From: Jörg Oster <osterj165@googlemail.com>
Date: Sun, 10 Nov 2013 14:24:32 +0000 (+0100)
Subject: Remove opposed flag for doubled pawns
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=4ef6b2c32a0f4e7b6193349312da5e335d48416b;hp=1d18647e738951a7e94530fef231f4b4e13b1786

Remove opposed flag for doubled pawns

Actually, it is not used, as both arrays have the
same values. Some local tests in either direction
showed no improvement.

Also some minor corrections in the comments.

No functional change.
---

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 91da8a7b..d2a53ef9 100644
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -30,26 +30,24 @@ namespace {
   #define V Value
   #define S(mg, eg) make_score(mg, eg)
 
-  // Doubled pawn penalty by opposed flag and file
-  const Score Doubled[2][FILE_NB] = {
-  { S(13, 43), S(20, 48), S(23, 48), S(23, 48),
-    S(23, 48), S(23, 48), S(20, 48), S(13, 43) },
-  { S(13, 43), S(20, 48), S(23, 48), S(23, 48),
-    S(23, 48), S(23, 48), S(20, 48), S(13, 43) }};
+  // Doubled pawn penalty by file
+  const Score Doubled[FILE_NB] = {
+    S(13, 43), S(20, 48), S(23, 48), S(23, 48),
+    S(23, 48), S(23, 48), S(20, 48), S(13, 43) };
 
   // Isolated pawn penalty by opposed flag and file
   const Score Isolated[2][FILE_NB] = {
   { S(37, 45), S(54, 52), S(60, 52), S(60, 52),
     S(60, 52), S(60, 52), S(54, 52), S(37, 45) },
   { S(25, 30), S(36, 35), S(40, 35), S(40, 35),
-    S(40, 35), S(40, 35), S(36, 35), S(25, 30) }};
+    S(40, 35), S(40, 35), S(36, 35), S(25, 30) } };
 
   // Backward pawn penalty by opposed flag and file
   const Score Backward[2][FILE_NB] = {
   { S(30, 42), S(43, 46), S(49, 46), S(49, 46),
     S(49, 46), S(49, 46), S(43, 46), S(30, 42) },
   { S(20, 28), S(29, 31), S(33, 31), S(33, 31),
-    S(33, 31), S(33, 31), S(29, 31), S(20, 28) }};
+    S(33, 31), S(33, 31), S(29, 31), S(20, 28) } };
 
   // Pawn chain membership bonus by file and rank (initialized by formula)
   Score ChainMember[FILE_NB][RANK_NB];
@@ -57,8 +55,7 @@ namespace {
   // Candidate passed pawn bonus by rank
   const Score CandidatePassed[RANK_NB] = {
     S( 0, 0), S( 6, 13), S(6,13), S(14,29),
-    S(34,68), S(83,166), S(0, 0), S( 0, 0)
-  };
+    S(34,68), S(83,166), S(0, 0), S( 0, 0) };
 
   // Weakness of our pawn shelter in front of the king indexed by [rank]
   const Value ShelterWeakness[RANK_NB] =
@@ -69,10 +66,10 @@ namespace {
   const Value StormDanger[3][RANK_NB] = {
   { V( 0),  V(64), V(128), V(51), V(26) },
   { V(26),  V(32), V( 96), V(38), V(20) },
-  { V( 0),  V( 0), V( 64), V(25), V(13) }};
+  { V( 0),  V( 0), V( 64), V(25), V(13) } };
 
   // Max bonus for king safety. Corresponds to start position with all the pawns
-  // in front of the king and no enemy pawn on the horizont.
+  // in front of the king and no enemy pawn on the horizon.
   const Value MaxSafetyBonus = V(263);
 
   #undef S
@@ -148,7 +145,7 @@ namespace {
 
         assert(opposed | passed | (pawn_attack_span(Us, s) & theirPawns));
 
-        // A not passed pawn is a candidate to become passed if it is free to
+        // A not passed pawn is a candidate to become passed, if it is free to
         // advance and if the number of friendly pawns beside or behind this
         // pawn on adjacent files is higher or equal than the number of
         // enemy pawns in the forward direction on the adjacent files.
@@ -167,7 +164,7 @@ namespace {
             value -= Isolated[opposed][f];
 
         if (doubled)
-            value -= Doubled[opposed][f];
+            value -= Doubled[f];
 
         if (backward)
             value -= Backward[opposed][f];
@@ -274,7 +271,7 @@ Score Entry::update_safety(const Position& pos, Square ksq) {
 
   Value bonus = shelter_storm<Us>(pos, ksq);
 
-  // If we can castle use the bonus after the castle if is bigger
+  // If we can castle use the bonus after the castle if it is bigger
   if (pos.can_castle(make_castle_right(Us, KING_SIDE)))
       bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_G1)));