Author: Christophe Theron
Date: 22:38:07 01/25/00
Go up one level in this thread
On January 26, 2000 at 00:42:20, Robert Hyatt wrote:
>On January 25, 2000 at 21:54:44, Christophe Theron wrote:
>
>>On January 25, 2000 at 14:40:57, Jeremiah Penery wrote:
>>
>>>On January 25, 2000 at 14:02:01, Christophe Theron wrote:
>>>
>>>>Actually many programs prove everyday that using an imperfect pruning scheme is
>>>>much better than no pruning at all. Yours included (I don't mean your pruning is
>>>>imperfect).
>>>>
>>>>I see no reason to believe that this would change just because you are be able
>>>>to compute 4, 5 or even 10 plies deeper.
>>>>
>>>>Is it really still debatable? It was maybe, 20 years ago, but now we all know
>>>>the answer...
>>>
>>><snip>
>>>
>>>>My main point is that not using a pruning scheme is somewhat... stup...
>>>>Ahem... not really optimal.
>>>
>>><snip>
>>>
>>>>But I'm sorry, not using any pruning scheme, if it is really what they did,
>>>>sounds like a "political" decision. I cannot believe that Hsu is stupid enough
>>>>to really believe that DB plays better without pruning.
>>>>
>>>>It is either a huge professional mistake or a deliberate public relations
>>>>choice. You guess.
>>>
>>><snip>
>>>
>>>>OK, he had all this power as a result of his very hard work. So he deserved it.
>>>>But the total package could have been much better with a pruning scheme. The
>>>>thing that has played against Kasparov was far from being finished.
>>>
>>>Even the best selective-search algorithm will sometimes cause you to play a
>>>different move than you would without it. You will 'miss something', so to
>>>speak. If you were writing a program to play against arguably the best chess
>>>player _ever_, would you want to risk this happening even once and losing
>>>because of it?
>>
>>
>>Of course I would implement a selective search.
>>
>>It has been the main source of improvements in computer chess for the last 2
>>decades.
>>
>>The drawbacks are very small when compared to the advantages.
>>
>>This is clearly demonstrated by the success of microcomputer chess programs
>>since Psion chess in 1981. And even before.
>
>maybe or maybe not. In 1970 we were _all_ selective searchers. Chess 4.x
>changed that in 1975. By 1980 nobody that was winning was selective. Then
>we went the other way with null-move and so forth. Maybe the right way is
>not risky forward pruning, when you have enough horsepower. Which sounds
>_exactly_ like what Slate/Atkin said in 1975 when you think about it. :)
You are right, if you have enough computational power to search to the end of
the game, you don't need any pruning system.
But this is not the case here. And as far as I know, computing deeper, even if
imperfectly, increases your program's strength.
Most of the programmers here, and most of the users of chess programs, would
certainly have a word or two to say to Slate and Atkin on this subject. :)
Anyway the case "you have enough horsepower" is not very interesting. If you
mean by this that if you can beat your opponent without pruning you don't need
to prune, then you definitely have a point. That's not "maybe ot maybe not",
that's for sure this time.
>>> Especially if you had the speed not to really worry about it, as
>>>they did. Also, it may have been a matter of time. Since there was little time
>>>to do much testing, it would've been way too hard to write and debug a good
>>>selective search algorithm. They had other problems to worry about.
>>
>>
>>The lack of time is indeed the reason I think.
>
>I think it was lack of interest. Hsu was determined to do it without any
>inaccurate forward pruning. We could second-guess all we want. But don't
>lose sight of the fact that what he did worked well enough to beat Kasparov.
I don't forget this.
I'm just saying that the thing could have been much stronger if they had worked
on implementing a good pruning scheme rather than this SE thing.
>>>In effect, they did do a bit of selective search, through their extensions. You
>>>could call their search a highly-selective 30-ply+ search. :) They just were
>>>not selective in the first part of the search.
>>
>>
>>It is a related idea, but it's not the same.
>
>
>The effect is essentially the same. Either extend some branches far deeper
>than others, or cut some off far earlier than others. Both tend to make the
>tree taller but narrower, which is a 'human-like' goal that may or may not be
>good over the long-haul.
>>>I do agree that they may have been a bit better if they had some sort of
>>>selective search, however. I just don't think it was practical or really
>>>important for them to worry about.
>>
>>
>>Because they had no serious competition. Kasparov could have punished them, but
>>he failed too, unfortunately. Not that I think he is not able to. But on this
>>particular occasion, he failed.
>>
>>
>>
>> Christophe
>
>
>I don't think he had a prayer of punishing them tactically. Perhaps
>positionally, but then that is unrelated to search. And I think he would
>punish any other program tactically _and_ positionally. IMHO of course.
Maybe or maybe not.
My interest was rather in the fact that they used a probably suboptimal approach
in a multimillion dollars project.
Not sure anymore if you are interested in talking about this...
Christophe
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