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Tweak KingFlank when king is on edge files

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This tweak excludes files D and E from the KingFlank bitboard when our
king is on the A or H files respectively. As far as I can tell, this
affects two things: the calculation for CloseEnemies and PawnlessFlank.
Aside from filtering out slightly less relevant attacks in the flank,
I suspect this helps with king prophylaxis, avoiding attacks and moving
towards the center when the pawns start to come off.

STC
LLR: 2.95 (-2.94,2.94) [0.00,4.00]
Total: 56755 W: 12881 L: 12489 D: 31385
http://tests.stockfishchess.org/tests/view/5b58a94c0ebc5902bdb88c72

LTC
LLR: 2.95 (-2.94,2.94) [0.00,4.00]
Total: 130205 W: 22536 L: 21957 D: 85712
http://tests.stockfishchess.org/tests/view/5b58b7580ebc5902bdb89029

How to continue: Tweaking the two bonuses mentioned might give some
gain, although as far as I can tell, CloseEnemies is very sensitive to
even small changes.

Closes https://github.com/official-stockfish/Stockfish/pull/1705

Bench: 5026009
This commit is contained in:
Miguel Lahoz 2018-07-26 00:11:51 +08:00 • committed by Stéphane Nicolet
parent c9f80660a6
commit 313f403733
1 changed files with 2 additions and 2 deletions
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4
src/evaluate.cpp
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@ -79,9 +79,9 @@ namespace {
constexpr Bitboard Center = (FileDBB | FileEBB) & (Rank4BB | Rank5BB);
constexpr Bitboard KingFlank[FILE_NB] = {
QueenSide, QueenSide, QueenSide,
QueenSide ^ FileDBB, QueenSide, QueenSide,
CenterFiles, CenterFiles,
KingSide, KingSide, KingSide
KingSide, KingSide, KingSide ^ FileEBB
};
// Threshold for lazy and space evaluation