Author: blass uri
Date: 22:53:48 05/23/00
Go up one level in this thread
On May 24, 2000 at 00:17:35, Robert Hyatt wrote: >On May 23, 2000 at 22:54:45, Peter Kappler wrote: > >>On May 23, 2000 at 21:30:26, Dann Corbit wrote: >> >>>On May 23, 2000 at 18:24:21, Mark Young wrote: >>>[snip] >>>>Lets be generous and say a ply is worth 100 rating points, and we can take Fritz >>>>6a for an example. Now you said it does not matter if it?s the 1st going to 2 or >>>>14 ply going to 15 ply. Its pretty much the same, if I understand you >>>>correctly. Lets assume Fritz 6a plays at a 2500 rating +/- 100 rating points, >>>>with a average middle games search depth of 15 plies. >>>> >>>>15ply X 100 rating points = 1500 rating. Where are the extra 1000 rating points >>>>coming from? Is Fritz really rated 1500, or are some plies worth much more the >>>>others. >>>> >>>>It is clear that the early plies are worth much more the later plies, and if you >>>>plot it out it?s a curve. I don't know of one program that does not exhibit a >>>>curve. >>> >>>That is well established, as both Dr. Hyatt's and Dr. Heinz's experiments >>>showed. However, as the depths increased, two very surprising things surfaced. >>> >>>At extreme depths, a linear model fits just as well as an exponential one. >>>Hence, there may (or may not be) additional loss in the value of additional >>>plies. >>> >>>Far more surprisingly (to me at least) is that the number of fresh ideas do not >>>drop off. IOW, if the program liked one move at ply 10, and another at ply 11, >>>and yet another completely different one at ply 12, they can just keep coming up >>>with new moves that have not been considered best at deeper plies. This one is >>>(to me at least) both astonishing and counter-intuitive. Obviously, it can't >>>possibly find more fresh ideas than the number of possible moves! >>> >> >>I need to go back and re-read the "Crafty/Dark Thought Go Deep" articles. >> >>I hope that "new best moves" were only counted if the evaluation also changed >>significantly. If the change was just a few centipawns, then I think it's >>misleading to report the new move as "better". > >Why would you want to call such moves "not better"??? _many_ moves made by >today's engines are just "slightly" better than other moves that would be >made at shorter time limits. But either you believe that .01 is better, or >you have to ignore evaluations completely. > > > >> >>This stuff interests me, because I fundamentally believe that playing strength >>must diminish with each additional ply. This topic was discussed a couple of >>months ago, and I was surprised that many people here don't agree. >> > > >The problem is that the only "old" evidence was self-play with varied depth. >Which is probably not a good test, since small changes are often magnified in >self-test play, while at other times small changes have no effect at all. > >New evidence suggests that at least thru 15-16 plies, things are still picking >up with each additional ply... > >Which you believe is up to you... > >Neither is exactly overwhelming evidence... > >DB did make a statement however, with its 17 ply searches. DT at 10-12 plies >got destroyed by Kasparov. DB at 15-18 plies played far differently. We cannot learn much from comparison between deep thought and deep blue because they had not the same evaluation function and deep thought had search problems and could not detect repetitions in the search. Uri
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