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Simplify away SEE verification

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After 4 simplificatons over PR#4453 the idea does not yield significant
improvement anymore. Maybe also
https://tests.stockfishchess.org/tests/view/640c88092644b62c3394c1c5 was
a fluke.

Passed non-regression bounds:

STC:
https://tests.stockfishchess.org/tests/view/64705389c079b6583146d873
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 131936 W: 35040 L: 34930 D: 61966
Ptnml(0-2): 336, 14559, 36035, 14735, 303

LTC:
https://tests.stockfishchess.org/tests/view/6471a2ade549d9cf2fb213cd
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 407700 W: 109999 L: 110164 D: 187537
Ptnml(0-2): 279, 39913, 123689, 39632, 337

closes https://github.com/official-stockfish/Stockfish/pull/4595

bench: 2675974
This commit is contained in:
Guenther Demetz
2023-05-31 11:48:18 +02:00
committed by Joost VandeVondele
parent 6cf8d938c5
commit 5930c0defb
3 changed files with 8 additions and 30 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/position.cpp
+7 -12
View File
@@ -1061,7 +1061,7 @@ Key Position::key_after(Move m) const {
/// SEE value of move is greater or equal to the given threshold. We'll use an
/// algorithm similar to alpha-beta pruning with a null window.
bool Position::see_ge(Move m, Bitboard& occupied, Value threshold) const {
bool Position::see_ge(Move m, Value threshold) const {
assert(is_ok(m));
@@ -1080,7 +1080,7 @@ bool Position::see_ge(Move m, Bitboard& occupied, Value threshold) const {
return true;
assert(color_of(piece_on(from)) == sideToMove);
occupied = pieces() ^ from ^ to; // xoring to is important for pinned piece logic
Bitboard occupied = pieces() ^ from ^ to; // xoring to is important for pinned piece logic
Color stm = sideToMove;
Bitboard attackers = attackers_to(to, occupied);
Bitboard stmAttackers, bb;
@@ -1111,43 +1111,43 @@ bool Position::see_ge(Move m, Bitboard& occupied, Value threshold) const {
// the bitboard 'attackers' any X-ray attackers behind it.
if ((bb = stmAttackers & pieces(PAWN)))
{
occupied ^= least_significant_square_bb(bb);
if ((swap = PawnValueMg - swap) < res)
break;
occupied ^= least_significant_square_bb(bb);
attackers |= attacks_bb<BISHOP>(to, occupied) & pieces(BISHOP, QUEEN);
}
else if ((bb = stmAttackers & pieces(KNIGHT)))
{
occupied ^= least_significant_square_bb(bb);
if ((swap = KnightValueMg - swap) < res)
break;
occupied ^= least_significant_square_bb(bb);
}
else if ((bb = stmAttackers & pieces(BISHOP)))
{
occupied ^= least_significant_square_bb(bb);
if ((swap = BishopValueMg - swap) < res)
break;
occupied ^= least_significant_square_bb(bb);
attackers |= attacks_bb<BISHOP>(to, occupied) & pieces(BISHOP, QUEEN);
}
else if ((bb = stmAttackers & pieces(ROOK)))
{
occupied ^= least_significant_square_bb(bb);
if ((swap = RookValueMg - swap) < res)
break;
occupied ^= least_significant_square_bb(bb);
attackers |= attacks_bb<ROOK>(to, occupied) & pieces(ROOK, QUEEN);
}
else if ((bb = stmAttackers & pieces(QUEEN)))
{
occupied ^= least_significant_square_bb(bb);
if ((swap = QueenValueMg - swap) < res)
break;
occupied ^= least_significant_square_bb(bb);
attackers |= (attacks_bb<BISHOP>(to, occupied) & pieces(BISHOP, QUEEN))
| (attacks_bb<ROOK >(to, occupied) & pieces(ROOK , QUEEN));
@@ -1162,11 +1162,6 @@ bool Position::see_ge(Move m, Bitboard& occupied, Value threshold) const {
return bool(res);
}
bool Position::see_ge(Move m, Value threshold) const {
Bitboard occupied;
return see_ge(m, occupied, threshold);
}
/// Position::is_draw() tests whether the position is drawn by 50-move rule
/// or by repetition. It does not detect stalemates.