Author: Robert Hyatt
Date: 14:12:34 01/28/01
Go up one level in this thread
On January 28, 2001 at 12:57:30, guy haworth wrote: > >Eugene's EGTs are best in real-time because: > 1) they cover wtm and btm > 2) physical file-compression and front-end caching have been used > 3) the indexes are more compact because 'unblockable checks' are avoided > >See ICGA_J v23.3 last year. I don't believe that significant improvements can >be made just by taking these ideas further. There are ideas for reducing the >index-size of (e.g.) KQR... and KQP.... EGTs but they only save a few %. > >It would seem better to preface the Nalimov/Thompson EGTs with a values-only >EGT, two bits per position (1-0, draw, 0-1 and 'broken') so that it is not >necessary to go to the disc to find out the 'depth' of moves that reduce the >theoretical value of the position. > >Peter Karrer has revisited ideas first demonstrated by Thompson (KQPKQ, KRPKR) >and Schaeffer (checkers) whereby positions with the same P-positions form a >contiguous sub-EGT of the EGT. Thompson also separated positions with different >patterns of Bishop-square-colours. > > >The best way to get compression would seem to be to preface the EGTs of 'ground >data' with some higher-level rules, avoiding the need to keep data about >positions that can be dealt with by the rules. Do you realize how big that would be? the 3/4/5 piece files use 8 bit scores. If you cut that to 2 bits as you suggest, you _still_ need 2 gigs of memory to hold them. I/O is going to happen no matter what you do... > >A trivial example would seem to be: > "In KQQQQK, sacrifice Queens until it is KQK provided that ...." > [What point is there in computing this EGT?] > >Christoph Wirth and Ernst Heinz have both, independently, done some work on >pragmatic rules that may not play optimally and may not even win every >half-point ... but DO shrink the EGT-size bigtime. > >By surveying databases of games, you can see which endgames are most likely to >come up. Some 6-man pawnless 3-3 endgames have never featured on these >databases. > >G > > > > > >The set of available EGTs can be slightly improved by using other metrics than >DTM. Minimaxing DTC instead of DTM, DTZ instead of DTC (and sometimes, oddly, >DTC instead of DTZ, and DTM instead of DTC) can avoid a 50-move draw. > >See some examples of mine in ICGA v23.2 last year. > >The guaranteed way to avoid a 50-m draw-claim is to use (what I call) the DTR >metric ... 'Distance by The Rule' ... which minimises the length of the longest >phase in the subsequent game. It is used in conjunction with the DTZ table.
This page took 0.01 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.