Stockfish NNUE

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Stockfish NNUE, a Stockfish branch by Hisayori Noda aka Nodchip, which uses Efficiently Updatable Neural Networks - stylized as &#398;U&#1048;&#1048; or reversed as NNUE - to replace its standard evaluation. NNUE, introduced in 2018 by Yu Nasu , were previously successfully applied in Shogi evaluation functions embedded in a Stockfish based search, such as YaneuraOu , and Kristallweizen. In 2019, Nodchip incorporated NNUE into Stockfish 10 - as a proof of concept, and with the intention to give something back to the Stockfish community. After support and announcements by Henk Drost in May 2020 and subsequent enhancements, Stockfish NNUE was established and recognized. In summer 2020, with more people involved in testing and training, the computer chess community bursts 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, Stockfish NNUE seemingly became stronger than its original. In August 2020, Fishtest revealed Stockfish NNUE was stronger than the classical one at least 80 Elo. In July 2020, the playing code of NNUE was put into the official Stockfish repository as a branch for further development and examination. In August that playing code merged to the master branch and become an official part of the engine. However, the training code still remained in Nodchip's repository.

=NNUE Structure= The neural network consists of four layers. The input layer is heavily overparametrized, feeding in the board representation for all king placements per side. The efficiency of NNUE is due to incremental update of the input layer outputs in make and unmake move, where only a tiny fraction of its neurons need to be considered. The remaining three layers with 2x256x32, 32x32 and 32x1 weights are computational less expensive, best calculated using appropriate SIMD instructions performing fast 16-bit integer arithmetic, like SSE2 or AVX2 on x86-64, or if available, AVX-512.

NNUE layers in action

=Networks= All networks are built by some volunteers but not by any big community (differs from Leela Chess Zero) and can be uploaded into Fishtest for testing. Networks with good test results will be released officially on Fishtest website.

=Hybrid= In August 2020 a new patch changed Stockfish NNUE into a hybrid engine: it uses NNUE evaluation only on quite balanced material positions, otherwise uses the classical one.

=Strong Points=
 * Reuses and gets benefits from the very optimized search function of Stockfish as well as almost all Stockfish's code
 * Runs with CPU only, and doesn't require expensive video cards, as well the need for installing drivers and specific libraries. Thus it is much easier to install (compared to engines using deep convolutional neural networks, such as Leela Chess Zero) and suitable for almost all modern computers. Using a GPU is even not practical for that small net - host-device-latency aka. kernel-launch-overhead to a then underemployed GPU are not sufficient for the intended NPS range
 * Requires much smaller training sets. Some high score networks can be built with the effort of one or a few people within a few days. It doesn't require the massive computing from a supercomputer and/or from community

=See also=
 * Category: Neural Network Engines
 * Neural Networks
 * NNUE
 * Winter

=Forum Posts=

January ...

 * The Stockfish of shogi by Larry Kaufman, CCC, January 07, 2020 » Shogi
 * Stockfish NNUE by Henk Drost, CCC, May 31, 2020 » Stockfish
 * Stockfish NN release (NNUE) by Henk Drost, CCC, May 31, 2020
 * nnue-gui 1.0 released by Norman Schmidt, CCC, June 17, 2020
 * stockfish-NNUE as grist for SF development? by Warren D. Smith, FishCooking, June 21, 2020

July

 * Can the sardine! NNUE clobbers SF by Henk Drost, CCC, July 16, 2020
 * End of an era? by Michel Van den Bergh, FishCooking, July 20, 2020
 * Sergio Vieri second net is out by Sylwy, CCC, July 21, 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
 * Re: NNUE accessible explanation by Jonathan Rosenthal, CCC, August 03, 2020


 * Stockfisch NNUE macOS binary requested by Steppenwolf, CCC, July 25, 2020
 * Stockfish NNUE by Lion, CCC, July 25, 2020
 * 7000 games testrun of SFnnue sv200724_0123 finished by Stefan Pohl, FishCooking, July 26, 2020
 * SF-NNUE going forward... by Zenmastur, CCC, July 27, 2020
 * New sf+nnue play-only compiles by Norman Schmidt, CCC, July 27, 2020
 * Stockfish+NNUEsv +80 Elo vs Stockfish 17jul !! by Kris, Rybka Forum, July 28, 2020
 * LC0 vs. NNUE - some tech details... by Srdja Matovic, CCC, July 29, 2020 » Lc0
 * Stockfish NNUE and testsuites by Jouni Uski, CCC, July 29, 2020
 * Stockfish NNue [download ] by Ed Schröder, CCC, July 30, 2020

August

 * Repository for Stockfish+NNUE Android Builds by AdminX, CCC, August 02, 2020
 * SF NNUE Problem by Stephen Ham, CCC, August 03, 2020
 * Re: NNUE accessible explanation by Jonathan Rosenthal, CCC, August 03, 2020 » NNUE accessible explanation
 * [NNUE Worker update on fishtest ] by Joost VandeVondele, FishCooking, August 03, 2020
 * this will be the merge of a lifetime : SF 80 Elo+ by MikeB, CCC, August 04, 2020
 * Re: this will be the merge of a lifetime : SF 80 Elo+ by Henk Drost, CCC, August 04, 2020


 * You can now look inside NNUE and look at its Per square value estimation by Henk Drost, CCC, August 04, 2020
 * Is this SF NN almost like 20 MB book? by Jouni Uski, CCC, August 04, 2020
 * NNUE evaluation merged in master by Joost VandeVondele, FishCooking, August 06, 2020
 * SF NNUE training questions by Jouni Uski, CCC, August 10, 2020
 * Neural Networks weights type by Fabio Gobbato, CCC, August 13, 2020

=External Links=

Basics

 * Stockfish NNUE – The Complete Guide, June 19, 2020 (Japanese and English)
 * Stockfish NNUE Wiki
 * NNUE merge · Issue #2823 · official-stockfish/Stockfish · GitHub by Joost VandeVondele, July 25, 2020
 * Stockfish Evaluation Guide

Source

 * GitHub - nodchip/Stockfish: UCI chess engine by Nodchip
 * GitHub - vondele/Stockfish at nnue-player-wip by Joost VandeVondele
 * GitHub - tttak/Stockfish: UCI chess engine
 * GitHub - joergoster/Stockfish-NNUE: UCI Chess engine Stockfish with an Efficiently Updatable Neural-Network-based evaluation function hosted by Jörg Oster
 * GitHub - FireFather/sf-nnue: Stockfish NNUE (efficiently updateable neural network) by Norman Schmidt
 * GitHub - FireFather/nnue-gui: basic windows application for using nodchip's stockfish-nnue software by Norman Schmidt

Networks

 * Neural Net download and statistics
 * Index of /~sergio-v/nnue by Sergio Vieri

Binaries

 * Stockfish NNUE | Home of the Dutch Rebel hosted by Ed Schröder
 * Stockfish NNUE Development Versions

Rating Lists

 * Stockfish+NNUE 150720 64-bit 4CPU in CCRL Blitz

Misc

 * Stockfish from Wikipedia
 * Nue from Wikipedia
 * Hiromi - Spectrum, 2019, YouTube Video

=References= Up one Level