Author: Robert Hyatt
Date: 12:27:14 12/10/03
Go up one level in this thread
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. :)
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