NNUE

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NNUE, (&#398;U&#1048;&#1048; Efficiently Updatable Neural Networks) a Neural Network architecture intended to replace the evaluation of Shogi, chess and other board game playing alpha-beta searchers running on a CPU. NNUE was introduced in 2018 by Yu Nasu , and was used in Shogi adaptations of Stockfish such as YaneuraOu , and Kristallweizen-kai, apparently with AlphaZero strength.

Stockfish NNUE
As reported by Henk Drost , Nodchip incorporated NNUE into the chess playing Stockfish 10 as a proof of concept. Stockfish NNUE was born incorporating recent search enhancements, and in summer 2020 the computer chess community burst out enthusiastically due to its rapidly raising playing strength with different networks trained using a mixture of supervised and reinforcement learning methods - despite the approximately halved search speed, even becoming stronger than its original.

=NN Structure= The neural network consists of four layers, W1 through W4. The input layer W1 is heavily overparametrized, feeding in the board representation for various king and pawn configurations. The efficiency of the net is due to incremental update of W1 in make and unmake move, where only a fractions of neurons need to be recalculated. The remaining three layers with 256x2-32-32 channels are computational less expensive, best calculated using appropriate SIMD instructions like AVX2 on x86-64, or if available, AVX-512.

NNUE structure with incremental update

=Publications=
 * Yu Nasu (2018). &#398;U&#1048;&#1048; Efficiently Updatable Neural-Network based Evaluation Functions for Computer Shogi. Ziosoft Computer Shogi Club, pdf (Japanese with English abstract)

=Forum Posts=
 * The Stockfish of shogi by Larry Kaufman, CCC, January 07, 2020 » Stockfish, Shogi
 * Stockfish NNUE by Henk Drost, CCC, May 31, 2020 » Stockfish
 * Stockfish NN release (NNUE) by Henk Drost, CCC, May 31, 2020
 * Can the sardine! NNUE clobbers SF by Henk Drost, CCC, July 16, 2020
 * NNUE accessible explanation by Martin Fierz, CCC, July 21, 2020
 * Re: NNUE accessible explanation by Jonathan Rosenthal, CCC, July 23, 2020
 * Re: NNUE accessible explanation by Jonathan Rosenthal, CCC, July 24, 2020


 * Stockfish NNUE by Lion, CCC, July 25, 2020
 * SF-NNUE going forward... by Zenmastur, CCC, July 27, 2020

=External Links=
 * Stockfish NNUE – The Complete Guide, June 19, 2020 (Japanese and English)
 * GitHub - nodchip/Stockfish: UCI chess engine (Stockfish NNUE by Nodchip)
 * Stockfish NNUE Wiki
 * NNUE merge · Issue #2823 · official-stockfish/Stockfish · GitHub by Joost VandeVondele, July 25, 2020

=References= Up one Level