " score " << UCI::value(v);
- do {
- pv.push_back(m);
+ if (!tb && i == PVIdx)
+ ss << (v >= beta ? " lowerbound" : v <= alpha ? " upperbound" : "");
- assert(MoveList<LEGAL>(pos).contains(pv[ply - 1]));
+ ss << " nodes " << pos.nodes_searched()
+ << " nps " << pos.nodes_searched() * 1000 / elapsed;
- pos.do_move(pv[ply++ - 1], *st++);
- tte = TT.probe(pos.key());
- expectedScore = -expectedScore;
+ if (elapsed > 1000) // Earlier makes little sense
+ ss << " hashfull " << TT.hashfull();
- } 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));
+ ss << " tbhits " << TB::Hits
+ << " time " << elapsed
+ << " pv";
- pv.push_back(MOVE_NONE); // Must be zero-terminating
+ for (Move m : RootMoves[i].pv)
+ ss << " " << UCI::move(m, pos.is_chess960());
+ }
- while (--ply) pos.undo_move(pv[ply - 1]);
+ return ss.str();
}
void RootMove::insert_pv_in_tt(Position& pos) {
StateInfo state[MAX_PLY], *st = state;
- const TTEntry* tte;
- int idx = 0; // Ply starts from 1, we need to start from 0
+ bool ttHit;
+
+ for (Move m : pv)
+ {
+ assert(MoveList<LEGAL>(pos).contains(m));
+
+ TTEntry* tte = TT.probe(pos.key(), ttHit);
- do {
- tte = TT.probe(pos.key());
+ if (!ttHit || tte->move() != m) // Don't overwrite correct entries
+ tte->save(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, m, VALUE_NONE, TT.generation());
- 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);
+ pos.do_move(m, *st++, pos.gives_check(m, CheckInfo(pos)));
+ }
+
+ for (size_t i = pv.size(); i > 0; )
+ pos.undo_move(pv[--i]);
+}
- assert(MoveList<LEGAL>(pos).contains(pv[idx]));
- pos.do_move(pv[idx++], *st++);
+/// RootMove::extract_ponder_from_tt() is called in case we have no ponder move before
+/// exiting the search, for instance in case we stop the search during a fail high at
+/// root. We try hard to have a ponder move to return to the GUI, otherwise in case of
+/// 'ponder on' we have nothing to think on.
+
+bool RootMove::extract_ponder_from_tt(Position& pos)
+{
+ StateInfo st;
+ bool ttHit;
+
+ assert(pv.size() == 1);
- } while (pv[idx] != MOVE_NONE);
+ pos.do_move(pv[0], st, pos.gives_check(pv[0], CheckInfo(pos)));
+ TTEntry* tte = TT.probe(pos.key(), ttHit);
+ pos.undo_move(pv[0]);
- while (idx) pos.undo_move(pv[--idx]);
+ if (ttHit)
+ {
+ Move m = tte->move(); // Local copy to be SMP safe
+ if (MoveList<LEGAL>(pos).contains(m))
+ return pv.push_back(m), true;
+ }
+
+ return false;
}
// 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;
+ SplitPoint* this_sp = activeSplitPoint;
- assert(!this_sp || (this_sp->masterThread == this && searching));
+ assert(!this_sp || (this_sp->master == this && searching));
- while (!exit)
+ while (!exit && !(this_sp && this_sp->slavesMask.none()))
{
// If this thread has been assigned work, launch a search
while (searching)
{
- Threads.mutex.lock();
+ spinlock.acquire();
assert(activeSplitPoint);
SplitPoint* sp = activeSplitPoint;
- Threads.mutex.unlock();
+ spinlock.release();
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));
ss->splitPoint = sp;
- sp->mutex.lock();
+ sp->spinlock.acquire();
- assert(activePosition == NULL);
+ assert(activePosition == nullptr);
activePosition = &pos;
assert(searching);
searching = false;
- activePosition = NULL;
+ activePosition = nullptr;
sp->slavesMask.reset(idx);
sp->allSlavesSearching = false;
sp->nodes += pos.nodes_searched();
- // 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();
+ sp->spinlock.release();
// 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)
+ SplitPoint* bestSp = NULL;
+ int minLevel = INT_MAX;
+
+ for (Thread* th : Threads)
+ {
+ const size_t size = th->splitPointsSize; // Local copy
+ sp = size ? &th->splitPoints[size - 1] : nullptr;
+
+ if ( sp
+ && sp->allSlavesSearching
+ && sp->slavesMask.count() < MAX_SLAVES_PER_SPLITPOINT
+ && can_join(sp))
{
- const int size = Threads[i]->splitPointsSize; // Local copy
- sp = size ? &Threads[i]->splitPoints[size - 1] : NULL;
+ assert(this != th);
+ assert(!(this_sp && this_sp->slavesMask.none()));
+ assert(Threads.size() > 2);
- if ( sp
- && sp->allSlavesSearching
- && available_to(Threads[i]))
+ // Prefer to join to SP with few parents to reduce the probability
+ // that a cut-off occurs above us, and hence we waste our work.
+ int level = 0;
+ for (SplitPoint* p = th->activeSplitPoint; p; p = p->parentSplitPoint)
+ level++;
+
+ if (level < minLevel)
{
- // 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
+ bestSp = sp;
+ minLevel = level;
}
}
- }
+ }
- // Grab the lock to avoid races with Thread::notify_one()
- mutex.lock();
+ if (bestSp)
+ {
+ sp = bestSp;
- // 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;
+ // Recheck the conditions under lock protection
+ sp->spinlock.acquire();
+
+ if ( sp->allSlavesSearching
+ && sp->slavesMask.count() < MAX_SLAVES_PER_SPLITPOINT)
+ {
+ spinlock.acquire();
+
+ if (can_join(sp))
+ {
+ sp->slavesMask.set(idx);
+ activeSplitPoint = sp;
+ searching = true;
+ }
+
+ spinlock.release();
+ }
+
+ sp->spinlock.release();
+ }
}
- // 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);
+ // If search is finished then sleep, otherwise just yield
+ if (!Threads.main()->thinking)
+ {
+ assert(!this_sp);
- mutex.unlock();
+ std::unique_lock<Mutex> lk(mutex);
+ while (!exit && !Threads.main()->thinking)
+ sleepCondition.wait(lk);
+ }
+ else
+ std::this_thread::yield(); // Wait for a new job or for our slaves to finish
}
}
void check_time() {
- static Time::point lastInfoTime = Time::now();
- int64_t nodes = 0; // Workaround silly 'uninitialized' gcc warning
+ static TimePoint lastInfoTime = now();
+ int elapsed = Time.elapsed();
- if (Time::now() - lastInfoTime >= 1000)
+ if (now() - lastInfoTime >= 1000)
{
- lastInfoTime = Time::now();
+ lastInfoTime = now();
dbg_print();
}
+ // An engine may not stop pondering until told so by the GUI
if (Limits.ponder)
return;
- if (Limits.nodes)
+ if (Limits.use_time_management())
{
- Threads.mutex.lock();
+ bool stillAtFirstMove = Signals.firstRootMove
+ && !Signals.failedLowAtRoot
+ && elapsed > Time.available() * 75 / 100;
- nodes = RootPos.nodes_searched();
+ if ( stillAtFirstMove
+ || elapsed > Time.maximum() - 2 * TimerThread::Resolution)
+ Signals.stop = true;
+ }
+ else if (Limits.movetime && elapsed >= Limits.movetime)
+ Signals.stop = true;
+
+ else if (Limits.nodes)
+ {
+ 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)
+ // FIXME: Racy...
+ for (Thread* th : Threads)
+ for (size_t i = 0; i < th->splitPointsSize; ++i)
{
- SplitPoint& sp = Threads[i]->splitPoints[j];
+ SplitPoint& sp = th->splitPoints[i];
- sp.mutex.lock();
+ sp.spinlock.acquire();
nodes += sp.nodes;
if (sp.slavesMask.test(idx) && Threads[idx]->activePosition)
nodes += Threads[idx]->activePosition->nodes_searched();
- sp.mutex.unlock();
+ sp.spinlock.release();
}
- Threads.mutex.unlock();
+ if (nodes >= Limits.nodes)
+ Signals.stop = true;
}
-
- Time::point elapsed = Time::now() - SearchTime;
- bool stillAtFirstMove = Signals.firstRootMove
- && !Signals.failedLowAtRoot
- && elapsed > TimeMgr.available_time() * 75 / 100;
-
- bool noMoreTime = elapsed > TimeMgr.maximum_time() - 2 * TimerThread::Resolution
- || stillAtFirstMove;
-
- if ( (Limits.use_time_management() && noMoreTime)
- || (Limits.movetime && elapsed >= Limits.movetime)
- || (Limits.nodes && nodes >= Limits.nodes))
- Signals.stop = true;
}