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a compact six piece endgame database developed by [[Ronald de Man]], published on April 01, 2013. Since August 2018, '''seven piece''' Syzygy Bases are available after an effort by [[Bojun Guo]] started in March 2018 <ref>[http://talkchess.com/forum3/viewtopic.php?f=7&t=66797&start=472 Re: 7-men Syzygy attempt] by [[Bojun Guo]], [[CCC]], August 19, 2018 </ref>. Syzygy Bases consist of two sets of files, '''WDL''' files storing win/draw/loss information considering the [[Fifty-move Rule|fifty-move rule]] for access during [[Search|search]], and '''DTZ''' files with [[Endgame Tablebases#DTZ50|distance-to-zero]] information for access at the [[Root|root]]. The generator is released under the [[Free Software Foundation#GPL|GNU General Public License Version 2]], the [[Thread|thread safe]] probing code is released without restrictions <ref>[http://www.talkchess.com/forum/viewtopic.php?t=47681 New 6-piece tablebases] by [[Ronald de Man]], [[CCC]], April 01, 2013</ref> . As of February 2015, all 3-5 and most important 6-men Syzygy Bases are commercially available on 4 [https://en.wikipedia.org/wiki/DVD DVDs] by [[ChessBase]] as ''Endgame Turbo 4'' for their products [[Fritz|Deep Fritz 14]], [[Komodo#8|Komodo Chess 8]], [[Houdini|Houdini 4]] or [[ChessBase (Database)|ChessBase 12/13]] <ref>[http://shop.chessbase.com/en/products/endspiel_turbo_4 Endgame Turbo 4] by [[ChessBase]]</ref> <ref>[http://en.chessbase.com/post/syzygy-tablebases-newest-fastest-smallest Syzygy Tablebases: newest, fastest, smallest] by [[Albert Silver]], [[ChessBase|ChessBase News]], February 08, 2015</ref>.

 =Data===File Types==Syzygy Bases consist of two sets of files, '''WDL''' files (extension .rtbw) storing win/draw/loss information considering the [[Fifty-move Rule|fifty-move rule]] for access during [[Search|search]], and '''DTZ''' files (extension .rtbz) with [[Endgame Tablebases#DTZ50|distance-to-zero]] information for access at the [[Root|root]]. WDL has full data for two sides but DTZ50 omitted data of one side to save space. Each endgame has a pair of those types. ==File Sizes==

=7-man=Generation of 7-man tablebases would require about 1 TB of RAM. Generation time will be about 64 x per table, which means around 175 x time total <ref>[http://kirill-kryukov.com/chess/discussion-board/viewtopic.php?fComparision=6&t=7396#p83338 Re: Syzygy tb generator for windows] by EGTB is significantly smaller than any [[Ronald de ManEndgame Tablebases#DTM|syzygyDTM]]EGTB. It is 7 times as small as Gaviota for 5 men, [[Computer Chess Forums|CCRL Discussion Board]]8 times as small as Nalimov for 6 men, June 018 times as small as Lomonosov for 7 men. However, 2014</ref> . Ronald de Man wasn't initially interested in creation when all DTM EGTBs have full data of 7-men two sides, Syzygy Based <ref>[http://kirill-kryukov.com/chess/discussion-board/viewtopicEGTB omits data of one side for DTZ data to save space.php?f=6&t=7618#p83771 Re: 7-piece syzygy] by [[Ronald de Man|syzygy]]estimated if keep them all, [[Computer Chess Forums|CCRL Discussion Board]], July 03, 2014</ref>. But in 2018, he supported [[Bojun Guo]] in his 5 month attempt to generated them <ref>[http://www.talkchess.com/forum/viewtopic.php?t=66797 7-men the Syzygy attempt] by [[Bojun Guo]], [[CCC]], March 10, 2018</ref>. In August of 2018 their creation was completed<ref>[https://syzygy-tables.info/ Powered by Ronald de Man's Syzygy endgame tablebases6 men size may increase 158 GB, 7-piece tables generated by Bojun Guo and a public API hosted by lichess.org], August 19become 307 GB in total, 2018</ref><ref>[http://tablebase.lichess.ovh/tables/standard/7/ Index of /tables/standard/7/ double on lichess]size, August 19, 2018</ref>4 times as small as Nalimov 6 men.

=Generation===Up to 6-man==On the first release (Apr 01, 2013) the generator was ready to generate all endgames up to 6 men. The generation is multithreaded and processes completely in RAM. To generate all 6 men, it requires a system with at least 32 GB of RAM and may run in 5 days (the period was measured with a computer 6-core i3930K @ 4.2Ghz, 64 GB). ==7-man==Ronald de Man wasn't initially interested in the creation of 7-men Syzygy Based <ref>[http://kirill-kryukov.com/chess/discussion-board/viewtopic.php?f=6&t=7618#p83771 Re: 7-piece syzygy] by [[Ronald de Man|syzygy]], [[Computer Chess Forums|CCRL Discussion Board]], July 03, 2014</ref> since the generation would require about 1 TB of RAM, too expensive at that time. Generation time would be about 64 x per table, which means around 175 x time total <ref>[http://kirill-kryukov.com/chess/discussion-board/viewtopic.php?f=6&t=7396#p83338 Re: Syzygy tb generator for windows] by [[Ronald de Man|syzygy]], [[Computer Chess Forums|CCRL Discussion Board]], June 01, 2014</ref>.His original generator could not create them. But in 2018, he supported [[Bojun Guo]] in his 5-month attempt to generated them <ref>[http://www.talkchess.com/forum/viewtopic.php?t=66797 7-men Syzygy attempt] by [[Bojun Guo]], [[CCC]], March 10, 2018</ref>. His hardware was estimated at over US$ 90K. In August of 2018 their creation was completed<ref>[https://syzygy-tables.info/ Powered by Ronald de Man's Syzygy endgame tablebases, 7-piece tables generated by Bojun Guo and a public API hosted by lichess.org], August 19, 2018</ref><ref>[http://tablebase.lichess.ovh/tables/standard/7/ Index of /tables/standard/7/ on lichess], August 19, 2018</ref>. ==Checksums== Syzygy endgame files may contain 128-bit checksum keys at the end of those files. It also has its own code for checksums (based on Google's cityhash library).  =Search= ==During the Search==

==At the Root== At the [[Root|root]], since pure DTZ50-optimal play (i.e. minimaxing the number of moves to the next [[Captures|capture]] or [[Pawn Push|pawn move]] by either side) can be very unnatural, it might be desirable to let the engine search on the winning moves until it becomes clear that insufficient progress is being made and only then switch to DTZ-optimal play (e.g. by detecting [[Repetitions|repetitions]] and monitoring the [[Halfmove Clock|halfmove clock]]) <ref>[http://www.talkchess.com/forum/viewtopic.php?t=47681&start=8 Re: New 6-piece tablebases] by [[Ronald de Man]], [[CCC]], April 05, 2013</ref> .  =Pros & Cons===Pros==* Small sizes. It is about 8 times as small as the second-best EGTBs. Having small sizes is the main success key of Syzygy Bases since it is much easier to create, store, provide, download than other EGTBs* Free and more popular (than other EGTBs) to find on the Internet* Support [[Endgame Tablebases#DTZ50|DTZ50]] metric. That metric can help engines to have better results than [[Endgame Tablebases#DTM|DTM]] which is supported widely by other EGTBs ==Cons==* Hard to integrate with chess engines. [[Ronald de Man]] has not provided probing code as an independent library but as a part of [[Stockfish]] chess engines. The probe code has integrated too deeply with that chess engine code and it requires a lot of effort to de-integrate, modify and integrate with other chess projects* Hard to understand and contribute to the project. ETGB itself is a hard topic. Syzygy EGTB has also integrated with many advanced techniques/tricks. It is written in old-style C language. All make it become very hard to understand and/or modify to improve or for other purposes* [[Endgame Tablebases#DTZ50|DTZ50]] metric may lead the engines to win in much longer and ugly ways, compared with [[Endgame Tablebases#DTM|DTM]] one  =Data publish=[[Ronald de Man]] has provided only open source code for generators/probers but not endgame files themselves. Using his tools some people have generated endgames and published them via DVD or online. ==DVD==As of February 2015, all 3-5 and most important 6-men Syzygy Bases are commercially available on 4 [https://en.wikipedia.org/wiki/DVD DVDs] by [[ChessBase]] as ''Endgame Turbo 4'' for their products [[Fritz|Deep Fritz 14]], [[Komodo#8|Komodo Chess 8]], [[Houdini|Houdini 4]] or [[ChessBase (Database)|ChessBase 12/13]] <ref>[http://shop.chessbase.com/en/products/endspiel_turbo_4 Endgame Turbo 4] by [[ChessBase]]</ref> <ref>[http://en.chessbase.com/post/syzygy-tablebases-newest-fastest-smallest Syzygy Tablebases: newest, fastest, smallest] by [[Albert Silver]], [[ChessBase|ChessBase News]], February 08, 2015</ref>.  ==Free Download==There are some free FTP servers for downloading such as [[Bojun Guo]] and [[Lichess]] servers. ===3-6 men===The sizes of those men are small enough to download and store on modern computers. Users should download them in full sets (3, 4, 5, 6 men). ===7 men===All 7 men files' size is over 16.7 TiB, over storages of typical modern computers. They also require a long time to download too. Thus some users choose to download one or a few endgames only, based on their statistics of use in endgames. Bellow is the top 20 of those endgames by their order. The first one, KRPPvKRP, has a significantly higher frequency of use than the others and should be always downloaded: 1) KRPPvKRP 2) KBPPvKBP 3) KPPPvKPP 4) KRPPPvKR 5) KQPPvKQP 6) KNPPvKNP 7) KNPPvKBP 8) KRBPvKRP 9) KQPPvKPP 10) KQPPPvKP11) KBPPvKNP 12) KRPPvKRB 13) KRPPvKPP 14) KBPPvKRP 15) KRNPvKRP 16) KRBPPvKR 17) KBPPvKPP 18) KRPPPvKP 19) KRBPvKRB 20) KRPPvKRN =Probe Code and Tools===Stockfish==[[Ronald de Man]] did not provide the probe code as an independent library. Instead, he published it firstly as an already integrated code for [[Stockfish]] chess engines. It is c++ code and it has been rewritten, updated several times by [[Stockfish]] team. ==Fathom=='''Fathom''' is a stand-alone Syzygy based probing tool and [https://en.wikipedia.org/wiki/Application_programming_interface API] by [[Basil Falcinelli]], introduced in November 2015 along with his [[Gull|Gull 3]] release <ref>[http://www.talkchess.com/forum/viewtopic.php?t=58299 Gull 3 Linux+Syzygy and Fathom released] by [[Basil Falcinelli]], [[CCC]], November 20, 2015</ref> . Unlike the original tbprobe code, Fathom does not necessarily require the callee to provide [[Move Generation|move generation]] functionality. The new modifications and extensions to Ronald de Man's original code which can be "redistributed and/or modified without restrictions", are released under the permissive [[Massachusetts Institute of Technology#License|MIT License]]. The API consists of three functions <ref>[https://github.com/basil00/Fathom GitHub - basil00/Fathom: Syzygy TB probe tool] by [[Basil Falcinelli]]</ref> :* tb_init initializes the tablebase* tb_probe_wdl probes the Win-Draw-Loss (WDL) table for a given position* tb_probe_root probes the Distance-To-Zero (DTZ) table for the given position. [[Jon Dart]] has a fork of Fathom with some bug fixes and enhancements <ref>[https://github.com/jdart1/Fathom jdart1/Fathom · GitHub] by [[Jon Dart]]</ref>, also supporting 7-man <ref>[http://www.talkchess.com/forum3/viewtopic.php?f=7&t=70568 7-man Syzygy support in Fathom] by [[Jon Dart]], [[CCC]], April 23, 2019</ref>.. 

=Quotes=

A pure WDL/DTZ pair is not of much use for creating WDL50+/DTZ50+. I create tables in RAM that have all the information necessary for WDL50+ and DTZ50+, then permute them to different indexing schemes and compress. I do test runs on subsets of the data to find good permutations. (The idea to try permutations is from [[Jesper Torp Kristensen|Jesper Torp Kristensen's]] master thesis.) <ref>[[Jesper Torp Kristensen]] ('''2005'''). ''[httphttps://jespertkissuu.dkcom/Jesperjespertk/publicdocs/master_thesis/ Generation and compression of endgame tables in chess with fast random access using OBDDs]''. Master thesis, Supervisor supervisor [[Mathematician#Miltersen|Peter Bro Miltersen]], [https://en.wikipedia.org/wiki/Aarhus_University Aarhus University], [http://jespertk.dk/Jesper/public/master_thesis/report/report.pdf pdf]</ref> <ref>[https://en.wikipedia.org/wiki/Binary_decision_diagram OBDD - Ordered Binary Decision Diagram from Wikipedia]</ref>  [[Ronald de Man]] in a reply to [[Pham Hong Nguyen|Nguyen Pham]], April 15, 2020 <ref>[http://talkchess.com/forum3/viewtopic.php?f=7&t=73598 Re: Almost perfect DTM tablebase] by [[Dann Corbit]], [[Computer Chess Forums|CCRL Discussion Board]], April 15, 2020</ref> : Syzygy WDL is double sided, DTZ is single sided. So to know whether a 7-piece position is winning, losing or drawn (or cursed), the engine needs to do only a single probe of a 7-piece WDL table. (It may in addition have to do some probes of 6-piece WDL tables if any direct captures are available.) If the engine needs to know the DTZ value (which is only necessary when a TB root position has been reached), the probing code may have to do a 1-ply search to get to the "right" side of the DTZ table. For 6-piece TBs, DTZ is 81.9GB when storing only the smaller side of each table. Storing both sides might require perhaps 240GB. 

* [http://www.talkchess.com/forum3/viewtopic.php?f=7&t=70074 Testing the implementation of Syzygy] by konsolas[[Vincent Tang]], [[CCC]], March 02, 2019

==2020 ...==* [http://www.talkchess.com/forum3/viewtopic.php?f=7&t=73598 Almost perfect DTM tablebase] by [[Dann Corbit]], [[CCC]], April 08, 2020 =External Links=