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Merge pawn count terms using their average

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This simplification patch merges the pawn count terms in the eval
formula with the material term, updating the offset constant for
the nnue part of the formula from 34000 to 34300 because the average
pawn count in middlegame positions evaluated during search is around 8.

STC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 138240 W: 35834 L: 35723 D: 66683
Ptnml(0-2): 527, 16587, 34817, 16626, 563
https://tests.stockfishchess.org/tests/view/6653f474a86388d5e27daaac

LTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 454272 W: 114787 L: 115012 D: 224473
Ptnml(0-2): 246, 51168, 124553, 50903, 266
https://tests.stockfishchess.org/tests/view/6654f256a86388d5e27db131

closes https://github.com/official-stockfish/Stockfish/pull/5303

Bench: 1279635
This commit is contained in:
Stéphane Nicolet 2024-05-27 04:32:04 +02:00 • committed by Disservin
parent 41acbcae1a
commit c7b80f6c8a
1 changed files with 2 additions and 4 deletions
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6
src/evaluate.cpp
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@ -77,12 +77,10 @@ Value Eval::evaluate(const Eval::NNUE::Networks& networks,
optimism += optimism * nnueComplexity / 470;
nnue -= nnue * (nnueComplexity * 5 / 3) / 32621;
int material = 200 * pos.count<PAWN>() + 350 * pos.count<KNIGHT>() + 400 * pos.count<BISHOP>()
int material = 300 * pos.count<PAWN>() + 350 * pos.count<KNIGHT>() + 400 * pos.count<BISHOP>()
+ 640 * pos.count<ROOK>() + 1200 * pos.count<QUEEN>();
v = (nnue * (34000 + material + 135 * pos.count<PAWN>())
+ optimism * (4400 + material + 99 * pos.count<PAWN>()))
/ 35967;
v = (nnue * (34300 + material) + optimism * (4400 + material)) / 35967;
// Damp down the evaluation linearly when shuffling
v = v * (204 - pos.rule50_count()) / 208;