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Tweak optimism with complexity

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This patch increases the optimism bonus for "complex positions", where the
complexity is measured as the absolute value of the difference between material
and the sophisticated NNUE evaluation (idea by Joost VandeVondele).

Also rename some variables in evaluate() while there.

passed STC:
LLR: 2.94 (-2.94,2.94) <0.00,2.50>
Total: 88392 W: 23150 L: 22781 D: 42461
Ptnml(0-2): 318, 9961, 23257, 10354, 306
https://tests.stockfishchess.org/tests/view/61cbbedee68b2a714b6eb110

passed LTC:
LLR: 2.93 (-2.94,2.94) <0.50,3.00>
Total: 37848 W: 10043 L: 9766 D: 18039
Ptnml(0-2): 26, 3815, 10961, 4100, 22
https://tests.stockfishchess.org/tests/view/61cc0cc3e68b2a714b6ec28c

Closes https://github.com/official-stockfish/Stockfish/pull/3875
Follow-up from a5a89b27c8

Bench: 4125221
This commit is contained in:
Stéphane Nicolet 2021-12-30 11:23:40 +01:00
parent 93b14a17d1
commit 1066119083
1 changed files with 7 additions and 8 deletions
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15
src/evaluate.cpp
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@ -1082,29 +1082,28 @@ make_v:
Value Eval::evaluate(const Position& pos) {
Value v;
bool useClassical = false;
// Deciding between classical and NNUE eval (~10 Elo): for high PSQ imbalance we use classical,
// but we switch to NNUE during long shuffling or with high material on the board.
bool classical = false;
if ( !useNNUE
|| abs(eg_value(pos.psq_score())) * 5 > (850 + pos.non_pawn_material() / 64) * (5 + pos.rule50_count()))
{
v = Evaluation<NO_TRACE>(pos).value(); // classical
classical = abs(v) >= 300;
useClassical = abs(v) >= 300;
}
// If result of a classical evaluation is much lower than threshold fall back to NNUE
if (!classical && useNNUE)
if (useNNUE && !useClassical)
{
int scale = 1136
+ 20 * pos.non_pawn_material() / 1024;
Value nnue = NNUE::evaluate(pos, true); // NNUE
int scale = 1136 + 20 * pos.non_pawn_material() / 1024;
Color stm = pos.side_to_move();
Value optimism = pos.this_thread()->optimism[stm];
Value psq = (stm == WHITE ? 1 : -1) * eg_value(pos.psq_score());
int complexity = abs(nnue - psq) / 256;
optimism *= (1 + complexity);
v = (nnue + optimism) * scale / 1024 - optimism;
if (pos.is_chess960())