From: Mike Whiteley <mike@whiteley.org>
Date: Thu, 15 Feb 2018 18:34:23 +0000 (+0100)
Subject: Simplify trapped rook
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=80ea80e4515e8ed7033ab2a8b22463865fb68979;hp=860223c5e6b2df53af0415dbbbfdd4834f083708

Simplify trapped rook

As far as can tell, semiopenFiles are set if there is a pawn anywhere on
the file. The removed condition would be true even if the pawns were very
advanced, which doesn't make sense if we're looking for a trapped rook.
Seems the engine fairs better with this removed. My guess s that the
condition that mobility is 3 or less does this well enough.

Begs the question whether this is a mobility issue alone... not sure.
Should I do LTC test?

STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 13377 W: 3009 L: 2871 D: 7497
http://tests.stockfishchess.org/tests/view/5a855be40ebc590297cc8166

Passed LTC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 16288 W: 2813 L: 2685 D: 10790
http://tests.stockfishchess.org/tests/view/5a8575a80ebc590297cc817e

Bench: 5006365
---

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 1c30a5ac..c0c7e5ff 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -396,10 +396,9 @@ namespace {
             // Penalty when trapped by the king, even more if the king cannot castle
             else if (mob <= 3)
             {
-                Square ksq = pos.square<KING>(Us);
+                File kf = file_of(pos.square<KING>(Us));
 
-                if (   ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
-                    && !pe->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
+                if ((kf < FILE_E) == (file_of(s) < kf))
                     score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
             }
         }
diff --git a/src/pawns.h b/src/pawns.h
index a9c21ffb..669999bf 100644
--- a/src/pawns.h
+++ b/src/pawns.h
@@ -45,10 +45,6 @@ struct Entry {
     return semiopenFiles[c] & (1 << f);
   }
 
-  int semiopen_side(Color c, File f, bool leftSide) const {
-    return semiopenFiles[c] & (leftSide ? (1 << f) - 1 : ~((1 << (f + 1)) - 1));
-  }
-
   int pawns_on_same_color_squares(Color c, Square s) const {
     return pawnsOnSquares[c][bool(DarkSquares & s)];
   }