Author: Matthew Hull
Date: 13:52:47 12/10/03
Go up one level in this thread
On December 10, 2003 at 15:27:14, Robert Hyatt wrote: >On December 10, 2003 at 10:25:20, Bob Durrett wrote: > >>On December 10, 2003 at 10:07:07, Robert Hyatt wrote: >> >>>On December 10, 2003 at 09:41:18, Bob Durrett wrote: >>> >>>>On December 09, 2003 at 23:22:12, Robert Hyatt wrote: >>>> >>>>>On December 09, 2003 at 19:36:05, Bob Durrett wrote: >>>>> >>>>>>On December 09, 2003 at 13:21:35, Robert Hyatt wrote: >>>>>> >>>>>>>On December 09, 2003 at 13:02:56, Bob Durrett wrote: >>>>>>> >>>>>>>>On December 09, 2003 at 11:13:56, martin fierz wrote: >>>>>>>> >>>>>>>>>On December 09, 2003 at 10:50:23, Sune Fischer wrote: >>>>>>>>> >>>>>>>>>[snip] >>>>>>>>> >>>>>>>>>>If the bare engine had been playing he would have had to add a few things the >>>>>>>>>>GUI normally takes care of. >>>>>>>>>>For UCI engines it is expected that the GUI handles certain (trivial) things. >>>>>>>>> >>>>>>>>>claiming a draw on 3-fold repetition is *not* a trivial thing. there are >>>>>>>>>different possible cases: >>>>>>>>> >>>>>>>>>1) if your opponent avoids it, he loses >>>>>>>>>2) if your opponent avoids it, he wins >>>>>>>>> >>>>>>>>>in case 2) you should of course claim the draw, because perhaps he will notice >>>>>>>>>he could avoid it. in case 1) however, you can safely repeat the moves, and not >>>>>>>>>claim the draw. it is *not* mandatory to claim a draw on the 3rd repetition. so >>>>>>>>>you should basically not claim it if you might win if your opponent avoids the >>>>>>>>>draw. >>>>>>>>> >>>>>>>>>how do you expect a GUI to make the right decision? imagine the following >>>>>>>>>absurdity: jonny is running without GUI and happily repeats moves against >>>>>>>>>shredder, and does not claim the draw because the engine doesn't know about it. >>>>>>>>>shredder has a bug and allows a 3-fold repetition but will deviate before the >>>>>>>>>fourth repetition. now shredders GUI stops shredder from moving, and says "i >>>>>>>>>claim a draw with my move XY because of 3fold repetition" - this would have been >>>>>>>>>hilarious for everybody except SMK :-) >>>>>>>>> >>>>>>>>>since 3fold repetition is something you claim or don't claim based on the >>>>>>>>>current position, it is clearly something the GUI shouldn't be doing! >>>>>>>>> >>>>>>>>>cheers >>>>>>>>> martin >>>>>>>> >>>>>>>>THIS suggests the obvious changes which should be made to engines and GUIs ASAP >>>>>>>>by all chess programmers. >>>>>>>> >>>>>>>>Before an engine &/or GUI claims a draw, it should evaluate the position and >>>>>>>>determine whether or not it has a strong advantage. >>>>>>> >>>>>>>The engine already _does_ this. It searches every root move individually >>>>>>>and chooses the one that produces the best score. If you get a draw >>>>>>>score back, you can safely assume that no other move will give you a >>>>>>>"strong advantage" since the score of 0.00 was better than any other move. >>>>>>> >>>>>>>QED. It chose the drawing move, thinking a draw was the best outcome >>>>>>>possible in this particular position. >>>>>>> >>>>>>> >>>>>>>> If it does have a strong >>>>>>>>advantage, then claiming a draw would be precluded by the programmer. In other >>>>>>>>words, the software would be programmed in advance to make the sensible choice. >>>>>>> >>>>>>>Which it already does, as I explained. >>>>>>> >>>>>>> >>>>>>>> >>>>>>>>Similarly, the engine/GUI should be programmed to claim a draw by repetition in >>>>>>>>cases where repetition can be played and when also the engine evaluates the >>>>>>>>position as being a strong disadvantage. >>>>>>>> >>>>>>> >>>>>>>The engine will evaluate the position as 0.00 in the above case. >>>>>>> >>>>>>> >>>>>>> >>>>>>>>Obviously, humans avoid claiming repetition draws whenever they are winning and >>>>>>>>claim repetition draws whenever they can if they are losing otherwise. In >>>>>>>>positions perceived to be equal, humans may or may not claim the draw by >>>>>>>>repetition depending on other factors such as tournament standing. >>>>>>> >>>>>>>If you play a move that repeats for the third time. You can claim the >>>>>>>draw. Or your opponent can claim the draw immediately when it is his >>>>>>>move. Playing a repetition for the 3rd time and wishing your opponent >>>>>>>would not notice reminds me of "Grumpy old men". "You can wish in one >>>>>>>hand and crap in the other, and see which one fills up first." >>>>>>> >>>>>>>:) >>>>>>> >>>>>>>> >>>>>>>>Chess computers should be programmed similarly. >>>>>>>> >>>>>>>>Bob D. >>>>>> >>>>>>Bob Hyatt: I don't mean to be unkind, but perhaps you should read my bulletin >>>>>>again. >>>>>> >>>>>>Bob D. >>>>> >>>>>I also don't mean to be unkind, but must respond "why". Do you think I >>>>>missed something or misunderstood something? >>>>> >>>>>This nonsense about playing a 3-repeat move and hoping the opponent won't >>>>>see it is totally ridiculous in the context of alpha/beta searching that we >>>>>are all using. >>>> >>>>Another relevant thought: >>>> >>>>I have seen engines play a move [and display 0.00] which is obviously intended >>>>to give the opponent an opportunity to repeat the position a third time. Upon >>>>further extensive analysis, I have sometimes found that the engine's doing so >>>>was a terrible mistake. Two types of "terrible mistakes" can occur: >>>> >>>>(a) the engine could have played a much stronger move but didn't, or >>>>(b) the opponent engine does not repeat the position a third time but instead >>>>plays a much stronger move which could have been prevented. >>>> >>>>In my view, engines which make these mistakes have "bugs" in them, or simple >>>>programming errors. >>>> >>>>Bob D. >>> >>> >>>Let's define the context precisely here. I have seen what you describe. But >>>it is not a bug. Any more than an engine grabbing a pawn that later loses the >>>game is a bug. The context is "the engine search space". If this search >>>space says "repeating for a 3rd time to get a draw score is the best I can do" >>>then that is the best the engine can do, within its search horizon and search >>>space. That isn't a "bug". It is a "shortcoming" of insufficient depth or >>>knowledge. As a human have you ever played a move that you later discovered >>>was bad? Was that a "bug" in your neurons, or just a lack of search or >>>understanding? >> >>Only a computer programmer can define the word "bug." : ) >> >>Bob D. > >Actually I believe Grace Hopper originally defined it. :) > >A moth in a relay. :) We had a possum get fried in an electrical power breaker box, taking down the entire datacenter. Stank horribly, too.
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