From: Jerry Donald Watson <j1.donald1@gmail.com>
Date: Mon, 9 Apr 2018 23:28:26 +0000 (+0100)
Subject: Simplify condition in space definition
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=62619fa228ff9b1f1adfbe023ce4c417807fdeba

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
---

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 6377faf2..69a36cf5 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -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);