From: snicolet <cassio@free.fr>
Date: Sun, 27 Mar 2016 19:54:39 +0000 (+0100)
Subject: Bonus for loose enemies
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=24dac5ccd309837c6767dcf6b145be385eea2e21

Bonus for loose enemies

STC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 30504 W: 5743 L: 5485 D: 19276

LTC:
LLR: 2.97 (-2.94,2.94) [0.00,5.00]
Total: 11936 W: 1651 L: 1493 D: 8792

Bench: 8880041

Resolves #606
---

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index d8017065..a63b40ae 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -185,6 +185,7 @@ namespace {
   const Score TrappedRook         = S(92,  0);
   const Score Checked             = S(20, 20);
   const Score ThreatByHangingPawn = S(70, 63);
+  const Score LooseEnemies        = S( 0, 25);
   const Score Hanging             = S(48, 28);
   const Score ThreatByPawnPush    = S(31, 19);
   const Score Unstoppable         = S( 0, 20);
@@ -469,6 +470,11 @@ namespace {
     Bitboard b, weak, defended, safeThreats;
     Score score = SCORE_ZERO;
 
+    // Small bonus if the opponent has loose pawns or pieces
+    if (   (pos.pieces(Them) ^ pos.pieces(Them, QUEEN, KING))
+        & ~(ei.attackedBy[Us][ALL_PIECES] | ei.attackedBy[Them][ALL_PIECES]))
+        score += LooseEnemies;
+
     // Non-pawn enemies attacked by a pawn
     weak = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Us][PAWN];