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Scale up space weight with number of blocked pawns

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This idea is loosely based on stockfish losses in closed positions in different tournaments. Space weight symmetrically increases for both sides the more blocked position is.

passed STC
https://tests.stockfishchess.org/tests/view/5e919eefaf0a0143109dc8ce
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 16994 W: 3389 L: 3172 D: 10433
Ptnml(0-2): 277, 1931, 3918, 2040, 331

passed LTC
https://tests.stockfishchess.org/tests/view/5e91d04faf0a0143109dc8ea
LLR: 2.94 (-2.94,2.94) {0.25,1.75}
Total: 133386 W: 17316 L: 16763 D: 99307
Ptnml(0-2): 945, 12407, 39524, 12784, 1033

closes https://github.com/official-stockfish/Stockfish/pull/2626

Bench: 4966867
This commit is contained in:
Vizvezdenec 2020-04-13 03:48:52 +03:00 • committed by Joost VandeVondele
parent d7a2d5a445
commit db59696aaf
3 changed files with 6 additions and 1 deletions
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2
src/evaluate.cpp
View file

@ -695,7 +695,7 @@ namespace {
behind |= shift<Down+Down>(behind);
int bonus = popcount(safe) + popcount(behind & safe & ~attackedBy[Them][ALL_PIECES]);
int weight = pos.count<ALL_PIECES>(Us) - 1;
int weight = pos.count<ALL_PIECES>(Us) - 2 + pe->blocked_count() / 2;
Score score = make_score(bonus * weight * weight / 16, 0);
if (T)

3
src/pawns.cpp
View file

@ -86,6 +86,7 @@ namespace {
e->passedPawns[Us] = 0;
e->kingSquares[Us] = SQ_NONE;
e->pawnAttacks[Us] = e->pawnAttacksSpan[Us] = pawn_attacks_bb<Us>(ourPawns);
e->blockedCount[Us] = 0;
// Loop through all pawns of the current color and score each pawn
while ((s = *pl++) != SQ_NONE)
@ -105,6 +106,8 @@ namespace {
phalanx = neighbours & rank_bb(s);
support = neighbours & rank_bb(s - Up);
e->blockedCount[Us] += bool(blocked);
// A pawn is backward when it is behind all pawns of the same color on
// the adjacent files and cannot safely advance.
backward = !(neighbours & forward_ranks_bb(Them, s + Up))

2
src/pawns.h
View file

@ -38,6 +38,7 @@ struct Entry {
Bitboard passed_pawns(Color c) const { return passedPawns[c]; }
Bitboard pawn_attacks_span(Color c) const { return pawnAttacksSpan[c]; }
int passed_count() const { return popcount(passedPawns[WHITE] | passedPawns[BLACK]); }
int blocked_count() const { return blockedCount[WHITE] + blockedCount[BLACK]; }
template<Color Us>
Score king_safety(const Position& pos) {
@ -59,6 +60,7 @@ struct Entry {
Square kingSquares[COLOR_NB];
Score kingSafety[COLOR_NB];
int castlingRights[COLOR_NB];
int blockedCount[COLOR_NB];
};
typedef HashTable<Entry, 131072> Table;