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From: anw@nott-cs.UUCP
Newsgroups: net.games.chess
Subject: Re: Deterministic Chess (Re: Perfect Play?)
Message-ID: <220@tuck.nott-cs.UUCP>
Date: Tue, 25-Mar-86 17:12:45 EST
Article-I.D.: tuck.220
Posted: Tue Mar 25 17:12:45 1986
Date-Received: Sat, 29-Mar-86 15:55:22 EST
References: <912@whuxlm.UUCP>
Reply-To: anw@nott-cs.UUCP (Dr A. N. Walker)
Organization: Maths Department, University of Nottingham, ENGLAND.
Lines: 32

In article <912@whuxlm.UUCP> dim@whuxlm.UUCP writes:
>	1. Since there is no way we will ever be able to fully analyze
>	   chess, is it possible nonetheless to determine the PROBABILITY
>	   of BLACK having a forced win from the opening position?
>	   (The same goes for a forced DRAW or for a forced WHITE win.)
    ... If your move evaluation routine returned whatever it felt was some
	measure of this probability for leaf nodes, then of course these
	values could be backed up the tree.  It's doubtful whether the
	result would have any practical value, however.  I don't altogether
	share your pessimism about "no way ever ...";  there is no extant
	satisfactory calculation of how many positions we NEED to analyse--
	pruning can be very drastic once a position is a clear win, which
	soon happens if one side strays too far from the best moves.  Eg,
	if White is winning, only ONE move needs to be considered in each
	"White to move" position, and most games will be very short.  Some
	will be very long, but good use of transposition tables could make
	a huge improvement in the analysis.  The problem is a few orders of
	magnitude beyond present-day calculation, but "never" is rather a
	long time.

>	2. Can anyone find a symmetric position (like the opening position)
>	   where it is WHITE to move but BLACK has a forced win?  In
>	   other words, are there any symmetric zugzwangs for WHITE?
>	   (I'm sure there must be some real simple position...)
    ... The simplest mutual zugzwang is typified by W: Kf5,Pe4; B: Kd4,Pe5,
	which has a pleasing symmetry, but not the one you ask for.  The
	simplest such position is typified by W: Kg1,Pf6,Ph6; B: similar.

>					Dave McCooey
>					AT&T Bell Labs, Whippany
>					ihnp4!whuxlk!dim
			-- Andy Walker, Maths Dept, Nottingham Univ.