Author: Frank Schneider
Date: 21:46:19 07/21/02
Go up one level in this thread
Thanks, cool experiment. Frank On July 21, 2002 at 21:16:37, Mike S. wrote: >What is the value of having the advantage of the two bishops? Can it be >expressed in figures, i.e. evaluations, or as an %-impact on the performance >percentage? > > >The previous experiment: > >In an old and quite large experiment I did in 1996, I let play chess programs >against themselves from 8 special starting positions, where only one side had >the bishop pair, each (i.e. without Nb1, Bc8 etc.). To avoid having rating >bonuses still included in the evaluation, I waited until one of the two bishops >had disappeared, so I could read a kind of "real rating gain" which the 2 >bishops achieved, as the programs evaluated it. > >The average "rating success" so to speak, of the 2 bishops was > >+0.46 pawns (1996) >----------- > >with white and also with black (IOW, there was no advantage of the first move >visible). These games were not finished. > > >New approach: > >Meanwhile, GUIs were much improved. For a new two bishops experiment, I used the >same old 8 starting positions (EPD see below), but let play more games, and >engines against each other (not against themselves). Also, I decided to use only >final results for the statistics, no evaluations. > >5 engines played each of the 8 positions twice (w/b) against each of the 4 >opponents, which results in 160 games total. > >Results: W /D /L % (from the 2 bishop's viewpoint!) >---------------------------------------- >White with the 2 bishops: 38/20/22 60,0% >Black with the 2 bishops: 29/19/32 48,1% -> advantage of first move visible! >---------------------------------------- > 2 bishops total: 67/39/54 54,1% > >Based on the previous experiment (and on other experiments without opening >theory), I thought the advantage of the first move would only matter in computer >chess, when opening books or theory positions are used. Without books no white >advantage was visible to me, so far. This seems to have changed. The results >above indicate an advantage for the first move of ~ +6% compared to a >theoretical 50% result. It can also be expressed by the w/b points ratio which >was 89,5:70,5 = 1,27:1 (or ~56:44) > >For comparison: In human games (2400+ elo), White scores ~55,2% according to my >database. Chess programs score similar; I got 54,0% and 55,7% for White, from >two large comp-comp databases which are partially identical (a few comp-human >games are included). The main difference is the number of drawn games btw., >which is ~51% among strong humans, but only ~24%...25% among computers. > >The 2 bishops fought with White and with Black, in 80 games each. > >Main result: > >Having the 2 Bishops Advantage during the experiment, led to a score plus of > >~ +4 %, or 86,5:73,5 points = 1,177:1 (or ~54:46) >------ > >The figures varied comparing the engines: Hiarcs 7.32 - seemingly* - showed the >strongest impact of the 2 bishops (17:12 points), while Junior 5 scored 11,0 >with, and 11,5 without the bishop pair. > >*) The results inavoidably are a mixture of (A) having the 2 bishops or not, (B) >having the first move or not, and (C) the strength relation between the >opponents. (A) and (B) were separated, see above. (C) shouldn't be a problem >because full round robins were played. - But more important to consider is: The >2 bishops were the only difference at the start, but probably many games were >decided by other factors. For example, in a few games I watched live, the bishop >pair disappeared soon and/or the adavantage seemd to change several times from >one side to the other. > > >Addendum: >--------- > >Start positions, i.e. to use in opening databases for engine matches: > >rn1qkbnr/pppppppp/8/8/8/8/PPPPPPPP/R1BQKBNR w KQkq - 0 1 >rnbqk1nr/pppppppp/8/8/8/8/PPPPPPPP/R1BQKBNR w KQkq - 0 1 >rn1qkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKB1R w KQkq - 0 1 >rnbqk1nr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKB1R w KQkq - 0 1 >r1bqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RN1QKBNR w KQkq - 0 1 >rnbqkb1r/pppppppp/8/8/8/8/PPPPPPPP/RN1QKBNR w KQkq - 0 1 >r1bqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQK1NR w KQkq - 0 1 >rnbqkb1r/pppppppp/8/8/8/8/PPPPPPPP/RNBQK1NR w KQkq - 0 1 > > >Program's total scores: > >1 Chess Tiger 14.0 42.0/64 >2 Fritz 7 41.0/64 >3 Hiarcs 7.32 29.0/64 >4 Shredder 5.32 25.5/64 >5 Junior 5.0 22.5/64 > > >Regards, >M.Scheidl
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