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Syzygy EGTB is significantly smaller than all [[DTM]] EGTBs. It is 7 times as small as Gaviota for 5 men, 8 times as small as Nalimov for 7 men, 8 times as small as Lomonosov for 7 men. However, when all DTM EGTBs have full data of two sides, Syzygy EGTB omits data of one side for DTZ data to save space. [[Ronald de Man]] estimated that if keep them all, the Syzygy's 6 men may increase 158 GB, become 307 GB, double on size, 4 times as small as Nalimov 5 men.
[[Ronald de Man]] in a reply to [[phhnguyen]], 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.
if some data is omitted, what the (roughly) size of full data, say 5 men? Just for comparing with other EGTBs. We don't need the fairest comparison, but enough for a quick evaluation.
For 6-piece TBs, DTZ is 81.9GB when storing only the smaller side of each table. Storing both sides might require perhaps 240GB.
