Don't include backward pawns in space evaluation.

mbootsector · Jun 16, 2017 · 55dbf76 · 55dbf76
1 parent 659990b
commit 55dbf76
Show file tree

Hide file tree

Showing 3 changed files with 6 additions and 2 deletions.
diff --git a/src/evaluate.cpp b/src/evaluate.cpp
@@ -710,7 +710,7 @@ namespace {
                    & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
 
     // Find all squares which are at most three squares behind some friendly pawn
-    Bitboard behind = pos.pieces(Us, PAWN);
+    Bitboard behind = pos.pieces(Us, PAWN) ^ ei.pe->backwardPawns[Us];
     behind |= (Us == WHITE ? behind >>  8 : behind <<  8);
     behind |= (Us == WHITE ? behind >> 16 : behind << 16);
 

diff --git a/src/pawns.cpp b/src/pawns.cpp
@@ -108,7 +108,7 @@ namespace {
     Bitboard ourPawns   = pos.pieces(Us  , PAWN);
     Bitboard theirPawns = pos.pieces(Them, PAWN);
 
-    e->passedPawns[Us]   = e->pawnAttacksSpan[Us] = 0;
+    e->backwardPawns[Us] = e->passedPawns[Us]   = e->pawnAttacksSpan[Us] = 0;
     e->semiopenFiles[Us] = 0xFF;
     e->kingSquares[Us]   = SQ_NONE;
     e->pawnAttacks[Us]   = shift<Right>(ourPawns) | shift<Left>(ourPawns);
@@ -177,7 +177,10 @@ namespace {
             score -= Isolated[opposed];
 
         else if (backward)
+        {
             score -= Backward[opposed];
+            e->backwardPawns[Us] |= s;
+        }
 
         else if (!supported)
             score -= Unsupported;

diff --git a/src/pawns.h b/src/pawns.h
@@ -69,6 +69,7 @@ struct Entry {
   Bitboard passedPawns[COLOR_NB];
   Bitboard pawnAttacks[COLOR_NB];
   Bitboard pawnAttacksSpan[COLOR_NB];
+  Bitboard backwardPawns[COLOR_NB];
   Square kingSquares[COLOR_NB];
   Score kingSafety[COLOR_NB];
   int castlingRights[COLOR_NB];