Author: Robert Hyatt
Date: 14:43:44 09/11/01
Go up one level in this thread
On September 11, 2001 at 17:12:16, Bruce Moreland wrote: >On September 11, 2001 at 15:04:28, Robert Hyatt wrote: > >>On September 11, 2001 at 12:54:32, Bruce Moreland wrote: >> >>>On September 11, 2001 at 11:40:22, Rafael Andrist wrote: >>> >>>>On September 11, 2001 at 10:36:00, Robert Hyatt wrote: >>>> >>>>>On September 10, 2001 at 13:37:58, Rafael Andrist wrote: >>>>> >>>>>>On September 07, 2001 at 13:41:57, Robert Hyatt wrote: >>>>>> >>>>>>>I did this in Cray Blitz _many_ years ago (coordinated squares is the term I >>>>>>>hear used most often). And I was amazed that it took longer to find the right >>>>>>>move. After a mountain of debugging output, I discovered what I mentioned >>>>>>>previously... "hash grafting" (the art of grafting parts of the tree from >>>>>>>one zone to another by using the hash table) was helping the dumber version, >>>>>>>but not the smarter one. >>>>>>> >>>>>> >>>>>>You mix some things together! Knowledge about opposition is only one of the >>>>>>tools you need to to construct a system of co-ordinated squares (german: >>>>>>Gegenfeldsystem). If you implement this correctly, you should find the correct >>>>>>move instantly i.e at ply 1 as my chess program Wilhelm does. >>>>>> >>>>>>Rafael B. Andrist >>>>> >>>>> >>>>>You find the right move instantly... But you don't _know_ it is the right move >>>>>until the score jumps. It _could_ just be a draw. And in the case of Cray >>>>>Blitz, using coordinated squares, it took 25-26 plies to see the big score. >>>>>It saw the right move normally at around ply=18 with the +2.5 score. With >>>>>the coordinated squares stuff, it got the Kb1 move instantly, but the score >>>>>didn't reach +2.5 until 7-8 plies longer than the simple version. >>>>> >>>>>That was the point. The better the move ordering, the less "grafting" helps >>>>>a shallow search find a deep solution. >>>> >>>>I now by eval from ply 1 that i win a pawn. In Fine 70, White is already a pawn >>>>up, so I get instantly an evaluation around 2. >>>> >>>>Rafael B. Andrist >>> >>>Nobody has written an article on how to use coordinate squares in a chess >>>program. If you write this up, I bet the ICCAJ would publish it. >>> >>>bruce >> >> >>What I did was pretty simple... and was very similar to what I do in pawn-only >>endings in Crafty. IE detecting/maintaining opposition. Note that I didn't >>keep this code in Cray Blitz. It was just something that Harry or someone >>suggested that I try to see what I thought. I ran into problems in that in >>some cases, staying on the right "square" is the grossly wrong plan, when you >>do that rather than centralizing. > >I don't think that coordinate squares have anything to do with maintaining >opposition. > >bruce Of course it doesn't. I do opposition in crafty. The coordinate squares idea came from Ivan Bratko (from the Bratko/Kopec test from the early 80's) in a conversation we had in 1984 in London at the Levy vs Cray Blitz match. Didn't mean to 'connect' the ideas at all, other than if you look at many of the endgame books, they explain coordinate squares in pretty simple terms, that is pretty easy to compute just like normal/distant opposition. But it doesn't (in the cases I have studied) guarantee the win of material, which is what I didn't understand in the post I queried. I should say that coordinate squares is related to opposition, as it does translate to opposition in many cases, after a lot of moves.
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