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Add min pawn-king distance to endgame evaluation

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At endgame time push the king near his pawns (actually
one of them).

Original idea is from Critter (although slightly different),
implementation is mine and is completely different from the
original, in particular it is different the algorithm to
compute the minimum distance from pawns.

After 19895 games at 15"+0.05
Mod vs Orig 3638 - 3248 - 13009 ELO +7

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2012-06-17 09:18:18 +01:00
parent 9793fa1906
commit 4f5680950a
1 changed files with 2 additions and 2 deletions
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4
src/pawns.cpp
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@ -268,7 +268,7 @@ Score PawnEntry::update_safety(const Position& pos, Square ksq) {
while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {}
if (relative_rank(Us, ksq) > RANK_4)
return kingSafety[Us] = SCORE_ZERO;
return kingSafety[Us] = make_score(0, -16 * minKPdistance[Us]);
Value bonus = shelter_storm<Us>(pos, ksq);
@ -279,7 +279,7 @@ Score PawnEntry::update_safety(const Position& pos, Square ksq) {
if (pos.can_castle(make_castle_right(Us, QUEEN_SIDE)))
bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_C1)));
return kingSafety[Us] = make_score(bonus, 0);
return kingSafety[Us] = make_score(bonus, -16 * minKPdistance[Us]);
}
// Explicit template instantiation