From: GuardianRM <strimr25@mail.ru>
Date: Fri, 24 Feb 2017 05:26:59 +0000 (-0800)
Subject: Pieces protecting king
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=9f48e1ec15b8bec038338e2c4404a234af8c6364

Pieces protecting king

Initial protective idea by Snicolet for knight, for other pieces too
Patch add penalties and bonuses for pieces, depending on the distance from the own king

STC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 21192 W: 3919 L: 3704 D: 13569

LTC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 26177 W: 3642 L: 3435 D: 19100

Bench : 6687377

Closes #1012
---

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 6180c482..84c83269 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -180,6 +180,16 @@ namespace {
     S(  9, 10), S( 2, 10), S( 1, -8), S(-20,-12),
     S(-20,-12), S( 1, -8), S( 2, 10), S(  9, 10)
   };
+  
+  // Protector[PieceType][distance] contains a protecting bonus for our king, 
+  // indexed by piece type and distance between the piece and the king.
+  const Score Protector[PIECE_TYPE_NB][8] = {
+  {}, {},
+    { S(0, 0), S( 7, 9), S( 7, 1), S( 1, 5), S(-10,-4), S( -1,-4), S( -7,-3), S(-16,-10) }, // Knight
+    { S(0, 0), S(11, 8), S(-7,-1), S(-1,-2), S( -1,-7), S(-11,-3), S( -9,-1), S(-16, -1) }, // Bishop
+    { S(0, 0), S(10, 0), S(-2, 2), S(-5, 4), S( -6, 2), S(-14,-3), S( -2,-9), S(-12, -7) }, // Rook
+    { S(0, 0), S( 3,-5), S( 2,-5), S(-4, 0), S( -9,-6),  S(-4, 7), S(-13,-7), S(-10, -7) }  // Queen
+  };
 
   // Assorted bonuses and penalties used by evaluation
   const Score MinorBehindPawn     = S(16,  0);
@@ -294,6 +304,9 @@ namespace {
         int mob = popcount(b & ei.mobilityArea[Us]);
 
         mobility[Us] += MobilityBonus[Pt][mob];
+        
+        // Bonus for this piece as a king protector
+        score += Protector[Pt][distance(s, pos.square<KING>(Us))];
 
         if (Pt == BISHOP || Pt == KNIGHT)
         {