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Sometimes change the (materialist, positional) balance

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Our new nets output two values for the side to move in the last layer.
We can interpret the first value as a material evaluation of the
position, and the second one as the dynamic, positional value of the
location of pieces.

This patch changes the balance for the (materialist, positional) parts
of the score from (128, 128) to (121, 135) when the piece material is
equal between the two players, but keeps the standard (128, 128) balance
when one player is at least an exchange up.

Passed STC:
LLR: 2.93 (-2.94,2.94) <-0.50,2.50>
Total: 15936 W: 1421 L: 1266 D: 13249
Ptnml(0-2): 37, 1037, 5694, 1134, 66
https://tests.stockfishchess.org/tests/view/60a82df9ce8ea25a3ef0408f

Passed LTC:
LLR: 2.94 (-2.94,2.94) <0.50,3.50>
Total: 13904 W: 516 L: 410 D: 12978
Ptnml(0-2): 4, 374, 6088, 484, 2
https://tests.stockfishchess.org/tests/view/60a8bbf9ce8ea25a3ef04101

closes https://github.com/official-stockfish/Stockfish/pull/3492

Bench: 3856635
This commit is contained in:
Stéphane Nicolet 2021-05-22 19:44:15 +02:00 • committed by Joost VandeVondele
parent ff4c22238a
commit a2f01c07eb
3 changed files with 20 additions and 7 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
src/evaluate.cpp
View file

@ -1119,7 +1119,7 @@ Value Eval::evaluate(const Position& pos) {
int scale = 903 + 28 * pos.count<PAWN>() + 28 * pos.non_pawn_material() / 1024; int scale = 903 + 28 * pos.count<PAWN>() + 28 * pos.non_pawn_material() / 1024;
Value nnue = NNUE::evaluate(pos) * scale / 1024; Value nnue = NNUE::evaluate(pos, true) * scale / 1024;
if (pos.is_chess960()) if (pos.is_chess960())
nnue += fix_FRC(pos); nnue += fix_FRC(pos);

2
src/evaluate.h
View file

@ -43,7 +43,7 @@ namespace Eval {
namespace NNUE { namespace NNUE {
Value evaluate(const Position& pos); Value evaluate(const Position& pos, bool adjusted = false);
bool load_eval(std::string name, std::istream& stream); bool load_eval(std::string name, std::istream& stream);
bool save_eval(std::ostream& stream); bool save_eval(std::ostream& stream);
void init(); void init();

23
src/nnue/evaluate_nnue.cpp
View file

@ -134,7 +134,7 @@ namespace Stockfish::Eval::NNUE {
} }
// Evaluation function. Perform differential calculation. // Evaluation function. Perform differential calculation.
Value evaluate(const Position& pos) { Value evaluate(const Position& pos, bool adjusted) {
// We manually align the arrays on the stack because with gcc < 9.3 // We manually align the arrays on the stack because with gcc < 9.3
// overaligning stack variables with alignas() doesn't work correctly. // overaligning stack variables with alignas() doesn't work correctly.
@ -158,13 +158,26 @@ namespace Stockfish::Eval::NNUE {
ASSERT_ALIGNED(buffer, alignment); ASSERT_ALIGNED(buffer, alignment);
const std::size_t bucket = (pos.count<ALL_PIECES>() - 1) / 4; const std::size_t bucket = (pos.count<ALL_PIECES>() - 1) / 4;
const auto [psqt, lazy] = featureTransformer->transform(pos, transformedFeatures, bucket); const auto [psqt, lazy] = featureTransformer->transform(pos, transformedFeatures, bucket);
if (lazy) {
if (lazy)
return static_cast<Value>(psqt / OutputScale); return static_cast<Value>(psqt / OutputScale);
} else { else
{
const auto output = network[bucket]->propagate(transformedFeatures, buffer); const auto output = network[bucket]->propagate(transformedFeatures, buffer);
return static_cast<Value>((output[0] + psqt) / OutputScale);
int materialist = psqt;
int positional = output[0];
int delta_npm = abs(pos.non_pawn_material(WHITE) - pos.non_pawn_material(BLACK));
int entertainment = (adjusted && delta_npm <= BishopValueMg - KnightValueMg ? 7 : 0);
int A = 128 - entertainment;
int B = 128 + entertainment;
int sum = (A * materialist + B * positional) / 128;
return static_cast<Value>( sum / OutputScale );
} }
} }