From: Marco Costalba <mcostalba@gmail.com>
Date: Mon, 5 Jan 2009 14:14:16 +0000 (+0100)
Subject: Piece mobility: filter out squares protected by pawns
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=d0804341c5ec422c19e34db20756d123d03464e0

Piece mobility: filter out squares protected by pawns

Do not consider squares protected by enemy pawns
in mobility evaluation.

This reduces the mobility value by about 15%

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
---

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 12329fcd..d261f448 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -575,8 +575,11 @@ namespace {
             ei.kingAdjacentZoneAttacksCount[us] += count_1s_max_15(bb);
     }
 
+    // Remove squares protected by enemy pawns
+    Bitboard bb = (b & ~ei.attackedBy[them][PAWN]);
+
     // Mobility
-    int mob = count_1s_max_15(b & ~p.pieces_of_color(us));
+    int mob = count_1s_max_15(bb & ~p.pieces_of_color(us));
     ei.mgMobility += Sign[us] * mgBonus[mob];
     ei.egMobility += Sign[us] * egBonus[mob];