From 8352977b91d9246618c7273d59400a4a05a32e2a Mon Sep 17 00:00:00 2001
From: 31m059 <37052095+31m059@users.noreply.github.com>
Date: Sat, 22 Feb 2020 21:27:32 -0500
Subject: [PATCH] Use single param for Outpost and ReachableOutpost.

In November 2019, as a result of the simplification of rank-based outposts by 37698b0,
separate bonuses were introduced for outposts that are currently occupied and outposts
that are reachable on the next move. However, the values of these two bonuses are
quite similar, and they have remained that way for three months of development.

It appears that we can safely retire the separate ReachableOutpost parameter and
use the same Outpost bonus in both cases, restoring the basic principles of Stockfish
outpost evaluation to their pre-November state, while also reducing
the size of the parameter space.

STC:
LLR: 2.96 (-2.94,2.94) {-1.50,0.50}
Total: 47680 W: 9213 L: 9092 D: 29375
Ptnml(0-2): 776, 5573, 11071, 5594, 826
https://tests.stockfishchess.org/tests/view/5e51e33190a0a02810d09802

LTC:
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 14690 W: 1960 L: 1854 D: 10876
Ptnml(0-2): 93, 1381, 4317, 1435, 119
https://tests.stockfishchess.org/tests/view/5e52197990a0a02810d0980f

closes https://github.com/official-stockfish/Stockfish/pull/2559

Bench: 4697493
---
 src/evaluate.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index ceba2588..25aba644 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -139,7 +139,6 @@ namespace {
   constexpr Score PassedFile         = S( 11,  8);
   constexpr Score PawnlessFlank      = S( 17, 95);
   constexpr Score RestrictedPiece    = S(  7,  7);
-  constexpr Score ReachableOutpost   = S( 32, 10);
   constexpr Score RookOnQueenFile    = S(  7,  6);
   constexpr Score SliderOnQueen      = S( 59, 18);
   constexpr Score ThreatByKing       = S( 24, 89);
@@ -296,7 +295,7 @@ namespace {
                 score += Outpost * (Pt == KNIGHT ? 2 : 1);
 
             else if (Pt == KNIGHT && bb & b & ~pos.pieces(Us))
-                score += ReachableOutpost;
+                score += Outpost;
 
             // Knight and Bishop bonus for being right behind a pawn
             if (shift<Down>(pos.pieces(PAWN)) & s)
-- 
2.39.2