Author: Vincent Diepeveen
Date: 08:01:23 07/16/02
Go up one level in this thread
On July 15, 2002 at 13:11:09, Christophe Theron wrote: >On July 15, 2002 at 08:37:34, Omid David wrote: > >>I don't think using double null-move is a good idea in practice, since in >>midgame the chance of zugzwang is negligible and thus it's superfluous (I doubt >>if even DIEP uses it). However the contribution of double null-move is that it >>gives legitimacy to the null-move pruning idea, proving that it _is_ a correct >>search method (anyway, no one doubts null-move nowadays). > > > >Why does double null move prove that null move is a correct search method???? > >Doing two null moves in a row means going back to standard search (a search not >involving an illegal move like null move is). > >I fail to see how it legitimates null move. Double nullmove legitimates (duh can't you use easier to spell words) itself, for the obvious reason that it is provable now that a search depth of n ply, where i may pick n, is going to solve any problem you give it. Normal nullmove, if you remember the discussions a few years ago, especially around 98 and 99, it was told to be an inferior way of search, because for *any* selfpicked depth n for the nullmove search it could conclude less than a small outdated fullwidth search, so was the theory. This is not true of course. Reality is that only a few problems need a bit bigger search depth with double nullmove, and most are far endgames. In middlegame it's very seldom one needs 3 ply more than a fullwidth search would get. Note that getting a fullwidth search of more than 12 ply is impossible whereas most get 14-15 ply with nullmove nowadays easily in tournament practice. DIEP's probably only exception here, it needs a supercomputer to get that depth ;) > > > Christophe
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