Penalty for bad bishop with blocked central files

We increase the penalty for bad bishops by a factor proportional
to the number of our blocked pawns in the center files C, D, E or F.

STC:
LLR: 2.97 (-2.94,2.94) [0.00,5.00]
Total: 8868 W: 1870 L: 1700 D: 5298
http://tests.stockfishchess.org/html/live_elo.html?5ae7674f0ebc590e39268b34

LTC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 5813 W: 950 L: 808 D: 4055
http://tests.stockfishchess.org/html/live_elo.html?5ae77bae0ebc5926dba90dd9

Closes https://github.com/official-stockfish/Stockfish/pull/1573

Bench: 5364190

diff --git a/AUTHORS b/AUTHORS
index 66ad6b5f804ce01f119bb7ffa6621335db10e87a..305d8b313d62e3087413d8566ca0982527ba1fda 100644 (file)
--- a/AUTHORS
+++ b/AUTHORS
@@ -85,6 +85,7 @@ Michel Van den Bergh (vdbergh)
 Mikael Bäckman (mbootsector)
 Mike Whiteley (protonspring)
 Miroslav Fontán (Hexik)
 Mikael Bäckman (mbootsector)
 Mike Whiteley (protonspring)
 Miroslav Fontán (Hexik)

+Moez Jellouli (MJZ1977)

 Mohammed Li (tthsqe12)
 Nathan Rugg (nmrugg)
 Nicklas Persson (NicklasPersson)
 Mohammed Li (tthsqe12)
 Nathan Rugg (nmrugg)
 Nicklas Persson (NicklasPersson)

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index c98a83fc81a777806b111d80200946eaeb271da7..275d7ae16ae33681013ab6fc76f6fab23c39a1c5 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -162,7 +162,7 @@ namespace {
   constexpr Score KingProtector[] = { S(3, 5), S(4, 3), S(3, 0), S(1, -1) };
 
   // Assorted bonuses and penalties
   constexpr Score KingProtector[] = { S(3, 5), S(4, 3), S(3, 0), S(1, -1) };
 
   // Assorted bonuses and penalties

-  constexpr Score BishopPawns        = S(  8, 12);
+  constexpr Score BishopPawns        = S(  3,  5);

   constexpr Score CloseEnemies       = S(  7,  0);
   constexpr Score Connectivity       = S(  3,  1);
   constexpr Score CorneredBishop     = S( 50, 50);
   constexpr Score CloseEnemies       = S(  7,  0);
   constexpr Score Connectivity       = S(  3,  1);
   constexpr Score CorneredBishop     = S( 50, 50);


@@ -293,7 +293,8 @@ namespace {
   template<Tracing T> template<Color Us, PieceType Pt>
   Score Evaluation<T>::pieces() {
 
   template<Tracing T> template<Color Us, PieceType Pt>
   Score Evaluation<T>::pieces() {
 

-    constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
+    constexpr Color     Them = (Us == WHITE ? BLACK : WHITE);
+    constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);

     constexpr Bitboard OutpostRanks = (Us == WHITE ? Rank4BB | Rank5BB | Rank6BB
                                                    : Rank5BB | Rank4BB | Rank3BB);
     const Square* pl = pos.squares<Pt>(Us);
     constexpr Bitboard OutpostRanks = (Us == WHITE ? Rank4BB | Rank5BB | Rank6BB
                                                    : Rank5BB | Rank4BB | Rank3BB);
     const Square* pl = pos.squares<Pt>(Us);


@@ -349,8 +350,12 @@ namespace {
 
             if (Pt == BISHOP)
             {
 
             if (Pt == BISHOP)
             {

-                // Penalty according to number of pawns on the same color square as the bishop
-                score -= BishopPawns * pe->pawns_on_same_color_squares(Us, s);
+                // Penalty according to number of pawns on the same color square as the
+                // bishop, bigger when the center files are blocked with pawns.
+                Bitboard blocked = pos.pieces(Us, PAWN) & shift<Down>(pos.pieces());
+
+                score -= BishopPawns * pe->pawns_on_same_color_squares(Us, s)
+                                     * (1 + popcount(blocked & CenterFiles));

 
                 // Bonus for bishop on a long diagonal which can "see" both center squares
                 if (more_than_one(Center & (attacks_bb<BISHOP>(s, pos.pieces(PAWN)) | s)))
 
                 // Bonus for bishop on a long diagonal which can "see" both center squares
                 if (more_than_one(Center & (attacks_bb<BISHOP>(s, pos.pieces(PAWN)) | s)))