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I have recently found the following place, where I can find the outcome for any 6-piece endgame with Nalimov endtables.

I was surprised to see this, because I have recently read that set of tables requires 1153 GB of hard disk space. This is significant amount of space and also it is not so easy to search through it. But nonetheless this website can give you the result together with a mating series in < 1 second.

My first guess is that they are not using all endtables. There is little point of searching the mate of lonely king VS 4 pieces. But at the very best it takes away 1/4 of all the size.

My vague question is: how can it be done? My normal question is: what is the smallest size of reasonable 6-pieces Nalimov endgametables (by reasonable I mean where the result is not obvious)? Also it would be nice if someone can tell where can I get this smallest size endtables.

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    For vague question: The tablebases are stored in a way that is quick to know where the result of a certain position is stored.
    – JiK
    Aug 31, 2014 at 17:45
  • NoSql databases store this amount without a problem. For example we store 24 TB of data in a cheap 8 node setup with Cassandra. If keys are designed properly, you can get an answer in 20 - 50 msec as it is an O(1) operation.
    – oleksii
    Sep 16, 2014 at 22:17
  • @oleksii thanks for the explanation. Right now looking at the size it does not look too big to me.
    – Salvador Dali
    Sep 16, 2014 at 23:16
  • 2 TB hard drives are readily available and not very expensive. Searching isn't necessarily slow with a good index.
    – RemcoGerlich
    Sep 17, 2014 at 10:14
  • Your position of the lonely king vs 4 pieces needs to be included. It may not be needed from the perspective of the player, but from the perspective of the computer it is required. Tables like this are built outward from winning positions. The more complex positions are built outward from the simpler positions. A position with King and Queen vs King and three other pieces would be an extension of King vs King and three other pieces after capturing the Queen.
    – LeppyR64
    Sep 17, 2014 at 13:16

2 Answers 2

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+50

You can get a smaller 6-piece tablebase here, fully compressed.

https://github.com/syzygy1/tb

While I have personally not tried that, I know because of a friend that they are really good. If you were hoping for smaller stuff, this is as small as you can get. After all, there are lost of positions with 6 pieces.

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    Just a note: the syzygy bases use a different metric. Nalimov gives DTM, syzygy is DTZ50.
    – Eiko
    Oct 1, 2016 at 14:00
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As a matter of fact, they do not use the whole tablebase, as one may check by introducing the following pieces on the board:

White: Kg8. Black: Bc3, Bd4, Kf2, Pf3.

The thing is, some positions are considered "uninteresting" because of the inevitable and obvious outcome of the game. Some of them, like the the positions with a lone king versus a king and five pieces, are simply omited from the calculations. However, every user of a tablebase may reject certain positions as trivial, and I believe the restriction used by the website you mention has many (or at least a few) of this rejections.

They certainly reduce the size of the standard tableblases at least to a tenth of the size you mention, since not even some basic pawn and kings endgames are covered (try Kg7 for white and Kg2 plus Pg3 for black), and this goes for both sides. Moreover, provided they use a similar technology as @oleksii does, I doubt they have any problem.

@Jason Lepack on the comments to the question said that the computer needs them. I ignore that, but after reading the article on Wikipedia and what I've seen on the website you provide and a few tries, I'm pretty sure that one does not.

About the smallest size, I would consider how to decide wether a position is "trivial" or not. I guess that esentially all positions involving a lone king vs king plus any number of pieces should be eliminated. Plus, most of the endings of king vs king and pawns, even with pawns on both sides, can be "solved" on a decent time by a computer. I'd also leave out any position where the material difference is greater than 3, since this would mean a piece down or four pawns up, which cannot be drawn even with different colour bishops... Continuing this way, one may get pretty light on memory size, I guess.

And the generator provided by @MikhailTal looks pretty awesome, now that's condensed information.

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