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Observator bias or...
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Eelco de Groot



Joined: 12 Mar 2006
Posts: 2595
Location: Groningen
PostPost subject: Re: Observator bias or...    Posted: Sat Jun 02, 2007 11:15 pm Reply to topic Reply with quote
hgm wrote:
Alessandro Scotti wrote:
I remember since testing with Kiwi that results with 100 games are very unreliable. It sometimes happen that a version gets a bad start but gets better at the end of the long test. On the other hand, I had a version reach 64% after 100 games and finish with a disappointing 50% after 720 games... I will now increase the number to 800 and see if that brings some benefits (not much is expected though).

64% after 100 games between approximately equal engines is extreme: the standard error over 100 games should be 0.4/sqrt(100) = 4%, so a 14% deviation represents 3.5 sigma. This should happen on the average only 1 in ~4000 tries.

I noted a very strange effect when I was testing uMax in self play. The standard error over 100 games should be 4%, but when I played 1000 games between the same versions, and looked at the scores of the ten individual 100-game runs, these results deviated on the average much more from each other (and the final average result) than you would expect from the calculated standard error. This can only happen if the games are not independent! I can indeed not exclude this, as all the games were played in a single run, and were using the random seed the previous game ended with. So with a bad randomizer, if a single game repeats due to an equal or very close seed at the start of the game, it might imply that the following game repeats as well, destroying the independence of the game.

Whatever the cause, the effect was that the error in the win percentage was always a lot larger than you would expect based on the number of games.


Hello Harm,

Sorry if I interpret all this wrong, but is it not more likely that this interdependance you saw of games played shortly after or before another game, has to do with assigning resources by the operating system to the different processes? (I mean, rather than with your random seed generator?) At any one time Windows for instance here has to shift memory and CPU time to on average thirty processes on my PC and this can never be handled perfectly in such a way that two chess programs would get completely equal resources.

I'm no Windows expert at all, but, even if you unload and reload the two chessprograms after every game I would think it is possible that this could make matters even worse, if, in the worst case scenario, clearing up memory and terminating process is not done without leaving any traces.

In Ed's case I suppose he would prefer to test everything under DOS but as this was about Chessbase matches I suspect it was all done under Windows? Rebel never ran perfect under Windows, so I would expect some imperfect assigning memory and time could very well have occured because of Windows imperfections, and not because of Chessbase bugs.

Maybe certain chessprograms are more susceptible than others, and not clearing up used memory etc. could degrade match results for certain programs more than for others in the long run?

Well, that would just be my first guess as one possible cause of what could have happened?

Regards, Eelco
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Subject Author Date/Time
Observator bias or... Alessandro Scotti Tue May 29, 2007 6:25 pm
      Re: Observator bias or... Dann Corbit Tue May 29, 2007 6:33 pm
      Re: Observator bias or... ed Tue May 29, 2007 6:59 pm
            Re: Observator bias or... H.G.Muller Wed May 30, 2007 9:43 am
                  Re: Observator bias or... ed Wed May 30, 2007 3:02 pm
                        Re: Observator bias or... cwb Wed May 30, 2007 4:48 pm
                        Re: Observator bias or... Peter Fendrich Wed May 30, 2007 6:36 pm
                        Re: Observator bias or... Robert Hyatt Sun Jun 10, 2007 3:30 pm
      Re: Observator bias or... Uri Blass Wed May 30, 2007 10:17 am
            Re: Observator bias or... Alessandro Scotti Wed May 30, 2007 12:35 pm
                  Re: Observator bias or... Robert Hyatt Sat Jun 02, 2007 6:41 am
                        Re: Observator bias or... H.G.Muller Sat Jun 02, 2007 10:18 am
                              Re: Observator bias or... Robert Hyatt Sun Jun 03, 2007 12:54 am
                                    Re: Observator bias or... Uri Blass Sun Jun 03, 2007 5:44 am
                                          Re: Observator bias or... Robert Hyatt Sun Jun 03, 2007 8:34 pm
                                                Re: Observator bias or... H.G.Muller Mon Jun 04, 2007 9:52 am
                                                      Re: Observator bias or... Robert Hyatt Mon Jun 04, 2007 6:58 pm
                                                            Re: Observator bias or... H.G.Muller Tue Jun 05, 2007 2:24 pm
                                                                  Re: Observator bias or... Robert Hyatt Wed Jun 06, 2007 1:31 am
                                                                        Re: Observator bias or... Uri Blass Wed Jun 06, 2007 6:42 am
                                                                              Re: Observator bias or... Robert Hyatt Thu Jun 07, 2007 2:18 am
                                                                        Re: Observator bias or... H.G.Muller Thu Jun 07, 2007 2:20 pm
                                                                              Re: Observator bias or... Robert Hyatt Fri Jun 08, 2007 3:31 am
                                                                                    time for some real data Robert Hyatt Fri Jun 08, 2007 4:02 pm
                                                                                          Re: time for some real data H.G.Muller Fri Jun 08, 2007 4:51 pm
                                                                                          Re: time for some real data Robert Hyatt Sat Jun 09, 2007 1:43 am
                                    Re: Observator bias or... H.G.Muller Fri Jun 08, 2007 9:40 am
                                          Re: Observator bias or... Robert Hyatt Sun Jun 10, 2007 2:24 am
                              Re: Observator bias or... Charles Roberson Wed Jun 06, 2007 2:44 am
                                    Re: Observator bias or... Uri Blass Wed Jun 06, 2007 6:46 am
      Re: Observator bias or... Ron Murawski Wed May 30, 2007 8:26 pm
            Re: Observator bias or... Alessandro Scotti Wed May 30, 2007 8:31 pm
                  Re: Observator bias or... ed Wed May 30, 2007 11:50 pm
                        Re: Observator bias or... Dann Corbit Thu May 31, 2007 12:19 am
                              Re: Observator bias or... Dann Corbit Thu May 31, 2007 12:33 am
                                    Re: Observator bias or... Dann Corbit Thu May 31, 2007 12:40 am
                                          Re: Observator bias or... ed Thu May 31, 2007 9:40 am
                  Re: Observator bias or... H.G.Muller Thu May 31, 2007 11:02 am
                        Re: Observator bias or... Tony Thu May 31, 2007 12:04 pm
                              Re: Observator bias or... Uri Blass Thu May 31, 2007 12:51 pm
                                    Re: Observator bias or... Tony Thu May 31, 2007 12:55 pm
                        Re: Observator bias or... Alessandro Scotti Thu May 31, 2007 12:56 pm
                        Re: Observator bias or... Robert Hyatt Sat Jun 02, 2007 6:37 am
                        Re: Observator bias or... Eelco de Groot Sat Jun 02, 2007 11:15 pm
      Re: Observator bias or... Michael Sherwin Sun Jun 03, 2007 6:29 am
            Re: Observator bias or... Uri Blass Sun Jun 03, 2007 8:11 am
                  Re: Observator bias or... Eelco de Groot Sun Jun 03, 2007 9:07 am
                        Re: Observator bias or... Uri Blass Sun Jun 03, 2007 9:39 am
                        Re: Observator bias or... H.G.Muller Sun Jun 03, 2007 9:47 am
            Re: Observator bias or... Alessandro Scotti Sun Jun 03, 2007 8:36 am
                  Re: Observator bias or... Ron Murawski Sun Jun 03, 2007 5:50 pm
      Re: Observator bias or... MartinBryant Sun Jun 03, 2007 9:07 am
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