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Limit the king distance factor when evaluating passed pawns (#1373)

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Limit the king distance factor when evaluating passed pawns
Passed STC
http://tests.stockfishchess.org/tests/view/5a6bf7290ebc590d945d5a3a
LLR: 3.31 (-2.94,2.94) [0.00,5.00]
Total: 23987 W: 5550 L: 5281 D: 13156

and LTC
http://tests.stockfishchess.org/tests/view/5a6c57710ebc590297c36af2
LLR: 2.97 (-2.94,2.94) [0.00,5.00]
Total: 16926 W: 3014 L: 2820 D: 11092

Bench: 5059457
This commit is contained in:
Rocky640 2018-01-28 08:56:45 -05:00 • committed by Marco Costalba
parent fd4d800c98
commit 0a5b03af3f
1 changed files with 17 additions and 9 deletions
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26
src/evaluate.cpp
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@ -97,6 +97,7 @@ namespace {
template<Color Us> void initialize();
template<Color Us> Score evaluate_king();
template<Color Us> Score evaluate_threats();
int king_distance(Color c, Square s);
template<Color Us> Score evaluate_passed_pawns();
template<Color Us> Score evaluate_space();
template<Color Us, PieceType Pt> Score evaluate_pieces();
@ -198,8 +199,8 @@ namespace {
// Passed[mg/eg][Rank] contains midgame and endgame bonuses for passed pawns.
// We don't use a Score because we process the two components independently.
const Value Passed[][RANK_NB] = {
{ V(5), V( 5), V(31), V(73), V(166), V(252) },
{ V(7), V(14), V(38), V(73), V(166), V(252) }
{ V(0), V(5), V( 5), V(31), V(73), V(166), V(252) },
{ V(0), V(7), V(14), V(38), V(73), V(166), V(252) }
};
// PassedFile[File] contains a bonus according to the file of a passed pawn
@ -208,6 +209,9 @@ namespace {
S(-20,-12), S( 1, -8), S( 2, 10), S( 9, 10)
};
// Rank factor applied on some bonus for passed pawn on rank 4 or beyond
const int RankFactor[RANK_NB] = {0, 0, 0, 2, 6, 11, 16};
// KingProtector[PieceType-2] contains a bonus according to distance from king
const Score KingProtector[] = { S(-3, -5), S(-4, -3), S(-3, 0), S(-1, 1) };
@ -486,7 +490,7 @@ namespace {
- 9 * mg_value(score) / 8
+ 40;
// Transform the kingDanger units into a Score, and substract it from the evaluation
// Transform the kingDanger units into a Score, and subtract it from the evaluation
if (kingDanger > 0)
{
int mobilityDanger = mg_value(mobility[Them] - mobility[Us]);
@ -622,6 +626,11 @@ namespace {
return score;
}
// helper used by evaluate_passed_pawns to cap the distance
template<Tracing T>
int Evaluation<T>::king_distance(Color c, Square s) {
return std::min(distance(pos.square<KING>(c), s), 5);
}
// evaluate_passed_pawns() evaluates the passed pawns and candidate passed
// pawns of the given color.
@ -646,8 +655,8 @@ namespace {
bb = forward_file_bb(Us, s) & (attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
score -= HinderPassedPawn * popcount(bb);
int r = relative_rank(Us, s) - RANK_2;
int rr = r * (r - 1);
int r = relative_rank(Us, s);
int rr = RankFactor[r];
Value mbonus = Passed[MG][r], ebonus = Passed[EG][r];
@ -656,12 +665,11 @@ namespace {
Square blockSq = s + Up;
// Adjust bonus based on the king's proximity
ebonus += distance(pos.square<KING>(Them), blockSq) * 5 * rr
- distance(pos.square<KING>( Us), blockSq) * 2 * rr;
ebonus += (king_distance(Them, blockSq) * 5 - king_distance(Us, blockSq) * 2) * rr;
// If blockSq is not the queening square then consider also a second push
if (relative_rank(Us, blockSq) != RANK_8)
ebonus -= distance(pos.square<KING>(Us), blockSq + Up) * rr;
if (r != RANK_7)
ebonus -= king_distance(Us, blockSq + Up) * rr;
// If the pawn is free to advance, then increase the bonus
if (pos.empty(blockSq))