#include "evaluate.h"
#include "history.h"
#include "misc.h"
-#include "move.h"
#include "movegen.h"
#include "movepick.h"
#include "search.h"
#include "tt.h"
#include "ucioption.h"
+namespace Search {
+
+ volatile SignalsType Signals;
+ LimitsType Limits;
+ std::vector<Move> RootMoves;
+ Position RootPosition;
+}
+
using std::cout;
using std::endl;
using std::string;
+using namespace Search;
namespace {
// RootMoveList struct is mainly a std::vector of RootMove objects
struct RootMoveList : public std::vector<RootMove> {
- void init(Position& pos, Move searchMoves[]);
+ void init(Position& pos, Move rootMoves[]);
RootMove* find(const Move& m, int startIndex = 0);
int bestMoveChanges;
const bool Slidings[18] = { 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1 };
inline bool piece_is_slider(Piece p) { return Slidings[p]; }
- // Step 6. Razoring
-
// Maximum depth for razoring
const Depth RazorDepth = 4 * ONE_PLY;
// Maximum depth for use of dynamic threat detection when null move fails low
const Depth ThreatDepth = 5 * ONE_PLY;
- // Step 9. Internal iterative deepening
-
// Minimum depth for use of internal iterative deepening
const Depth IIDDepth[] = { 8 * ONE_PLY, 5 * ONE_PLY };
// when the static evaluation is bigger then beta - IIDMargin.
const Value IIDMargin = Value(0x100);
- // Step 11. Decide the new search depth
-
- // Extensions. Array index 0 is used for non-PV nodes, index 1 for PV nodes
- const Depth CheckExtension[] = { ONE_PLY / 2, ONE_PLY / 1 };
- const Depth PawnEndgameExtension[] = { ONE_PLY / 1, ONE_PLY / 1 };
- const Depth PawnPushTo7thExtension[] = { ONE_PLY / 2, ONE_PLY / 2 };
- const Depth PassedPawnExtension[] = { DEPTH_ZERO, ONE_PLY / 2 };
-
// Minimum depth for use of singular extension
const Depth SingularExtensionDepth[] = { 8 * ONE_PLY, 6 * ONE_PLY };
- // Step 12. Futility pruning
-
// Futility margin for quiescence search
const Value FutilityMarginQS = Value(0x80);
return d < 16 * ONE_PLY ? FutilityMoveCounts[d] : MAX_MOVES;
}
- // Step 14. Reduced search
-
// Reduction lookup tables (initialized at startup) and their access function
int8_t Reductions[2][64][64]; // [pv][depth][moveNumber]
/// Namespace variables
- // Root move list
RootMoveList Rml;
-
- // MultiPV mode
- int MultiPV, UCIMultiPV, MultiPVIdx;
-
- // Time management variables
- volatile bool StopOnPonderhit, FirstRootMove, StopRequest, QuitRequest, AspirationFailLow;
+ size_t MultiPV, UCIMultiPV, MultiPVIdx;
TimeManager TimeMgr;
- SearchLimits Limits;
-
- // Skill level adjustment
int SkillLevel;
bool SkillLevelEnabled;
-
- // History table
History H;
/// Local functions
- Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove);
+ Move id_loop(Position& pos, Move rootMoves[], Move* ponderMove);
template <NodeType NT>
- Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth);
+ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth);
template <NodeType NT>
- Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth);
+ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth);
bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue);
bool connected_moves(const Position& pos, Move m1, Move m2);
void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
void do_skill_level(Move* best, Move* ponder);
- int elapsed_search_time(int set = 0);
+ int elapsed_time(bool reset = false);
string score_to_uci(Value v, Value alpha = -VALUE_INFINITE, Value beta = VALUE_INFINITE);
string speed_to_uci(int64_t nodes);
string pv_to_uci(const Move pv[], int pvNum, bool chess960);
string pretty_pv(Position& pos, int depth, Value score, int time, Move pv[]);
string depth_to_uci(Depth depth);
- void wait_for_stop_or_ponderhit();
// MovePickerExt template class extends MovePicker and allows to choose at compile
// time the proper moves source according to the type of node. In the default case
// we simply create and use a standard MovePicker object.
template<bool SpNode> struct MovePickerExt : public MovePicker {
- MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b)
+ MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, Stack* ss, Value b)
: MovePicker(p, ttm, d, h, ss, b) {}
};
// In case of a SpNode we use split point's shared MovePicker object as moves source
template<> struct MovePickerExt<true> : public MovePicker {
- MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b)
+ MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, Stack* ss, Value b)
: MovePicker(p, ttm, d, h, ss, b), mp(ss->sp->mp) {}
Move get_next_move() { return mp->get_next_move(); }
return os;
}
- // extension() decides whether a move should be searched with normal depth,
- // or with extended depth. Certain classes of moves (checking moves, in
- // particular) are searched with bigger depth than ordinary moves and in
- // any case are marked as 'dangerous'. Note that also if a move is not
- // extended, as example because the corresponding UCI option is set to zero,
- // the move is marked as 'dangerous' so, at least, we avoid to prune it.
- template <bool PvNode>
- FORCE_INLINE Depth extension(const Position& pos, Move m, bool captureOrPromotion,
- bool moveIsCheck, bool* dangerous) {
- assert(m != MOVE_NONE);
-
- Depth result = DEPTH_ZERO;
- *dangerous = moveIsCheck;
-
- if (moveIsCheck && pos.see_sign(m) >= 0)
- result += CheckExtension[PvNode];
+ // is_dangerous() checks whether a move belongs to some classes of known
+ // 'dangerous' moves so that we avoid to prune it.
+ FORCE_INLINE bool is_dangerous(const Position& pos, Move m, bool captureOrPromotion) {
+ // Test for a pawn pushed to 7th or a passed pawn move
if (type_of(pos.piece_on(move_from(m))) == PAWN)
{
Color c = pos.side_to_move();
- if (relative_rank(c, move_to(m)) == RANK_7)
- {
- result += PawnPushTo7thExtension[PvNode];
- *dangerous = true;
- }
- if (pos.pawn_is_passed(c, move_to(m)))
- {
- result += PassedPawnExtension[PvNode];
- *dangerous = true;
- }
+ if ( relative_rank(c, move_to(m)) == RANK_7
+ || pos.pawn_is_passed(c, move_to(m)))
+ return true;
}
+ // Test for a capture that triggers a pawn endgame
if ( captureOrPromotion
&& type_of(pos.piece_on(move_to(m))) != PAWN
&& ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
- PieceValueMidgame[pos.piece_on(move_to(m))] == VALUE_ZERO)
&& !is_special(m))
- {
- result += PawnEndgameExtension[PvNode];
- *dangerous = true;
- }
+ return true;
- return std::min(result, ONE_PLY);
+ return false;
}
} // namespace
/// init_search() is called during startup to initialize various lookup tables
-void init_search() {
+void Search::init() {
int d; // depth (ONE_PLY == 2)
int hd; // half depth (ONE_PLY == 1)
/// perft() is our utility to verify move generation. All the leaf nodes up to
/// the given depth are generated and counted and the sum returned.
-int64_t perft(Position& pos, Depth depth) {
+int64_t Search::perft(Position& pos, Depth depth) {
StateInfo st;
int64_t sum = 0;
- // Generate all legal moves
MoveList<MV_LEGAL> ml(pos);
- // If we are at the last ply we don't need to do and undo
- // the moves, just to count them.
+ // At the last ply just return the number of moves (leaf nodes)
if (depth <= ONE_PLY)
return ml.size();
- // Loop through all legal moves
CheckInfo ci(pos);
for ( ; !ml.end(); ++ml)
{
}
-/// think() is the external interface to Stockfish's search, and is called when
-/// the program receives the UCI 'go' command. It initializes various global
-/// variables, and calls id_loop(). It returns false when a "quit" command is
-/// received during the search.
+/// think() is the external interface to Stockfish's search, and is called by the
+/// main thread when the program receives the UCI 'go' command. It searches from
+/// RootPosition and at the end prints the "bestmove" to output.
-bool think(Position& pos, const SearchLimits& limits, Move searchMoves[]) {
+void Search::think() {
static Book book; // Defined static to initialize the PRNG only once
- // Save "search start" time and reset elapsed time to zero
- elapsed_search_time(get_system_time());
-
- // Initialize global search-related variables
- StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = false;
- Limits = limits;
+ Position& pos = RootPosition;
+ elapsed_time(true);
+ TimeMgr.init(Limits, pos.startpos_ply_counter());
// Set output stream mode: normal or chess960. Castling notation is different
cout << set960(pos.is_chess960());
- // Look for a book move
if (Options["OwnBook"].value<bool>())
{
if (Options["Book File"].value<string>() != book.name())
Move bookMove = book.probe(pos, Options["Best Book Move"].value<bool>());
if (bookMove != MOVE_NONE)
{
- if (Limits.ponder)
- wait_for_stop_or_ponderhit();
+ if (!Signals.stop && (Limits.ponder || Limits.infinite))
+ Threads.wait_for_stop_or_ponderhit();
cout << "bestmove " << bookMove << endl;
- return !QuitRequest;
+ return;
}
}
read_evaluation_uci_options(pos.side_to_move());
Threads.read_uci_options();
- // Set a new TT size if changed
TT.set_size(Options["Hash"].value<int>());
-
if (Options["Clear Hash"].value<bool>())
{
Options["Clear Hash"].set_value("false");
TT.clear();
}
- UCIMultiPV = Options["MultiPV"].value<int>();
- SkillLevel = Options["Skill Level"].value<int>();
+ UCIMultiPV = Options["MultiPV"].value<size_t>();
+ SkillLevel = Options["Skill Level"].value<size_t>();
// Do we have to play with skill handicap? In this case enable MultiPV that
// we will use behind the scenes to retrieve a set of possible moves.
SkillLevelEnabled = (SkillLevel < 20);
- MultiPV = (SkillLevelEnabled ? std::max(UCIMultiPV, 4) : UCIMultiPV);
+ MultiPV = (SkillLevelEnabled ? std::max(UCIMultiPV, (size_t)4) : UCIMultiPV);
- // Write current search header to log file
if (Options["Use Search Log"].value<bool>())
{
Log log(Options["Search Log Filename"].value<string>());
// Set best timer interval to avoid lagging under time pressure. Timer is
// used to check for remaining available thinking time.
- TimeMgr.init(Limits, pos.startpos_ply_counter());
-
if (TimeMgr.available_time())
Threads.set_timer(std::min(100, std::max(TimeMgr.available_time() / 8, 20)));
else
Threads.set_timer(100);
- // Start async mode to catch UCI commands sent to us while searching,
- // like "quit", "stop", etc.
- Threads.start_listener();
-
// We're ready to start thinking. Call the iterative deepening loop function
Move ponderMove = MOVE_NONE;
- Move bestMove = id_loop(pos, searchMoves, &ponderMove);
-
- // From now on any UCI command will be read in-sync with Threads.getline()
- Threads.stop_listener();
+ Move bestMove = id_loop(pos, &RootMoves[0], &ponderMove);
- // Stop timer, no need to check for available time any more
+ // Stop timer and send all the slaves to sleep, if not already sleeping
Threads.set_timer(0);
-
- // This makes all the slave threads to go to sleep, if not already sleeping
Threads.set_size(1);
- // Write current search final statistics to log file
if (Options["Use Search Log"].value<bool>())
{
- int e = elapsed_search_time();
+ int e = elapsed_time();
Log log(Options["Search Log Filename"].value<string>());
log << "Nodes: " << pos.nodes_searched()
// When we reach max depth we arrive here even without a StopRequest, but if
// we are pondering or in infinite search, we shouldn't print the best move
// before we are told to do so.
- if (!StopRequest && (Limits.ponder || Limits.infinite))
- wait_for_stop_or_ponderhit();
+ if (!Signals.stop && (Limits.ponder || Limits.infinite))
+ Threads.wait_for_stop_or_ponderhit();
// Could be MOVE_NONE when searching on a stalemate position
cout << "bestmove " << bestMove;
cout << " ponder " << ponderMove;
cout << endl;
-
- return !QuitRequest;
}
// with increasing depth until the allocated thinking time has been consumed,
// user stops the search, or the maximum search depth is reached.
- Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
+ Move id_loop(Position& pos, Move rootMoves[], Move* ponderMove) {
- SearchStack ss[PLY_MAX_PLUS_2];
+ Stack ss[PLY_MAX_PLUS_2];
Value bestValues[PLY_MAX_PLUS_2];
int bestMoveChanges[PLY_MAX_PLUS_2];
int depth, aspirationDelta;
Move bestMove, skillBest, skillPonder;
bool bestMoveNeverChanged = true;
- // Initialize stuff before a new search
- memset(ss, 0, 4 * sizeof(SearchStack));
+ memset(ss, 0, 4 * sizeof(Stack));
TT.new_search();
H.clear();
*ponderMove = bestMove = skillBest = skillPonder = MOVE_NONE;
depth = aspirationDelta = 0;
bestValue = alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
ss->currentMove = MOVE_NULL; // Hack to skip update gains
-
- // Moves to search are verified and copied
- Rml.init(pos, searchMoves);
+ Rml.init(pos, rootMoves);
// Handle special case of searching on a mate/stalemate position
- if (!Rml.size())
+ if (Rml.empty())
{
cout << "info" << depth_to_uci(DEPTH_ZERO)
<< score_to_uci(pos.in_check() ? -VALUE_MATE : VALUE_DRAW, alpha, beta) << endl;
}
// Iterative deepening loop until requested to stop or target depth reached
- while (!StopRequest && ++depth <= PLY_MAX && (!Limits.maxDepth || depth <= Limits.maxDepth))
+ while (!Signals.stop && ++depth <= PLY_MAX && (!Limits.maxDepth || depth <= Limits.maxDepth))
{
// Save now last iteration's scores, before Rml moves are reordered
for (size_t i = 0; i < Rml.size(); i++)
Rml.bestMoveChanges = 0;
// MultiPV loop. We perform a full root search for each PV line
- for (MultiPVIdx = 0; MultiPVIdx < std::min(MultiPV, (int)Rml.size()); MultiPVIdx++)
+ for (MultiPVIdx = 0; MultiPVIdx < std::min(MultiPV, Rml.size()); MultiPVIdx++)
{
// Calculate dynamic aspiration window based on previous iterations
if (depth >= 5 && abs(Rml[MultiPVIdx].prevScore) < VALUE_KNOWN_WIN)
// Write PV back to transposition table in case the relevant entries
// have been overwritten during the search.
- for (int i = 0; i <= MultiPVIdx; i++)
+ for (size_t i = 0; i <= MultiPVIdx; i++)
Rml[i].insert_pv_in_tt(pos);
// If search has been stopped exit the aspiration window loop,
// note that sorting and writing PV back to TT is safe becuase
// Rml is still valid, although refers to the previous iteration.
- if (StopRequest)
+ if (Signals.stop)
break;
// Send full PV info to GUI if we are going to leave the loop or
// if we have a fail high/low and we are deep in the search. UCI
// protocol requires to send all the PV lines also if are still
// to be searched and so refer to the previous search's score.
- if ((bestValue > alpha && bestValue < beta) || elapsed_search_time() > 2000)
- for (int i = 0; i < std::min(UCIMultiPV, (int)Rml.size()); i++)
+ if ((bestValue > alpha && bestValue < beta) || elapsed_time() > 2000)
+ for (size_t i = 0; i < std::min(UCIMultiPV, Rml.size()); i++)
{
bool updated = (i <= MultiPVIdx);
}
else if (bestValue <= alpha)
{
- AspirationFailLow = true;
- StopOnPonderhit = false;
+ Signals.failedLowAtRoot = true;
+ Signals.stopOnPonderhit = false;
alpha = std::max(alpha - aspirationDelta, -VALUE_INFINITE);
aspirationDelta += aspirationDelta / 2;
} while (abs(bestValue) < VALUE_KNOWN_WIN);
}
- // Collect info about search result
bestMove = Rml[0].pv[0];
*ponderMove = Rml[0].pv[1];
bestValues[depth] = bestValue;
if (Options["Use Search Log"].value<bool>())
{
Log log(Options["Search Log Filename"].value<string>());
- log << pretty_pv(pos, depth, bestValue, elapsed_search_time(), &Rml[0].pv[0]) << endl;
+ log << pretty_pv(pos, depth, bestValue, elapsed_time(), &Rml[0].pv[0]) << endl;
}
// Filter out startup noise when monitoring best move stability
bestMoveNeverChanged = false;
// Do we have time for the next iteration? Can we stop searching now?
- if (!StopRequest && !StopOnPonderhit && Limits.useTimeManagement())
+ if (!Signals.stop && !Signals.stopOnPonderhit && Limits.useTimeManagement())
{
+ bool stop = false; // Local variable instead of the volatile Signals.stop
+
// Take in account some extra time if the best move has changed
if (depth > 4 && depth < 50)
TimeMgr.pv_instability(bestMoveChanges[depth], bestMoveChanges[depth - 1]);
// 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 (elapsed_search_time() > (TimeMgr.available_time() * 62) / 100)
- StopRequest = true;
+ if (elapsed_time() > (TimeMgr.available_time() * 62) / 100)
+ stop = true;
// Stop search early if one move seems to be much better than others
if ( depth >= 10
- && !StopRequest
+ && !stop
&& ( bestMoveNeverChanged
- || elapsed_search_time() > (TimeMgr.available_time() * 40) / 100))
+ || elapsed_time() > (TimeMgr.available_time() * 40) / 100))
{
Value rBeta = bestValue - EasyMoveMargin;
(ss+1)->excludedMove = bestMove;
(ss+1)->excludedMove = MOVE_NONE;
if (v < rBeta)
- StopRequest = true;
+ stop = true;
}
- // If we are allowed to ponder do not stop the search now but keep pondering
- if (StopRequest && Limits.ponder) // FIXME Limits.ponder is racy
+ if (stop)
{
- StopRequest = false;
- StopOnPonderhit = true;
+ // If we are allowed to ponder do not stop the search now but
+ // keep pondering until GUI sends "ponderhit" or "stop".
+ if (Limits.ponder)
+ Signals.stopOnPonderhit = true;
+ else
+ Signals.stop = true;
}
}
}
// here: This is taken care of after we return from the split point.
template <NodeType NT>
- Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth) {
+ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
const bool PvNode = (NT == PV || NT == Root || NT == SplitPointPV || NT == SplitPointRoot);
const bool SpNode = (NT == SplitPointPV || NT == SplitPointNonPV || NT == SplitPointRoot);
ValueType vt;
Value bestValue, value, oldAlpha;
Value refinedValue, nullValue, futilityBase, futilityValue;
- bool isPvMove, inCheck, singularExtensionNode, givesCheck, captureOrPromotion, dangerous;
+ bool isPvMove, inCheck, singularExtensionNode, givesCheck;
+ bool captureOrPromotion, dangerous, doFullDepthSearch;
int moveCount = 0, playedMoveCount = 0;
Thread& thread = Threads[pos.thread()];
SplitPoint* sp = NULL;
}
// Step 2. Check for aborted search and immediate draw
- if (( StopRequest
+ if (( Signals.stop
|| pos.is_draw<false>()
|| ss->ply > PLY_MAX) && !RootNode)
return VALUE_DRAW;
split_point_start: // At split points actual search starts from here
- // Initialize a MovePicker object for the current position
MovePickerExt<SpNode> mp(pos, ttMove, depth, H, ss, PvNode ? -VALUE_INFINITE : beta);
CheckInfo ci(pos);
ss->bestMove = MOVE_NONE;
&& !SpNode
&& depth >= SingularExtensionDepth[PvNode]
&& ttMove != MOVE_NONE
- && !excludedMove // Do not allow recursive singular extension search
+ && !excludedMove // Recursive singular search is not allowed
&& (tte->type() & VALUE_TYPE_LOWER)
&& tte->depth() >= depth - 3 * ONE_PLY;
if (SpNode)
{
lock_grab(&(sp->lock));
bestValue = sp->bestValue;
+ moveCount = sp->moveCount;
+
+ assert(bestValue > -VALUE_INFINITE && moveCount > 0);
}
// Step 11. Loop through moves
if (RootNode)
{
// This is used by time management
- FirstRootMove = (moveCount == 1);
+ Signals.firstRootMove = (moveCount == 1);
- // Save the current node count before the move is searched
nodes = pos.nodes_searched();
- // For long searches send current move info to GUI
- if (pos.thread() == 0 && elapsed_search_time() > 2000)
+ if (pos.thread() == 0 && elapsed_time() > 2000)
cout << "info" << depth_to_uci(depth)
<< " currmove " << move
<< " currmovenumber " << moveCount + MultiPVIdx << endl;
}
isPvMove = (PvNode && moveCount <= 1);
- givesCheck = pos.move_gives_check(move, ci);
captureOrPromotion = pos.is_capture_or_promotion(move);
+ givesCheck = pos.move_gives_check(move, ci);
+ dangerous = givesCheck || is_dangerous(pos, move, captureOrPromotion);
+ ext = DEPTH_ZERO;
+
+ // Step 12. Extend checks and, in PV nodes, also dangerous moves
+ if (PvNode && dangerous)
+ ext = ONE_PLY;
- // Step 12. Decide the new search depth
- ext = extension<PvNode>(pos, move, captureOrPromotion, givesCheck, &dangerous);
+ else if (givesCheck && pos.see_sign(move) >= 0)
+ ext = PvNode ? ONE_PLY : ONE_PLY / 2;
// Singular extension search. If all moves but one fail low on a search of
// (alpha-s, beta-s), and just one fails high on (alpha, beta), then that move
// on all the other moves but the ttMove, if result is lower than ttValue minus
// a margin then we extend ttMove.
if ( singularExtensionNode
+ && !ext
&& move == ttMove
- && pos.pl_move_is_legal(move, ci.pinned)
- && ext < ONE_PLY)
+ && pos.pl_move_is_legal(move, ci.pinned))
{
Value ttValue = value_from_tt(tte->value(), ss->ply);
Value rBeta = ttValue - int(depth);
ss->excludedMove = move;
ss->skipNullMove = true;
- Value v = search<NonPV>(pos, ss, rBeta - 1, rBeta, depth / 2);
+ value = search<NonPV>(pos, ss, rBeta - 1, rBeta, depth / 2);
ss->skipNullMove = false;
ss->excludedMove = MOVE_NONE;
ss->bestMove = MOVE_NONE;
- if (v < rBeta)
+ if (value < rBeta)
ext = ONE_PLY;
}
}
&& !inCheck
&& !dangerous
&& move != ttMove
- && !is_castle(move))
+ && !is_castle(move)
+ && (bestValue > VALUE_MATED_IN_PLY_MAX || bestValue == -VALUE_INFINITE))
{
// Move count based pruning
if ( moveCount >= futility_move_count(depth)
- && (!threatMove || !connected_threat(pos, move, threatMove))
- && bestValue > VALUE_MATED_IN_PLY_MAX) // FIXME bestValue is racy
+ && (!threatMove || !connected_threat(pos, move, threatMove)))
{
if (SpNode)
lock_grab(&(sp->lock));
if (futilityValue < beta)
{
if (SpNode)
- {
lock_grab(&(sp->lock));
- if (futilityValue > sp->bestValue)
- sp->bestValue = bestValue = futilityValue;
- }
- else if (futilityValue > bestValue)
- bestValue = futilityValue;
continue;
}
// Prune moves with negative SEE at low depths
if ( predictedDepth < 2 * ONE_PLY
- && bestValue > VALUE_MATED_IN_PLY_MAX
&& pos.see_sign(move) < 0)
{
if (SpNode)
// Step 14. Make the move
pos.do_move(move, st, ci, givesCheck);
- // Step extra. pv search (only in PV nodes)
- // The first move in list is the expected PV
- if (isPvMove)
- value = newDepth < ONE_PLY ? -qsearch<PV>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
- : - search<PV>(pos, ss+1, -beta, -alpha, newDepth);
- else
+ // Step 15. Reduced depth search (LMR). If the move fails high will be
+ // re-searched at full depth.
+ if ( depth > 3 * ONE_PLY
+ && !isPvMove
+ && !captureOrPromotion
+ && !dangerous
+ && !is_castle(move)
+ && ss->killers[0] != move
+ && ss->killers[1] != move)
{
- // Step 15. Reduced depth search
- // If the move fails high will be re-searched at full depth.
- bool doFullDepthSearch = true;
-
- if ( depth > 3 * ONE_PLY
- && !captureOrPromotion
- && !dangerous
- && !is_castle(move)
- && ss->killers[0] != move
- && ss->killers[1] != move
- && (ss->reduction = reduction<PvNode>(depth, moveCount)) != DEPTH_ZERO)
- {
- Depth d = newDepth - ss->reduction;
- alpha = SpNode ? sp->alpha : alpha;
+ ss->reduction = reduction<PvNode>(depth, moveCount);
+ Depth d = newDepth - ss->reduction;
+ alpha = SpNode ? sp->alpha : alpha;
- value = d < ONE_PLY ? -qsearch<NonPV>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
- : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d);
+ value = d < ONE_PLY ? -qsearch<NonPV>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
+ : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d);
- ss->reduction = DEPTH_ZERO;
- doFullDepthSearch = (value > alpha);
- }
+ doFullDepthSearch = (value > alpha && ss->reduction != DEPTH_ZERO);
+ ss->reduction = DEPTH_ZERO;
+ }
+ else
+ doFullDepthSearch = !isPvMove;
- // Step 16. Full depth search
- if (doFullDepthSearch)
- {
- alpha = SpNode ? sp->alpha : alpha;
- value = newDepth < ONE_PLY ? -qsearch<NonPV>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
- : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth);
-
- // Step extra. pv search (only in PV nodes)
- // Search only for possible new PV nodes, if instead value >= beta then
- // parent node fails low with value <= alpha and tries another move.
- if (PvNode && value > alpha && (RootNode || value < beta))
- value = newDepth < ONE_PLY ? -qsearch<PV>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
- : - search<PV>(pos, ss+1, -beta, -alpha, newDepth);
- }
+ // Step 16. Full depth search, when LMR is skipped or fails high
+ if (doFullDepthSearch)
+ {
+ alpha = SpNode ? sp->alpha : alpha;
+ value = newDepth < ONE_PLY ? -qsearch<NonPV>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
+ : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth);
}
+ // Only for PV nodes do a full PV search on the first move or after a fail
+ // high, in the latter case search only if value < beta, otherwise let the
+ // parent node to fail low with value <= alpha and to try another move.
+ if (PvNode && (isPvMove || (value > alpha && (RootNode || value < beta))))
+ value = newDepth < ONE_PLY ? -qsearch<PV>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
+ : - search<PV>(pos, ss+1, -beta, -alpha, newDepth);
+
// Step 17. Undo move
pos.undo_move(move);
// was aborted because the user interrupted the search or because we
// ran out of time. In this case, the return value of the search cannot
// be trusted, and we don't update the best move and/or PV.
- if (RootNode && !StopRequest)
+ if (RootNode && !Signals.stop)
{
- // Remember searched nodes counts for this move
RootMove* rm = Rml.find(move);
rm->nodes += pos.nodes_searched() - nodes;
// PV move or new best move ?
if (isPvMove || value > alpha)
{
- // Update PV
rm->score = value;
rm->extract_pv_from_tt(pos);
// position in the list is preserved, just the PV is pushed up.
rm->score = -VALUE_INFINITE;
- } // RootNode
+ }
if (value > bestValue)
{
&& depth >= Threads.min_split_depth()
&& bestValue < beta
&& Threads.available_slave_exists(pos.thread())
- && !StopRequest
+ && !Signals.stop
&& !thread.cutoff_occurred())
bestValue = Threads.split<FakeSplit>(pos, ss, alpha, beta, bestValue, depth,
threatMove, moveCount, &mp, NT);
// case of StopRequest or thread.cutoff_occurred() are set, but this is
// harmless because return value is discarded anyhow in the parent nodes.
// If we are in a singular extension search then return a fail low score.
- if (!SpNode && !moveCount)
+ if (!moveCount)
return excludedMove ? oldAlpha : inCheck ? value_mated_in(ss->ply) : VALUE_DRAW;
+ // If we have pruned all the moves without searching return a fail-low score
+ if (bestValue == -VALUE_INFINITE)
+ {
+ assert(!playedMoveCount);
+
+ bestValue = alpha;
+ }
+
// Step 21. Update tables
- // If the search is not aborted, update the transposition table,
- // history counters, and killer moves.
- if (!SpNode && !StopRequest && !thread.cutoff_occurred())
+ // Update transposition table entry, history and killers
+ if (!SpNode && !Signals.stop && !thread.cutoff_occurred())
{
move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
return bestValue;
}
+
// qsearch() is the quiescence search function, which is called by the main
// search function when the remaining depth is zero (or, to be more precise,
// less than ONE_PLY).
template <NodeType NT>
- Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth) {
+ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
const bool PvNode = (NT == PV);
if (PvNode && bestValue > alpha)
alpha = bestValue;
- // Futility pruning parameters, not needed when in check
futilityBase = ss->eval + evalMargin + FutilityMarginQS;
enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
}
if (!pos.pl_move_is_legal(move, ci.pinned))
continue;
- // Update current move
ss->currentMove = move;
// Make and search the move
}
- // can_return_tt() returns true if a transposition table score
- // can be used to cut-off at a given point in search.
+ // can_return_tt() returns true if a transposition table score can be used to
+ // cut-off at a given point in search.
bool can_return_tt(const TTEntry* tte, Depth depth, Value beta, int ply) {
}
- // refine_eval() returns the transposition table score if
- // possible otherwise falls back on static position evaluation.
+ // refine_eval() returns the transposition table score if possible, otherwise
+ // falls back on static position evaluation.
Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
}
- // update_history() registers a good move that produced a beta-cutoff
- // in history and marks as failures all the other moves of that ply.
+ // update_history() registers a good move that produced a beta-cutoff in
+ // history and marks as failures all the other moves of that ply.
void update_history(const Position& pos, Move move, Depth depth,
Move movesSearched[], int moveCount) {
// current_search_time() returns the number of milliseconds which have passed
// since the beginning of the current search.
- int elapsed_search_time(int set) {
+ int elapsed_time(bool reset) {
static int searchStartTime;
- if (set)
- searchStartTime = set;
+ if (reset)
+ searchStartTime = get_system_time();
return get_system_time() - searchStartTime;
}
string speed_to_uci(int64_t nodes) {
std::stringstream s;
- int t = elapsed_search_time();
+ int t = elapsed_time();
s << " nodes " << nodes
<< " nps " << (t > 0 ? int(nodes * 1000 / t) : 0)
return s.str();
}
+
+ // pretty_pv() creates a human-readable string from a position and a PV.
+ // It is used to write search information to the log file (which is created
+ // when the UCI parameter "Use Search Log" is "true"). It uses the two helpers
+ // time_to_string() and score_to_string() to format time and score respectively.
+
string time_to_string(int millisecs) {
const int MSecMinute = 1000 * 60;
return s.str();
}
-
- // pretty_pv() creates a human-readable string from a position and a PV.
- // It is used to write search information to the log file (which is created
- // when the UCI parameter "Use Search Log" is "true").
-
string pretty_pv(Position& pos, int depth, Value value, int time, Move pv[]) {
const int64_t K = 1000;
}
- // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
- // while the program is pondering. The point is to work around a wrinkle in
- // the UCI protocol: When pondering, the engine is not allowed to give a
- // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
- // We simply wait here until one of these commands (that raise StopRequest) is
- // sent, and return, after which the bestmove and pondermove will be printed.
-
- void wait_for_stop_or_ponderhit() {
-
- string cmd;
- StopOnPonderhit = true;
-
- while (!StopRequest)
- {
- Threads.getline(cmd);
- do_uci_async_cmd(cmd);
- }
- }
-
-
// When playing with strength handicap choose best move among the MultiPV set
// using a statistical rule dependent on SkillLevel. Idea by Heinz van Saanen.
// Rml list is already sorted by score in descending order
int s;
+ size_t size = std::min(MultiPV, Rml.size());
int max_s = -VALUE_INFINITE;
- int size = std::min(MultiPV, (int)Rml.size());
int max = Rml[0].score;
int var = std::min(max - Rml[size - 1].score, int(PawnValueMidgame));
int wk = 120 - 2 * SkillLevel;
// Choose best move. For each move's score we add two terms both dependent
// on wk, one deterministic and bigger for weaker moves, and one random,
// then we choose the move with the resulting highest score.
- for (int i = 0; i < size; i++)
+ for (size_t i = 0; i < size; i++)
{
s = Rml[i].score;
}
- /// RootMove and RootMoveList method's definitions
+ // RootMove and RootMoveList method's definitions
- void RootMoveList::init(Position& pos, Move searchMoves[]) {
+ void RootMoveList::init(Position& pos, Move rootMoves[]) {
Move* sm;
bestMoveChanges = 0;
// Generate all legal moves and add them to RootMoveList
for (MoveList<MV_LEGAL> ml(pos); !ml.end(); ++ml)
{
- // If we have a searchMoves[] list then verify the move
+ // If we have a rootMoves[] list then verify the move
// is in the list before to add it.
- for (sm = searchMoves; *sm && *sm != ml.move(); sm++) {}
+ for (sm = rootMoves; *sm && *sm != ml.move(); sm++) {}
- if (sm != searchMoves && *sm != ml.move())
+ if (sm != rootMoves && *sm != ml.move())
continue;
RootMove rm;
} // namespace
-// Thread::idle_loop() is where the thread is parked when it has no work to do.
-// The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint object
-// for which the thread is the master.
+/// Thread::idle_loop() is where the thread is parked when it has no work to do.
+/// The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint object
+/// for which the thread is the master.
void Thread::idle_loop(SplitPoint* sp) {
{
assert((!sp && threadID) || Threads.use_sleeping_threads());
- // Slave thread should exit as soon as do_terminate flag raises
if (do_terminate)
{
assert(!sp);
assert(!do_terminate);
// Copy split point position and search stack and call search()
- SearchStack ss[PLY_MAX_PLUS_2];
+ Stack ss[PLY_MAX_PLUS_2];
SplitPoint* tsp = splitPoint;
Position pos(*tsp->pos, threadID);
- memcpy(ss, tsp->ss - 1, 4 * sizeof(SearchStack));
+ memcpy(ss, tsp->ss - 1, 4 * sizeof(Stack));
(ss+1)->sp = tsp;
if (tsp->nodeType == Root)
}
-// do_uci_async_cmd() is called by listener thread when in async mode and 'cmd'
-// input line is received from the GUI.
-
-void do_uci_async_cmd(const std::string& cmd) {
-
- if (cmd == "quit")
- QuitRequest = StopRequest = true;
-
- else if (cmd == "stop")
- StopRequest = true;
-
- else if (cmd == "ponderhit")
- {
- // The opponent has played the expected move. GUI sends "ponderhit" if
- // we were told to ponder on the same move the opponent has played. We
- // should continue searching but switching from pondering to normal search.
- Limits.ponder = false;
-
- if (StopOnPonderhit)
- StopRequest = true;
- }
-}
-
-
-// do_timer_event() is called by the timer thread when the timer triggers
+/// do_timer_event() 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.
void do_timer_event() {
static int lastInfoTime;
- int e = elapsed_search_time();
+ int e = elapsed_time();
- // Print debug information every second
- if (get_system_time() - lastInfoTime >= 1000)
+ if (get_system_time() - lastInfoTime >= 1000 || !lastInfoTime)
{
lastInfoTime = get_system_time();
dbg_print_hit_rate();
}
- // Should we stop the search?
if (Limits.ponder)
return;
- bool stillAtFirstMove = FirstRootMove
- && !AspirationFailLow
+ bool stillAtFirstMove = Signals.firstRootMove
+ && !Signals.failedLowAtRoot
&& e > TimeMgr.available_time();
bool noMoreTime = e > TimeMgr.maximum_time()
if ( (Limits.useTimeManagement() && noMoreTime)
|| (Limits.maxTime && e >= Limits.maxTime)
/* missing nodes limit */ ) // FIXME
- StopRequest = true;
+ Signals.stop = true;
}
projects / stockfish / blobdiff