////
#include <cassert>
+#include <cmath>
#include <cstring>
#include <fstream>
#include <iostream>
// and near frontier nodes.
const Value FutilityMarginQS = Value(0x80);
+ Value FutilityMargins[2 * PLY_MAX_PLUS_2]; // Initialized at startup.
+
// Each move futility margin is decreased
const Value IncrementalFutilityMargin = Value(0x8);
/// Variables initialized by UCI options
- // Minimum number of full depth (i.e. non-reduced) moves at PV and non-PV nodes
- int LMRPVMoves, LMRNonPVMoves;
-
// Depth limit for use of dynamic threat detection
Depth ThreatDepth;
IterationInfoType IterationInfo[PLY_MAX_PLUS_2];
int BestMoveChangesByIteration[PLY_MAX_PLUS_2];
+ // Search window management
+ int AspirationDelta;
+
// MultiPV mode
int MultiPV;
bool UseLogFile;
std::ofstream LogFile;
+ // Natural logarithmic lookup table and its getter function
+ float lnArray[512];
+ inline float ln(int i) { return lnArray[i]; }
+
// MP related variables
int ActiveThreads = 1;
Depth MinimumSplitDepth;
// History table
History H;
-
/// Functions
Value id_loop(const Position& pos, Move searchMoves[]);
- Value root_search(Position& pos, SearchStack ss[], RootMoveList& rml, Value alpha, Value beta);
+ Value root_search(Position& pos, SearchStack ss[], RootMoveList& rml, Value& oldAlpha, Value& beta);
Value search_pv(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
Value search(Position& pos, SearchStack ss[], Value beta, Depth depth, int ply, bool allowNullmove, int threadID, Move excludedMove = MOVE_NONE);
Value qsearch(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
bool ok_to_prune(const Position& pos, Move m, Move threat);
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 reduction_parameters(float base, float Inhibitor, Depth depth, float& logLimit, float& gradient);
+ Depth reduction(int moveCount, const float LogLimit, const float BaseRed, const float Gradient);
void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
void update_killers(Move m, SearchStack& ss);
+ void update_gains(const Position& pos, Move move, Value before, Value after);
bool fail_high_ply_1();
int current_search_time();
//// Functions
////
-//FIXME: HACK
-static double lnArray[512];
-
-inline double ln(int i)
-{
- return lnArray[i];
-}
/// 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.
MateThreatExtension[1] = Depth(get_option_value_int("Mate Threat Extension (PV nodes)"));
MateThreatExtension[0] = Depth(get_option_value_int("Mate Threat Extension (non-PV nodes)"));
- LMRPVMoves = get_option_value_int("Full Depth Moves (PV nodes)") + 1;
- LMRNonPVMoves = get_option_value_int("Full Depth Moves (non-PV nodes)") + 1;
ThreatDepth = get_option_value_int("Threat Depth") * OnePly;
Chess960 = get_option_value_bool("UCI_Chess960");
{
ActiveThreads = newActiveThreads;
init_eval(ActiveThreads);
+ // HACK: init_eval() destroys the static castleRightsMask[] array in the
+ // Position class. The below line repairs the damage.
+ Position p(pos.to_fen());
+ assert(pos.is_ok());
}
// Wake up sleeping threads
// We're ready to start thinking. Call the iterative deepening loop function
Value v = id_loop(pos, searchMoves);
-
if (UseLSNFiltering)
{
// Step 1. If this is sudden death game and our position is hopeless,
/// and initializes the split point stack and the global locks and condition
/// objects.
-#include <cmath> //FIXME: HACK
-
void init_threads() {
- // FIXME: HACK!!
- for (int i = 0; i < 512; i++)
- lnArray[i] = log(double(i));
-
volatile int i;
+ bool ok;
#if !defined(_MSC_VER)
pthread_t pthread[1];
#endif
+ // Init our logarithmic lookup table
+ for (i = 0; i < 512; i++)
+ lnArray[i] = float(log(double(i))); // log() returns base-e logarithm
+
for (i = 0; i < THREAD_MAX; i++)
Threads[i].activeSplitPoints = 0;
+ // Init futility margins array
+ FutilityMargins[0] = FutilityMargins[1] = Value(0);
+
+ for (i = 2; i < 2 * PLY_MAX_PLUS_2; i++)
+ {
+ FutilityMargins[i] = Value(112 * bitScanReverse32(i * i / 2)); // FIXME: test using log instead of BSR
+ }
+
// Initialize global locks
lock_init(&MPLock, NULL);
lock_init(&IOLock, NULL);
for (i = 1; i < THREAD_MAX; i++)
{
#if !defined(_MSC_VER)
- pthread_create(pthread, NULL, init_thread, (void*)(&i));
+ ok = (pthread_create(pthread, NULL, init_thread, (void*)(&i)) == 0);
#else
DWORD iID[1];
- CreateThread(NULL, 0, init_thread, (LPVOID)(&i), 0, iID);
+ ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&i), 0, iID) != NULL);
#endif
+ if (!ok)
+ {
+ cout << "Failed to create thread number " << i << endl;
+ Application::exit_with_failure();
+ }
+
// Wait until the thread has finished launching
while (!Threads[i].running);
}
currentMove = threatMove = MOVE_NONE;
reduction = Depth(0);
eval = VALUE_NONE;
+ evalInfo = NULL;
}
void SearchStack::initKillers() {
// searchMoves are verified, copied, scored and sorted
RootMoveList rml(p, searchMoves);
+ // Handle special case of searching on a mate/stale position
if (rml.move_count() == 0)
{
if (PonderSearch)
int prevDelta1 = IterationInfo[Iteration - 1].speculatedValue - IterationInfo[Iteration - 2].speculatedValue;
int prevDelta2 = IterationInfo[Iteration - 2].speculatedValue - IterationInfo[Iteration - 3].speculatedValue;
- int delta = Max(2 * abs(prevDelta1) + abs(prevDelta2), ProblemMargin);
+ AspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16);
+ AspirationDelta = (AspirationDelta + 7) / 8 * 8; // Round to match grainSize
- alpha = Max(IterationInfo[Iteration - 1].value - delta, -VALUE_INFINITE);
- beta = Min(IterationInfo[Iteration - 1].value + delta, VALUE_INFINITE);
+ alpha = Max(IterationInfo[Iteration - 1].value - AspirationDelta, -VALUE_INFINITE);
+ beta = Min(IterationInfo[Iteration - 1].value + AspirationDelta, VALUE_INFINITE);
}
else
{
// similar to search_pv except that it uses a different move ordering
// scheme and prints some information to the standard output.
- Value root_search(Position& pos, SearchStack ss[], RootMoveList& rml, Value alpha, Value beta) {
+ Value root_search(Position& pos, SearchStack ss[], RootMoveList& rml, Value& oldAlpha, Value& beta) {
- Value oldAlpha = alpha;
+ int64_t nodes;
+ Move move;
+ StateInfo st;
+ Depth depth, ext, newDepth;
Value value;
CheckInfo ci(pos);
+ int researchCount = 0;
+ bool moveIsCheck, captureOrPromotion, dangerous;
+ Value alpha = oldAlpha;
+ bool isCheck = pos.is_check();
+
+ // Evaluate the position statically
+ EvalInfo ei;
+ ss[0].eval = !isCheck ? evaluate(pos, ei, 0) : VALUE_NONE;
+
+ while (1) // Fail low loop
+ {
// Loop through all the moves in the root move list
for (int i = 0; i < rml.move_count() && !AbortSearch; i++)
rml.set_move_score(i, -VALUE_INFINITE);
continue;
}
- int64_t nodes;
- Move move;
- StateInfo st;
- Depth depth, ext, newDepth;
RootMoveNumber = i + 1;
FailHigh = false;
<< " currmovenumber " << RootMoveNumber << endl;
// Decide search depth for this move
- bool moveIsCheck = pos.move_is_check(move);
- bool captureOrPromotion = pos.move_is_capture_or_promotion(move);
- bool dangerous;
- depth = (Iteration - 2) * OnePly + InitialDepth;
+ moveIsCheck = pos.move_is_check(move);
+ captureOrPromotion = pos.move_is_capture_or_promotion(move);
+ depth = (Iteration - 2) * OnePly + InitialDepth;
ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, false, false, &dangerous);
newDepth = depth + ext;
+ value = - VALUE_INFINITE;
+
+ // Precalculate reduction parameters
+ float LogLimit, Gradient, BaseReduction = 0.5;
+ reduction_parameters(BaseReduction, 6.0, depth, LogLimit, Gradient);
+
+ while (1) // Fail high loop
+ {
+
// Make the move, and search it
pos.do_move(move, st, ci, moveIsCheck);
- if (i < MultiPV)
+ if (i < MultiPV || value > alpha)
{
// Aspiration window is disabled in multi-pv case
if (MultiPV > 1)
&& !captureOrPromotion
&& !move_is_castle(move))
{
- double red = 0.5 + ln(RootMoveNumber - MultiPV + 1) * ln(depth / 2) / 6.0;
- if (red >= 1.0)
+ ss[0].reduction = reduction(RootMoveNumber - MultiPV + 1, LogLimit, BaseReduction, Gradient);
+ if (ss[0].reduction)
{
- ss[0].reduction = Depth(int(floor(red * int(OnePly))));
value = -search(pos, ss, -alpha, newDepth-ss[0].reduction, 1, true, 0);
doFullDepthSearch = (value > alpha);
}
if (doFullDepthSearch)
{
+ ss[0].reduction = Depth(0);
value = -search(pos, ss, -alpha, newDepth, 1, true, 0);
if (value > alpha)
pos.undo_move(move);
+ // Can we exit fail high loop ?
+ if (AbortSearch || value < beta)
+ break;
+
+ // We are failing high and going to do a research. It's important to update score
+ // before research in case we run out of time while researching.
+ rml.set_move_score(i, value);
+ update_pv(ss, 0);
+ TT.extract_pv(pos, ss[0].pv, PLY_MAX);
+ rml.set_move_pv(i, ss[0].pv);
+
+ // Print search information to the standard output
+ cout << "info depth " << Iteration
+ << " score " << value_to_string(value)
+ << ((value >= beta) ? " lowerbound" :
+ ((value <= alpha)? " upperbound" : ""))
+ << " time " << current_search_time()
+ << " nodes " << nodes_searched()
+ << " nps " << nps()
+ << " pv ";
+
+ for (int j = 0; ss[0].pv[j] != MOVE_NONE && j < PLY_MAX; j++)
+ cout << ss[0].pv[j] << " ";
+
+ cout << endl;
+
+ if (UseLogFile)
+ {
+ ValueType type = (value >= beta ? VALUE_TYPE_LOWER
+ : (value <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT));
+
+ LogFile << pretty_pv(pos, current_search_time(), Iteration,
+ nodes_searched(), value, type, ss[0].pv) << endl;
+ }
+
+ // Prepare for a research after a fail high, each time with a wider window
+ researchCount++;
+ beta = Min(beta + AspirationDelta * (1 << researchCount), VALUE_INFINITE);
+
+ } // End of fail high loop
+
// Finished searching the move. If AbortSearch is true, the search
// was aborted because the user interrupted the search or because we
// ran out of time. In this case, the return value of the search cannot
FailLow = (alpha == oldAlpha);
}
+
+ // Can we exit fail low loop ?
+ if (AbortSearch || alpha > oldAlpha)
+ break;
+
+ // Prepare for a research after a fail low, each time with a wider window
+ researchCount++;
+ alpha = Max(alpha - AspirationDelta * (1 << researchCount), -VALUE_INFINITE);
+ oldAlpha = alpha;
+
+ } // Fail low loop
+
return alpha;
}
Value oldAlpha, value;
bool isCheck, mateThreat, singleEvasion, moveIsCheck, captureOrPromotion, dangerous;
int moveCount = 0;
- Value bestValue = -VALUE_INFINITE;
+ Value bestValue = value = -VALUE_INFINITE;
if (depth < OnePly)
return qsearch(pos, ss, alpha, beta, Depth(0), ply, threadID);
tte = TT.retrieve(pos.get_key());
}
+ isCheck = pos.is_check();
+ if (!isCheck)
+ {
+ // Update gain statistics of the previous move that lead
+ // us in this position.
+ EvalInfo ei;
+ ss[ply].eval = evaluate(pos, ei, threadID);
+ update_gains(pos, ss[ply - 1].currentMove, ss[ply - 1].eval, ss[ply].eval);
+ }
+
// Initialize a MovePicker object for the current position, and prepare
// to search all moves
- isCheck = pos.is_check();
mateThreat = pos.has_mate_threat(opposite_color(pos.side_to_move()));
CheckInfo ci(pos);
MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply]);
+ // Precalculate reduction parameters
+ float LogLimit, Gradient, BaseReduction = 0.5;
+ reduction_parameters(BaseReduction, 6.0, depth, LogLimit, Gradient);
+
// Loop through all legal moves until no moves remain or a beta cutoff
// occurs.
while ( alpha < beta
&& !move_is_castle(move)
&& !move_is_killer(move, ss[ply]))
{
- double red = 0.5 + ln(moveCount) * ln(depth / 2) / 6.0;
- if (red >= 1.0)
- {
- ss[ply].reduction = Depth(int(floor(red * int(OnePly))));
- value = -search(pos, ss, -alpha, newDepth-ss[ply].reduction, ply+1, true, threadID);
- doFullDepthSearch = (value > alpha);
- }
+ ss[ply].reduction = reduction(moveCount, LogLimit, BaseReduction, Gradient);
+ if (ss[ply].reduction)
+ {
+ value = -search(pos, ss, -alpha, newDepth-ss[ply].reduction, ply+1, true, threadID);
+ doFullDepthSearch = (value > alpha);
+ }
}
if (doFullDepthSearch) // Go with full depth non-pv search
Move ttMove, move;
Depth ext, newDepth;
Value bestValue, staticValue, nullValue, value, futilityValue, futilityValueScaled;
- bool isCheck, useFutilityPruning, singleEvasion, moveIsCheck, captureOrPromotion, dangerous;
+ bool isCheck, singleEvasion, moveIsCheck, captureOrPromotion, dangerous;
bool mateThreat = false;
int moveCount = 0;
- futilityValue = staticValue = bestValue = -VALUE_INFINITE;
+ futilityValue = staticValue = bestValue = value = -VALUE_INFINITE;
if (depth < OnePly)
return qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
// Calculate depth dependant futility pruning parameters
const int FutilityMoveCountMargin = 3 + (1 << (3 * int(depth) / 8));
- const int FutilityValueMargin = 112 * bitScanReverse32(int(depth) * int(depth) / 2);
// Evaluate the position statically
- if (isCheck)
- ss[ply].eval = VALUE_NONE;
- else
+ if (!isCheck)
{
if (tte && (tte->type() & VALUE_TYPE_EVAL))
staticValue = value_from_tt(tte->value(), ply);
else
+ {
staticValue = evaluate(pos, ei, threadID);
+ ss[ply].evalInfo = &ei;
+ }
ss[ply].eval = staticValue;
- futilityValue = staticValue + FutilityValueMargin;
+ futilityValue = staticValue + FutilityMargins[int(depth)]; //FIXME: Remove me, only for split
staticValue = refine_eval(tte, staticValue, ply); // Enhance accuracy with TT value if possible
+ update_gains(pos, ss[ply - 1].currentMove, ss[ply - 1].eval, ss[ply].eval);
}
+ // Do a "stand pat". If we are above beta by a good margin then
+ // return immediately.
+ if ( !isCheck
+ && allowNullmove
+ && depth < RazorDepth
+ && staticValue - FutilityMargins[int(depth)] >= beta)
+ return staticValue - FutilityMargins[int(depth)];
+
// Null move search
if ( allowNullmove
&& depth > OnePly
// Go with internal iterative deepening if we don't have a TT move
if (UseIIDAtNonPVNodes && ttMove == MOVE_NONE && depth >= 8*OnePly &&
- !isCheck && evaluate(pos, ei, threadID) >= beta - IIDMargin)
+ !isCheck && ss[ply].eval >= beta - IIDMargin)
{
search(pos, ss, beta, Min(depth/2, depth-2*OnePly), ply, false, threadID);
ttMove = ss[ply].pv[ply];
// to search all moves.
MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply]);
CheckInfo ci(pos);
- useFutilityPruning = depth < SelectiveDepth && !isCheck;
+
+ // Precalculate reduction parameters
+ float LogLimit, Gradient, BaseReduction = 0.5;
+ reduction_parameters(BaseReduction, 3.0, depth, LogLimit, Gradient);
// Loop through all legal moves until no moves remain or a beta cutoff occurs
while ( bestValue < beta
movesSearched[moveCount++] = ss[ply].currentMove = move;
// Futility pruning
- if ( useFutilityPruning
+ if ( !isCheck
&& !dangerous
&& !captureOrPromotion
+ && !move_is_castle(move)
&& move != ttMove)
{
// Move count based pruning
continue;
// Value based pruning
- futilityValueScaled = futilityValue - moveCount * IncrementalFutilityMargin;
+ Depth predictedDepth = newDepth;
- if (futilityValueScaled < beta)
+ //FIXME: We are ignoring condition: depth >= 3*OnePly, BUG??
+ ss[ply].reduction = reduction(moveCount, LogLimit, BaseReduction, Gradient);
+ if (ss[ply].reduction)
+ predictedDepth -= ss[ply].reduction;
+
+ if (predictedDepth < SelectiveDepth)
{
- if (futilityValueScaled > bestValue)
- bestValue = futilityValueScaled;
- continue;
+ int preFutilityValueMargin = 0;
+ if (predictedDepth >= OnePly)
+ preFutilityValueMargin = FutilityMargins[int(predictedDepth)];
+
+ preFutilityValueMargin += H.gain(pos.piece_on(move_from(move)), move_from(move), move_to(move)) + 45;
+
+ futilityValueScaled = ss[ply].eval + preFutilityValueMargin - moveCount * IncrementalFutilityMargin;
+
+ if (futilityValueScaled < beta)
+ {
+ if (futilityValueScaled > bestValue)
+ bestValue = futilityValueScaled;
+ continue;
+ }
}
}
&& !dangerous
&& !captureOrPromotion
&& !move_is_castle(move)
- && !move_is_killer(move, ss[ply])
- /* && move != ttMove*/)
+ && !move_is_killer(move, ss[ply]))
{
- double red = 0.5 + ln(moveCount) * ln(depth / 2) / 3.0;
- if (red >= 1.0)
+ ss[ply].reduction = reduction(moveCount, LogLimit, BaseReduction, Gradient);
+ if (ss[ply].reduction)
{
- ss[ply].reduction = Depth(int(floor(red * int(OnePly))));
value = -search(pos, ss, -(beta-1), newDepth-ss[ply].reduction, ply+1, true, threadID);
doFullDepthSearch = (value >= beta);
}
&& idle_thread_exists(threadID)
&& !AbortSearch
&& !thread_should_stop(threadID)
- && split(pos, ss, ply, &beta, &beta, &bestValue, futilityValue,
+ && split(pos, ss, ply, &beta, &beta, &bestValue, futilityValue, //FIXME: SMP & futilityValue
depth, &moveCount, &mp, threadID, false))
break;
}
StateInfo st;
Move ttMove, move;
Value staticValue, bestValue, value, futilityBase, futilityValue;
- bool isCheck, enoughMaterial, moveIsCheck;
+ bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
const TTEntry* tte = NULL;
int moveCount = 0;
bool pvNode = (beta - alpha != 1);
+ Value oldAlpha = alpha;
// Initialize, and make an early exit in case of an aborted search,
// an instant draw, maximum ply reached, etc.
else
staticValue = evaluate(pos, ei, threadID);
+ if (!isCheck)
+ {
+ ss[ply].eval = staticValue;
+ update_gains(pos, ss[ply - 1].currentMove, ss[ply - 1].eval, ss[ply].eval);
+ }
+
// Initialize "stand pat score", and return it immediately if it is
// at least beta.
bestValue = staticValue;
if (bestValue >= beta)
{
// Store the score to avoid a future costly evaluation() call
- if (!isCheck && !tte && ei.futilityMargin == 0)
+ if (!isCheck && !tte && ei.futilityMargin[pos.side_to_move()] == 0)
TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_EV_LO, Depth(-127*OnePly), MOVE_NONE);
return bestValue;
if (bestValue > alpha)
alpha = bestValue;
+ // If we are near beta then try to get a cutoff pushing checks a bit further
+ bool deepChecks = depth == -OnePly && staticValue >= beta - PawnValueMidgame / 8;
+
// Initialize a MovePicker object for the current position, and prepare
- // to search the moves. Because the depth is <= 0 here, only captures,
- // queen promotions and checks (only if depth == 0) will be generated.
- MovePicker mp = MovePicker(pos, ttMove, depth, H);
+ // to search the moves. Because the depth is <= 0 here, only captures,
+ // queen promotions and checks (only if depth == 0 or depth == -OnePly
+ // and we are near beta) will be generated.
+ MovePicker mp = MovePicker(pos, ttMove, deepChecks ? Depth(0) : depth, H);
CheckInfo ci(pos);
enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
- futilityBase = staticValue + FutilityMarginQS + ei.futilityMargin;
+ futilityBase = staticValue + FutilityMarginQS + ei.futilityMargin[pos.side_to_move()];
// Loop through the moves until no moves remain or a beta cutoff
// occurs.
}
}
- // Don't search captures and checks with negative SEE values
- if ( !isCheck
+ // Detect blocking evasions that are candidate to be pruned
+ evasionPrunable = isCheck
+ && bestValue != -VALUE_INFINITE
+ && !pos.move_is_capture(move)
+ && pos.type_of_piece_on(move_from(move)) != KING
+ && !pos.can_castle(pos.side_to_move());
+
+ // Don't search moves with negative SEE values
+ if ( (!isCheck || evasionPrunable)
&& move != ttMove
&& !move_is_promotion(move)
&& pos.see_sign(move) < 0)
// Update transposition table
Depth d = (depth == Depth(0) ? Depth(0) : Depth(-1));
- if (bestValue < beta)
+ if (bestValue <= oldAlpha)
{
// If bestValue isn't changed it means it is still the static evaluation
// of the node, so keep this info to avoid a future evaluation() call.
- ValueType type = (bestValue == staticValue && !ei.futilityMargin ? VALUE_TYPE_EV_UP : VALUE_TYPE_UPPER);
+ ValueType type = (bestValue == staticValue && !ei.futilityMargin[pos.side_to_move()] ? VALUE_TYPE_EV_UP : VALUE_TYPE_UPPER);
TT.store(pos.get_key(), value_to_tt(bestValue, ply), type, d, MOVE_NONE);
}
- else
+ else if (bestValue >= beta)
{
move = ss[ply].pv[ply];
TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, d, move);
if (!pos.move_is_capture_or_promotion(move))
update_killers(move, ss[ply]);
}
+ else
+ TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_EXACT, d, ss[ply].pv[ply]);
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
assert(threadID >= 0 && threadID < ActiveThreads);
assert(ActiveThreads > 1);
- Position pos = Position(sp->pos);
+ Position pos(*sp->pos);
CheckInfo ci(pos);
SearchStack* ss = sp->sstack[threadID];
- Value value;
+ Value value = -VALUE_INFINITE;
Move move;
+ int moveCount;
bool isCheck = pos.is_check();
bool useFutilityPruning = sp->depth < SelectiveDepth
&& !isCheck;
const int FutilityMoveCountMargin = 3 + (1 << (3 * int(sp->depth) / 8));
- while ( sp->bestValue < sp->beta
+ // Precalculate reduction parameters
+ float LogLimit, Gradient, BaseReduction = 0.5;
+ reduction_parameters(BaseReduction, 3.0, sp->depth, LogLimit, Gradient);
+
+ while ( lock_grab_bool(&(sp->lock))
+ && sp->bestValue < sp->beta
&& !thread_should_stop(threadID)
- && (move = sp->mp->get_next_move(sp->lock)) != MOVE_NONE)
+ && (move = sp->mp->get_next_move()) != MOVE_NONE)
{
+ moveCount = ++sp->moves;
+ lock_release(&(sp->lock));
+
assert(move_is_ok(move));
bool moveIsCheck = pos.move_is_check(move, ci);
bool captureOrPromotion = pos.move_is_capture_or_promotion(move);
- lock_grab(&(sp->lock));
- int moveCount = ++sp->moves;
- lock_release(&(sp->lock));
-
ss[sp->ply].currentMove = move;
- // Decide the new search depth.
+ // Decide the new search depth
bool dangerous;
Depth ext = extension(pos, move, false, captureOrPromotion, moveIsCheck, false, false, &dangerous);
Depth newDepth = sp->depth - OnePly + ext;
&& !move_is_castle(move)
&& !move_is_killer(move, ss[sp->ply]))
{
- double red = 0.5 + ln(moveCount) * ln(sp->depth / 2) / 3.0;
- if (red >= 1.0)
+ ss[sp->ply].reduction = reduction(moveCount, LogLimit, BaseReduction, Gradient);
+ if (ss[sp->ply].reduction)
{
- ss[sp->ply].reduction = Depth(int(floor(red * int(OnePly))));
value = -search(pos, ss, -(sp->beta-1), newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID);
doFullDepthSearch = (value >= sp->beta);
}
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
if (thread_should_stop(threadID))
+ {
+ lock_grab(&(sp->lock));
break;
+ }
// New best move?
if (value > sp->bestValue) // Less then 2% of cases
}
}
- lock_grab(&(sp->lock));
+ /* Here we have the lock still grabbed */
// If this is the master thread and we have been asked to stop because of
// a beta cutoff higher up in the tree, stop all slave threads.
assert(threadID >= 0 && threadID < ActiveThreads);
assert(ActiveThreads > 1);
- Position pos = Position(sp->pos);
+ Position pos(*sp->pos);
CheckInfo ci(pos);
SearchStack* ss = sp->sstack[threadID];
- Value value;
+ Value value = -VALUE_INFINITE;
+ int moveCount;
Move move;
- while ( sp->alpha < sp->beta
+ // Precalculate reduction parameters
+ float LogLimit, Gradient, BaseReduction = 0.5;
+ reduction_parameters(BaseReduction, 6.0, sp->depth, LogLimit, Gradient);
+
+ while ( lock_grab_bool(&(sp->lock))
+ && sp->alpha < sp->beta
&& !thread_should_stop(threadID)
- && (move = sp->mp->get_next_move(sp->lock)) != MOVE_NONE)
+ && (move = sp->mp->get_next_move()) != MOVE_NONE)
{
- bool moveIsCheck = pos.move_is_check(move, ci);
- bool captureOrPromotion = pos.move_is_capture_or_promotion(move);
+ moveCount = ++sp->moves;
+ lock_release(&(sp->lock));
assert(move_is_ok(move));
- lock_grab(&(sp->lock));
- int moveCount = ++sp->moves;
- lock_release(&(sp->lock));
+ bool moveIsCheck = pos.move_is_check(move, ci);
+ bool captureOrPromotion = pos.move_is_capture_or_promotion(move);
ss[sp->ply].currentMove = move;
- // Decide the new search depth.
+ // Decide the new search depth
bool dangerous;
Depth ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, false, false, &dangerous);
Depth newDepth = sp->depth - OnePly + ext;
&& !move_is_castle(move)
&& !move_is_killer(move, ss[sp->ply]))
{
- double red = 0.5 + ln(moveCount) * ln(sp->depth / 2) / 6.0;
- if (red >= 1.0)
+ ss[sp->ply].reduction = reduction(moveCount, LogLimit, BaseReduction, Gradient);
+ if (ss[sp->ply].reduction)
{
Value localAlpha = sp->alpha;
- ss[sp->ply].reduction = Depth(int(floor(red * int(OnePly))));
value = -search(pos, ss, -localAlpha, newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID);
doFullDepthSearch = (value > localAlpha);
}
if (sp->ply == 1 && RootMoveNumber == 1)
Threads[threadID].failHighPly1 = true;
- value = -search_pv(pos, ss, -sp->beta, -sp->alpha, newDepth, sp->ply+1, threadID);
+ // If another thread has failed high then sp->alpha has been increased
+ // to be higher or equal then beta, if so, avoid to start a PV search.
+ localAlpha = sp->alpha;
+ if (localAlpha < sp->beta)
+ value = -search_pv(pos, ss, -sp->beta, -localAlpha, newDepth, sp->ply+1, threadID);
+ else
+ assert(thread_should_stop(threadID));
+
Threads[threadID].failHighPly1 = false;
}
}
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
if (thread_should_stop(threadID))
+ {
+ lock_grab(&(sp->lock));
break;
+ }
// New best move?
- lock_grab(&(sp->lock));
- if (value > sp->bestValue && !thread_should_stop(threadID))
+ if (value > sp->bestValue) // Less then 2% of cases
{
- sp->bestValue = value;
- if (value > sp->alpha)
+ lock_grab(&(sp->lock));
+ if (value > sp->bestValue && !thread_should_stop(threadID))
{
- sp->alpha = value;
- sp_update_pv(sp->parentSstack, ss, sp->ply);
- if (value == value_mate_in(sp->ply + 1))
- ss[sp->ply].mateKiller = move;
-
- if (value >= sp->beta)
+ sp->bestValue = value;
+ if (value > sp->alpha)
{
- for (int i = 0; i < ActiveThreads; i++)
- if (i != threadID && (i == sp->master || sp->slaves[i]))
- Threads[i].stop = true;
+ // Ask threads to stop before to modify sp->alpha
+ if (value >= sp->beta)
+ {
+ for (int i = 0; i < ActiveThreads; i++)
+ if (i != threadID && (i == sp->master || sp->slaves[i]))
+ Threads[i].stop = true;
- sp->finished = true;
+ sp->finished = true;
+ }
+
+ sp->alpha = value;
+
+ sp_update_pv(sp->parentSstack, ss, sp->ply);
+ if (value == value_mate_in(sp->ply + 1))
+ ss[sp->ply].mateKiller = move;
}
- }
- // If we are at ply 1, and we are searching the first root move at
- // ply 0, set the 'Problem' variable if the score has dropped a lot
- // (from the computer's point of view) since the previous iteration.
- if ( sp->ply == 1
- && Iteration >= 2
- && -value <= IterationInfo[Iteration-1].value - ProblemMargin)
- Problem = true;
+ // If we are at ply 1, and we are searching the first root move at
+ // ply 0, set the 'Problem' variable if the score has dropped a lot
+ // (from the computer's point of view) since the previous iteration.
+ if ( sp->ply == 1
+ && Iteration >= 2
+ && -value <= IterationInfo[Iteration-1].value - ProblemMargin)
+ Problem = true;
+ }
+ lock_release(&(sp->lock));
}
- lock_release(&(sp->lock));
}
- lock_grab(&(sp->lock));
+ /* Here we have the lock still grabbed */
// If this is the master thread and we have been asked to stop because of
// a beta cutoff higher up in the tree, stop all slave threads.
RootMoveList::RootMoveList(Position& pos, Move searchMoves[]) : count(0) {
+ SearchStack ss[PLY_MAX_PLUS_2];
MoveStack mlist[MaxRootMoves];
+ StateInfo st;
bool includeAllMoves = (searchMoves[0] == MOVE_NONE);
// Generate all legal moves
continue;
// Find a quick score for the move
- StateInfo st;
- SearchStack ss[PLY_MAX_PLUS_2];
init_ss_array(ss);
-
+ pos.do_move(cur->move, st);
moves[count].move = cur->move;
- pos.do_move(moves[count].move, st);
moves[count].score = -qsearch(pos, ss, -VALUE_INFINITE, VALUE_INFINITE, Depth(0), 1, 0);
- pos.undo_move(moves[count].move);
- moves[count].pv[0] = moves[count].move;
+ moves[count].pv[0] = cur->move;
moves[count].pv[1] = MOVE_NONE;
+ pos.undo_move(cur->move);
count++;
}
sort();
Square mfrom, mto, tfrom, tto;
- // Prune if there isn't any threat move and
- // is not a castling move (common case).
- if (threat == MOVE_NONE && !move_is_castle(m))
+ // Prune if there isn't any threat move
+ if (threat == MOVE_NONE)
return true;
mfrom = move_from(m);
tfrom = move_from(threat);
tto = move_to(threat);
- // Case 1: Castling moves are never pruned
- if (move_is_castle(m))
- return false;
-
- // Case 2: Don't prune moves which move the threatened piece
+ // Case 1: Don't prune moves which move the threatened piece
if (mfrom == tto)
return false;
- // Case 3: If the threatened piece has value less than or equal to the
+ // Case 2: If the threatened piece has value less than or equal to the
// value of the threatening piece, don't prune move which defend it.
if ( pos.move_is_capture(threat)
&& ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
&& pos.move_attacks_square(m, tto))
return false;
- // Case 4: If the moving piece in the threatened move is a slider, don't
+ // Case 3: If the moving piece in the threatened move is a slider, don't
// prune safe moves which block its ray.
if ( piece_is_slider(pos.piece_on(tfrom))
&& bit_is_set(squares_between(tfrom, tto), mto)
return defaultEval;
}
+
+ // reduction_parameters() precalculates some parameters used later by reduction. Becasue
+ // floating point operations are involved we try to recalculate reduction at each move, but
+ // we do the most consuming computation only once per node.
+
+ void reduction_parameters(float baseReduction, float reductionInhibitor, Depth depth, float& logLimit, float& gradient)
+ {
+ // Precalculate some parameters to avoid to calculate the following formula for each move:
+ //
+ // red = baseReduction + ln(moveCount) * ln(depth / 2) / reductionInhibitor;
+ //
+ logLimit = depth > OnePly ? (1 - baseReduction) * reductionInhibitor / ln(depth / 2) : 1000;
+ gradient = depth > OnePly ? ln(depth / 2) / reductionInhibitor : 0;
+ }
+
+
+ // reduction() returns reduction in plies based on moveCount and depth.
+ // Reduction is always at least one ply.
+
+ Depth reduction(int moveCount, float logLimit, float baseReduction, float gradient) {
+
+ if (ln(moveCount) < logLimit)
+ return Depth(0);
+
+ float red = baseReduction + ln(moveCount) * gradient;
+ return Depth(int(floor(red * int(OnePly))));
+ }
+
+
// 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_gains() updates the gains table of a non-capture move given
+ // the static position evaluation before and after the move.
+
+ void update_gains(const Position& pos, Move m, Value before, Value after) {
+
+ if ( m != MOVE_NULL
+ && before != VALUE_NONE
+ && after != VALUE_NONE
+ && pos.captured_piece() == NO_PIECE_TYPE
+ && !move_is_castle(m)
+ && !move_is_promotion(m))
+ H.set_gain(pos.piece_on(move_to(m)), move_from(m), move_to(m), -(before + after));
+ }
+
+
// fail_high_ply_1() checks if some thread is currently resolving a fail
// high at ply 1 at the node below the first root node. This information
// is used for time management.
// If this thread has been assigned work, launch a search
if (Threads[threadID].workIsWaiting)
{
+ assert(!Threads[threadID].idle);
+
Threads[threadID].workIsWaiting = false;
if (Threads[threadID].splitPoint->pvNode)
sp_search_pv(Threads[threadID].splitPoint, threadID);
if (!Threads[slave].idle || slave == master)
return false;
- if (Threads[slave].activeSplitPoints == 0)
+ // Make a local copy to be sure doesn't change under our feet
+ int localActiveSplitPoints = Threads[slave].activeSplitPoints;
+
+ if (localActiveSplitPoints == 0)
// No active split points means that the thread is available as
// a slave for any other thread.
return true;
if (ActiveThreads == 2)
return true;
- // Apply the "helpful master" concept if possible
- if (SplitPointStack[slave][Threads[slave].activeSplitPoints - 1].slaves[master])
+ // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
+ // that is known to be > 0, instead of Threads[slave].activeSplitPoints that
+ // could have been set to 0 by another thread leading to an out of bound access.
+ if (SplitPointStack[slave][localActiveSplitPoints - 1].slaves[master])
return true;
return false;
assert(ActiveThreads > 1);
SplitPoint* splitPoint;
- int i;
lock_grab(&MPLock);
splitPoint = SplitPointStack[master] + Threads[master].activeSplitPoints;
Threads[master].activeSplitPoints++;
- // Initialize the split point object and copy current position
+ // Initialize the split point object
splitPoint->parent = Threads[master].splitPoint;
splitPoint->finished = false;
splitPoint->ply = ply;
splitPoint->mp = mp;
splitPoint->moves = *moves;
splitPoint->cpus = 1;
- splitPoint->pos.copy(p);
+ splitPoint->pos = &p;
splitPoint->parentSstack = sstck;
- for (i = 0; i < ActiveThreads; i++)
+ for (int i = 0; i < ActiveThreads; i++)
splitPoint->slaves[i] = 0;
- // Copy the current search stack to the master thread
- memcpy(splitPoint->sstack[master], sstck, (ply+1) * sizeof(SearchStack));
+ Threads[master].idle = false;
+ Threads[master].stop = false;
Threads[master].splitPoint = splitPoint;
- // Make copies of the current position and search stack for each thread
- for (i = 0; i < ActiveThreads && splitPoint->cpus < MaxThreadsPerSplitPoint; i++)
+ // Allocate available threads setting idle flag to false
+ for (int i = 0; i < ActiveThreads && splitPoint->cpus < MaxThreadsPerSplitPoint; i++)
if (thread_is_available(i, master))
{
- memcpy(splitPoint->sstack[i], sstck, (ply+1) * sizeof(SearchStack));
+ Threads[i].idle = false;
+ Threads[i].stop = false;
Threads[i].splitPoint = splitPoint;
splitPoint->slaves[i] = 1;
splitPoint->cpus++;
}
+ assert(splitPoint->cpus > 1);
+
+ // We can release the lock because master and slave threads are already booked
+ lock_release(&MPLock);
+
// Tell the threads that they have work to do. This will make them leave
- // their idle loop.
- for (i = 0; i < ActiveThreads; i++)
+ // their idle loop. But before copy search stack tail for each thread.
+ for (int i = 0; i < ActiveThreads; i++)
if (i == master || splitPoint->slaves[i])
{
- Threads[i].workIsWaiting = true;
- Threads[i].idle = false;
- Threads[i].stop = false;
+ memcpy(splitPoint->sstack[i] + ply - 1, sstck + ply - 1, 3 * sizeof(SearchStack));
+ Threads[i].workIsWaiting = true; // This makes the slave to exit from idle_loop()
}
- lock_release(&MPLock);
-
// Everything is set up. The master thread enters the idle loop, from
// which it will instantly launch a search, because its workIsWaiting
// slot is 'true'. We send the split point as a second parameter to the
projects / stockfish / blobdiff