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Retire KingDanger array
Rescales the king danger variables in evaluate_king() to suppress the KingDanger[] array. This avoids the cost of the memory accesses to the array and simplifies the non-linear transformation used. Full credits to "hxim" for the seminal idea and implementation, see pull request #786. https://github.com/official-stockfish/Stockfish/pull/786 Passed STC: LLR: 2.95 (-2.94,2.94) [-3.00,1.00] Total: 9649 W: 1829 L: 1689 D: 6131 Passed LTC: LLR: 2.95 (-2.94,2.94) [-3.00,1.00] Total: 53494 W: 7254 L: 7178 D: 39062 Bench: 6116200
This commit is contained in:
Stéphane Nicolet
Marco Costalba
parent
5c58d1f5cb
commit
01f2466f6e
4 changed files with 25 additions and 50 deletions
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@ -206,21 +206,15 @@ namespace {
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#undef S
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#undef V
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// King danger constants and variables. The king danger scores are looked-up
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// in KingDanger[]. Various little "meta-bonuses" measuring the strength
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// of the enemy attack are added up into an integer, which is used as an
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// index to KingDanger[].
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Score KingDanger[400];
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// KingAttackWeights[PieceType] contains king attack weights by piece type
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const int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 7, 5, 4, 1 };
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const int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 78, 56, 45, 11 };
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// Penalties for enemy's safe checks
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const int QueenContactCheck = 89;
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const int QueenCheck = 62;
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const int RookCheck = 57;
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const int BishopCheck = 48;
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const int KnightCheck = 78;
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const int QueenContactCheck = 997;
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const int QueenCheck = 695;
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const int RookCheck = 638;
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const int BishopCheck = 538;
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const int KnightCheck = 874;
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// eval_init() initializes king and attack bitboards for a given color
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@ -401,7 +395,7 @@ namespace {
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const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
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Bitboard undefended, b, b1, b2, safe, other;
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int attackUnits;
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int kingDanger;
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const Square ksq = pos.square<KING>(Us);
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// King shelter and enemy pawns storm
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@ -419,24 +413,24 @@ namespace {
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b = ei.attackedBy[Them][ALL_PIECES] & ~ei.attackedBy[Us][ALL_PIECES]
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& ei.kingRing[Us] & ~pos.pieces(Them);
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// Initialize the 'attackUnits' variable, which is used later on as an
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// index into the KingDanger[] array. The initial value is based on the
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// Initialize the 'kingDanger' variable, which will be transformed
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// later into a king danger score. The initial value is based on the
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// number and types of the enemy's attacking pieces, the number of
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// attacked and undefended squares around our king and the quality of
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// the pawn shelter (current 'score' value).
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attackUnits = std::min(72, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
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+ 9 * ei.kingAdjacentZoneAttacksCount[Them]
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+ 21 * popcount(undefended)
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+ 12 * (popcount(b) + !!ei.pinnedPieces[Us])
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- 64 * !pos.count<QUEEN>(Them)
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- mg_value(score) / 8;
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kingDanger = std::min(807, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
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+ 101 * ei.kingAdjacentZoneAttacksCount[Them]
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+ 235 * popcount(undefended)
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+ 134 * (popcount(b) + !!ei.pinnedPieces[Us])
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- 717 * !pos.count<QUEEN>(Them)
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- 7 * mg_value(score) / 5 - 5;
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// Analyse the enemy's safe queen contact checks. Firstly, find the
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// undefended squares around the king reachable by the enemy queen...
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b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
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// ...and keep squares supported by another enemy piece
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attackUnits += QueenContactCheck * popcount(b & ei.attackedBy2[Them]);
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kingDanger += QueenContactCheck * popcount(b & ei.attackedBy2[Them]);
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// Analyse the safe enemy's checks which are possible on next move...
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safe = ~(ei.attackedBy[Us][ALL_PIECES] | pos.pieces(Them));
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@ -451,7 +445,7 @@ namespace {
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// Enemy queen safe checks
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if ((b1 | b2) & ei.attackedBy[Them][QUEEN] & safe)
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attackUnits += QueenCheck, score -= SafeCheck;
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kingDanger += QueenCheck, score -= SafeCheck;
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// For other pieces, also consider the square safe if attacked twice,
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// and only defended by a queen.
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@ -461,14 +455,14 @@ namespace {
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// Enemy rooks safe and other checks
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if (b1 & ei.attackedBy[Them][ROOK] & safe)
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attackUnits += RookCheck, score -= SafeCheck;
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kingDanger += RookCheck, score -= SafeCheck;
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else if (b1 & ei.attackedBy[Them][ROOK] & other)
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score -= OtherCheck;
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// Enemy bishops safe and other checks
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if (b2 & ei.attackedBy[Them][BISHOP] & safe)
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attackUnits += BishopCheck, score -= SafeCheck;
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kingDanger += BishopCheck, score -= SafeCheck;
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else if (b2 & ei.attackedBy[Them][BISHOP] & other)
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score -= OtherCheck;
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@ -476,14 +470,14 @@ namespace {
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// Enemy knights safe and other checks
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b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT];
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if (b & safe)
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attackUnits += KnightCheck, score -= SafeCheck;
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kingDanger += KnightCheck, score -= SafeCheck;
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else if (b & other)
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score -= OtherCheck;
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// Finally, extract the king danger score from the KingDanger[]
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// array and subtract the score from the evaluation.
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score -= KingDanger[std::max(std::min(attackUnits, 399), 0)];
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// Compute the king danger score and subtract it from the evaluation
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if (kingDanger > 0)
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score -= make_score(std::min(kingDanger * kingDanger / 4096, 2 * int(BishopValueMg)), 0);
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}
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// King tropism: firstly, find squares that opponent attacks in our king flank
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@ -920,19 +914,3 @@ std::string Eval::trace(const Position& pos) {
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return ss.str();
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}
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/// init() computes evaluation weights, usually at startup
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void Eval::init() {
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const int MaxSlope = 322;
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const int Peak = 47410;
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int t = 0;
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for (int i = 0; i < 400; ++i)
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{
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t = std::min(Peak, std::min(i * i - 16, t + MaxSlope));
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KingDanger[i] = make_score(t * 268 / 7700, 0);
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}
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}
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@ -31,7 +31,6 @@ namespace Eval {
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const Value Tempo = Value(20); // Must be visible to search
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void init();
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std::string trace(const Position& pos);
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template<bool DoTrace = false>
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@ -21,7 +21,6 @@
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#include <iostream>
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#include "bitboard.h"
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#include "evaluate.h"
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#include "position.h"
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#include "search.h"
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#include "thread.h"
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@ -39,7 +38,6 @@ int main(int argc, char* argv[]) {
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Position::init();
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Bitbases::init();
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Search::init();
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Eval::init();
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Pawns::init();
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Threads.init();
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Tablebases::init(Options["SyzygyPath"]);
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@ -920,8 +920,8 @@ moves_loop: // When in check search starts from here
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// Step 13. Pruning at shallow depth
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if ( !rootNode
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&& !inCheck
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&& bestValue > VALUE_MATED_IN_MAX_PLY)
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&& !inCheck
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&& bestValue > VALUE_MATED_IN_MAX_PLY)
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{
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if ( !captureOrPromotion
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&& !givesCheck
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