Author: Amir Ban
Date: 01:20:33 11/24/98
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On November 23, 1998 at 22:38:17, Robert Hyatt wrote: >On November 23, 1998 at 17:49:30, Amir Ban wrote: > >I'll play that game. we are talking about a factor of 1,000. You implied >this could easily be explained by their not doing null-move or other forward- >pruning tricks? That is your explanation? > >I'd like to suggest you break out the calculator. Null move does *not* >reduce the search by a factor of 1,000. Not by a factor of 100. Generally >not by a factor of 10. So, I re-ask... if they are only searching to 10 >plies, *why* does it take them so many nodes to get to ply=10. Want some >math? perfect tree ought to be 2*38^5 moves. They search that many nodes in >under 1 second (that is about 160M nodes). Most agree that current programs >search within a factor of two of the optimal tree size (references available >if needed). so lets say they can fully search this tree in 1 second, even >assuming imperfect ordering... Now, again, I'd like to ask the >*same* question again, and this time get a *reasonable* answer: > > > >If they take (say) 5 minutes to do a 10 ply search, at 250M+ nodes per second, >that is over 300X the number of nodes a full-width search to depth=10 should >search. If you factor in a q-search that is the same size as the full-width >part, we have a missing factor of 150 to account for. I say that is *all* >search extensions. And I say that is *far* more than any of the rest of us do >in terms of extensions. How *else* would you characterize this? > 1. I'm not an expert on null-move, but I got the impression that it buys much more than a factor of 10 at great depths. The factor should be an exponential anyway, no ? 2. Programs are within a factor of 2 of optimal tree size ? I don't believe this. I don't think I am there. Perhaps your references talk about 4-5 ply searches ? Anyway, this factor also needs to be written as an exponential. 3. You neglect the parallel overhead (factor of 3-4 according to a recent post). 4. You underestimate the Deeper Blue depth. In fact I see one move doing 11 ply in 6:56 minutes, and another is 12 ply in 3:19. So I don't see a problem in the numbers. Amir
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