Improved King Safety values

[stockfish] / src / pawns.cpp

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 6ec718ff5167c6ca47c5fded3d31161b7072ce29..ef456307cafbacb4479a53627a7a1d7b58aa362d 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -1,7 +1,7 @@
 /*
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
-  Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad
+  Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
 
   Stockfish is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
@@ -63,33 +63,33 @@ namespace {
 
   // Weakness of our pawn shelter in front of the king by [distance from edge][rank]
   const Value ShelterWeakness[][RANK_NB] = {
-  { V(100), V(13), V(24), V(64), V(89), V( 93), V(104) },
-  { V(110), V( 1), V(29), V(75), V(96), V(102), V(107) },
-  { V(102), V( 0), V(39), V(74), V(88), V(101), V( 98) },
-  { V( 88), V( 4), V(33), V(67), V(92), V( 94), V(107) } };
+  { V( 99), V(20), V(26), V(54), V(85), V( 92), V(108) },
+  { V(117), V( 1), V(27), V(71), V(94), V(104), V(118) },
+  { V(104), V( 4), V(51), V(76), V(82), V(102), V( 97) },
+  { V( 80), V(12), V(43), V(65), V(88), V( 91), V(115) } };
 
   // Danger of enemy pawns moving toward our king by [type][distance from edge][rank]
   const Value StormDanger[][4][RANK_NB] = {
-  { { V( 0),  V(  63), V( 128), V(43), V(27) },
-    { V( 0),  V(  62), V( 131), V(44), V(26) },
-    { V( 0),  V(  59), V( 121), V(50), V(28) },
-    { V( 0),  V(  62), V( 127), V(54), V(28) } },
-  { { V(24),  V(  40), V(  93), V(42), V(22) },
-    { V(24),  V(  28), V( 101), V(38), V(20) },
-    { V(24),  V(  32), V(  95), V(36), V(23) },
-    { V(27),  V(  24), V(  99), V(36), V(24) } },
-  { { V( 0),  V(   0), V(  81), V(16), V( 6) },
-    { V( 0),  V(   0), V( 165), V(29), V( 9) },
-    { V( 0),  V(   0), V( 163), V(23), V(12) },
-    { V( 0),  V(   0), V( 161), V(28), V(13) } },
-  { { V( 0),  V(-296), V(-299), V(55), V(25) },
-    { V( 0),  V(  67), V( 131), V(46), V(21) },
-    { V( 0),  V(  65), V( 135), V(50), V(31) },
-    { V( 0),  V(  62), V( 128), V(51), V(24) } } };
+  { { V( 0),  V(  65), V( 126), V(36), V(30) },
+    { V( 0),  V(  55), V( 135), V(36), V(23) },
+    { V( 0),  V(  47), V( 116), V(45), V(26) },
+    { V( 0),  V(  62), V( 127), V(57), V(34) } },
+  { { V(21),  V(  45), V(  93), V(50), V(19) },
+    { V(23),  V(  24), V( 105), V(41), V(13) },
+    { V(23),  V(  36), V( 101), V(38), V(20) },
+    { V(30),  V(  19), V( 110), V(41), V(27) } },
+  { { V( 0),  V(   0), V(  81), V(14), V( 4) },
+    { V( 0),  V(   0), V( 169), V(30), V( 3) },
+    { V( 0),  V(   0), V( 168), V(24), V( 5) },
+    { V( 0),  V(   0), V( 162), V(26), V(10) } },
+  { { V( 0),  V(-283), V(-298), V(57), V(29) },
+    { V( 0),  V(  63), V( 137), V(42), V(18) },
+    { V( 0),  V(  67), V( 145), V(49), V(33) },
+    { V( 0),  V(  62), V( 126), V(53), V(21) } } };
 
   // Max bonus for king safety. Corresponds to start position with all the pawns
   // in front of the king and no enemy pawn on the horizon.
-  const Value MaxSafetyBonus = V(257);
+  const Value MaxSafetyBonus = V(258);
 
   #undef S
   #undef V
@@ -144,12 +144,11 @@ namespace {
         lever       =   theirPawns & pawnAttacksBB[s];
 
         // Test for backward pawn.
-        // If the pawn is passed, isolated, or connected it cannot be
+        // If the pawn is passed, isolated, connected or a lever it cannot be
         // backward. If there are friendly pawns behind on adjacent files
-        // or if it can capture an enemy pawn it cannot be backward either.
-        if (   (passed | isolated | connected)
-            || (ourPawns & pawn_attack_span(Them, s))
-            || (pos.attacks_from<PAWN>(s, Us) & theirPawns))
+        // it cannot be backward either.
+        if (   (passed | isolated | lever | connected)
+            || (ourPawns & pawn_attack_span(Them, s)))
             backward = false;
         else
         {
@@ -288,7 +287,7 @@ Score Entry::do_king_safety(const Position& pos, Square ksq) {
 
   Bitboard pawns = pos.pieces(Us, PAWN);
   if (pawns)
-      while (!(DistanceRingsBB[ksq][minKingPawnDistance[Us]++] & pawns)) {}
+      while (!(DistanceRingBB[ksq][minKingPawnDistance[Us]++] & pawns)) {}
 
   if (relative_rank(Us, ksq) > RANK_4)
       return make_score(0, -16 * minKingPawnDistance[Us]);