// Function prototypes
template<bool Trace>
- Value do_evaluate(const Position& pos);
+ Value do_evaluate(const Position& pos, Value& margin);
template<Color Us>
void init_eval_info(const Position& pos, EvalInfo& ei);
Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score* mobility);
template<Color Us, bool Trace>
- Score evaluate_king(const Position& pos, const EvalInfo& ei);
+ Score evaluate_king(const Position& pos, const EvalInfo& ei, Value margins[]);
template<Color Us, bool Trace>
Score evaluate_threats(const Position& pos, const EvalInfo& ei);
/// values, an endgame score and a middle game score, and interpolates
/// between them based on the remaining material.
- Value evaluate(const Position& pos) {
- return do_evaluate<false>(pos);
+ Value evaluate(const Position& pos, Value& margin) {
+ return do_evaluate<false>(pos, margin);
}
namespace {
template<bool Trace>
-Value do_evaluate(const Position& pos) {
+Value do_evaluate(const Position& pos, Value& margin) {
assert(!pos.checkers());
EvalInfo ei;
+ Value margins[COLOR_NB];
Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
Thread* th = pos.this_thread();
+ // margins[] store the uncertainty estimation of position's evaluation
+ // that typically is used by the search for pruning decisions.
+ margins[WHITE] = margins[BLACK] = VALUE_ZERO;
+
// Initialize score by reading the incrementally updated scores included
// in the position object (material + piece square tables) and adding
// Tempo bonus. Score is computed from the point of view of white.
// If we have a specialized evaluation function for the current material
// configuration, call it and return.
if (ei.mi->specialized_eval_exists())
+ {
+ margin = VALUE_ZERO;
return ei.mi->evaluate(pos);
+ }
// Probe the pawn hash table
ei.pi = Pawns::probe(pos, th->pawnsTable);
// Evaluate kings after all other pieces because we need complete attack
// information when computing the king safety evaluation.
- score += evaluate_king<WHITE, Trace>(pos, ei)
- - evaluate_king<BLACK, Trace>(pos, ei);
+ score += evaluate_king<WHITE, Trace>(pos, ei, margins)
+ - evaluate_king<BLACK, Trace>(pos, ei, margins);
// Evaluate tactical threats, we need full attack information including king
score += evaluate_threats<WHITE, Trace>(pos, ei)
sf = ScaleFactor(50);
}
+ margin = margins[pos.side_to_move()];
Value v = interpolate(score, ei.mi->game_phase(), sf);
// In case of tracing add all single evaluation contributions for both white and black
Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
Tracing::add(SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
Tracing::add(TOTAL, score);
- Tracing::stream << "\nScaling: " << std::noshowpos
+ Tracing::stream << "\nUncertainty margin: White: " << to_cp(margins[WHITE])
+ << ", Black: " << to_cp(margins[BLACK])
+ << "\nScaling: " << std::noshowpos
<< std::setw(6) << 100.0 * ei.mi->game_phase() / 128.0 << "% MG, "
<< std::setw(6) << 100.0 * (1.0 - ei.mi->game_phase() / 128.0) << "% * "
<< std::setw(6) << (100.0 * sf) / SCALE_FACTOR_NORMAL << "% EG.\n"
// evaluate_king() assigns bonuses and penalties to a king of a given color
template<Color Us, bool Trace>
- Score evaluate_king(const Position& pos, const EvalInfo& ei) {
+ Score evaluate_king(const Position& pos, const EvalInfo& ei, Value margins[]) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
attackUnits = std::min(99, std::max(0, attackUnits));
// Finally, extract the king danger score from the KingDanger[]
- // array and subtract the score from evaluation.
+ // array and subtract the score from evaluation. Set also margins[]
+ // value that will be used for pruning because this value can sometimes
+ // be very big, and so capturing a single attacking piece can therefore
+ // result in a score change far bigger than the value of the captured piece.
score -= KingDanger[Us == Search::RootColor][attackUnits];
+ margins[Us] += mg_value(KingDanger[Us == Search::RootColor][attackUnits]);
}
if (Trace)
stream << std::showpoint << std::showpos << std::fixed << std::setprecision(2);
std::memset(scores, 0, 2 * (TOTAL + 1) * sizeof(Score));
- do_evaluate<true>(pos);
+ Value margin;
+ do_evaluate<true>(pos, margin);
std::string totals = stream.str();
stream.str("");
namespace Eval {
extern void init();
-extern Value evaluate(const Position& pos);
+extern Value evaluate(const Position& pos, Value& margin);
extern std::string trace(const Position& pos);
}
/// The Stats struct stores moves statistics. According to the template parameter
-/// the class can store History and Countermoves. History records how often
+/// the class can store History, Gains and Countermoves. History records how often
/// different moves have been successful or unsuccessful during the current search
-/// and is used for reduction and move ordering decisions.
+/// and is used for reduction and move ordering decisions. Gains records the move's
+/// best evaluation gain from one ply to the next and is used for pruning decisions.
/// Countermoves store the move that refute a previous one. Entries are stored
/// according only to moving piece and destination square, hence two moves with
/// different origin but same destination and piece will be considered identical.
-template<typename T>
+template<bool Gain, typename T>
struct Stats {
static const Value Max = Value(2000);
void update(Piece p, Square to, Value v) {
- if (abs(table[p][to] + v) < Max)
+ if (Gain)
+ table[p][to] = std::max(v, table[p][to] - 1);
+
+ else if (abs(table[p][to] + v) < Max)
table[p][to] += v;
}
T table[PIECE_NB][SQUARE_NB];
};
-typedef Stats<Value> HistoryStats;
-typedef Stats<std::pair<Move, Move> > CountermovesStats;
+typedef Stats< true, Value> GainsStats;
+typedef Stats<false, Value> HistoryStats;
+typedef Stats<false, std::pair<Move, Move> > CountermovesStats;
/// MovePicker class is used to pick one pseudo legal move at a time from the
inline Value razor_margin(Depth d) { return Value(512 + 16 * int(d)); }
// Futility lookup tables (initialized at startup) and their access functions
- Value FutilityMargins[14][64]; // [depth][moveNumber]
+ Value FutilityMargins[16][64]; // [depth][moveNumber]
int FutilityMoveCounts[2][32]; // [improving][depth]
inline Value futility_margin(Depth d, int mn) {
- assert(DEPTH_ZERO <= d && d < 7 * ONE_PLY);
- return FutilityMargins[d][std::min(mn, 63)];
+
+ return d < 7 * ONE_PLY ? FutilityMargins[std::max(int(d), 1)][std::min(mn, 63)]
+ : 2 * VALUE_INFINITE;
}
// Reduction lookup tables (initialized at startup) and their access function
double BestMoveChanges;
Value DrawValue[COLOR_NB];
HistoryStats History;
+ GainsStats Gains;
CountermovesStats Countermoves;
template <NodeType NT>
}
// Init futility margins array
- for (d = 0; d < 14; ++d) for (mc = 0; mc < 64; ++mc)
- FutilityMargins[d][mc] = Value(112 * int(2.9 * log(d >= 1 ? double(d) : 1.0)) - 8 * mc + 45);
+ for (d = 1; d < 16; ++d) for (mc = 0; mc < 64; ++mc)
+ FutilityMargins[d][mc] = Value(112 * int(2.9 * log(double(d))) - 8 * mc + 45);
// Init futility move count array
for (d = 0; d < 32; ++d)
Value bestValue, alpha, beta, delta;
std::memset(ss-2, 0, 5 * sizeof(Stack));
+ (ss-1)->currentMove = MOVE_NULL; // Hack to skip update gains
depth = 0;
BestMoveChanges = 0;
TT.new_search();
History.clear();
+ Gains.clear();
Countermoves.clear();
PVSize = Options["MultiPV"];
Move ttMove, move, excludedMove, bestMove, threatMove;
Depth ext, newDepth;
Value bestValue, value, ttValue;
- Value eval, nullValue;
+ Value eval, nullValue, futilityValue;
bool inCheck, givesCheck, pvMove, singularExtensionNode, improving;
bool captureOrPromotion, dangerous, doFullDepthSearch;
int moveCount, quietCount;
// Step 5. Evaluate the position statically and update parent's gain statistics
if (inCheck)
{
- ss->staticEval = eval = VALUE_NONE;
+ ss->staticEval = ss->evalMargin = eval = VALUE_NONE;
goto moves_loop;
}
else if (tte)
{
// Never assume anything on values stored in TT
- if ((ss->staticEval = eval = tte->eval_value()) == VALUE_NONE)
- eval = ss->staticEval = evaluate(pos);
+ if ( (ss->staticEval = eval = tte->eval_value()) == VALUE_NONE
+ ||(ss->evalMargin = tte->eval_margin()) == VALUE_NONE)
+ eval = ss->staticEval = evaluate(pos, ss->evalMargin);
// Can ttValue be used as a better position evaluation?
if (ttValue != VALUE_NONE)
}
else
{
- eval = ss->staticEval = evaluate(pos);
- TT.store(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, ss->staticEval);
+ eval = ss->staticEval = evaluate(pos, ss->evalMargin);
+ TT.store(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE,
+ ss->staticEval, ss->evalMargin);
+ }
+
+ // Update gain for the parent non-capture move given the static position
+ // evaluation before and after the move.
+ if ( !pos.captured_piece_type()
+ && ss->staticEval != VALUE_NONE
+ && (ss-1)->staticEval != VALUE_NONE
+ && (move = (ss-1)->currentMove) != MOVE_NULL
+ && type_of(move) == NORMAL)
+ {
+ Square to = to_sq(move);
+ Gains.update(pos.piece_on(to), to, -(ss-1)->staticEval - ss->staticEval);
}
// Step 6. Razoring (skipped when in check)
return v;
}
- // Step 7. post-Futility pruning (skipped when in check)
+ // Step 7. Static null move pruning (skipped when in check)
+ // We're betting that the opponent doesn't have a move that will reduce
+ // the score by more than futility_margin(depth) if we do a null move.
if ( !PvNode
&& !ss->skipNullMove
- && depth < 7 * ONE_PLY
+ && depth < 4 * ONE_PLY
&& eval - futility_margin(depth, (ss-1)->futilityMoveCount) >= beta
&& abs(beta) < VALUE_MATE_IN_MAX_PLY
&& abs(eval) < VALUE_KNOWN_WIN
// Update current move (this must be done after singular extension search)
newDepth = depth - ONE_PLY + ext;
- Depth predictedDepth = newDepth - reduction<PvNode>(improving, depth, moveCount);
// Step 13. Futility pruning (is omitted in PV nodes)
if ( !PvNode
&& !captureOrPromotion
&& !inCheck
&& !dangerous
+ /* && move != ttMove Already implicit in the next condition */
&& bestValue > VALUE_MATED_IN_MAX_PLY)
{
// Move count based pruning
continue;
}
+ // Value based pruning
+ // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
+ // but fixing this made program slightly weaker.
+ Depth predictedDepth = newDepth - reduction<PvNode>(improving, depth, moveCount);
+ futilityValue = ss->staticEval + ss->evalMargin + futility_margin(predictedDepth, moveCount)
+ + Gains[pos.moved_piece(move)][to_sq(move)];
+
+ if (futilityValue < beta)
+ {
+ bestValue = std::max(bestValue, futilityValue);
+
+ if (SpNode)
+ {
+ splitPoint->mutex.lock();
+ if (bestValue > splitPoint->bestValue)
+ splitPoint->bestValue = bestValue;
+ }
+ continue;
+ }
+
// Prune moves with negative SEE at low depths
if ( predictedDepth < 4 * ONE_PLY
&& pos.see_sign(move) < 0)
TT.store(posKey, value_to_tt(bestValue, ss->ply),
bestValue >= beta ? BOUND_LOWER :
PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER,
- depth, bestMove, ss->staticEval);
+ depth, bestMove, ss->staticEval, ss->evalMargin);
// Quiet best move: update killers, history and countermoves
if ( bestValue >= beta
// Evaluate the position statically
if (InCheck)
{
- ss->staticEval = VALUE_NONE;
+ ss->staticEval = ss->evalMargin = VALUE_NONE;
bestValue = futilityBase = -VALUE_INFINITE;
}
else
if (tte)
{
// Never assume anything on values stored in TT
- if ((ss->staticEval = bestValue = tte->eval_value()) == VALUE_NONE)
- ss->staticEval = bestValue = evaluate(pos);
+ if ( (ss->staticEval = bestValue = tte->eval_value()) == VALUE_NONE
+ ||(ss->evalMargin = tte->eval_margin()) == VALUE_NONE)
+ ss->staticEval = bestValue = evaluate(pos, ss->evalMargin);
// Can ttValue be used as a better position evaluation?
if (ttValue != VALUE_NONE)
bestValue = ttValue;
}
else
- ss->staticEval = bestValue = evaluate(pos);
+ ss->staticEval = bestValue = evaluate(pos, ss->evalMargin);
// Stand pat. Return immediately if static value is at least beta
if (bestValue >= beta)
{
if (!tte)
TT.store(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER,
- DEPTH_NONE, MOVE_NONE, ss->staticEval);
+ DEPTH_NONE, MOVE_NONE, ss->staticEval, ss->evalMargin);
return bestValue;
}
if (PvNode && bestValue > alpha)
alpha = bestValue;
- futilityBase = bestValue + Value(128);
+ futilityBase = bestValue + ss->evalMargin + Value(128);
}
// Initialize a MovePicker object for the current position, and prepare
else // Fail high
{
TT.store(posKey, value_to_tt(value, ss->ply), BOUND_LOWER,
- ttDepth, move, ss->staticEval);
+ ttDepth, move, ss->staticEval, ss->evalMargin);
return value;
}
TT.store(posKey, value_to_tt(bestValue, ss->ply),
PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER,
- ttDepth, bestMove, ss->staticEval);
+ ttDepth, bestMove, ss->staticEval, ss->evalMargin);
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
tte = TT.probe(pos.key());
if (!tte || tte->move() != pv[ply]) // Don't overwrite correct entries
- TT.store(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[ply], VALUE_NONE);
+ TT.store(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[ply], VALUE_NONE, VALUE_NONE);
assert(MoveList<LEGAL>(pos).contains(pv[ply]));
Move killers[2];
Depth reduction;
Value staticEval;
+ Value evalMargin;
int skipNullMove;
int futilityMoveCount;
};
/// more valuable than a TTEntry t2 if t1 is from the current search and t2 is from
/// a previous search, or if the depth of t1 is bigger than the depth of t2.
-void TranspositionTable::store(const Key key, Value v, Bound b, Depth d, Move m, Value statV) {
+void TranspositionTable::store(const Key key, Value v, Bound b, Depth d, Move m, Value statV, Value evalM) {
int c1, c2, c3;
TTEntry *tte, *replace;
replace = tte;
}
- replace->save(key32, v, b, d, m, generation, statV);
+ replace->save(key32, v, b, d, m, generation, statV, evalM);
}
struct TTEntry {
- void save(uint32_t k, Value v, Bound b, Depth d, Move m, int g, Value ev) {
+ void save(uint32_t k, Value v, Bound b, Depth d, Move m, int g, Value ev, Value em) {
key32 = (uint32_t)k;
move16 = (uint16_t)m;
value16 = (int16_t)v;
depth16 = (int16_t)d;
evalValue = (int16_t)ev;
+ evalMargin = (int16_t)em;
}
void set_generation(uint8_t g) { generation8 = g; }
Bound bound() const { return (Bound)bound8; }
int generation() const { return (int)generation8; }
Value eval_value() const { return (Value)evalValue; }
+ Value eval_margin() const { return (Value)evalMargin; }
private:
uint32_t key32;
uint16_t move16;
uint8_t bound8, generation8;
- int16_t value16, depth16, evalValue;
+ int16_t value16, depth16, evalValue, evalMargin;
};
void refresh(const TTEntry* tte) const;
void set_size(size_t mbSize);
void clear();
- void store(const Key key, Value v, Bound type, Depth d, Move m, Value statV);
+ void store(const Key key, Value v, Bound type, Depth d, Move m, Value statV, Value kingD);
private:
uint32_t hashMask;
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