From: Miguel Lahoz <miguel_lahoz@protonmail.com>
Date: Mon, 16 Jul 2018 16:51:43 +0000 (+0800)
Subject: Use single value for KingProtector.
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=3913726d1c8ef3b994dd8090c98814fa7e7f5874

Use single value for KingProtector.

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
index b396db81..029109ac 100644
--- 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
index 2fb0e55a..b1e94ab7 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -154,9 +154,6 @@ 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);
@@ -164,6 +161,7 @@ namespace {
   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)
             {