Author: José Carlos
Date: 06:16:58 06/12/01
Go up one level in this thread
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.
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