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Simplify condition in space definition 

We remove an unnecessary condition in the definition of safe squares
in the space evaluation. Only the squares which are occupied by our
pawns or attacked by our opponent's pawns are now excluded.

STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 21096 W: 4321 L: 4199 D: 12576
http://tests.stockfishchess.org/tests/view/5acbf7510ebc59547e537d4e

LTC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 23437 W: 3577 L: 3460 D: 16400
http://tests.stockfishchess.org/tests/view/5acc0f750ebc59547e537d6a

It may be possible to further refine the definition of such safe squares.

Bench: 5351765
pull/1539/merge
Jerry Donald Watson 2018-04-10 00:28:26 +01:00 committed by Stéphane Nicolet
parent b88374b14a
commit 62619fa228
1 changed files with 1 additions and 2 deletions
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3
src/evaluate.cpp
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@ -738,8 +738,7 @@ namespace {
// pawn, or if it is undefended and attacked by an enemy piece.
Bitboard safe = SpaceMask
& ~pos.pieces(Us, PAWN)
& ~attackedBy[Them][PAWN]
& (attackedBy[Us][ALL_PIECES] | ~attackedBy[Them][ALL_PIECES]);
& ~attackedBy[Them][PAWN];
// Find all squares which are at most three squares behind some friendly pawn
Bitboard behind = pos.pieces(Us, PAWN);