Author: Robert Hyatt
Date: 07:06:28 05/04/00
Go up one level in this thread
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.
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