From 170bdf40cd47f7f3a601107fae0a32667a9d72a9 Mon Sep 17 00:00:00 2001
From: Marco Costalba <mcostalba@gmail.com>
Date: Sat, 7 Feb 2015 11:15:38 +0100
Subject: [PATCH 1/2] Rename dbg_hit_on_c() to dbg_hit_on()

Use an overload instead of a new named function.

I have found this handier and easier when adding
some quick debug code.

No functional change.
---
 src/evaluate.cpp | 2 +-
 src/misc.cpp     | 2 +-
 src/misc.h       | 2 +-
 src/position.cpp | 6 +++---
 4 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 822be015..be3c6497 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -559,7 +559,7 @@ namespace {
        &  pos.pieces(Them)
        & ~ei.attackedBy[Us][PAWN];
 
-    if(b)
+    if (b)
         score += popcount<Max15>(b) * PawnAttackThreat;
 
     if (Trace)
diff --git a/src/misc.cpp b/src/misc.cpp
index 656b3155..aa2b2331 100644
--- a/src/misc.cpp
+++ b/src/misc.cpp
@@ -126,7 +126,7 @@ const string engine_info(bool to_uci) {
 /// Debug functions used mainly to collect run-time statistics
 
 void dbg_hit_on(bool b) { ++hits[0]; if (b) ++hits[1]; }
-void dbg_hit_on_c(bool c, bool b) { if (c) dbg_hit_on(b); }
+void dbg_hit_on(bool c, bool b) { if (c) dbg_hit_on(b); }
 void dbg_mean_of(int v) { ++means[0]; means[1] += v; }
 
 void dbg_print() {
diff --git a/src/misc.h b/src/misc.h
index 965a0ee8..246a56a0 100644
--- a/src/misc.h
+++ b/src/misc.h
@@ -33,7 +33,7 @@ void prefetch(char* addr);
 void start_logger(bool b);
 
 void dbg_hit_on(bool b);
-void dbg_hit_on_c(bool c, bool b);
+void dbg_hit_on(bool c, bool b);
 void dbg_mean_of(int v);
 void dbg_print();
 
diff --git a/src/position.cpp b/src/position.cpp
index 994e1c76..ef31d58d 100644
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -47,7 +47,7 @@ namespace Zobrist {
   Key exclusion;
 }
 
-Key Position::exclusion_key() const { return st->key ^ Zobrist::exclusion;}
+Key Position::exclusion_key() const { return st->key ^ Zobrist::exclusion; }
 
 namespace {
 
@@ -1060,8 +1060,8 @@ Value Position::see(Move m) const {
   stm = color_of(piece_on(from));
   occupied = pieces() ^ from;
 
-  // Castling moves are implemented as king capturing the rook so cannot be
-  // handled correctly. Simply return 0 that is always the correct value
+  // Castling moves are implemented as king capturing the rook so cannot
+  // be handled correctly. Simply return VALUE_ZERO that is always correct
   // unless in the rare case the rook ends up under attack.
   if (type_of(m) == CASTLING)
       return VALUE_ZERO;

From e118570038f2d9b668b445fe6d31df94151a717b Mon Sep 17 00:00:00 2001
From: Joona Kiiski <zamar@meripeto.(none)>
Date: Sun, 8 Feb 2015 19:20:39 +0000
Subject: [PATCH 2/2] Pawn Center Bind Bonus

Bonus for two pawns controlling the same central square

STC:

LLR: 3.14 (-2.94,2.94) [-1.50,4.50]
Total: 15974 W: 3291 L: 3133 D: 9550

LTC:

LLR: 3.24 (-2.94,2.94) [0.00,6.00]
Total: 10449 W: 1837 L: 1674 D: 6938

Idea from Lyudmil Tsvetkov.

Bench: 7699138

Resolves #248
---
 src/pawns.cpp | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/pawns.cpp b/src/pawns.cpp
index ef456307..d66233ca 100644
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -61,6 +61,14 @@ namespace {
   // Unsupported pawn penalty
   const Score UnsupportedPawnPenalty = S(20, 10);
 
+  // Center bind bonus: Two pawns controlling the same central square
+  const Bitboard CenterBindMask[COLOR_NB] = {
+    (FileDBB | FileEBB) & (Rank5BB | Rank6BB | Rank7BB),
+    (FileDBB | FileEBB) & (Rank4BB | Rank3BB | Rank2BB)
+  };
+
+  const Score CenterBind = S(16, 0);
+
   // Weakness of our pawn shelter in front of the king by [distance from edge][rank]
   const Value ShelterWeakness[][RANK_NB] = {
   { V( 99), V(20), V(26), V(54), V(85), V( 92), V(108) },
@@ -195,6 +203,10 @@ namespace {
     b = e->semiopenFiles[Us] ^ 0xFF;
     e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0;
 
+    // Center binds: Two pawns controlling the same central square
+    b = shift_bb<Right>(ourPawns) & shift_bb<Left>(ourPawns) & CenterBindMask[Us];
+    score += popcount<Max15>(b) * CenterBind;
+
     return score;
   }