Use single value for KingProtector.

miguel-l · snicolet · commit 3913726d1c8e · 2018-07-18T08:44:45.000+02:00
After some recent big tuning session, the values for King Protector were simplified to only be used on minor pieces. This patch tries to further simplify by just using a single value, since current S(6,5) and S(5,6) are close to each other. The value S(6,6) ended up passing, although S(5,5) was also tried and failed STC. STC LLR: 2.95 (-2.94,2.94) [-3.00,1.00] Total: 14261 W: 3288 L: 3151 D: 7822 http://tests.stockfishchess.org/tests/view/5b4ccdf50ebc5902bdb77f65 LTC LLR: 2.96 (-2.94,2.94) [-3.00,1.00] Total: 19606 W: 3396 L: 3273 D: 12937 http://tests.stockfishchess.org/tests/view/5b4ce4280ebc5902bdb7803b Bench: 5448998
diff --git a/AUTHORS b/AUTHORS
@@ -82,6 +82,7 @@ Mark Tenzer (31m059)
 Michael Byrne (MichaelB7)
 Michael Stembera (mstembera)
 Michel Van den Bergh (vdbergh)
+Miguel Lahoz (miguel-l)
 Mikael Bäckman (mbootsector)
 Mike Whiteley (protonspring)
 Miroslav Fontán (Hexik)
@@ -118,4 +119,3 @@ Tom Vijlbrief (tomtor)
 Torsten Franz (torfranz)
 Uri Blass (uriblass)
 Vince Negri
-xoroshiro
diff --git a/src/evaluate.cpp b/src/evaluate.cpp
@@ -154,16 +154,14 @@ namespace {
   // PassedDanger[Rank] contains a term to weight the passed score
   constexpr int PassedDanger[RANK_NB] = { 0, 0, 0, 3, 7, 11, 20 };
 
-  // KingProtector[knight/bishop] contains a penalty according to distance from king
-  constexpr Score KingProtector[] = { S(5, 6), S(6, 5) };
-
   // Assorted bonuses and penalties
   constexpr Score BishopPawns        = S(  3,  7);
   constexpr Score CloseEnemies       = S(  6,  0);
   constexpr Score Connectivity       = S(  3,  1);
   constexpr Score CorneredBishop     = S( 50, 50);
   constexpr Score Hanging            = S( 52, 30);
   constexpr Score HinderPassedPawn   = S(  4,  0);
+  constexpr Score KingProtector      = S(  6,  6);
   constexpr Score KnightOnQueen      = S( 21, 11);
   constexpr Score LongDiagonalBishop = S( 22,  0);
   constexpr Score MinorBehindPawn    = S( 16,  0);
@@ -342,7 +340,7 @@ namespace {
                 score += MinorBehindPawn;
 
             // Penalty if the piece is far from the king
-            score -= KingProtector[Pt == BISHOP] * distance(s, pos.square<KING>(Us));
+            score -= KingProtector * distance(s, pos.square<KING>(Us));
 
             if (Pt == BISHOP)
             {
