Author: Thorsten Czub
Date: 04:24:36 12/28/97
Go up one level in this thread
>* When it is the opponent's turn, select every move >* Your turn: select the best move (from a SEE+positional 1 ply >evaluation) and the very threatening moves (including checks of course) >* Opponent's turn: select several best moves and any threatening move. I call this the asymmetrie-search ! It effects the playing style. You can try out yourself by using Genius as an email-analyze instrument (some of my friends play mail-chess) and you will see that genius often misses GOOD strong moves or sacs other programs see because they don't prune their 1,3,5,7...plies. But you can easily force genius to see the sac/overseen moves itself by taking back one move or playing forward and switch sides. Than the brute-force part has the job to play with the side that has the key-moves and will see anything in an instant. The senseless thing with genius is that you can let it compute 12 hours about a position, write down evaluation and main-line and you think you have a RESULT you can work with. It has maybe computed 9 searches deep and you think: Oh - now I am save. But input the first ply of the anaylzed main line and SCORE AND main-line will not come back to the same ! Not because of preprocessing or whatever, but because now the 2,4,6,8 sees different things because you are one ply shifted. If you analyze , after you have sent YOUR move, with genius on the opponents move something horrible can happen: You let it again compute 9 searches or 11 and it plays a boring move. And than you get a sac by another mail-chess guy who has NOT genius but e.g. Wchess and the enemy plays a sac and you input the move in genius and genius sees in an instant that it is lost !! This effect comes from what I call the asymmetrie-search. The advantage of this search was on the other hand: I don't have to compute that many branches. I am always seing threads. Sometimes I don't play the killer-move but a 2nd or 3rd best move. THIS is the reason genius plays boring ! If you would see all threads of your opponent, but not your own chances as good, you would change into a paranoic, careful creature. This is exactly what Genius is. Of course Weiner and Lang have tried to change this behaviour over the years to compete with Fritz and Mchess. But the main problem cannot be solved without giving up the asymmetrical search from my point of view. This causes the bori ng playing style. Try it out with your own program. But implement it right. Suddenly your program will develop into what Levy called the: do nothing but do it right Genius style. > >About the "shifted search": usually, the program is careful about what >could happen to him (looks at a lot of the opponent's moves). But if you >detect an agressive move (attacking the opponent), it could make sense >to "shift" and be careful for the opponent (looking at a lot of your >moves to see if a combination is possible). When I know I have a good main-line 1 ply 2 ply 3 ply 4 ply 5 ply 6 ply 7 ply 2nd best best 3rd best best 2nd best best 2nd best I could try to prove my 1,3,5,7 moves by shifting the principle. I know the best defense on ply1 is ply2. But i am NOT sure if ply 1 is really the best move. There must be a method to shift it and to keep the blunders in the 1,3,5,7,9 iterations very small. Genius-level-small. One other thing: I don't think the MxSy indication of the old Mephisto machines has something to do with plies. lets say M2S15. Or M4S17. Many people always said: This could mean M2 = 2 plies "brute-force" with overall S15=15 plies selective peak. I don't think this interpretation was ever true. Try it out with an old dedicated Mephisto machine. Use e.g. the Roma 16 Bit (68000 12 Mhz). Let it compute 1 second and force move. Write down the evaluation and the complete main-line and the MxSy = search-indicators. And you will be very astonished: Although M is often 0 or 1 the main line is very good, long, and accurate ! HOW can any chess program create these accurate main-lines in 1 second on such a slow machine without hash-tables ?? NO ! We always misunderstood the MxSy indicator. I think I know what it means. But it is very difficult to explain here (typing it down without examples, high telephone costs, beeing on-line). I take my Roma16 Bit to my next tournament. MAybe Paderborn. There I could show you what I mean by example and we can write down the main-lines and all this stuff. As I said, there is a matrix that correlates the length and the search depth and (DAN, Vincent, I need your memory-help) when I remember it was (2 to the power of search-depth)+1 = length of main-line. You can try yourself by taking genius3 and knock off hash and book and use different selectivity and force different plies search depth as LEVEL. Than you see the matrix. From my point of view THIS search was the secret of all richards programs. And I am not sure if he can ever come out of this trap. >And still another thing: none of the above ideas tells us how to extend >the search beyond the nominal depth. Everybody here has seen Genius very >long lines (we are back to the idea of this thread and Junior's long >lines), going 12 plies beyond the normal exhaustive search. How would >you do it? If you prune heavily in the odd plies, and less in the even ones, and you have a static-exchange evaluation instead of capture-search, you can spare much computation time. The old Mephisto machines indicated search depths components much better than the new genius. And anything was slower that you could study it easier. If it comes to a capture in the main line the root evalaluation of genius if very very very often bullshit. All the advantage he had in the 80ties were eaten by opponent programs using null-move and hash-tables. Today his concept is rusty. It still works but cannot reach the top again. What a pity.
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