Author: Robert Hyatt
Date: 19:26:06 05/04/00
Go up one level in this thread
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
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