In two-or-more-playersequential games,aplyis one turn taken by one of the players. The word is used to clarify what is meant when one might otherwise say "turn".
The word "turn" can be a problem since it means different things in different traditions. For example, in standardchessterminology, onemoveconsists of a turn by each player; therefore a ply in chess is ahalf-move.Thus, after 20 moves in a chess game, 40 plies have been completed—20 by white and 20 by black. In the game ofGo,by contrast, a ply is the normal unit of counting moves; so for example to say that a game is250 moves longis to imply 250 plies.
In poker withnplayers the word "street" is used for a full betting round consisting ofnplies; each dealt card may sometimes also be called a "street". For instance, in heads upTexas hold'em,a street consists of 2 plies, with possible plays being check/raise/call/fold: the first by the player at the big blind, and the second by the dealer, who posts the small blind; and there are 4 streets: preflop, flop, turn, river (the latter 3 corresponding tocommunity cards). The terms "half-street" and "half-street game" are sometimes used to describe, respectively, a single bet in a heads up game, and a simplified heads up poker game where only a single player bets.[1]
The word "ply" used as a synonym for "layer" goes back to the 15th century.[2]Arthur Samuelfirst used the term in its game-theoretic sense in his seminal paper onmachine learningincheckersin 1959,[3]but with a slightly different meaning: the "ply", in Samuel's terminology, is actually the depth of analysis ( "Certain expressions were introduced which we will find useful. These are: Ply, defined as the number of moves ahead, where a ply of two consists of one proposed move by the machine and one anticipated reply by the opponent"[4]).
In computing, the concept of a ply is important because one ply corresponds to one level of thegame tree.TheDeep Bluechess computerwhich defeatedKasparovin 1997 would typically search to a depth of between six and sixteen plies to a maximum of forty plies in some situations.[5]
See also
editReferences
edit- ^Chen, Bill and Ankenman, Jerrod. The Mathematics of Poker,p110
- ^Online Etymology Dictionary, "ply"(cited 24 April 2011)
- ^A.L. Samuel, March 3, 1959:Some Studies in Machine Learning Using the Game of Checkers(cited 25 August 2006)
- ^A.L. Samuel, March 3, 1959:Some Studies in Machine Learning Using the Game of Checkers,p. 601 (cited 2 May 2018)
- ^Campbell, Murray; Hoane, A.Joseph; Hsu, Feng-Hsiung (2002)."Deep Blue".Artificial Intelligence.134(1–2):57–83.doi:10.1016/S0004-3702(01)00129-1.S2CID662187.
Further reading
edit- Levy, David;Newborn, Monty (1991),How Computers Play Chess,Computer Science Press,ISBN978-0-7167-8121-9
External links
edit
The dictionary definition ofplyat Wiktionary
