Author: Amir Ban
Date: 08:50:01 11/23/98
Go up one level in this thread
On November 23, 1998 at 09:37:25, Robert Hyatt wrote: >On November 22, 1998 at 11:49:54, blass uri wrote: > >> >>I did not ask for all the tree but only the tree up to the point that my >>programs can see by search of 3 minutes that black has at least 1 pawn >>advantage. >> >>This is clearly less positions >>because if in the leaves it is -2.xx then Junior can see some moves before the >>leaves that it is -1.xx > > >ok... rather than 10 million pages, it might only be 1 million pages. How >would we get those to you? :) > I wonder how many people reading the last few posts of this thread have been reminded of the story of the King's New Clothes. >what you are overlooking is the point that junior (and all the other programs) >look at a fat, shallow tree. I am quite sure that the opposite is true. All PC programs have a much smaller effective branching factor than DT/DB. This is because they all do forward pruning, many of them aggressively, while DT/DB did none, and they do extensions, most at least as much as DT/DB, and at least in Junior, much more aggressively than DT/DB. > IE how do you think a program like Crafty, doing >300K nodes per second, reaches 12 plies in the middlegame, while Deep Blue, >doing 1,000 times as many nodes per second, only reaches to 10-11 plies in the >middlegame? Because Crafty does null-move and other forward pruning tricks while they don't. Turn off null-move and see what you get. > Because *they* are searching 10 times deeper than I am on most >moves, thru their "singular extensions" (and other extensions). This doesn't agree at all with what Deep Thought and others found about this, or even with common sense. Even if singular extensions are always a great thing to do (doubtful even according to the inventors), it covers only one side of the game. Most tactical situations are non-singular, so SE has nothing to do there. To argue, as you do, that it effectively adds several plies to the search depth is quite a hyperbole. To say that today's top program are not only unable to discover the c5 line, but even to find that any move within this line is singular is beyond their capabilities, is one of the greatest exaggerations yet seen on this newsgroup. > We've already >seen that in the Deep Blue vs Kasparov game two, Dark Thought and Ferret have >searched axb5/Qb6 to depth 20 or 21 without seeing anything to cause it to fail >low, yet we know deep blue did. At 1/2 that depth. So it might take a program >like junior *fifty* plies to find what is going on there for all I know at >present. And if I could somehow give you a PV to get you down to the point >where Junior sees this, it would be so deep, probably, that it would be easy >to say "but this isn't the best move, white or black should try this instead. >And we end right back up at square zero. > Quite an exaggeration, don't you think ? So we can calculate for many centuries and not find it ? Why didn't you say so before we already wasted about a week on this ? But besides, this is a switch you are pulling here: We put all the computers on this position to vindicate DB's axb5. Now it's become a tautology that it's best ? It should also be remembered that we don't even have a hypothetical line that Deep Blue saw to make it dislike Qb6. >There are just some things they can see at 250M+ nodes per second that we won't >ever see... > Why ? The computers are now thinking for tens of billions of nodes. They should be able to see as far as DB now. Probably much farther because of their deeper nominal depth. However, if you are concerned about the selectivity of the computers looking at it, why not disable it and put a program searching on it to 11 ply or more ? I think Rebel has such a config option, and you can certainly organize this for crafty. > > >> >>>I don't have their "output" for this move. As I said before, we sat at the >>>same table playing this game at the 88 ACM event (I think). I saw their output, >>>they saw ours. We both saw them fail high with a score > 2.0, while we were >>>reasonably happy with our score... until the roof fell in about 10 moves >>>later... and their eval didn't vary by much for the entire sequence... So I >>>can't give you their output, since I don't have it (they were using a laptop >>>to display their stuff). I can only tell you what actually happened in the >>>game. >> >>I believe that cray blitz lost because of a mistake that came after c5(maybe at >>move 32 because I do not see what is wrong with 32.Bg5) >>The fact that they have score>2.0 does not prove that they were right in the >>evaluation. > > >You'll have to believe what you want here. This is a Thorsten-like statement. Is 32.Bg5 okay or isn't it ? If it is, then 27...c5 is a good positional move, but not more. > I *know* that a program that doesn't >do any selective forward pruning and which doesn't use null-move is *not* going >to make that kind of mistake, except perhaps for some sort of horizon effect on >the end where they can't actually take the piece due to a mate threat or some- >thing more serious. But that's not the case in this position... > > > >> >>I saw newspapers do the same mistake when a human player does a sacrifice and >>win and they see it as a proof that the sacrifice was a good move. >> >>Uri > > >Humans make mistakes very frequently. non-selective computers don't make these >errors nearly so frequently. And when you consider two different types of >programs (Cray Blitz vs Deep Thought) the likelihood of *both* making this >mistake to let black win that bishop is *very* low indeed... As I mentioned >before, Cray Blitz is far from a pushover... We didn't think it was, quite the opposite: The conclusion from taking you at face value is that back in the late 80's and early 90's computers were playing at at least 1000 ELO stronger than today, to the extent that today's top programs are not able to reconstruct their moves, or even to follow their reasoning. All I wanted to see, by the way, was a demonstration of singular extension in action by DT/DB. Surely something like this exists. Amir
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