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Tweak hybrid treshold. 

Increase the first hybrid threshold with more material.
Rewrite the hybrid rules for clarity.

STC:
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 24416 W: 3039 L: 2848 D: 18529
Ptnml(0-2): 135, 2136, 7503, 2271, 163
https://tests.stockfishchess.org/tests/view/5f6451efbb0cae038ca8f4dc

LTC;
LLR: 2.95 (-2.94,2.94) {0.25,1.25}
Total: 65016 W: 3702 L: 3455 D: 57859
Ptnml(0-2): 66, 2991, 26157, 3218, 76
https://tests.stockfishchess.org/tests/view/5f64b143bb0cae038ca8f51f

closes https://github.com/official-stockfish/Stockfish/pull/3140

Bench: 3973739
pull/3142/head
Stefan Geschwentner 2020-09-20 22:25:19 +02:00 committed by Joost VandeVondele
parent 8559c43914
commit 16b4578cc1
1 changed files with 21 additions and 13 deletions
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34
src/evaluate.cpp
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@ -1015,20 +1015,28 @@ make_v:
Value Eval::evaluate(const Position& pos) {
// Use classical eval if there is a large imbalance
// If there is a moderate imbalance, use classical eval with probability (1/8),
// as derived from the node counter.
bool useClassical = abs(eg_value(pos.psq_score())) * 16 > NNUEThreshold1 * (16 + pos.rule50_count());
bool classical = !Eval::useNNUE
|| useClassical
|| (abs(eg_value(pos.psq_score())) > PawnValueMg / 4 && !(pos.this_thread()->nodes & 0xB));
Value v = classical ? Evaluation<NO_TRACE>(pos).value()
: NNUE::evaluate(pos) * 5 / 4 + Tempo;
Value v;
if ( useClassical
&& Eval::useNNUE
&& abs(v) * 16 < NNUEThreshold2 * (16 + pos.rule50_count()))
v = NNUE::evaluate(pos) * 5 / 4 + Tempo;
if (!Eval::useNNUE)
v = Evaluation<NO_TRACE>(pos).value();
else
{
// scale and shift NNUE for compatibility with search and classical evaluation
auto adjusted_NNUE = [&](){ return NNUE::evaluate(pos) * 5 / 4 + Tempo; };
// if there is PSQ imbalance use classical eval, with small probability if it is small
Value psq = Value(abs(eg_value(pos.psq_score())));
int r50 = 16 + pos.rule50_count();
bool largePsq = psq * 16 > (NNUEThreshold1 + pos.non_pawn_material() / 64) * r50;
bool classical = largePsq || (psq > PawnValueMg / 4 && !(pos.this_thread()->nodes & 0xB));
v = classical ? Evaluation<NO_TRACE>(pos).value() : adjusted_NNUE();
// if the classical eval is small and imbalance large, use NNUE nevertheless.
if ( largePsq
&& abs(v) * 16 < NNUEThreshold2 * r50)
v = adjusted_NNUE();
}
// Damp down the evaluation linearly when shuffling
v = v * (100 - pos.rule50_count()) / 100;