/*
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 <algorithm>
#include <cassert>
+#include <cfloat>
#include <cmath>
#include <cstring>
#include <iostream>
std::vector<RootMove> RootMoves;
Position RootPos;
Color RootColor;
- Time::point SearchTime;
+ Time::point SearchTime, IterationTime;
StateStackPtr SetupStates;
}
// 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 };
inline Value razor_margin(Depth d) { return Value(512 + 16 * int(d)); }
// Futility lookup tables (initialized at startup) and their access functions
- Value FutilityMargins[16][64]; // [depth][moveNumber]
- int FutilityMoveCounts[32]; // [depth]
-
- inline Value futility_margin(Depth d, int mn) {
+ int FutilityMoveCounts[2][32]; // [improving][depth]
- 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(100 * int(d));
}
// Reduction lookup tables (initialized at startup) and their access function
- int8_t Reductions[2][64][64]; // [pv][depth][moveNumber]
+ int8_t Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber]
- template <bool PvNode> inline Depth reduction(Depth d, int mn) {
+ template <bool PvNode> inline Depth reduction(bool i, Depth d, int mn) {
- return (Depth) Reductions[PvNode][std::min(int(d) / ONE_PLY, 63)][std::min(mn, 63)];
+ return (Depth) Reductions[PvNode][i][std::min(int(d) / ONE_PLY, 63)][std::min(mn, 63)];
}
size_t PVSize, PVIdx;
TimeManager TimeMgr;
- int BestMoveChanges;
+ double BestMoveChanges;
Value DrawValue[COLOR_NB];
HistoryStats History;
GainsStats Gains;
- CountermovesStats Countermoves;
+ MovesStats Countermoves, Followupmoves;
template <NodeType NT>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode);
void id_loop(Position& pos);
Value value_to_tt(Value v, int ply);
Value value_from_tt(Value v, int ply);
- bool check_is_dangerous(const Position& pos, Move move, Value futilityBase, Value beta);
- bool allows(const Position& pos, Move first, Move second);
- bool refutes(const Position& pos, Move first, Move second);
+ void update_stats(Position& pos, Stack* ss, Move move, Depth depth, Move* quiets, int quietsCnt);
string uci_pv(const Position& pos, int depth, Value alpha, Value beta);
struct Skill {
int mc; // moveCount
// Init reductions array
- for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
+ for (hd = 1; hd < 64; ++hd) for (mc = 1; mc < 64; ++mc)
{
double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
- Reductions[1][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0);
- Reductions[0][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0);
- }
+ 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);
- // Init futility margins array
- for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++)
- FutilityMargins[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45);
+ Reductions[1][0][hd][mc] = Reductions[1][1][hd][mc];
+ Reductions[0][0][hd][mc] = Reductions[0][1][hd][mc];
+
+ if (Reductions[0][0][hd][mc] > 2 * ONE_PLY)
+ Reductions[0][0][hd][mc] += ONE_PLY;
+
+ else if (Reductions[0][0][hd][mc] > 1 * ONE_PLY)
+ Reductions[0][0][hd][mc] += ONE_PLY / 2;
+ }
// Init futility move count array
- for (d = 0; d < 32; d++)
- FutilityMoveCounts[d] = int(3.001 + 0.3 * pow(double(d), 1.8));
+ for (d = 0; d < 32; ++d)
+ {
+ FutilityMoveCounts[0][d] = int(2.4 + 0.222 * pow(d + 0.0, 1.8));
+ FutilityMoveCounts[1][d] = int(3.0 + 0.3 * pow(d + 0.98, 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) {
+static uint64_t perft(Position& pos, Depth depth) {
StateInfo st;
- size_t cnt = 0;
+ uint64_t cnt = 0;
CheckInfo ci(pos);
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));
+ pos.do_move(*it, st, ci, pos.gives_check(*it, ci));
cnt += leaf ? MoveList<LEGAL>(pos).size() : ::perft(pos, depth - ONE_PLY);
pos.undo_move(*it);
}
return cnt;
}
-size_t Search::perft(Position& pos, Depth depth) {
+uint64_t Search::perft(Position& pos, Depth depth) {
return depth > ONE_PLY ? ::perft(pos, depth) : MoveList<LEGAL>(pos).size();
}
<< std::endl;
}
- // Reset the threads, still sleeping: will be wake up at split time
- for (size_t i = 0; i < Threads.size(); i++)
+ // 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.timer->run = false; // Stop the timer
Threads.sleepWhileIdle = true; // Send idle threads to sleep
if (Options["Write Search Log"])
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;
void id_loop(Position& pos) {
- Stack stack[MAX_PLY_PLUS_2], *ss = stack+1; // To allow referencing (ss-1)
- int depth, prevBestMoveChanges;
+ Stack stack[MAX_PLY_PLUS_6], *ss = stack+2; // To allow referencing (ss-2)
+ int depth;
Value bestValue, alpha, beta, delta;
- memset(ss-1, 0, 4 * sizeof(Stack));
+ std::memset(ss-2, 0, 5 * sizeof(Stack));
(ss-1)->currentMove = MOVE_NULL; // Hack to skip update gains
- depth = BestMoveChanges = 0;
+ depth = 0;
+ BestMoveChanges = 0;
bestValue = delta = alpha = -VALUE_INFINITE;
beta = VALUE_INFINITE;
History.clear();
Gains.clear();
Countermoves.clear();
+ Followupmoves.clear();
PVSize = Options["MultiPV"];
Skill skill(Options["Skill Level"]);
// Iterative deepening loop until requested to stop or target depth reached
while (++depth <= MAX_PLY && !Signals.stop && (!Limits.depth || depth <= Limits.depth))
{
- // Save last iteration's scores before first PV line is searched and all
- // the move scores but the (new) PV are set to -VALUE_INFINITE.
- for (size_t i = 0; i < RootMoves.size(); i++)
- RootMoves[i].prevScore = RootMoves[i].score;
+ // Age out PV variability metric
+ BestMoveChanges *= 0.5;
- prevBestMoveChanges = BestMoveChanges; // Only sensible when PVSize == 1
- BestMoveChanges = 0;
+ // Save the last iteration's scores before first PV line is searched and
+ // all the move scores except the (new) PV are set to -VALUE_INFINITE.
+ for (size_t i = 0; i < RootMoves.size(); ++i)
+ RootMoves[i].prevScore = RootMoves[i].score;
// MultiPV loop. We perform a full root search for each PV line
- for (PVIdx = 0; PVIdx < PVSize; PVIdx++)
+ for (PVIdx = 0; PVIdx < PVSize && !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.
+ // Bring the best move to the front. It is critical that sorting
+ // is done with a stable algorithm because all the values but the
+ // first and eventually the new best one are set to -VALUE_INFINITE
+ // and we want to keep the same order for all the moves except the
+ // new PV that goes to the front. Note that in case of MultiPV
+ // search the already searched PV lines are preserved.
std::stable_sort(RootMoves.begin() + PVIdx, RootMoves.end());
// Write PV back to transposition table in case the relevant
// entries have been overwritten during the search.
- for (size_t i = 0; i <= PVIdx; i++)
+ for (size_t i = 0; i <= PVIdx; ++i)
RootMoves[i].insert_pv_in_tt(pos);
- // If search has been stopped 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)
{
alpha = std::max(bestValue - delta, -VALUE_INFINITE);
sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
}
- // Do we need to pick now the sub-optimal best move ?
+ IterationTime = Time::now() - SearchTime;
+
+ // If skill levels are enabled and time is up, pick a sub-optimal best move
if (skill.enabled() && skill.time_to_pick(depth))
skill.pick_move();
<< 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
+ // Take some extra time if the best move has changed
if (depth > 4 && depth < 50 && PVSize == 1)
- TimeMgr.pv_instability(BestMoveChanges, prevBestMoveChanges);
+ 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 the search if only one legal move is available or all
+ // of the available time has been used.
+ if ( RootMoves.size() == 1
+ || IterationTime > TimeMgr.available_time() )
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)
{
// 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>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) {
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;
+ Move ttMove, move, excludedMove, bestMove;
+ Depth ext, newDepth, predictedDepth;
+ Value bestValue, value, ttValue, eval, nullValue, futilityValue;
+ bool inCheck, givesCheck, pvMove, singularExtensionNode, improving;
bool captureOrPromotion, dangerous, doFullDepthSearch;
int moveCount, 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->currentMove = ss->ttMove = (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;
{
// 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()];
+ 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)
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
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 = evaluate(pos);
+ 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
Gains.update(pos.piece_on(to), to, -(ss-1)->staticEval - ss->staticEval);
}
- // Step 6. Razoring (is omitted in PV nodes)
+ // Step 6. Razoring (skipped when in check)
if ( !PvNode
&& depth < 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.
+ Value ralpha = alpha - razor_margin(depth);
+ Value v = qsearch<NonPV, false>(pos, ss, ralpha, ralpha+1, DEPTH_ZERO);
+ if (v <= ralpha)
return v;
}
- // Step 7. Static null move pruning (is omitted in PV nodes)
- // We're betting that the opponent doesn't have a move that will reduce
- // the score by more than futility_margin(depth) if we do a null move.
+ // Step 7. Futility pruning: child node (skipped when in check)
if ( !PvNode
&& !ss->skipNullMove
- && depth < 4 * ONE_PLY
- && eval - futility_margin(depth, (ss-1)->futilityMoveCount) >= beta
+ && depth < 7 * ONE_PLY
+ && eval - futility_margin(depth) >= beta
&& abs(beta) < VALUE_MATE_IN_MAX_PLY
&& abs(eval) < VALUE_KNOWN_WIN
&& 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 > ONE_PLY
+ && 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 * ONE_PLY
+ + depth / 4
+ + int(eval - beta) / PawnValueMg * ONE_PLY;
pos.do_null_move(st);
(ss+1)->skipNullMove = true;
- nullValue = depth-R < ONE_PLY ? -qsearch<NonPV, false>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
- : - search<NonPV>(pos, ss+1, -beta, -alpha, depth-R, !cutNode);
+ nullValue = depth-R < ONE_PLY ? -qsearch<NonPV, false>(pos, ss+1, -beta, -beta+1, DEPTH_ZERO)
+ : - search<NonPV>(pos, ss+1, -beta, -beta+1, depth-R, !cutNode);
(ss+1)->skipNullMove = false;
pos.undo_null_move();
// 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>(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 (is omitted in PV nodes)
+ // Step 9. ProbCut (skipped when in check)
// If we have a very good capture (i.e. SEE > seeValues[captured_piece_type])
// and a reduced search returns a value much above beta, we can (almost) safely
// prune the previous move.
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));
+ pos.do_move(move, st, ci, pos.gives_check(move, ci));
value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode);
pos.undo_move(move);
if (value >= rbeta)
}
}
- // Step 10. Internal iterative deepening
+ // 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))
Move countermoves[] = { Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq].first,
Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq].second };
- MovePicker mp(pos, ttMove, depth, History, countermoves, ss, PvNode ? -VALUE_INFINITE : beta);
+ Square prevOwnMoveSq = to_sq((ss-2)->currentMove);
+ Move followupmoves[] = { Followupmoves[pos.piece_on(prevOwnMoveSq)][prevOwnMoveSq].first,
+ Followupmoves[pos.piece_on(prevOwnMoveSq)][prevOwnMoveSq].second };
+
+ MovePicker mp(pos, ttMove, depth, History, countermoves, followupmoves, ss);
CheckInfo ci(pos);
value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
+ improving = ss->staticEval >= (ss-2)->staticEval
+ || ss->staticEval == VALUE_NONE
+ ||(ss-2)->staticEval == VALUE_NONE;
+
singularExtensionNode = !RootNode
&& !SpNode
- && depth >= (PvNode ? 6 * ONE_PLY : 8 * ONE_PLY)
+ && depth >= 8 * ONE_PLY
&& ttMove != MOVE_NONE
&& !excludedMove // Recursive singular search is not allowed
&& (tte->bound() & BOUND_LOWER)
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_thread() && Time::now() - SearchTime > 3000)
+ if (thisThread == Threads.main() && Time::now() - SearchTime > 3000)
sync_cout << "info depth " << depth / ONE_PLY
<< " currmove " << move_to_uci(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) >= 0)
ext = ONE_PLY;
- else if (givesCheck && pos.see_sign(move) >= 0)
- ext = 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)
+ && pos.legal(move, ci.pinned)
&& abs(ttValue) < VALUE_KNOWN_WIN)
{
assert(ttValue != VALUE_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
{
// Move count based pruning
if ( depth < 16 * ONE_PLY
- && moveCount >= FutilityMoveCounts[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>(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)
+ + Value(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) < 0)
{
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))
+ // Check for legality just before making the move
+ if (!RootNode && !SpNode && !pos.legal(move, ci.pinned))
{
moveCount--;
continue;
// 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
+ if ( depth >= 3 * ONE_PLY
&& !pvMove
&& !captureOrPromotion
- && !dangerous
&& move != ttMove
&& move != ss->killers[0]
&& move != ss->killers[1])
{
- ss->reduction = reduction<PvNode>(depth, moveCount);
+ ss->reduction = reduction<PvNode>(improving, depth, moveCount);
if (!PvNode && cutNode)
ss->reduction += ONE_PLY;
+ else if (History[pos.piece_on(to_sq(move))][to_sq(move)] < 0)
+ ss->reduction += ONE_PLY / 2;
+
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);
Depth d = std::max(newDepth - ss->reduction, ONE_PLY);
if (SpNode)
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);
+ // Research 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>(pos, ss+1, -(alpha+1), -alpha, d2, true);
+ }
+
doFullDepthSearch = (value > alpha && ss->reduction != DEPTH_ZERO);
ss->reduction = DEPTH_ZERO;
}
: - search<NonPV>(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.
+ // For PV nodes only, do a full PV search on the first move or after a fail
+ // high (in the latter case search only if value < beta), otherwise let the
+ // parent node fail low with value <= alpha and to try another move.
if (PvNode && (pvMove || (value > alpha && (RootNode || value < beta))))
value = newDepth < ONE_PLY ?
givesCheck ? -qsearch<PV, true>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
// iteration. This information is used for time management: When
// the best move changes frequently, we allocate some more time.
if (!pvMove)
- BestMoveChanges++;
+ ++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;
}
assert(bestValue < beta);
thisThread->split<FakeSplit>(pos, ss, alpha, beta, &bestValue, &bestMove,
- depth, threatMove, moveCount, &mp, NT, cutNode);
+ depth, moveCount, &mp, NT, cutNode);
if (bestValue >= beta)
break;
}
// 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.
+ // A split node has at least one move - the one tried before to be splitted.
if (!moveCount)
return excludedMove ? alpha
: inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()];
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);
+ depth, bestMove, ss->staticEval);
- // 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);
- }
+ // Quiet best move: update killers, history, countermoves and followupmoves
+ if (bestValue >= beta && !pos.capture_or_promotion(bestMove) && !inCheck)
+ update_stats(pos, ss, bestMove, depth, quietsSearched, quietCount - 1);
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
Key posKey;
Move ttMove, move, bestMove;
Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha;
- bool givesCheck, enoughMaterial, evasionPrunable;
+ bool givesCheck, evasionPrunable;
Depth ttDepth;
// To flag BOUND_EXACT a node with eval above alpha and no available moves
ss->currentMove = bestMove = MOVE_NONE;
ss->ply = (ss-1)->ply + 1;
- // Check for an instant draw or maximum ply reached
+ // Check for an instant draw or if the maximum ply has been reached
if (pos.is_draw() || ss->ply > MAX_PLY)
- return DrawValue[pos.side_to_move()];
+ return ss->ply > MAX_PLY && !InCheck ? evaluate(pos) : DrawValue[pos.side_to_move()];
- // Decide whether or not to include checks, this fixes also the type of
+ // Decide whether or not to include checks: this fixes also the type of
// TT entry depth that we are going to use. Note that in qsearch we use
// only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
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;
- enoughMaterial = false;
}
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 = evaluate(pos);
// 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);
- enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMg;
+ futilityBase = bestValue + Value(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
- && enoughMaterial
- && type_of(move) != PROMOTION
- && !pos.is_passed_pawn_push(move))
+ && futilityBase > -VALUE_KNOWN_WIN
+ && !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) <= 0)
{
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
&& pos.see_sign(move) < 0)
continue;
- // Don't search useless checks
- if ( !PvNode
- && !InCheck
- && givesCheck
- && move != ttMove
- && !pos.is_capture_or_promotion(move)
- && ss->staticEval + PawnValueMg / 4 < beta
- && !check_is_dangerous(pos, move, futilityBase, beta))
- continue;
-
- // Check for legality only before to do the move
- if (!pos.pl_move_is_legal(move, ci.pinned))
+ // Check for legality just before making the move
+ if (!pos.legal(move, ci.pinned))
continue;
ss->currentMove = move;
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) {
}
- // check_is_dangerous() tests if a checking move can be pruned in qsearch()
+ // update_stats() updates killers, history, countermoves and followupmoves stats after a fail-high
+ // of a quiet move.
- bool check_is_dangerous(const Position& pos, Move move, Value futilityBase, Value beta)
- {
- Piece pc = pos.piece_moved(move);
- Square from = from_sq(move);
- Square to = to_sq(move);
- Color them = ~pos.side_to_move();
- Square ksq = pos.king_square(them);
- Bitboard enemies = pos.pieces(them);
- Bitboard kingAtt = pos.attacks_from<KING>(ksq);
- Bitboard occ = pos.pieces() ^ from ^ ksq;
- Bitboard oldAtt = pos.attacks_from(pc, from, occ);
- Bitboard newAtt = pos.attacks_from(pc, to, occ);
-
- // Checks which give opponent's king at most one escape square are dangerous
- if (!more_than_one(kingAtt & ~(enemies | newAtt | to)))
- return true;
-
- // Queen contact check is very dangerous
- if (type_of(pc) == QUEEN && (kingAtt & to))
- return true;
-
- // Creating new double threats with checks is dangerous
- Bitboard b = (enemies ^ ksq) & newAtt & ~oldAtt;
- while (b)
+ void update_stats(Position& pos, Stack* ss, Move move, Depth depth, Move* quiets, int quietsCnt) {
+
+ if (ss->killers[0] != move)
{
- // Note that here we generate illegal "double move"!
- if (futilityBase + PieceValue[EG][pos.piece_on(pop_lsb(&b))] >= beta)
- return true;
+ ss->killers[1] = ss->killers[0];
+ ss->killers[0] = move;
}
- return false;
- }
-
-
- // 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(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
- if (m1to == m2from || m2to == m1from)
- return true;
-
- // Second one moves through the square vacated by first one
- if (between_bb(m2from, m2to) & m1from)
- return true;
-
- // 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;
-
- // Second move gives a discovered check through the first's checking piece
- if (m1att & pos.king_square(pos.side_to_move()))
+ // Increase history value of the cut-off move and decrease all the other
+ // played quiet moves.
+ Value bonus = Value(int(depth) * int(depth));
+ History.update(pos.moved_piece(move), to_sq(move), bonus);
+ for (int i = 0; i < quietsCnt; ++i)
{
- assert(between_bb(m1to, pos.king_square(pos.side_to_move())) & m2from);
- return true;
+ Move m = quiets[i];
+ History.update(pos.moved_piece(m), to_sq(m), -bonus);
}
- 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))
+ if (is_ok((ss-1)->currentMove))
{
- // 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 (xray && (xray ^ (xray & pos.attacks_from<QUEEN>(m2to))))
- return true;
+ Square prevMoveSq = to_sq((ss-1)->currentMove);
+ Countermoves.update(pos.piece_on(prevMoveSq), prevMoveSq, move);
}
- // Don't prune safe moves which block the threat path
- if ((between_bb(m2from, m2to) & m1to) && pos.see_sign(first) >= 0)
- return true;
-
- return false;
+ 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 MultiPV
+ // set 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
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 < PVSize; ++i)
{
int s = RootMoves[i].score;
}
- // 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) {
size_t uciPVSize = std::min((size_t)Options["MultiPV"], RootMoves.size());
int selDepth = 0;
- for (size_t i = 0; i < Threads.size(); i++)
+ 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++)
+ for (size_t i = 0; i < uciPVSize; ++i)
{
bool updated = (i <= PVIdx);
<< " multipv " << i + 1
<< " pv";
- for (size_t j = 0; RootMoves[i].pv[j] != MOVE_NONE; j++)
+ for (size_t j = 0; RootMoves[i].pv[j] != MOVE_NONE; ++j)
s << " " << move_to_uci(RootMoves[i].pv[j], pos.is_chess960());
}
/// RootMove::extract_pv_from_tt() builds a PV by adding moves from the TT table.
-/// We consider also failing high nodes and not only BOUND_EXACT nodes so to
-/// allow to always have a ponder move even when we fail high at root, and a
-/// long PV to print that is important for position analysis.
+/// We also consider both failing high nodes and BOUND_EXACT nodes here to
+/// ensure that we have a ponder move even when we fail high at root. This
+/// results in a long PV to print that is important for position analysis.
void RootMove::extract_pv_from_tt(Position& pos) {
- StateInfo state[MAX_PLY_PLUS_2], *st = state;
+ StateInfo state[MAX_PLY_PLUS_6], *st = state;
const TTEntry* tte;
int ply = 0;
Move m = pv[0];
tte = TT.probe(pos.key());
} while ( tte
- && pos.is_pseudo_legal(m = tte->move()) // Local copy, TT could change
- && pos.pl_move_is_legal(m, pos.pinned_pieces())
+ && 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));
void RootMove::insert_pv_in_tt(Position& pos) {
- StateInfo state[MAX_PLY_PLUS_2], *st = state;
+ StateInfo state[MAX_PLY_PLUS_6], *st = state;
const TTEntry* tte;
int ply = 0;
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);
+ TT.store(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[ply], VALUE_NONE);
assert(MoveList<LEGAL>(pos).contains(pv[ply]));
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));
break;
}
- // Do sleep after retesting sleep conditions under lock protection, in
+ // 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.
Threads.mutex.unlock();
- Stack stack[MAX_PLY_PLUS_2], *ss = stack+1; // To allow referencing (ss-1)
+ Stack stack[MAX_PLY_PLUS_6], *ss = stack+2; // To allow referencing (ss-2)
Position pos(*sp->pos, this);
- memcpy(ss-1, sp->ss-1, 4 * sizeof(Stack));
+ std::memcpy(ss-2, sp->ss-2, 5 * sizeof(Stack));
ss->splitPoint = sp;
sp->mutex.lock();
sp->slavesMask &= ~(1ULL << idx);
sp->nodes += pos.nodes_searched();
- // Wake up master thread so to allow it to return from the idle loop
- // in case we are the last slave of the split point.
+ // 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 ( Threads.sleepWhileIdle
&& this != sp->masterThread
&& !sp->slavesMask)
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. Also accessing other Thread objects is unsafe because
+ // if we are exiting there is a chance that they are already freed.
sp->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() {
// 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 (size_t i = 0; i < Threads.size(); ++i)
+ for (int j = 0; j < Threads[i]->splitPointsSize; ++j)
{
SplitPoint& sp = Threads[i]->splitPoints[j];
Time::point elapsed = Time::now() - SearchTime;
bool stillAtFirstMove = Signals.firstRootMove
&& !Signals.failedLowAtRoot
- && elapsed > TimeMgr.available_time();
+ && elapsed > TimeMgr.available_time()
+ && elapsed > IterationTime * 1.4;
- bool noMoreTime = elapsed > TimeMgr.maximum_time() - 2 * TimerResolution
+ bool noMoreTime = elapsed > TimeMgr.maximum_time() - 2 * TimerThread::Resolution
|| stillAtFirstMove;
if ( (Limits.use_time_management() && noMoreTime)
projects / stockfish / blobdiff