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'''Ethereal''',<br/>
an [[UCI]] compliant [[:Category:Open Source|open source chess engine]] written by [[Andrew Grant]] in [[C]], licensed under the [[Free Software Foundation#GPL|GNU GPL]] and first officially released in June 2016 <ref>[http://kirill-kryukov.com/chess/discussion-board/viewtopic.php?f=7&t=8645 Ethereal - Official Release] by [[Andrew Grant]], [[Computer Chess Forums|CCRL Discussion Board]], June 25, 2016</ref>. Ethereal is greatly influenced from [[Crafty]], [[Stockfish]], [[TSCP]], [[MadChess]], and [[Fruit]] <ref>[https://github.com/AndyGrant/Ethereal/blob/master/README.md Ethereal/README.md at master · AndyGrant/Ethereal · GitHub]</ref>.
On October 09, 2020, Andrew Grant initially announced his withdrawal from Ethereal's development with his final the releases of Ethereal '''V12.75'''
<ref>[http://www.talkchess.com/forum3/viewtopic.php?f=2&t=75335 Final Release of Ethereal, V12.75] by [[Andrew Grant]], [[CCC]], October 09, 2020</ref>
and Ethereal '''12.75 SF-NNUE''', the latter a [[NNUE]] implementation based on [[Stockfish NNUE]], to deliberately demonstrate how everybody may considerably improve the [[Playing Strength|playing strength]] of their engines without much effort
<ref>[http://www.talkchess.com/forum3/viewtopic.php?f=2&t=75335&start=91 Re: Final Release of Ethereal, V12.75] by [[Andrew Grant]], [[CCC]], October 09, 2020</ref> .However, Andrew Grant voted for another direction, and announced a commercial release of Ethereal '''13.00''' (NNUE) ,the free standard version still available on [https://en.wikipedia.org/wiki/GitHub Github] <ref name="Ethereal13NNUE">[http://www.talkchess.com/forum3/viewtopic.php?f=2&t=77438 Commercial Release of Ethereal 13.00 (NNUE) for AVX2 Systems] by [[Andrew Grant]], [[CCC]], June 04, 2021</ref>. =Ethereal 13 (NNUE)='''Ethereal 13 (NNUE)''', the commercial Ethereal version for [[AVX2]] systems was released on June 04, 2021. The program comes with two [[NNUE|NNUEs]] for [[Evaluation|evaluation]], one for standard chess, and the secondary network trained exclusively for [[Chess960]]. The NNUEs are not derived from, trained on, nor duplicated from the works of the [[Stockfish]] team <ref name="Ethereal13NNUE"/>. Andrew Grant on his NNUE approach <ref>[http://www.talkchess.com/forum3/viewtopic.php?f=2&t=77438&start=17 Re: Commercial Release of Ethereal 13.00 (NNUE) for AVX2 Systems] by [[Andrew Grant]], [[CCC]], June 04, 2021</ref>: Ethereal is using the [[Stockfish NNUE#NNUE Structure|HalfKP]] paradigm, with a 40960x256 - causing > 512x32x32x1 Network. This is the textbook approach, but with some changes. Firstly, not all weights are quantized to int8 / int16 for the input layer. Instead, the network goes like this: int16_t => int16_t => (int32_t -> [[Float|float_t]]) => float_t => float_t. This approach allows us to never have to pack the data downwards, saving many operations, and also lets us take a slightly more expensive approach to the later layers in exchange for massively increased precision. If I eventually add support for [[AVX]] (not avx2) machines, it will be a significant gain as AVX does not have 256-bit vector support for integer types in a meaningful way. During training the Network actually has 43850 input parameters, using a few factorization of the board to aid in training without having tens of billions of positions. In practice, each Net was trained somewhere between 2 and 4 billion positions total, evaluated by Ethereal / Ethereal NNUE. The networks are trained using a modified form of the author's [https://en.wikipedia.org/wiki/Frustration frustrationStochastic_gradient_descent#Adam Adam] optimizer, which allows better performance for datasets with extremely sparse input fields. For example, with a Batch Size of 16384, only about 50% of the 43,850 parameters are used on average. Data generation for a given network takes about 3 weeks, completed on a 104 core machine. From there, processing that data down into a list of [[Forsyth-Edwards Notation|FENs]] and then into the format used by Ethereal's NNTrainer takes another 12 hours or so. Finally, training the actual Network can take a few days, with many stops and starts to drop the learning rate and find a global optima. The trainer itself is a fully original work, written in [[C]] and making use of all 104 threads. It includes some AVX2 and even AVX512 code for use in updating the network parameters. This toolkit was used in training the Halogen networks as well. It is fairly flexible and trying things like HalfKA, changing layer sizes, adding layers, changing activation functions, or adding more factorizers is only a few minutes of effort in the code. It rivals speeds of [[GPU]]based trainers, by leveraging massive SMP and efficient implementations.
=Features=
** [[Piece-Square Tables]]
==[[Evaluation]]==
* [[NNUE]] (Ethereal 1213.75 SF-00 NNUE)
* [[Tapered Eval]]
* [[Material]]
* [http://www.talkchess.com/forum3/viewtopic.php?f=2&t=75335 Final Release of Ethereal, V12.75] by [[Andrew Grant]], [[CCC]], October 09, 2020
: [http://www.talkchess.com/forum3/viewtopic.php?f=2&t=75335&start=91 Re: Final Release of Ethereal, V12.75] by [[Andrew Grant]], [[CCC]], October 09, 2020
: [http://www.talkchess.com/forum3/viewtopic.php?f=2&t=75335&start=134 Re: Final Release of Ethereal, V12.75] by [[Andrew Grant]], [[CCC]], November 12, 2020
* [http://www.talkchess.com/forum3/viewtopic.php?f=7&t=75345 Request for someone to train an NNUE for Ethereal] by [[Andrew Grant]], [[CCC]], October 09, 2020 » [[NNUE]]
* [http://www.talkchess.com/forum3/viewtopic.php?f=7&t=75350 Ethereal Tuning - Data Dump] by [[Andrew Grant]], [[CCC]], October 10, 2020
* [http://www.talkchess.com/forum3/viewtopic.php?f=2&t=76049 Ethereal questions] by [[Gabor Szots]], [[CCC]], December 12, 2020
'''2021'''
* [http://www.talkchess.com/forum3/viewtopic.php?f=2&t=77438 Commercial Release of Ethereal 13.00 (NNUE) for AVX2 Systems] by [[Andrew Grant]], [[CCC]], June 04, 2021
: [http://www.talkchess.com/forum3/viewtopic.php?f=2&t=77438&start=17 Re: Commercial Release of Ethereal 13.00 (NNUE) for AVX2 Systems] by [[Andrew Grant]], [[CCC]], June 04, 2021
* [http://www.talkchess.com/forum3/viewtopic.php?f=2&t=77503&start=55 Re: will Tcec allow Stockfish with a Leela net to play?] by [[Connor McMonigle]], [[CCC]], June 17, 2021 » [[NNUE]]
* [http://www.talkchess.com/forum3/viewtopic.php?f=2&t=77571 I declare that HCE is dead...] by [[Andrew Grant]], [[CCC]], June 29, 2021 » [[Evaluation|HCE]], [[NNUE]]
'''2022'''
* [https://www.talkchess.com/forum3/viewtopic.php?f=7&t=79160 Resolving once in a trillion crashes] by [[Andrew Grant]], [[CCC]], January 18, 2022 » [[Debugging]]
* [https://www.talkchess.com/forum3/viewtopic.php?f=2&t=79179 Commercial Release of Ethereal 13.50] by [[Andrew Grant]], [[CCC]], January 20, 2022
'''2023'''
* [https://talkchess.com/forum3/viewtopic.php?f=2&t=82750 Commercial Release of Ethereal 14.25] by [[Andrew Grant]], [[CCC]], October 21, 2023
=External Links=
==Chess Engine==
* [http://chess.grantnet.us/Ethereal/ Ethereal 13.00 (NNUE)]
* [https://github.com/AndyGrant/Ethereal GitHub - AndyGrant/Ethereal: Ethereal UCI Chess Engine]
* [http://www.computerchess.org.uk/ccrl/404/cgi/compare_engines.cgi?family=Ethereal&print=Rating+list&print=Results+table&print=LOS+table&print=Ponder+hit+table&print=Eval+difference+table&print=Comopp+gamenum+table&print=Overlap+table&print=Score+with+common+opponents Ethereal] in [[CCRL|CCRL Blitz]]* [http://www.computerchess.org.uk/ccrl/4040/cgi/compare_engines.cgi?family=Ethereal&print=Rating+list&print=Results+table&print=LOS+table&print=Ponder+hit+table&print=Eval+difference+table&print=Comopp+gamenum+table&print=Overlap+table&print=Score+with+common+opponents Ethereal] in [[CCRL|CCRL 40/415]]
* [http://www.chessdom.com/ethereal-wins-tcec-division-4/ Ethereal wins TCEC Division 4], Interview with [[Andrew Grant]], [[Chessdom]], April 30, 2018 » [[TCEC Season 12]]
* [http://www.chessdom.com/ethereal-chess-engine-leads-tcec-div-3-convincingly/ Ethereal chess engine leads TCEC Div 3 convincingly], [[Chessdom]], August 12, 2018 » [[TCEC Season 13]]
* [http://www.chessdom.com/ethereal-chess-engine-wins-the-gold-at-tcec-div-3/ Ethereal chess engine wins the gold at TCEC Div 3], [[Chessdom]], August 17, 2018
==Misc==
* [https://en.wiktionary.org/wiki/ethereal ethereal - Wiktionary]
* [https://www.truth-is-beauty.com/blog/style-identities-the-ethereal The Ethereal] from [https://www.truth-is-beauty.com/home.html Truth is Beauty], July 07, 2015
* [[:Category:Jean-Luc Ponty|Jean-Luc Ponty]] - [https://en.wikipedia.org/wiki/Cosmic_Messenger Ethereal Mood] (1978), [https://en.wikipedia.org/wiki/YouTube YouTube] Video
: {{#evu:https://www.youtube.com/watch?v=JwibRL7Eqq4Va5_Y4QS3Eo|alignment=left|valignment=top}}
=References=
[[Category:Linux]]
[[Category:Windows]]
[[Category:Chess960]]
[[Category:OpenBench]]
[[Category:Commercial]]
[[Category:NNUE]]
[[Category:Jean-Luc Ponty]]
[[Category:Astronomy]]
