Simplify backward pawn definition

[stockfish] / src / pawns.cpp

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 336638eab48be66be4d45606518bb9a361a67b6b..798bc0a070319dc846986535e4480d9e3442d349 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -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(23), V(24), V(54), V(85), V( 93), V(107) },
+  { V(119), V( 2), V(28), V(72), V(96), V(104), V(114) },
+  { V(103), V( 6), V(47), V(74), V(84), V(103), V( 94) },
+  { V( 78), V(10), V(41), V(64), V(88), V( 92), 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( 125), V(37), V(30) },
+    { V( 0),  V(  57), V( 136), V(39), V(24) },
+    { V( 0),  V(  50), V( 114), V(45), V(29) },
+    { V( 0),  V(  58), V( 129), V(56), V(34) } },
+  { { V(20),  V(  45), V(  91), V(47), V(20) },
+    { V(25),  V(  23), V( 105), V(38), V(14) },
+    { V(21),  V(  37), V(  99), V(35), V(21) },
+    { V(30),  V(  18), V( 105), V(38), V(28) } },
+  { { V( 0),  V(   0), V(  81), V(13), V( 4) },
+    { V( 0),  V(   0), V( 169), V(30), V( 4) },
+    { V( 0),  V(   0), V( 166), V(24), V( 6) },
+    { V( 0),  V(   0), V( 164), V(24), V(11) } },
+  { { V( 0),  V(-289), V(-297), V(57), V(29) },
+    { V( 0),  V(  66), V( 136), V(43), V(16) },
+    { V( 0),  V(  66), V( 141), V(50), V(31) },
+    { V( 0),  V(  63), V( 126), V(52), V(23) } } };
 
   // 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(252);
 
   #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 | connected | lever)
+            || (ourPawns & pawn_attack_span(Them, s)))
             backward = false;
         else
         {