Talk:Endgame tablebase/GA1

GA Reassessment

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I will be doing the GA Reassessment on this article as part of the GA Sweeps project.

The article is well written and cogent. The wikilinks are solid and topical. The Lead is a good summary of the article. The images are solid though a few of the captions are a bit long.

The checklinks tool is down right now so I did a random selection of the links in the Reference section. Links 14, 35 and 52 appeared to be either unavailable or dead. Please check these and repair if necessary.

Otherwise the article appears to meet the GA Criteria and I will keep it as GA. H1nkles (talk) 15:29, 17 June 2009 (UTC)

Thanks for this review. I have reduced the size of the longest captions, and I have updated the url of the links you rightly cited as dead. SyG (talk) 14:59, 20 June 2009 (UTC)

Step 1: Generating all possible positions

This paragraph contains inaccuracies and is rather weak. Especially the sentence "Several hundred of these positions are illegal, impossible, or symmetrical reflections of each other, so the actual number is somewhat smaller." is with respect to "impossible, or symmetrical reflections" nonsense. The number of illegal positions can be calculated. Better is to remove the reference to Levy and Newborn and precise the calculation as follows:

David Levy, How Computers Play Chess

	a	b	c	d	e	f	g	h
8									8
7									7
6									6
5									5
4									4
3									3
2									2
1									1
	a	b	c	d	e	f	g	h

The ten unique squares (with symmetry)

Once a metric is chosen, the first step is to generate all the positions with a given material. For example, to generate a DTM tablebase for the endgame of king and queen versus king (KQK), the computer must describe 34,968 unique legal positions. This number derives from a symmetry argument. The Black king can be placed on any of ten squares: a1, b1, c1, d1, b2, c2, d2, c3, d3, and d4 (see diagram). On any other square, its position can be considered equivalent by symmetry of rotation or reflection. Thus, there is no difference whether a Black king in a corner resides on a1, a8, h8, or h1. Multiply the case of the Black king in the corner by 60; the other three places at the edge with 58, and the remaining six cases with the 55 squares for the White king and this all by the 62 remaining squares for placing the White queen. The product (60+3×58+6×55)×62 = 34,968.

Otto (talk) 20:38, 23 August 2009 (UTC)

Yes I agree. (Since symmetry has been "broken" by choosing the position of the (say) Black king among those 10 squares, the only "equivalent" positions arise when the king is on one of the 4 squares on the diagonal. In that case one can require the White king to be not above the diagonal to remove all redundancy. Also, I don't think there are "impossible" positions either, if the kings are at a minimum distance of 1 square: I think any such position can indeed be reached.)

OTOH, the whole procedure outlined here is contradictory to the claim that Tablebases are generated by retrograde analysis, working backward from a checkmated position. See the separate talk section I created further below for discussing that - thank you! — MFH:Talk 21:21, 3 February 2022 (UTC)

Chess ist just an example

Databases exist for checkers as well. for 8x8 checkers 10 piece table bases exist. Here is an example of a win in 140 moves: http://pages.prodigy.net/eyg/Checkers/longest-10pc-mtc.htm They also exist for chess variants http://www.gothicchess.com/javascript_endings.html -Koppapa (talk) 11:09, 6 June 2010 (UTC)

Mmm, true. That means the whole structure of the article should be changed, or the article should be renamed. :-( SyG (talk) 21:11, 11 January 2011 (UTC)