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Implement accumulator refresh table

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For each thread persist an accumulator cache for the network, where each
cache contains multiple entries for each of the possible king squares.
When the accumulator needs to be refreshed, the cached entry is used to more
efficiently update the accumulator, instead of rebuilding it from scratch.
This idea, was first described by Luecx (author of Koivisto) and
is commonly referred to as "Finny Tables".

When the accumulator needs to be refreshed, instead of filling it with
biases and adding every piece from scratch, we...

1. Take the `AccumulatorRefreshEntry` associated with the new king bucket
2. Calculate the features to activate and deactivate (from differences
   between bitboards in the entry and bitboards of the actual position)
3. Apply the updates on the refresh entry
4. Copy the content of the refresh entry accumulator to the accumulator
   we were refreshing
5. Copy the bitboards from the position to the refresh entry, to match
   the newly updated accumulator

Results at STC:
https://tests.stockfishchess.org/tests/view/662301573fe04ce4cefc1386
(first version)
https://tests.stockfishchess.org/tests/view/6627fa063fe04ce4cefc6560
(final)

Non-Regression between first and final:
https://tests.stockfishchess.org/tests/view/662801e33fe04ce4cefc660a

STC SMP:
https://tests.stockfishchess.org/tests/view/662808133fe04ce4cefc667c

closes https://github.com/official-stockfish/Stockfish/pull/5183

No functional change
This commit is contained in:
gab8192
2024-04-20 21:26:00 +02:00
committed by Disservin
parent fcba524793
commit 49ef4c935a
12 changed files with 349 additions and 80 deletions
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8
src/evaluate.h
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@@ -40,14 +40,16 @@ constexpr inline int SmallNetThreshold = 1274, PsqtOnlyThreshold = 2389;
namespace NNUE {
struct Networks;
struct AccumulatorCaches;
}
std::string trace(Position& pos, const Eval::NNUE::Networks& networks);
int simple_eval(const Position& pos, Color c);
Value evaluate(const NNUE::Networks& networks, const Position& pos, int optimism);
Value evaluate(const NNUE::Networks& networks,
const Position& pos,
Eval::NNUE::AccumulatorCaches& caches,
int optimism);
} // namespace Eval
} // namespace Stockfish