Talk:Ply (game theory)

From article

 * This correspondence between Elo points and ply search depth is unclear. Is there a reference? If Deep Blue could search to a depth of 12 ply, does this mean Deep Blue is rated at 12 x 80 = 960? Since Deep Blue defeated Kasparov who had a rating over 2800, this doesn't make sense. Nor does it make sense that a player rated 1600 could search 1600/80 = 20 ply. An example is needed to clarify this correspondence, if indeed it is valid.

This is a discussion of the article, so it belongs in the Talk namespace, not in the main namespace. Anyway, for your "sense" point, as I tried to point out in my previous edit summary, the article only claims that the correspondence is linear, not that it is proportional. That is, a 12 ply engine will be rated 80 points above a 11 ply engine, or 160 points above a 10 ply engine, etc. If 2800 corresponds to 12 ply (just my rough ballpark here), then the 1600 player would (if he was an engine, at least: I think it was only meant to be valid for engines) have a search depth of 1200/80 = 15 ply lower than that, i.e. -3 ply. Now, that's absurd, but that's only because the correlation doesn't extrapolate well.

As for the need for a reference, I'm very much in agreement about that, so I've added a fact tag to the statement. It would also be interesting to know how exact the correlation is and how well it extrapolates. -- Jao 20:17, 17 September 2007 (UTC)

The article stated that Deep Blue had a maximum of 40 plies, not 12. Scott —Preceding unsigned comment added by 108.8.67.180 (talk) 22:22, 21 July 2010 (UTC)

Thanks Jao. I didn't know how to use this discussion area.

The article doesn't specify whether the correspondence is linear or porportional. It merely says that "It has been found that an increase in search depth of one ply corresponds on the average to an increase in playing strength of approximately 80 Elo points."

Where has it been found? By whom? What is the precise nature of this correspondence? An example would help. The topic certainly is interesting and I would like to understand it better. Don Coyote 22:54, 17 September 2007 (UTC) Don Coyote

Ply or Plies (Plural)
Can someone tell me if it is intentional that many if not all of the Wikipedia articles which use the term 'ply' do not use 'plies' as the plural? i.e. "forty plies deep" instead of "forty ply deep". If this is a mistake, feel free to start changing them. —Preceding unsigned comment added by 12.40.50.1 (talk) 00:48, 29 April 2009 (UTC)


 * "Plies" is the correct plural term. I don't know of any of the cases you mention, but it depends on the context, i.e. "a search forty plies deep" or "a forty-ply search". Bubba73 (talk), 01:00, 29 April 2009 (UTC)

Two player only?
The opening sentence says "In two-player sequential games, a ply[...]" but I don't see any reason that this would be limited to two-player games. In a three-player game, the definition would be identical. I think "In multiplayer sequential games" would be better wording. -SColombo (talk) 19:53, 27 July 2016 (UTC)