Author: Robert Hyatt
Date: 07:10:07 07/07/02
Go up one level in this thread
On July 07, 2002 at 01:44:27, Uri Blass wrote: >On July 06, 2002 at 23:31:15, Robert Hyatt wrote: > >>On July 06, 2002 at 18:48:07, Uri Blass wrote: >> >>>On July 06, 2002 at 17:19:21, Robert Hyatt wrote: >>><snipped> >>>> >>>>OK... first, me, in Cray Blitz. 1994. GCP modified Crafty and used the >>>>Hsu-definition of SE in doing so. >>> >>>And what was the result? >> >>It was tactically significantly stronger with than without. Unfortunately >>we had a severe bug in 1994 and did poorly. Harry had limited the max >>search depth to 64 plies to match the older cray vector length (newer machines >>had 128 word vectors but he wanted it to run on older machines too since he >>had access to several of them). He also took out the MAXPLY check. And it >>never caused a problem thru 1993 as the search extensions were pretty "sane" >>and didn't go that deep. But in a few cases in 1994, singular extensions >>drove the search beyond 64 plies with devastating effect on the chess board >>and the alpha/beta scores backed up as a result. We never had a chance to play >>real games to see how deep the SE stuff could extend, which was a common problem >>with cray access back then... >> >>Crafty I am not sure about yet. Mike Byrne has been playing with this >>further and seems to like the results he is getting. I have not yet looked >>at the changes he is using, but I will when I have time. It does seem to be >>very good tactically, producing some good WAC test scores in very short time >>limits. >> >>> >>>Is the new crafty with singular extensions better? >>>I guess it is worse because you do not use it in games. >> >>I never found something I like. However, I am not sure that aggressive >>null-move mixes well with cute extensions. They almost work against each >>other without some controls to limit this interaction... >> >> >> >> >>> >>> >>><snipped> >>>>>There are programmers who use singular extensions but I know about no programmer >>>>>of one of the top programs of today that use it in the way that they use it. >>>> >>>> >>>>So? They choose to implement a less-than-optimal version to control the >>>>computational cost. >>> >>>Deep thought already used singular extensions in the past and the top programs >>>of today that search similiar number of nodes do not use them in the same way >>>because they prefer to play better and not to use "optimal" extensions. >> >>How can you possibly say "play better"? The current SE approach used in Ferret, >>and the way I did it originally for Crafty, is simply a 'cheapo version" that >>misses things that deep thought would not miss, extension wise. But the cost >>was more palatable for the much slower hardware we have to use. However, HiTech >>used it at 150K nodes per second, so it worked for them. And it worked fine in >>Cray Blitz as well... > >You always give examples that are not about the default version of the top >programs of today(Cray Blitz or Hitech are history and Crafty does not use the >GCP version because you did not like the result). > >It is possible that some people believed that it is better and did not have time >to compare results with and without it. > >I want example of one of the top programs of today that use it and not some GCP >version of Crafty that is not the best crafty. Wchess from Dave Kittinger. Implemented 1/2 of Hsu's algorithm, namely the PV-singular test. > >My point is that if the algorithms that they used in deep thought are not >inferior then it is logical to expect one of the top programs of today to use >them(they already search similiar number of nodes). The "singular extension algorithm" is precisely defined. At any node in the tree, you simply prove that one move is better than all other moves by a window "S". This is very precise. What Bruce does, and what I tried, was a very limited sub-set of that. It was not as accurate as a proper implementation. It was also not as expensive. But the main point is that it was not as accurate. > >If the algorithm helps to find some tactics and miss other things that are more >important in games and not in test positions because of smaller depth then the >algorithm is inferior. > >Uri They tested SE enough to _prove_ that it didn't hurt, if you read their paper.
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