From: Joost VandeVondele <Joost.VandeVondele@gmail.com>
Date: Tue, 5 Oct 2021 20:14:13 +0000 (+0200)
Subject: Improve the Chess960 correction for cornered bishops
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=329bdbd9cfa270dd7141e5184180fbde1b5898b4

Improve the Chess960 correction for cornered bishops

As Chess960 patches can not be tested on fishtest, this was locally tuned
and tested:

Elo: 2.36 +- 1.07
LOS: 0.999992

closes https://github.com/official-stockfish/Stockfish/pull/3730

Bench: 5714575
---

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 62d4be84..58dd0026 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -1053,26 +1053,22 @@ make_v:
 
     if (   pos.piece_on(SQ_A1) == W_BISHOP
         && pos.piece_on(SQ_B2) == W_PAWN)
-        correction += !pos.empty(SQ_B3) ? -CorneredBishop * 4
-                                        : -CorneredBishop * 3;
+        correction -= CorneredBishop;
 
     if (   pos.piece_on(SQ_H1) == W_BISHOP
         && pos.piece_on(SQ_G2) == W_PAWN)
-        correction += !pos.empty(SQ_G3) ? -CorneredBishop * 4
-                                        : -CorneredBishop * 3;
+        correction -= CorneredBishop;
 
     if (   pos.piece_on(SQ_A8) == B_BISHOP
         && pos.piece_on(SQ_B7) == B_PAWN)
-        correction += !pos.empty(SQ_B6) ? CorneredBishop * 4
-                                        : CorneredBishop * 3;
+        correction += CorneredBishop;
 
     if (   pos.piece_on(SQ_H8) == B_BISHOP
         && pos.piece_on(SQ_G7) == B_PAWN)
-        correction += !pos.empty(SQ_G6) ? CorneredBishop * 4
-                                        : CorneredBishop * 3;
+        correction += CorneredBishop;
 
-    return pos.side_to_move() == WHITE ?  Value(correction)
-                                       : -Value(correction);
+    return pos.side_to_move() == WHITE ?  Value(5 * correction)
+                                       : -Value(5 * correction);
   }
 
 } // namespace Eval