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Subject: Re: Question about Tablebases, Namilov's Paper

Author: GuyHaworth

Date: 11:19:22 12/31/03

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Maybe Eugene's e-address is to be found via one of his contributions to CCC.


The paper was I suspect a Nalimov/H/Heinz collaboration based on a presentation
by Ernst Heinz at ACG-9 (2000), and the result of a subsequent reworking by
Eugene and myself.

Certainly, EN's index to an EGT is a set of sub-indexes, one for each legal
Kk-position.  There are 462 anticipating no Ps and 1806 anticipating Ps.

Eugene then prevents stm pieces giving an unblockable check to the sntm-King,
though other checks will subsequently render the position 'broken' by virtue of
being 'clearly illegal'.  Thus, the subranges-size is KK-position-specific.

There is no general algorithm for avoiding all positions with sntm in check, and
therefore there is major 'waste' in the index in some endgames:  this seems to
increase with number of men on the board, so any impovement on this would be
welcome.

A downside of EN's index-function is that an inverse-index function, as would be
needed for the Wu/Beal fully-retro EGT-generation algorithm, involves
integer-division rather than 'division' by 64.  This has performance
implications for a method combining the Wu/Beal algorithm and Nalimov indexing.

g



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