along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
-
-////
-//// Includes
-////
-
#include <cassert>
#include <cmath>
#include <cstring>
using std::cout;
using std::endl;
-////
-//// Local definitions
-////
-
namespace {
- // Types
+ // Different node types, used as template parameter
enum NodeType { NonPV, PV };
- // Set to true to force running with one thread.
- // Used for debugging SMP code.
+ // Set to true to force running with one thread. Used for debugging.
const bool FakeSplit = false;
- // Fast lookup table of sliding pieces indexed by Piece
+ // Lookup table to check if a Piece is a slider and its access function
const bool Slidings[18] = { 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1 };
inline bool piece_is_slider(Piece p) { return Slidings[p]; }
- // ThreadsManager class is used to handle all the threads related stuff in search,
- // init, starting, parking and, the most important, launching a slave thread at a
- // split point are what this class does. All the access to shared thread data is
- // done through this class, so that we avoid using global variables instead.
+ // ThreadsManager class is used to handle all the threads related stuff like init,
+ // starting, parking and, the most important, launching a slave thread at a split
+ // point. All the access to shared thread data is done through this class.
class ThreadsManager {
/* As long as the single ThreadsManager object is defined as a global we don't
template <bool Fake>
void split(Position& pos, SearchStack* ss, int ply, Value* alpha, const Value beta, Value* bestValue,
- Depth depth, Move threatMove, bool mateThreat, int moveCount, MovePicker* mp, bool pvNode);
+ Depth depth, Move threatMove, int moveCount, MovePicker* mp, bool pvNode);
private:
Depth minimumSplitDepth;
};
- // RootMove struct is used for moves at the root at the tree. For each root
+ // RootMove struct is used for moves at the root of the tree. For each root
// move, we store two scores, a node count, and a PV (really a refutation
// in the case of moves which fail low). Value pv_score is normally set at
// -VALUE_INFINITE for all non-pv moves, while non_pv_score is computed
// RootMove::operator<() is the comparison function used when
// sorting the moves. A move m1 is considered to be better
// than a move m2 if it has an higher pv_score, or if it has
- // equal pv_score but m1 has the higher non_pv_score. In this
- // way we are guaranteed that PV moves are always sorted as first.
+ // equal pv_score but m1 has the higher non_pv_score. In this way
+ // we are guaranteed that PV moves are always sorted as first.
bool operator<(const RootMove& m) const {
return pv_score != m.pv_score ? pv_score < m.pv_score
: non_pv_score < m.non_pv_score;
void extract_pv_from_tt(Position& pos);
void insert_pv_in_tt(Position& pos);
- std::string pv_info_to_uci(Position& pos, int depth, Value alpha, Value beta, int pvLine);
+ std::string pv_info_to_uci(Position& pos, int depth, Value alpha, Value beta, int pvIdx);
int64_t nodes;
Value pv_score;
};
- // RootMoveList struct is essentially a std::vector<> of RootMove objects,
+ // RootMoveList struct is just a std::vector<> of RootMove objects,
// with an handful of methods above the standard ones.
struct RootMoveList : public std::vector<RootMove> {
};
+ // Overload operator<<() to make it easier to print moves in a coordinate
+ // notation compatible with UCI protocol.
+ std::ostream& operator<<(std::ostream& os, Move m) {
+
+ bool chess960 = (os.iword(0) != 0); // See set960()
+ return os << move_to_uci(m, chess960);
+ }
+
+
// When formatting a move for std::cout we must know if we are in Chess960
// or not. To keep using the handy operator<<() on the move the trick is to
// embed this flag in the stream itself. Function-like named enum set960 is
// used as a custom manipulator and the stream internal general-purpose array,
// accessed through ios_base::iword(), is used to pass the flag to the move's
- // operator<<() that will use it to properly format castling moves.
+ // operator<<() that will read it to properly format castling moves.
enum set960 {};
std::ostream& operator<< (std::ostream& os, const set960& f) {
}
- // Overload operator << for moves to make it easier to print moves in
- // coordinate notation compatible with UCI protocol.
- std::ostream& operator<<(std::ostream& os, Move m) {
-
- bool chess960 = (os.iword(0) != 0); // See set960()
- return os << move_to_uci(m, chess960);
- }
-
-
/// Adjustments
// Step 6. Razoring
// Extensions. Configurable UCI options
// Array index 0 is used at non-PV nodes, index 1 at PV nodes.
- Depth CheckExtension[2], PawnPushTo7thExtension[2], PassedPawnExtension[2];
- Depth PawnEndgameExtension[2], MateThreatExtension[2];
+ Depth CheckExtension[2], PawnPushTo7thExtension[2];
+ Depth PassedPawnExtension[2], PawnEndgameExtension[2];
// Minimum depth for use of singular extension
const Depth SingularExtensionDepth[2] = { 8 * ONE_PLY /* non-PV */, 6 * ONE_PLY /* PV */};
// Futility margin for quiescence search
const Value FutilityMarginQS = Value(0x80);
- // Futility lookup tables (initialized at startup) and their getter functions
+ // Futility lookup tables (initialized at startup) and their access functions
Value FutilityMarginsMatrix[16][64]; // [depth][moveNumber]
int FutilityMoveCountArray[32]; // [depth]
int8_t ReductionMatrix[2][64][64]; // [pv][depth][moveNumber]
template <NodeType PV>
- inline Depth reduction(Depth d, int mn) { return (Depth) ReductionMatrix[PV][Min(d / 2, 63)][Min(mn, 63)]; }
+ inline Depth reduction(Depth d, int mn) { return (Depth) ReductionMatrix[PV][Min(d / ONE_PLY, 63)][Min(mn, 63)]; }
// Easy move margin. An easy move candidate must be at least this much
// better than the second best move.
/// Namespace variables
- // Book object
+ // Book
Book OpeningBook;
// Root move list
// Skill level adjustment
int SkillLevel;
+ bool SkillLevelEnabled;
RKISS RK;
- // Multi-threads manager object
+ // Multi-threads manager
ThreadsManager ThreadsMgr;
// Node counters, used only by thread[0] but try to keep in different cache
// History table
History H;
+
/// Local functions
Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove);
template <NodeType PvNode>
inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
-
return depth < ONE_PLY ? qsearch<PvNode>(pos, ss, alpha, beta, DEPTH_ZERO, ply)
-
: search<PvNode, false, false>(pos, ss, alpha, beta, depth, ply);
+ return depth < ONE_PLY ? qsearch<PvNode>(pos, ss, alpha, beta, DEPTH_ZERO, ply)
+ : search<PvNode, false, false>(pos, ss, alpha, beta, depth, ply);
}
template <NodeType PvNode>
- Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool mateThreat, bool* dangerous);
+ Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool* dangerous);
bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue);
bool connected_moves(const Position& pos, Move m1, Move m2);
- bool value_is_mate(Value value);
Value value_to_tt(Value v, int ply);
Value value_from_tt(Value v, int ply);
bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
void update_gains(const Position& pos, Move move, Value before, Value after);
+ void do_skill_level(Move* best, Move* ponder);
int current_search_time();
std::string value_to_uci(Value v);
// the proper move source according to the type of node.
template<bool SpNode, bool Root> struct MovePickerExt;
- // In Root nodes use RootMoveList Rml as source. Score and sort the root moves
+ // In Root nodes use RootMoveList as source. Score and sort the root moves
// before to search them.
template<> struct MovePickerExt<false, true> : public MovePicker {
Move move;
Value score = VALUE_ZERO;
- // Score root moves using the standard way used in main search, the moves
+ // Score root moves using standard ordering used in main search, the moves
// are scored according to the order in which they are returned by MovePicker.
// This is the second order score that is used to compare the moves when
- // the first order pv scores of both moves are equal.
+ // the first orders pv_score of both moves are equal.
while ((move = MovePicker::get_next_move()) != MOVE_NONE)
for (rm = Rml.begin(); rm != Rml.end(); ++rm)
if (rm->pv[0] == move)
// In SpNodes use split point's shared MovePicker object as move source
template<> struct MovePickerExt<true, false> : public MovePicker {
- MovePickerExt(const Position& p, Move ttm, Depth d, const History& h,
- SearchStack* ss, Value b) : MovePicker(p, ttm, d, h, ss, b),
- mp(ss->sp->mp) {}
+ MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b)
+ : MovePicker(p, ttm, d, h, ss, b), mp(ss->sp->mp) {}
Move get_next_move() { return mp->get_next_move(); }
// Default case, create and use a MovePicker object as source
template<> struct MovePickerExt<false, false> : public MovePicker {
- MovePickerExt(const Position& p, Move ttm, Depth d, const History& h,
- SearchStack* ss, Value b) : MovePicker(p, ttm, d, h, ss, b) {}
+ MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b)
+ : MovePicker(p, ttm, d, h, ss, b) {}
RootMoveList::iterator rm; // Dummy, needed to compile
};
} // namespace
-////
-//// Functions
-////
+/// init_threads() is called during startup. It initializes various lookup tables
+/// and creates and launches search threads.
-/// init_threads(), exit_threads() and nodes_searched() are helpers to
-/// give accessibility to some TM methods from outside of current file.
-
-void init_threads() { ThreadsMgr.init_threads(); }
-void exit_threads() { ThreadsMgr.exit_threads(); }
-
-
-/// init_search() is called during startup. It initializes various lookup tables
-
-void init_search() {
+void init_threads() {
int d; // depth (ONE_PLY == 2)
int hd; // half depth (ONE_PLY == 1)
// Init futility move count array
for (d = 0; d < 32; d++)
FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0));
+
+ // Create and startup threads
+ ThreadsMgr.init_threads();
}
-/// perft() is our utility to verify move generation is bug free. All the legal
-/// moves up to given depth are generated and counted and the sum returned.
+/// exit_threads() is a trampoline to access ThreadsMgr from outside of current file
+void exit_threads() { ThreadsMgr.exit_threads(); }
-int64_t perft(Position& pos, Depth depth)
-{
- MoveStack mlist[MOVES_MAX];
- StateInfo st;
- Move m;
- int64_t sum = 0;
- // Generate all legal moves
- MoveStack* last = generate<MV_LEGAL>(pos, mlist);
+/// perft() is our utility to verify move generation. All the legal moves up to
+/// given depth are generated and counted and the sum returned.
- // If we are at the last ply we don't need to do and undo
- // the moves, just to count them.
- if (depth <= ONE_PLY)
- return int(last - mlist);
+int64_t perft(Position& pos, Depth depth) {
- // Loop through all legal moves
- CheckInfo ci(pos);
- for (MoveStack* cur = mlist; cur != last; cur++)
- {
- m = cur->move;
- pos.do_move(m, st, ci, pos.move_is_check(m, ci));
- sum += perft(pos, depth - ONE_PLY);
- pos.undo_move(m);
- }
- return sum;
+ MoveStack mlist[MOVES_MAX];
+ StateInfo st;
+ Move m;
+ int64_t sum = 0;
+
+ // Generate all legal moves
+ MoveStack* last = generate<MV_LEGAL>(pos, mlist);
+
+ // If we are at the last ply we don't need to do and undo
+ // the moves, just to count them.
+ if (depth <= ONE_PLY)
+ return int(last - mlist);
+
+ // Loop through all legal moves
+ CheckInfo ci(pos);
+ for (MoveStack* cur = mlist; cur != last; cur++)
+ {
+ m = cur->move;
+ pos.do_move(m, st, ci, pos.move_is_check(m, ci));
+ sum += perft(pos, depth - ONE_PLY);
+ pos.undo_move(m);
+ }
+ return sum;
}
/// think() is the external interface to Stockfish's search, and is called when
-/// the program receives the UCI 'go' command. It initializes various
-/// search-related global variables, and calls id_loop(). It returns false
-/// when a quit command is received during the search.
+/// 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.
bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[],
int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) {
- // Initialize global search variables
+ // Initialize global search-related variables
StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false;
NodesSincePoll = 0;
SearchStartTime = get_system_time();
}
}
- // Read UCI option values
- TT.set_size(Options["Hash"].value<int>());
- if (Options["Clear Hash"].value<bool>())
- {
- Options["Clear Hash"].set_value("false");
- TT.clear();
- }
-
+ // Read UCI options
CheckExtension[1] = Options["Check Extension (PV nodes)"].value<Depth>();
CheckExtension[0] = Options["Check Extension (non-PV nodes)"].value<Depth>();
PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value<Depth>();
PassedPawnExtension[0] = Options["Passed Pawn Extension (non-PV nodes)"].value<Depth>();
PawnEndgameExtension[1] = Options["Pawn Endgame Extension (PV nodes)"].value<Depth>();
PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value<Depth>();
- MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value<Depth>();
- MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value<Depth>();
UCIMultiPV = Options["MultiPV"].value<int>();
SkillLevel = Options["Skill level"].value<int>();
UseLogFile = Options["Use Search Log"].value<bool>();
read_evaluation_uci_options(pos.side_to_move());
+ if (Options["Clear Hash"].value<bool>())
+ {
+ Options["Clear Hash"].set_value("false");
+ TT.clear();
+ }
+ TT.set_size(Options["Hash"].value<int>());
+
// 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.
- MultiPV = (SkillLevel < 20 ? Max(UCIMultiPV, 4) : UCIMultiPV);
+ SkillLevelEnabled = (SkillLevel < 20);
+ MultiPV = (SkillLevelEnabled ? Max(UCIMultiPV, 4) : UCIMultiPV);
// Set the number of active threads
ThreadsMgr.read_uci_options();
init_eval(ThreadsMgr.active_threads());
- // Wake up needed threads
+ // Wake up needed threads. Main thread, with threadID == 0, is always active
for (int i = 1; i < ThreadsMgr.active_threads(); i++)
ThreadsMgr.wake_sleeping_thread(i);
if (UseTimeManagement)
TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter());
- // Set best NodesBetweenPolls interval to avoid lagging under
- // heavy time pressure.
+ // Set best NodesBetweenPolls interval to avoid lagging under time pressure
if (MaxNodes)
NodesBetweenPolls = Min(MaxNodes, 30000);
else if (myTime && myTime < 1000)
SearchStack ss[PLY_MAX_PLUS_2];
Value bestValues[PLY_MAX_PLUS_2];
int bestMoveChanges[PLY_MAX_PLUS_2];
- int depth, aspirationDelta;
+ int depth, aspirationDelta, skillSamplingDepth;
Value value, alpha, beta;
- Move bestMove, easyMove;
+ Move bestMove, easyMove, skillBest, skillPonder;
// Initialize stuff before a new search
memset(ss, 0, 4 * sizeof(SearchStack));
TT.new_search();
H.clear();
- *ponderMove = bestMove = easyMove = MOVE_NONE;
- depth = aspirationDelta = 0;
+ *ponderMove = bestMove = easyMove = skillBest = skillPonder = MOVE_NONE;
+ depth = aspirationDelta = skillSamplingDepth = 0;
alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
ss->currentMove = MOVE_NULL; // Hack to skip update_gains()
return MOVE_NONE;
}
+ // Choose a random sampling depth according to SkillLevel so that at low
+ // skills there is an higher risk to pick up a blunder.
+ if (SkillLevelEnabled)
+ skillSamplingDepth = 4 + SkillLevel + (RK.rand<unsigned>() % 4);
+
// Iterative deepening loop
while (++depth <= PLY_MAX && (!MaxDepth || depth <= MaxDepth) && !StopRequest)
{
bestValues[depth] = value;
bestMoveChanges[depth] = Rml.bestMoveChanges;
+ // Do we need to pick now the best and the ponder moves ?
+ if (SkillLevelEnabled && depth == skillSamplingDepth)
+ do_skill_level(&skillBest, &skillPonder);
+
// Send PV line to GUI and to log file
for (int i = 0; i < Min(UCIMultiPV, (int)Rml.size()); i++)
cout << Rml[i].pv_info_to_uci(pos, depth, alpha, beta, i) << endl;
}
}
- // When playing with strength handicap choose best move among the MultiPV set
- // using a statistical rule dependent on SkillLevel. Idea by Heinz van Saanen.
- if (SkillLevel < 20)
+ // When using skills fake best and ponder moves with the sub-optimal ones
+ if (SkillLevelEnabled)
{
- assert(MultiPV > 1);
-
- // Rml list is already sorted by pv_score in descending order
- int s;
- int max_s = -VALUE_INFINITE;
- int size = Min(MultiPV, (int)Rml.size());
- int max = Rml[0].pv_score;
- int var = Min(max - Rml[size - 1].pv_score, PawnValueMidgame);
- int wk = 120 - 2 * SkillLevel;
-
- // PRNG sequence should be non deterministic
- for (int i = abs(get_system_time() % 50); i > 0; i--)
- RK.rand<unsigned>();
-
- // 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++)
- {
- s = Rml[i].pv_score;
+ if (skillBest == MOVE_NONE) // Still unassigned ?
+ do_skill_level(&skillBest, &skillPonder);
- // Don't allow crazy blunders even at very low skills
- if (i > 0 && Rml[i-1].pv_score > s + EasyMoveMargin)
- break;
-
- // This is our magical formula
- s += ((max - s) * wk + var * (RK.rand<unsigned>() % wk)) / 128;
-
- if (s > max_s)
- {
- max_s = s;
- bestMove = Rml[i].pv[0];
- *ponderMove = Rml[i].pv[1];
- }
- }
+ bestMove = skillBest;
+ *ponderMove = skillPonder;
}
return bestMove;
ValueType vt;
Value bestValue, value, oldAlpha;
Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
- bool isPvMove, isCheck, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
- bool mateThreat = false;
+ bool isPvMove, isCheck, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous, isBadCap;
int moveCount = 0, playedMoveCount = 0;
int threadID = pos.thread();
SplitPoint* sp = NULL;
tte = NULL;
ttMove = excludedMove = MOVE_NONE;
threatMove = sp->threatMove;
- mateThreat = sp->mateThreat;
goto split_point_start;
}
else if (Root)
ttMove = tte ? tte->move() : MOVE_NONE;
// At PV nodes we check for exact scores, while at non-PV nodes we check for
- // and return a fail high/low. Biggest advantage at probing at PV nodes is
- // to have a smooth experience in analysis mode.
+ // a fail high/low. Biggest advantage at probing at PV nodes is to have a
+ // smooth experience in analysis mode.
if ( !Root
&& tte
&& (PvNode ? tte->depth() >= depth && tte->type() == VALUE_TYPE_EXACT
return value_from_tt(tte->value(), ply);
}
- // Step 5. Evaluate the position statically and
- // update gain statistics of parent move.
+ // Step 5. Evaluate the position statically and update parent's gain statistics
if (isCheck)
ss->eval = ss->evalMargin = VALUE_NONE;
else if (tte)
if ( !PvNode
&& depth < RazorDepth
&& !isCheck
- && refinedValue < beta - razor_margin(depth)
+ && refinedValue + razor_margin(depth) < beta
&& ttMove == MOVE_NONE
- && !value_is_mate(beta)
+ && abs(beta) < VALUE_MATE_IN_PLY_MAX
&& !pos.has_pawn_on_7th(pos.side_to_move()))
{
Value rbeta = beta - razor_margin(depth);
&& !ss->skipNullMove
&& depth < RazorDepth
&& !isCheck
- && refinedValue >= beta + futility_margin(depth, 0)
- && !value_is_mate(beta)
+ && refinedValue - futility_margin(depth, 0) >= beta
+ && abs(beta) < VALUE_MATE_IN_PLY_MAX
&& pos.non_pawn_material(pos.side_to_move()))
return refinedValue - futility_margin(depth, 0);
&& depth > ONE_PLY
&& !isCheck
&& refinedValue >= beta
- && !value_is_mate(beta)
+ && abs(beta) < VALUE_MATE_IN_PLY_MAX
&& pos.non_pawn_material(pos.side_to_move()))
{
ss->currentMove = MOVE_NULL;
int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
// Null move dynamic reduction based on value
- if (refinedValue - beta > PawnValueMidgame)
+ if (refinedValue - PawnValueMidgame > beta)
R++;
pos.do_null_move(st);
if (nullValue >= beta)
{
// Do not return unproven mate scores
- if (nullValue >= value_mate_in(PLY_MAX))
+ if (nullValue >= VALUE_MATE_IN_PLY_MAX)
nullValue = beta;
if (depth < 6 * ONE_PLY)
// 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).
- if (nullValue == value_mated_in(ply + 2))
- mateThreat = true;
-
threatMove = (ss+1)->bestMove;
+
if ( depth < ThreatDepth
&& (ss-1)->reduction
&& threatMove != MOVE_NONE
// Step 9. Internal iterative deepening
if ( depth >= IIDDepth[PvNode]
&& ttMove == MOVE_NONE
- && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
+ && (PvNode || (!isCheck && ss->eval + IIDMargin >= beta)))
{
Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
tte = TT.retrieve(posKey);
}
- // Expensive mate threat detection (only for PV nodes)
- if (PvNode)
- mateThreat = pos.has_mate_threat();
-
split_point_start: // At split points actual search starts from here
// Initialize a MovePicker object for the current position
cout << "info" << speed_to_uci(pos.nodes_searched()) << endl;
}
- if (current_search_time() >= 1000)
+ if (current_search_time() > 2000)
cout << "info currmove " << move
<< " currmovenumber " << moveCount << endl;
}
- // At Root and at first iteration do a PV search on all the moves
- // to score root moves. Otherwise only the first one is the PV.
- isPvMove = (PvNode && moveCount <= (Root ? MultiPV + 1000 * (depth <= ONE_PLY) : 1));
+ // At Root and at first iteration do a PV search on all the moves to score root moves
+ isPvMove = (PvNode && moveCount <= (Root ? depth <= ONE_PLY ? 1000 : MultiPV : 1));
moveIsCheck = pos.move_is_check(move, ci);
captureOrPromotion = pos.move_is_capture_or_promotion(move);
// Step 11. Decide the new search depth
- ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, mateThreat, &dangerous);
+ ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, &dangerous);
- // 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.
+ // 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.
if ( singularExtensionNode
&& move == tte->move()
&& ext < ONE_PLY)
if (abs(ttValue) < VALUE_KNOWN_WIN)
{
- Value b = ttValue - int(depth);
+ Value rBeta = ttValue - int(depth);
ss->excludedMove = move;
ss->skipNullMove = true;
- Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
+ Value v = search<NonPV>(pos, ss, rBeta - 1, rBeta, depth / 2, ply);
ss->skipNullMove = false;
ss->excludedMove = MOVE_NONE;
ss->bestMove = MOVE_NONE;
- if (v < b)
+ if (v < rBeta)
ext = ONE_PLY;
}
}
{
// 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))
+ && bestValue > VALUE_MATED_IN_PLY_MAX) // FIXME bestValue is racy
{
if (SpNode)
lock_grab(&(sp->lock));
// Prune moves with negative SEE at low depths
if ( predictedDepth < 2 * ONE_PLY
- && bestValue > value_mated_in(PLY_MAX)
+ && bestValue > VALUE_MATED_IN_PLY_MAX
&& pos.see_sign(move) < 0)
{
if (SpNode)
}
}
+ // Bad capture detection. Will be used by prob-cut search
+ isBadCap = depth >= 3 * ONE_PLY
+ && depth < 8 * ONE_PLY
+ && captureOrPromotion
+ && move != ttMove
+ && !dangerous
+ && !move_is_promotion(move)
+ && abs(alpha) < VALUE_MATE_IN_PLY_MAX
+ && pos.see_sign(move) < 0;
+
// Step 13. Make the move
pos.do_move(move, st, ci, moveIsCheck);
// Step 14. Reduced depth search
// If the move fails high will be re-searched at full depth.
bool doFullDepthSearch = true;
+ alpha = SpNode ? sp->alpha : alpha;
if ( depth >= 3 * ONE_PLY
&& !captureOrPromotion
ss->reduction = DEPTH_ZERO; // Restore original reduction
}
+ // Probcut search for bad captures. If a reduced search returns a value
+ // very below beta then we can (almost) safely prune the bad capture.
+ if (isBadCap)
+ {
+ ss->reduction = 3 * ONE_PLY;
+ Value rAlpha = alpha - 300;
+ Depth d = newDepth - ss->reduction;
+ value = -search<NonPV>(pos, ss+1, -(rAlpha+1), -rAlpha, d, ply+1);
+ doFullDepthSearch = (value > rAlpha);
+ ss->reduction = DEPTH_ZERO; // Restore original reduction
+ }
+
// Step 15. Full depth search
if (doFullDepthSearch)
{
&& !StopRequest
&& !ThreadsMgr.cutoff_at_splitpoint(threadID))
ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
- threatMove, mateThreat, moveCount, &mp, PvNode);
+ threatMove, moveCount, &mp, PvNode);
}
// Step 19. Check for mate and stalemate
// Detect non-capture evasions that are candidate to be pruned
evasionPrunable = isCheck
- && bestValue > value_mated_in(PLY_MAX)
+ && bestValue > VALUE_MATED_IN_PLY_MAX
&& !pos.move_is_capture(move)
&& !pos.can_castle(pos.side_to_move());
}
- // value_is_mate() checks if the given value is a mate one eventually
- // compensated for the ply.
-
- bool value_is_mate(Value value) {
-
- assert(abs(value) <= VALUE_INFINITE);
-
- return value <= value_mated_in(PLY_MAX)
- || value >= value_mate_in(PLY_MAX);
- }
-
-
// value_to_tt() adjusts a mate score from "plies to mate from the root" to
// "plies to mate from the current ply". Non-mate scores are unchanged.
// The function is called before storing a value to the transposition table.
Value value_to_tt(Value v, int ply) {
- if (v >= value_mate_in(PLY_MAX))
+ if (v >= VALUE_MATE_IN_PLY_MAX)
return v + ply;
- if (v <= value_mated_in(PLY_MAX))
+ if (v <= VALUE_MATED_IN_PLY_MAX)
return v - ply;
return v;
Value value_from_tt(Value v, int ply) {
- if (v >= value_mate_in(PLY_MAX))
+ if (v >= VALUE_MATE_IN_PLY_MAX)
return v - ply;
- if (v <= value_mated_in(PLY_MAX))
+ if (v <= VALUE_MATED_IN_PLY_MAX)
return v + ply;
return v;
// the move is marked as 'dangerous' so, at least, we avoid to prune it.
template <NodeType PvNode>
Depth extension(const Position& pos, Move m, bool captureOrPromotion,
- bool moveIsCheck, bool mateThreat, bool* dangerous) {
+ bool moveIsCheck, bool* dangerous) {
assert(m != MOVE_NONE);
Depth result = DEPTH_ZERO;
- *dangerous = moveIsCheck | mateThreat;
+ *dangerous = moveIsCheck;
- if (*dangerous)
- {
- if (moveIsCheck && pos.see_sign(m) >= 0)
- result += CheckExtension[PvNode];
-
- if (mateThreat)
- result += MateThreatExtension[PvNode];
- }
+ if (moveIsCheck && pos.see_sign(m) >= 0)
+ result += CheckExtension[PvNode];
if (pos.type_of_piece_on(move_from(m)) == PAWN)
{
*dangerous = true;
}
- if ( PvNode
- && captureOrPromotion
- && pos.type_of_piece_on(move_to(m)) != PAWN
- && pos.see_sign(m) >= 0)
- {
- result += ONE_PLY / 2;
- *dangerous = true;
- }
-
return Min(result, ONE_PLY);
}
Value v = value_from_tt(tte->value(), ply);
return ( tte->depth() >= depth
- || v >= Max(value_mate_in(PLY_MAX), beta)
- || v < Min(value_mated_in(PLY_MAX), beta))
+ || v >= Max(VALUE_MATE_IN_PLY_MAX, beta)
+ || v < Min(VALUE_MATED_IN_PLY_MAX, beta))
&& ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
|| ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
else
- s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2);
+ s << "mate " << (v > 0 ? VALUE_MATE - v + 1 : -VALUE_MATE - v) / 2;
return s.str();
}
{
lastInfoTime = t;
- if (dbg_show_mean)
- dbg_print_mean();
-
- if (dbg_show_hit_rate)
- dbg_print_hit_rate();
+ dbg_print_mean();
+ dbg_print_hit_rate();
// Send info on searched nodes as soon as we return to root
SendSearchedNodes = true;
template <bool Fake>
void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
const Value beta, Value* bestValue, Depth depth, Move threatMove,
- bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
+ int moveCount, MovePicker* mp, bool pvNode) {
assert(pos.is_ok());
assert(ply > 0 && ply < PLY_MAX);
assert(*bestValue >= -VALUE_INFINITE);
splitPoint.ply = ply;
splitPoint.depth = depth;
splitPoint.threatMove = threatMove;
- splitPoint.mateThreat = mateThreat;
splitPoint.alpha = *alpha;
splitPoint.beta = beta;
splitPoint.pvNode = pvNode;
TTEntry* tte;
int ply = 1;
- assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
+ assert(pv[0] != MOVE_NONE && pos.move_is_legal(pv[0]));
pos.do_move(pv[0], *st++);
while ( (tte = TT.retrieve(pos.get_key())) != NULL
&& tte->move() != MOVE_NONE
- && move_is_legal(pos, tte->move())
+ && pos.move_is_legal(tte->move())
&& ply < PLY_MAX
&& (!pos.is_draw() || ply < 2))
{
Value v, m = VALUE_NONE;
int ply = 0;
- assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
+ assert(pv[0] != MOVE_NONE && pos.move_is_legal(pv[0]));
do {
k = pos.get_key();
}
// pv_info_to_uci() returns a string with information on the current PV line
- // formatted according to UCI specification. It is called at each iteration
- // or after a new pv is found.
-
- std::string RootMove::pv_info_to_uci(Position& pos, int depth, Value alpha, Value beta, int pvLine) {
+ // formatted according to UCI specification.
+ std::string RootMove::pv_info_to_uci(Position& pos, int depth, Value alpha,
+ Value beta, int pvIdx) {
std::stringstream s, l;
Move* m = pv;
s << "info depth " << depth
<< " seldepth " << int(m - pv)
- << " multipv " << pvLine + 1
+ << " multipv " << pvIdx + 1
<< " score " << value_to_uci(pv_score)
<< (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
<< speed_to_uci(pos.nodes_searched())
}
}
+
+ // When playing with strength handicap choose best move among the MultiPV set
+ // using a statistical rule dependent on SkillLevel. Idea by Heinz van Saanen.
+ void do_skill_level(Move* best, Move* ponder) {
+
+ assert(MultiPV > 1);
+
+ // Rml list is already sorted by pv_score in descending order
+ int s;
+ int max_s = -VALUE_INFINITE;
+ int size = Min(MultiPV, (int)Rml.size());
+ int max = Rml[0].pv_score;
+ int var = Min(max - Rml[size - 1].pv_score, PawnValueMidgame);
+ int wk = 120 - 2 * SkillLevel;
+
+ // PRNG sequence should be non deterministic
+ for (int i = abs(get_system_time() % 50); i > 0; i--)
+ RK.rand<unsigned>();
+
+ // 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++)
+ {
+ s = Rml[i].pv_score;
+
+ // Don't allow crazy blunders even at very low skills
+ if (i > 0 && Rml[i-1].pv_score > s + EasyMoveMargin)
+ break;
+
+ // This is our magical formula
+ s += ((max - s) * wk + var * (RK.rand<unsigned>() % wk)) / 128;
+
+ if (s > max_s)
+ {
+ max_s = s;
+ *best = Rml[i].pv[0];
+ *ponder = Rml[i].pv[1];
+ }
+ }
+ }
+
} // namespace
projects / stockfish / blobdiff