Author: Robert Hyatt
Date: 20:50:45 01/28/00
Go up one level in this thread
On January 28, 2000 at 17:35:56, Robert Hyatt wrote: >On January 28, 2000 at 10:50:40, Dave Gomboc wrote: > >>On January 28, 2000 at 04:12:38, Jeremiah Penery wrote: >> >>>On January 28, 2000 at 01:35:20, Dave Gomboc wrote: >>> >>>>On January 27, 2000 at 21:20:46, Christophe Theron wrote: >>>> >>>>>On January 27, 2000 at 14:21:19, Dave Gomboc wrote: >>>>> >>>>>>On January 27, 2000 at 13:00:39, Christophe Theron wrote: >>>>>> >>>>>>>On January 27, 2000 at 00:06:19, Dave Gomboc wrote: >>>>>>> >>>>>>>>On January 25, 2000 at 21:26:19, Christophe Theron wrote: >>>>>>>> >>>>>>>>>On January 25, 2000 at 13:33:36, Dave Gomboc wrote: >>>>>>>>> >>>>>>>>>>It seems weird to me that when Ed Schroder says Rebel does better without >>>>>>>>>>null-move than with it, people believe it, but people criticize the DB team for >>>>>>>>>>not using it (e.g. from your text above: "by not using a good, known pruning >>>>>>>>>>system..."). >>>>>>>>> >>>>>>>>>If the DB team did not have enough time, they could simply take the null move >>>>>>>>>algorithm because there is documentation available on it. >>>>>>>>> >>>>>>>>>However null move is not the final say. Rebel does very well with ANOTHER >>>>>>>>>pruning system. Junior does very well with ANOTHER pruning system as well. And >>>>>>>>>there are other programs that do fine without null move, one of which I know >>>>>>>>>very well. >>>>>>>> >>>>>>>>Yes, and DB does very well with ANOTHER pruning system too. What's your point? >>>>>>>> >>>>>>>>Dave >>>>>>> >>>>>>> >>>>>>>My point is that they claimed that they did not use one. Several of us, looking >>>>>>>at the apparent branching factor shown in the DB log files, have doubts about >>>>>>>this. >>>>>>> >>>>>>> >>>>>>> Christophe >>>>>> >>>>>>Where did they claim that they did not use one? In their published work they >>>>>>clearly stated the contrary. >>>>>> >>>>>>Dave >>>>> >>>>> >>>>>What did they say? >>>>> >>>>> >>>>> Christophe >>>> >>>>Argh, I can't find the paper! >>>> >>>>In the software, there are some full-width plies, then some selective plies. In >>>>the hardware, there are some full-width plies again. >>>> >>>>That is from memory though. >>>> >>>>Maybe Ernst can pull out his copy of Search Control in Deep Blue? >>> >>>I think the 'selective plies' are the extensions. The full-width plies at the >>>end of the search, in hardware, coincide more with the evaluation function than >>>anything. Rather than doing a static evaluation at the end of the search, they >>>did that evaluation based on a 4-ply search done in hardware, to lessen any >>>error involved. >> >>That was not the impression I got from reading the article. Normally when one >>speaks of selective plies one speaks of pruning some moves out. I'm not saying >>that they're not extending some lines like crazy, though. >> >>Also, the hardware didn't have to do a 4-ply search. It was configurable. >>Looking at the logs, where you can clearly see the (3), (4), (5), (6) after the >>plies, it makes me want to guess that the number inside the brackets is the >>full-width depth that the hardware searched. But that's just speculation. >> >>Dave > > >No.. that I know didn't happen. I can explain the technical details but they >are messy.. but the deal is that the chess hardware has a pretty narrow range >of depths it can search to without (a) searching too quickly for the SP to >keep it busy or (b) searching so slowly that the SP is waiting all the time >and not helping. > >Hsu settled on 4 and stuck with it so far as I know, although it is possible >this was bumped up in endgames (I haven't seen anything suggesting that it was >however...) My guess was wrong. From the DT team, the number _is_ the hardware depth. In deep thought, it apparently could vary from roughly 3 to 5 depending on whatever, although the shallower the better, since there was no hashing in the hardware and the resulting search trees would get bigger quickly. But now the actual search depth should be treated as the sum of the two numbers, something we didn't know for certain before.
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