Author: Robert Hyatt
Date: 13:07:32 06/12/01
Go up one level in this thread
On June 12, 2001 at 09:16:58, José Carlos wrote: >On June 12, 2001 at 08:50:15, Robert Hyatt wrote: > >>On June 12, 2001 at 06:00:44, David Rasmussen wrote: >> >>>On June 11, 2001 at 20:48:19, Robert Hyatt wrote: >>> >>>>On June 11, 2001 at 14:17:37, David Rasmussen wrote: >>>> >>>>>Am I an idiot, or does that Crafty book scheme miss some transpositions, because >>>>>of it's clustering system? Wait, those two statements aren't mutually >>>>>exclusive... >>>>> >>>>>When some of the upper bits of the book hashkey, is from the parent position, >>>>>doesn't that mean that if I'm in an unknown position, that can make a move that >>>>>transposes into a book position, it won't, because the upper bits will only >>>>>match the actual parent position(s) from when the book was created? >>>>> >>>>>I'm having an idea of another book implementation that I think is quite smart, >>>>>but I won't reveal anything yet, primarily because I don't know if it works in >>>>>practice, secondarily because it might not be a new idea, tertiarily because it >>>>>might not be a smart idea at all :) >>>> >>>> >>>>I _intentionally_ want to miss those transpositions. One classic: >>>> >>>>1. e4 e5 Nf3 a6 Bb5. Do you _really_ want to transpose back into the book >>>>and play Nc6? Or do you want to rip the bishop and be a piece up in a won >>>>game? >>>> >>>>:) >>>> >>>>My thinking when I did this scheme was "Crafty will probably play Nc6 if it >>>>is reasonable, and _then_ we will transpose back into book after white plays >>>>Ba4, because that is a normal position. But the position given above is >>>>"not normal" and I won't try to transpose. >>>> >>>>It has happened in _real_ games in the past. But it won't happen to me >>>>here. :) >>> >>>But still, you're saying: "I'm afraid of that situationm so I won't do _any_ >>>transpositions from non-book positions to book positions", which is not as nice >>>as being able to do it from everywhere, while still taking care of the problem >>>you mention. I don't have a solution for this, but don't you think a solution >>>with those properties would be nicer? >> >> >>I don't see how it is possible. I can currently transpose from any known book >>line to any other known book line, with zero difficulty. The only requirement >>is that the position before I make a move must be a known book position, and the >>position after I make a move must be one also. >> >>Allowing others (ie full transpositions) is dangerous due to the given position >>where Nc6 is book _and_ BAD. > > If you allow transpostion from non-book positions, you can get the behavour >you discribed. But if you don't, you have to face the possibility of a human >player transposing to drive you into a trick. > I'm at work, so I can't figure a real example, but imagine that, in the >example you gave, axb5 was wrong due to a deep trick. A smart GM could drive you >into that position, and the Crafty would (possibly) take the bishop happily. > So, the way you do things, you'll take the piece and win easily most of the >times, but can fall into a trick, and lose badly in an important game. > Allowing trasposing always, you'll miss those easy wins (but you'll probably >win anyway, since a player that gives a bishop for free will always lose against >Crafty) but avoid the GM trick. > Of course, your cluster stuff is very good from a programming point of view. > > José C. I don't worry so much about the "tricks". What I do worry about is a good GM making a clever transposition into an opening that I don't like. IE if he can bypass my "don't play stonewall" opening moves, and keep crafty in book, then it will happily play down the stonewall lines. But if it drops out of book for a minute, it will _never_ voluntarily walk into a possible stonewall opening. That is one of several reasons why I do it like I do...
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