Author: Steve Coladonato
Date: 06:03:28 05/05/00
Go up one level in this thread
On May 04, 2000 at 22:26:06, Robert Hyatt wrote: >On May 04, 2000 at 10:31:39, Steve Coladonato wrote: > >>On May 04, 2000 at 10:06:28, Robert Hyatt wrote: >> >>>On May 04, 2000 at 08:13:51, Steve Coladonato wrote: >>> >>>>On May 03, 2000 at 18:26:09, Robert Hyatt wrote: >>>> >>>>>On May 03, 2000 at 12:52:01, Steve Coladonato wrote: >>>>> >>>>>>On May 03, 2000 at 10:38:57, blass uri wrote: >>>>>> >>>>>>>On May 03, 2000 at 09:41:19, Steve Coladonato wrote: >>>>>>> >>>>>>>>On May 03, 2000 at 03:29:48, Jouni Uski wrote: >>>>>>>> >>>>>>>>>On May 02, 2000 at 13:03:47, Steve Coladonato wrote: >>>>>>>>> >>>>>>>>>>There is a correspondence match going on between Steve Ham and both Fritz 6(a) >>>>>>>>>>and Nimzo 7.32. The games are documented at the following site: >>>>>>>>>> >>>>>>>>>>http://correspondencechess.com/campbell/index.htm >>>>>>>>>> >>>>>>>>>>They appear to be quite interesting and the analysis by Mr. Ham is very >>>>>>>>>>extensive. It's interesting that even after 19-21 hrs of evaluation, the >>>>>>>>>>computers are only getting to 15-16 ply. Also, it looks like Mr. Ham has the >>>>>>>>>>upper hand in the games. >>>>>>>>>> >>>>>>>>>>Regards. >>>>>>>>>> >>>>>>>>>>Steve >>>>>>>>> >>>>>>>>>I am not so sure if Ham has upper hand. And note, that most moves were played in >>>>>>>>>3-best move mode! >>>>>>>>> >>>>>>>>>Jouni >>>>>>>> >>>>>>>>Jouni, >>>>>>>> >>>>>>>>What is "3-best move mode"? >>>>>>> >>>>>>>Chessbase engines can search the 3 best move instead of only searching for the >>>>>>>best move. >>>>>>> >>>>>>>They did it in the beginning of the game and probably they could search more >>>>>>>deep by searching only for the best move. >>>>>>> >>>>>>>searching for 3 best moves instead of only the best move is about the same as >>>>>>>being 2-3 times slower. >>>>>>> >>>>>>>Even if we do not assume diminishing return from being 2-3 times faster >>>>>>>the demage for programs in this case is not more than 100 elo and if we consider >>>>>>>also the fact that the programs did it only in the opening the demage is >>>>>>>probably less than 50 elo so it will probably not change the reuslt of the match >>>>>>>because the expected changed in the result is less than 0.25 point >>>>>>> >>>>>>>Uri >>>>>> >>>>>>Uri, >>>>>> >>>>>>When a computer engine evaluates a position, does it not take all the possible >>>>>>moves and compute an evaluation for each move? In this case the three "highest" >>>>>>scores would be the top three and there is really no effect on the processing. >>>>>>I understand that variations within a given move are also calculated but is this >>>>>>not just normal processing? >>>>>> >>>>>>Steve >>>>> >>>>> >>>>>no. Alpha/beta finds the best move and only proves that the other moves are >>>>>worse, without proving how much worse they are. To do this requires a lot more >>>>>time. >>>> >>>>You have both given me essentially the same answer. I've never looked at the >>>>code for a chess engine so I don't know exactly what Alpha/Beta does. But the >>>>answers here are confusing to me. I was under the impression that the best move >>>>was determined by calculating the eval for the candidate moves. Your answers >>>>are implying that that is incorrect and something else is used to determine the >>>>best move, not the eval for the position. But if that is the case, is not what >>>>the program calculates somehow related to the eval? And if so, saving the >>>>result in an array would not incur that much more overhead so that the program >>>>would know what the top three moves are or rather the order of all candidate >>>>moves based on whatever it is calculating. >>>> >>>>Steve >>> >>> >>>Here is the idea: >>> >>>You have three holes in the wall. Your task is this: "stick your hand in >>>each hole, for exactly one minute, and then report which one gave you the >>>most pleasant (or least unpleasant) experience." >>> >>>You stick your hand in hole #1. For one minute, you get nothing but warm >>>water. You stick your hand in hole #1. You are instantly greeted by very >>>hot water. This is already more unpleasant than holee #1. Do you wait around >>>to see if it gets to the boiling point or do you leave _right now_. I leave >>>now, as I have already proved that it is worse than #1. I don't know how much >>>worse yet (to discover this I have to wait for the full minute). I go on to >>>hole #3 and immediately get doused by salt-water at about 30 degrees F. That >>>is very cold and much worse than hole number one. Do I stick around to see if >>>it gets worse, or do I quit not? >>> >>>Total time spent = 1 minute in hole 1, 1 sec in hole 2, one sec in hole 3. I >>>only proved that 2 and 3 were worse, but not how much worse. >>> >>>That is how alpha/beta works. >> >>That makes sense. But let's start with hole #2 first. So now I stick my hand >>in, get doused with very hot water but hang around for a minute. Now I go to >>hole #1 and get greeted with warm water. Nice. So now the best move is hole #1 >>not hole #2. But do I hang around in hole #1 for a while or immediately move on >>to check hole #3. And what about that shark that's about ready to snatch off my >>hand should I dally a bit longer in hole #1. >> >>It seems like the best move is determined by a very superficial ply movement >>once something is deemed to be best. But maybe the best move is actually that >>knight sac (very cold water) that is rewarded 6 ply later. >> >>Of course I can't argue with success. Am I correct in now believing that ply >>depth has nothing to do with best move? >> >>Steve > > >You fell for my trap. :) > >_now_ you see why move ordering is so critical for good alpha/beta performance. >If you start with the worst hole, and then the next-worst one, and finally the >best one, you spend 3 minutes... > >If you start with the best, you spend about 62 seconds. > >Moral of the story? Pick the best hole (or move) first, as often as you >can. Hence the idea of winning captures, hash move, killer moves, etc. > >Bob Thanks Bob. Because of this post I found a site that seems to have some good information about the algorithms that are used in chess software. http://www.xs4all.nl/~verhelst/chess/programming.html I'll be checking this site out before I delve into this area chess engines again. Steve
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