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More precise checks evaluation in king danger

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Remove overlapping safe checks from kingdanger:
- rook and queen checks from the same square: rook check is preferred
- bishop and queen checks form the same square: queen check is preferred

Increase bishop and rook check values as a compensation.

STC
LLR: 2.95 (-2.94,2.94) [0.50,4.50]
Total: 27480 W: 6111 L: 5813 D: 15556
http://tests.stockfishchess.org/tests/view/5c521d050ebc593af5d4e66a

LTC
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 78500 W: 13145 L: 12752 D: 52603
http://tests.stockfishchess.org/tests/view/5c52b9460ebc592fc7baecc5

Closes https://github.com/official-stockfish/Stockfish/pull/1983

------------------------------------------

I have quite a few ideas of how to improve this patch.

- actually rethinking it now it will maybe be useful to discount
  queen/bishop checks if there is only one square that they can
  give check from and it's "occupied" by more valuable check. Right
  now count of this squares does not really matter.

- maybe some small extra bonus can be given for overlapping checks.

- some ideas about using popcount() on safechecks can be retried.

- tune this safecheck values since they were more or less randomly handcrafted in this patch.

Bench: 3216489
This commit is contained in:
Vizvezdenec 2019-02-01 09:21:23 +03:00 • committed by Stéphane Nicolet
parent d1fd1a96bc
commit 3f7ec977cd
1 changed files with 29 additions and 14 deletions
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43
src/evaluate.cpp
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@ -93,8 +93,8 @@ namespace {
// Penalties for enemy's safe checks
constexpr int QueenSafeCheck = 780;
constexpr int RookSafeCheck = 880;
constexpr int BishopSafeCheck = 435;
constexpr int RookSafeCheck = 1080;
constexpr int BishopSafeCheck = 635;
constexpr int KnightSafeCheck = 790;
#define S(mg, eg) make_score(mg, eg)
@ -434,27 +434,42 @@ namespace {
b1 = attacks_bb<ROOK >(ksq, pos.pieces() ^ pos.pieces(Us, QUEEN));
b2 = attacks_bb<BISHOP>(ksq, pos.pieces() ^ pos.pieces(Us, QUEEN));
// Enemy queen safe checks
if ((b1 | b2) & attackedBy[Them][QUEEN] & safe & ~attackedBy[Us][QUEEN])
kingDanger += QueenSafeCheck;
b1 &= attackedBy[Them][ROOK];
b2 &= attackedBy[Them][BISHOP];
// Enemy rooks checks
if (b1 & safe)
Bitboard RookCheck = b1
& safe
& attackedBy[Them][ROOK];
if (RookCheck)
kingDanger += RookSafeCheck;
else
unsafeChecks |= b1;
unsafeChecks |= b1 & attackedBy[Them][ROOK];
// Enemy bishops checks
if (b2 & safe)
// Enemy queen safe checks: we count them only if they are from squares from
// which we can't give a rook check, because rook checks are more valuable.
Bitboard QueenCheck = (b1 | b2)
& attackedBy[Them][QUEEN]
& safe
& ~attackedBy[Us][QUEEN]
& ~RookCheck;
if (QueenCheck)
kingDanger += QueenSafeCheck;
// Enemy bishops checks: we count them only if they are from squares from
// which we can't give a queen check, because queen checks are more valuable.
Bitboard BishopCheck = b2
& attackedBy[Them][BISHOP]
& safe
& ~QueenCheck;
if (BishopCheck)
kingDanger += BishopSafeCheck;
else
unsafeChecks |= b2;
unsafeChecks |= b2 & attackedBy[Them][BISHOP];
// Enemy knights checks
b = pos.attacks_from<KNIGHT>(ksq) & attackedBy[Them][KNIGHT];
if (b & safe)
kingDanger += KnightSafeCheck;
else