From 9f48e1ec15b8bec038338e2c4404a234af8c6364 Mon Sep 17 00:00:00 2001
From: GuardianRM <strimr25@mail.ru>
Date: Thu, 23 Feb 2017 21:26:59 -0800
Subject: [PATCH] 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
---
 src/evaluate.cpp | 13 +++++++++++++
 1 file changed, 13 insertions(+)

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)
         {
-- 
2.39.2