Author: Vasik Rajlich
Date: 09:45:07 10/19/04
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On October 19, 2004 at 09:34:00, Tord Romstad wrote: >On October 19, 2004 at 05:57:06, Vasik Rajlich wrote: > >>It's a sort of interesting accident that computer vs human is balanced at the >>moment. If the game was more tactical, humans would already be crushed and we >>would accept it as a matter of course. If it was more positional, humans would >>still be stronger, maybe much stronger. > >I don't think it is quite that simple. Consider the game of shogi, which is >arguably a more tactical game than western chess. The best computers have no >chance against the best humans. > >I think there are two main reasons why computers are so good at chess: > >1. Material is very important in chess. A material advantage is usually >sufficient to win. This makes it easy to write reasonably accurate evaluation >functions for chess. In shogi, material is much less important, while factors >like initiative and king safety (which are much more difficult to quantify) >play a more significant role. True - although this is something which helps make chess more tactical and less strategic, as I understand those words. > >2. The branching factor in chess is not too high. This means that computer >programs running on current hardware can afford to waste lots of time analysing >nonsense variations, and still search deeply enough to see the relevant >tactical lines. This is not yet the case in shogi. The horizon effect is >still a very real program, and top human players are able to outsearch the >best programs in tactical lines. > >Even in chess, I am not sure it is strictly true that computers are better >than the best humans in tactics. The picture is a bit more complicated. >Computers are extremely good at finding short, bushy tactics, while the >best GMs are better at finding very deep, narrow tactics including non-checks >and quiet moves near the end of the lines. Consider the Nolot test suite, >which consists of problems solved by human players at a normal tournament >time control, but which the computers still struggle to solve. > Yes, it's probably an oversimplification to say that computers can calculate and humans can evaluate. Still, in practice, in chess, it's more-or-less true. The deep narrow tactics are not so common or so important. I don't see people losing because of this, or computers losing to humans because of it. >In chess, computer hardware has reached the stage where the programs' >superiority in short, bushy tactics almost exactly compensates for their >relative weakness at understanding deep, narrow tactics. In shogi, we >will have to wait a few more years before this happens. Actually, there is one other property which chess has which helps make chess engines strong. Given a primitive evaluation, as you search more, you play better positional moves. I am not sure that this is inevitable for any game. There is a related issue, that of validating changes to evaluation. Evaluation terms can be broken down into: 1) terms which are relatively dynamic, and can be viewed as approximations to a deeper search (for example, king safety) 2) terms which are relatively static - and not related to search (for example, pawn structure) Another way to say it: terms in group #1 can be validated by noting if they bring scores closer to scores from deeper searches, terms in group #2 cannot. Generally, a game whose group #1 is bigger will have a bigger search influence, and stronger play by computers. In chess, group #1 is quite big. Vas > >Tord
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