Author: Graham Laight
Date: 03:32:00 07/16/00
Go up one level in this thread
On July 16, 2000 at 03:34:45, Ed Schröder wrote: >Right. > >A few months ago Christophe posted some interesting stuff here regarding >this topic and nobody really was in agreement with him (me included) until >I did an experiment which worked as an eye opener for me. The story is not >funny and goes like this... > >In Rebel Century's Personalities you have the option [Strength of Play=100] >The value may vary from 1 to 100 and 100 is (of course) the default value. > >Lowering this value will cause Rebel to lower its NPS. This opens the >possibility to create (100% equal!) engines with as only difference >they run SLOWER. > >I was interested to know HOW MANY games it was needed to show that a 10% >faster version could beat a 10% slower version and with which numbers. So >I created two personalities: > >FAST.ENG (default settings) [Strength of Play=100] >SLOW.ENG (default settings) [Strength of Play=80] > >and started to play 600 eng-eng games with Rebel's build-in autoplayer >with pre-defined fixed opening lines both engines had to play with white >and black. > >The personality with as only change [Strength of Play=80] caused Rebel to >slow down with exactly 10% on the machine the marathon match took place. >Note that this value (80) may differ on other PC's in case you want to do >similar experiments. > >Here are the results of the 600 games played between the FAST and SLOW >personalities. The first 300 games were played on a time control of "5 >seconds average". The second 300 games were played on a time control of >"10 seconds average". > >FAST - SLOW 162.5 - 137.5 [ 0:05 ] >FAST - SLOW 147.0 - 153.0 [ 0:10 ] > >The first match of 300 games at 5-secs looks convincing. A 54.1% score >because of the 10% more speed seems a value one might expect. > >But what the crazy result of match-2? Apparently after 300 games it is >still not enough to proof that the 10% faster version is superior (of >course it is) but the match score indicates both versions are equal >which is not true. > >So how many games are needed to proof that version X is better than Y? > >I am sure I am trying to reinvent the wheel. The casino guys who make >themselves a good living (with red and black) have figured it all out >centuries ago. Perhaps there is a FAQ somewhere on Internet that >explains how many times you have to turn the wheel to get an exact >50.0% division between red and black. 1000? 2000? > >To answer this question I wrote a little program that randomly emulates >chess matches. It shows that 100 games is nothing, too often scores like >60-40 appear on the screen. 500 games (and higher) seems to do well as >most of the time match scores fall within the 49.0 - 51.0 area. > >The bad news (in any case for me) is that it hardly makes any sense to >test candidate program improvements using (even) long matches. Back to >common sense: 10% = 10% = better. Oh well... > >Ed I remember from doing a statistics ancillary in my computing degree that there is a distribution (not "normal" distribution) for calculating binary event result probabilities - but I can't remember what it is called. However, I have myself written programs to simulate these outcomes, and my observation is that if you do 10x as many simulations, your accuracy level increases by one decimal place. -g
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