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Simplify SEE verfication logic

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Passed STC
https://tests.stockfishchess.org/tests/view/6461d51887f6567dd4df27d0
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 177056 W: 47181 L: 47118 D: 82757
Ptnml(0-2): 456, 19381, 48792, 19442, 457

Passed LTC
https://tests.stockfishchess.org/tests/view/64631a9287f6567dd4df4502
2.94 (-2.94,2.94) <-1.75,0.25>
Total: 104346 W: 28062 L: 27935 D: 48349
Ptnml(0-2): 25, 10190, 31631, 10287, 40

closes https://github.com/official-stockfish/Stockfish/pull/4578

bench: 2903251
This commit is contained in:
pb00067 2023-05-17 09:22:02 +02:00 • committed by Joost VandeVondele
parent 4b085c4777
commit 7cd650f435
1 changed files with 2 additions and 4 deletions
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6
src/search.cpp
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@ -996,9 +996,7 @@ moves_loop: // When in check, search starts here
// SEE based pruning (~11 Elo) // SEE based pruning (~11 Elo)
if (!pos.see_ge(move, occupied, Value(-205) * depth)) if (!pos.see_ge(move, occupied, Value(-205) * depth))
{ {
if (depth < 2 - capture) // Don't prune the move if opponent King/Queen/Rook gets a discovered attack during or after the exchanges
continue;
// Don't prune the move if opp. King/Queen/Rook gets a discovered attack during or after the exchanges
Bitboard leftEnemies = pos.pieces(~us, KING, QUEEN, ROOK); Bitboard leftEnemies = pos.pieces(~us, KING, QUEEN, ROOK);
Bitboard attacks = 0; Bitboard attacks = 0;
occupied |= to_sq(move); occupied |= to_sq(move);
@ -1006,7 +1004,7 @@ moves_loop: // When in check, search starts here
{ {
Square sq = pop_lsb(leftEnemies); Square sq = pop_lsb(leftEnemies);
attacks = pos.attackers_to(sq, occupied) & pos.pieces(us) & occupied; attacks = pos.attackers_to(sq, occupied) & pos.pieces(us) & occupied;
// Exclude Queen/Rook(s) which were already threatened before SEE (opp King can't be in check when it's our turn) // Exclude Queen/Rook(s) which were already threatened before SEE (opponent King can't be in check when it's our turn)
if (attacks && sq != pos.square<KING>(~us) && (pos.attackers_to(sq, pos.pieces()) & pos.pieces(us))) if (attacks && sq != pos.square<KING>(~us) && (pos.attackers_to(sq, pos.pieces()) & pos.pieces(us)))
attacks = 0; attacks = 0;
} }