From 7f8166db89120960effa2ddda1a25188e5ab95b8 Mon Sep 17 00:00:00 2001
From: Linmiao Xu <linmiao.xu@gmail.com>
Date: Sat, 25 Apr 2020 15:55:35 -0400
Subject: [PATCH] Tuned safe checks and minor piece king protectors

A combination of terms related to king safety one tuned safe check weights,
the other tuned knight and bishop king protector weights separately with
some compensation in the high outpost bonuses given to the minor pieces.

passed STC
LLR: 2.95 (-2.94,2.94) {-0.50,1.50}
Total: 39892 W: 7594 L: 7350 D: 24948
Ptnml(0-2): 643, 4559, 9314, 4771, 659
https://tests.stockfishchess.org/tests/view/5ea49635b908f6dd28f34b82

passed LTC
LLR: 2.94 (-2.94,2.94) {0.25,1.75}
Total: 104934 W: 13300 L: 12834 D: 78800
Ptnml(0-2): 697, 9571, 31514, 9939, 746
https://tests.stockfishchess.org/tests/view/5ea4abf6b908f6dd28f34bcb

closes https://github.com/official-stockfish/Stockfish/pull/2649

Bench 4800754
---
 AUTHORS          |  1 +
 src/evaluate.cpp | 29 ++++++++++++++++-------------
 2 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/AUTHORS b/AUTHORS
index 79eb98a0..9fceebf7 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -42,6 +42,7 @@ Eelco de Groot (KingDefender)
 Elvin Liu (solarlight2)
 erbsenzaehler
 Ernesto Gatti
+Linmiao Xu (linrock)
 Fabian Beuke (madnight)
 Fabian Fichter (ianfab)
 fanon
diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 9d7728c4..874faa6b 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -81,10 +81,10 @@ namespace {
   constexpr int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 81, 52, 44, 10 };
 
   // Penalties for enemy's safe checks
-  constexpr int QueenSafeCheck  = 780;
-  constexpr int RookSafeCheck   = 1078;
-  constexpr int BishopSafeCheck = 635;
-  constexpr int KnightSafeCheck = 790;
+  constexpr int QueenSafeCheck  = 772;
+  constexpr int RookSafeCheck   = 1084;
+  constexpr int BishopSafeCheck = 645;
+  constexpr int KnightSafeCheck = 792;
 
 #define S(mg, eg) make_score(mg, eg)
 
@@ -131,11 +131,14 @@ namespace {
   constexpr Score CorneredBishop      = S( 50, 50);
   constexpr Score FlankAttacks        = S(  8,  0);
   constexpr Score Hanging             = S( 69, 36);
-  constexpr Score KingProtector       = S(  7,  8);
+  constexpr Score BishopKingProtector = S(  6,  9);
+  constexpr Score KnightKingProtector = S(  8,  9);
   constexpr Score KnightOnQueen       = S( 16, 11);
   constexpr Score LongDiagonalBishop  = S( 45,  0);
   constexpr Score MinorBehindPawn     = S( 18,  3);
-  constexpr Score Outpost             = S( 30, 21);
+  constexpr Score KnightOutpost       = S( 56, 36);
+  constexpr Score BishopOutpost       = S( 30, 23);
+  constexpr Score ReachableOutpost    = S( 31, 22);
   constexpr Score PassedFile          = S( 11,  8);
   constexpr Score PawnlessFlank       = S( 17, 95);
   constexpr Score RestrictedPiece     = S(  7,  7);
@@ -293,17 +296,17 @@ namespace {
             // Bonus if piece is on an outpost square or can reach one
             bb = OutpostRanks & attackedBy[Us][PAWN] & ~pe->pawn_attacks_span(Them);
             if (bb & s)
-                score += Outpost * (Pt == KNIGHT ? 2 : 1);
-
+                score += (Pt == KNIGHT) ? KnightOutpost : BishopOutpost;
             else if (Pt == KNIGHT && bb & b & ~pos.pieces(Us))
-                score += Outpost;
+                score += ReachableOutpost;
 
             // Bonus for a knight or bishop shielded by pawn
             if (shift<Down>(pos.pieces(PAWN)) & s)
                 score += MinorBehindPawn;
 
             // Penalty if the piece is far from the king
-            score -= KingProtector * distance(pos.square<KING>(Us), s);
+            score -= (Pt == KNIGHT ? KnightKingProtector
+                                   : BishopKingProtector) * distance(pos.square<KING>(Us), s);
 
             if (Pt == BISHOP)
             {
@@ -399,7 +402,7 @@ namespace {
     // Enemy rooks checks
     rookChecks = b1 & safe & attackedBy[Them][ROOK];
     if (rookChecks)
-        kingDanger += more_than_one(rookChecks) ? RookSafeCheck * 3/2
+        kingDanger += more_than_one(rookChecks) ? RookSafeCheck * 175/100
                                                 : RookSafeCheck;
     else
         unsafeChecks |= b1 & attackedBy[Them][ROOK];
@@ -412,7 +415,7 @@ namespace {
                  & ~attackedBy[Us][QUEEN]
                  & ~rookChecks;
     if (queenChecks)
-        kingDanger += more_than_one(queenChecks) ? QueenSafeCheck * 3/2
+        kingDanger += more_than_one(queenChecks) ? QueenSafeCheck * 145/100
                                                  : QueenSafeCheck;
 
     // Enemy bishops checks: we count them only if they are from squares from
@@ -430,7 +433,7 @@ namespace {
     // Enemy knights checks
     knightChecks = pos.attacks_from<KNIGHT>(ksq) & attackedBy[Them][KNIGHT];
     if (knightChecks & safe)
-        kingDanger += more_than_one(knightChecks & safe) ? KnightSafeCheck * 3/2
+        kingDanger += more_than_one(knightChecks & safe) ? KnightSafeCheck * 162/100
                                                          : KnightSafeCheck;
     else
         unsafeChecks |= knightChecks;
-- 
2.39.2