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'''[[Main Page|Home]] * [[Engines]] * [[Stockfish]] * CFish'''
[[FILE:Joachim Beuckelaer - Vismarkt..JPG|border|right|thumb| [[:Category:Joachim Beuckelaer|Joachim Beuckelaer]] - Fish Market <ref>[https://commons.wikimedia.org/wiki/File:Joachim_Beuckelaer_-_Vismarkt..JPG Fish Market] by [[Arts#:Category:Joachim Beuckelaer|Joachim Beuckelaer]] , 16th century, [https://en.wikipedia.org/wiki/Bonnefantenmuseum Bonnefantenmuseum], [https://en.wikipedia.org/wiki/Maastricht Maastricht], [https://en.wikipedia.org/wiki/Wikimedia_Commons Wikimedia Commons], [https://en.wikipedia.org/wiki/Cod Cod from Wikipedia]</ref> ]]
'''CFish''',<br/>
a [[Stockfish#ports|port]] of Stockfish written in plain [[C]] by [[Ronald de Man]], first published on [https://en.wikipedia.org/wiki/GitHub GitHub] in July 2016. Possibly inspired by the [[asmFish]] project to speed up Stockfish using a programming language closer to the machine, the purpose of CFish is to explore possible optimization issues of C versus [[Cpp|C++]] compilers <ref>[http://www.talkchess.com/forum/viewtopic.php?t=61280&start=9 Re: CFish] by [[Louis Zulli]], [[CCC]], September 01, 2016</ref>.
=AVX2 Attacks=
Since May 2020, CFish contains experimental [[AVX2]]/[[AVX-512]] computational [[Sliding Piece Attacks|sliding piece attack]] code by Okuhara
as memory saving alternative to [[Magic Bitboards|Magic bitboards]] <ref>[https://github.com/syzygy1/Cfish/blob/master/src/avx2-bitboard.h Cfish/avx2-bitboard.h at master · syzygy1/Cfish · GitHub]</ref>. It applies a kind of [[Classical Approach#Branchless|branchless classical approach]].
For instance, the four [[Classical Approach#Positive Rays|positive rays]] and [[Classical Approach#Negative Rays|negative rays]] of a [[Queen|queen]]
are processed as vector of 4 [[Bitboards|bitboards]] in one 256-bit ymm register each. Positive and negative rays were intersected with the vector of broadcast [[Occupancy|occupancies]],
to get the relevant blockers if any, [[General Setwise Operations#TheLeastSignificantOneBitLS1B|LS1B]] for positive, and [[General Setwise Operations#TheMostSignificantOneBitMS1B|MS1B]] for negative rays.
While the positive rays were processed by [[BMI1#BLSMSK|BLSMSK]] aka <code>((x-1) ^ x)</code> to clear the ray squares above the LS1B blockers,
the negative rays use a [[Parallel Prefix Algorithms#Fill Stuff|parallel prefix fill]] with three vector right shifts and ors, to clear all ray bits below the MS1B blockers.
The eight ray attack sets were vertically and two times horizontally ored together for the final result.
The conditional compiled AVX-512 version takes advantage of the [[AVX-512#VPLZCNT|_mm256_lzcnt_epi64]] <ref>[https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_mm256_lzcnt_epi64&expand=5560,5471,3497 _mm256_lzcnt_epi64]</ref> and [[AVX-512#VPTERNLOG|_mm256_ternarylogic_epi64]] <ref>[https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_mm256_ternarylogic_epi64&expand=5560,5471,3497,5873 _mm256_ternarylogic_epi64]</ref> intrinsics.
Rook and bishop naturally suffer from less vector utilization, and combine some other well known techniques, i.e. the bishop attack getter processes only positive rays by swapping bytes.
=[[NNUE]]=
Since August 2020, CFish also provides the [[NNUE]] evaluation ported from its C++ base [[Stockfish NNUE]] <ref>[https://github.com/syzygy1/Cfish/blob/master/src/nnue.c Cfish/nnue.c at master · syzygy1/Cfish · GitHub]</ref>,
further utilizing [[SIMD and SWAR Techniques|SIMD instructions]].
=See also=
* [[asmFish]]
* [[Fat Titz]]
* [[Portfish]]
* [[Rustfish]]
* [[Stockfish NNUE]]
=Forum Posts=
* [http://www.talkchess.com/forum/viewtopic.php?t=66347 Cfish-54302a... Search of startpos to depth 50] by [[Louis Zulli]], [[CCC]], January 17, 2018 » [[Initial Position]]
* [http://www.talkchess.com/forum/viewtopic.php?t=66462 Cfish 9 is OUT!] by [[Louis Zulli]], [[CCC]], January 31, 2018
* [http://www.talkchess.com/forum3/viewtopic.php?f=2&t=70932 Cfish, shiny and new...] by [[Dann Corbit]], [[CCC]], June 05, 2019
* [http://www.talkchess.com/forum3/viewtopic.php?f=7&t=71027 Some NUMA data for Stockfish-dev and Cfish-dev] by [[Louis Zulli]], [[CCC]], June 17, 2019 » [[NUMA]], [[Stockfish]]
* [http://www.talkchess.com/forum3/viewtopic.php?f=2&t=71311 Bin book adapter?] by Ovyron, [[CCC]], July 18, 2019 » [[PolyGlot]]
==2020 ...==
* [http://www.talkchess.com/forum3/viewtopic.php?f=2&t=74369 Where to find CFish 11 Latest exe file] by Eric Hughes Santiago, [[CCC]], July 05, 2020
: [http://www.talkchess.com/forum3/viewtopic.php?f=2&t=74369&start=6 Re: Where to find CFish 11 Latest exe file] by [[Ronald de Man]], [[CCC]], July 05, 2020
* [http://www.talkchess.com/forum3/viewtopic.php?f=2&t=74402 Cfish is back!] by [[Louis Zulli]], [[CCC]], July 07, 2020
: [http://www.talkchess.com/forum3/viewtopic.php?f=2&t=74402&start=10 Re: Cfish is back!] by [[Ronald de Man]], [[CCC]], July 07, 2020
* [http://www.talkchess.com/forum3/viewtopic.php?f=7&t=75400 Hacking around CFish NNUE] by [[Maksim Korzh]], [[CCC]], October 15, 2020 » [[NNUE]]
=External Links=
* [https://github.com/syzygy1/Cfish GitHub - syzygy1/Cfish: C port of Stockfish]
* [https://engithub.wikipedia.orgcom/okuhara/wikiCfish GitHub - okuhara/Fish_Go_Deep Cfish: C port of Stockfish]* [[:Category:Fish Go Deep|Fish Go Deep]] - The Jazz (2002), [https://en.wikipedia.org/wiki/YouTube YouTube] Video
: {{#evu:https://www.youtube.com/watch?v=biwGNuoaEyQ|alignment=left|valignment=top}}
<references />
'''[[Stockfish|Up one Level]]'''
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