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Anchored bishops

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Reduce the "bad bishop" penalty when the bishop is protected by
one of our pawns, as it may indicate that the bishop has found
a safe spot outside the pawn chain.

STC:
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 176942 W: 34142 L: 33696 D: 109104
Ptnml(0-2): 3129, 20422, 40919, 20876, 3125
http://tests.stockfishchess.org/tests/view/5e6f61aae42a5c3b3ca2e62d

LTC:
LLR: 2.95 (-2.94,2.94) {0.25,1.75}
Total: 42252 W: 5615 L: 5322 D: 31315
Ptnml(0-2): 308, 3881, 12500, 4084, 353
http://tests.stockfishchess.org/tests/view/5e701382e42a5c3b3ca2e661

closes https://github.com/official-stockfish/Stockfish/pull/2587

Bench: 4963440
This commit is contained in:
Stéphane Nicolet 2020-03-17 08:26:27 +01:00 • committed by Joost VandeVondele
parent ddcbacd04d
commit 07caca2587
1 changed files with 3 additions and 2 deletions
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5
src/evaluate.cpp
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@ -308,11 +308,12 @@ namespace {
if (Pt == BISHOP) if (Pt == BISHOP)
{ {
// Penalty according to number of pawns on the same color square as the // Penalty according to number of pawns on the same color square as the
// bishop, bigger when the center files are blocked with pawns. // bishop, bigger when the center files are blocked with pawns and smaller
// when the bishop is outside the pawn chain.
Bitboard blocked = pos.pieces(Us, PAWN) & shift<Down>(pos.pieces()); Bitboard blocked = pos.pieces(Us, PAWN) & shift<Down>(pos.pieces());
score -= BishopPawns * pos.pawns_on_same_color_squares(Us, s) score -= BishopPawns * pos.pawns_on_same_color_squares(Us, s)
* (1 + popcount(blocked & CenterFiles)); * (!bool(attackedBy[Us][PAWN] & s) + popcount(blocked & CenterFiles));
// Bonus for bishop on a long diagonal which can "see" both center squares // Bonus for bishop on a long diagonal which can "see" both center squares
if (more_than_one(attacks_bb<BISHOP>(s, pos.pieces(PAWN)) & Center)) if (more_than_one(attacks_bb<BISHOP>(s, pos.pieces(PAWN)) & Center))