Simplify Connected Pawn Scoring #2090

This is a functional simplification that simplifies
connected scoring of pawns.

STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 37472 W: 8318 L: 8228 D: 20926
http://tests.stockfishchess.org/tests/view/5cae74ef0ebc5925cf00f8a5

LTC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 43035 W: 7366 L: 7281 D: 28388
http://tests.stockfishchess.org/tests/view/5caea3b50ebc5925cf00fe1e

Bench: 3470173

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 7edaa6e1bb786bfa42ff341352f3d153b280e417..b034f478bede4e4456bd4ee3c741992c2ef6ef5d 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -36,7 +36,7 @@ namespace {
   constexpr Score Isolated = S( 5, 15);
 
   // Connected pawn bonus
-  constexpr int Connected[RANK_NB] = { 0, 13, 24, 18, 65, 100, 175, 330 };
+  constexpr int Connected[RANK_NB] = { 0, 13, 17, 24, 59, 96, 171 };
 
   // Strength of pawn shelter for our king by [distance from edge][rank].
   // RANK_1 = 0 is used for files where we have no pawn, or pawn is behind our king.
@@ -89,6 +89,7 @@ namespace {
         assert(pos.piece_on(s) == make_piece(Us, PAWN));
 
         File f = file_of(s);
+        Rank r = relative_rank(Us, s);
 
         e->semiopenFiles[Us]   &= ~(1 << f);
         e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s);
@@ -117,8 +118,7 @@ namespace {
             && popcount(phalanx) >= popcount(leverPush))
             e->passedPawns[Us] |= s;
 
-        else if (   stoppers == square_bb(s + Up)
-                 && relative_rank(Us, s) >= RANK_5)
+        else if (stoppers == square_bb(s + Up) && r >= RANK_5)
         {
             b = shift<Up>(support) & ~theirPawns;
             while (b)
@@ -129,8 +129,7 @@ namespace {
         // Score this pawn
         if (support | phalanx)
         {
-            int r = relative_rank(Us, s);
-            int v = phalanx ? Connected[r] + Connected[r + 1] : 2 * Connected[r];
+            int v = (phalanx ? 3 : 2) * Connected[r];
             v = 17 * popcount(support) + (v >> (opposed + 1));
             score += make_score(v, v * (r - 2) / 4);
         }