From: Stéphane Nicolet <cassio@free.fr>
Date: Sun, 4 Apr 2021 08:51:45 +0000 (+0200)
Subject: Keep more pawns
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=f40913f7f699d9d875e44929608b45947421ad03

Keep more pawns

This patch increases the weight of pawns in the scale factor applied
to the output of the NNUE evaluation. This has the effect that Stockfish
will try a little bit harder to keep more pawns in position where the
engine has the advantage, and exchange more pawns in bad positions.

STC:
LLR: 2.93 (-2.94,2.94) {-0.20,1.10}
Total: 42552 W: 3858 L: 3668 D: 35026
Ptnml(0-2): 152, 2956, 14876, 3134, 158
https://tests.stockfishchess.org/tests/view/606a06dd2b2df919fd5f0504

LTC:
LLR: 2.95 (-2.94,2.94) {0.20,0.90}
Total: 44328 W: 1703 L: 1531 D: 41094
Ptnml(0-2): 20, 1373, 19207, 1543, 21
https://tests.stockfishchess.org/tests/view/606aa4ec2b2df919fd5f053e

Closes https://github.com/official-stockfish/Stockfish/pull/3420

Bench: 4310076
---

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 437e753a..789e2859 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -1091,8 +1091,8 @@ Value Eval::evaluate(const Position& pos) {
       // Scale and shift NNUE for compatibility with search and classical evaluation
       auto  adjusted_NNUE = [&]()
       {
-         int material = pos.non_pawn_material() + 2 * PawnValueMg * pos.count<PAWN>();
-         int scale =  641
+         int material = pos.non_pawn_material() + 4 * PawnValueMg * pos.count<PAWN>();
+         int scale =  580
                     + material / 32
                     - 4 * pos.rule50_count();