Author: Andrew Dados
Date: 11:04:13 01/31/02
Go up one level in this thread
On January 31, 2002 at 10:33:22, Robert Hyatt wrote: >On January 31, 2002 at 03:35:50, Ed Schröder wrote: > >> >> >>Is this really you Bob? >> >>I have seen Cray Blitz playing, Mike Valvo in ecstasy calling through the >>microphone to the participants and spectators, "Cray Blitz is hitting the 9th >>ply folks!". And all the programmers trembled all over, myself included, gee 9 >>plies, who can win from that hardware monster. >> >>We are talking about Munich 1986, Cray Blitz was considered somewhat faster than >>Hi-Tech from Hans Berliner. Hi-Tech searched 8 plies average in the middle game >>and so did Cray Blitz. Been there, seen it. > >Not in Cologne it didn't. I still have the logs. Cray Blitz searched >to 9 plies on occasion and 10 plies many times. I can certainly post one >if you want to see it. We were searching 8 plies in 1983 at 40K nodes per >second on a dual cpu XMP... > > > > > >> >>Hi-Tech was able to get a 100K NPS, you somewhat higher, period! > >We were doing 200K-300K as I said. If you are talking about the Summer >when the WCCC was held, we were doing 200K. If you talk about the Fall, >Cray had a faster machine and we were doing 300K. I was talking about >the latter... > > > >> >>With a 100K NPS you typically search 8 plies (brute force!) in the middle game >>and not 10-12 plies as you imply. > >I'm not going to make this a big argument as I wrote the thing and in COlogne >you could _not_ see Cray Blitz's output. Because I was operating Cray Blitz >in Birmingham and relaying just the best move to Harry... I have no idea >what you thought you saw, but it wasn't _my_ program. As I said, in 1983 we >were doing 8 plies, _just_ like Belle which was running at 160K nodes per >second with a somewhat less efficient hardware search. In 1986 we were >hitting 9 all the time and saw 10 about every third search or so. Deep Thought >in 1989 was a ply or two deeper than us... and in 1989 we were doing 10 all >the time at about 500K nodes per second... > > > > >> >>Say 200K is good for 8 plies average, being 1000 x faster with a branching >>factor of 4 gives: 4x4x4x4x4 = 1024 -> 5 extra plies. >> >>So with 200M NPS you might be able to search 13 plies brute force in best case. >> >>Subtract a couple of plies (1 to 3) for the way DB did singular extensions and >>the picture fits, that is: DB was searching 10-12 plies as the log files >>confirm. >> >>This 12(6) isn't 18, you must have misunderstood its meaning. >> >>Ed > > >Did you see the email from the DB team? Is there any misunderstanding that? > >It seems pretty clear to me. And although I busted the math yesterday, here >is a better analysis: > >their branching factor was roughly 4, obtained from their logs. that means >that they multiply the time by 4 for each iteration. Looking at their logs, >they typically searched to 10(6) or 11(6). On occasion they got to 12(6) but >it seemed to timeout before finishing so I didn't count those. > >10(6) is 16 plies according to Hsu. > >I tried Crafty on several opening, middlegame and endgame positions. I averaged >the total nodes searched for a 1 ply search and got roughly 100. > >16 plies requires 4^15 more nodes than 1 ply... 4^15 is 2^30, which is >one billion. They need to search 100 billion nodes to get to depth=16, if >we assume their q-search looks something like mine. 100 billion nodes only >needs 1000 seconds if they searched 100M nodes per second. But we know they >averaged 200M according to Hsu/Campbell, which drops that to 500 seconds. >And we also know that deeper searches might not always need that many nodes to >complete when move ordering is good and hashing is lucky. > >I don't see _anything_ that says they can't reach 16-17 plies on normal >searches, and go beyond that in special cases. Crafty seems to search about >12 plies or so in the 60 10 time controls we used in CCT, but on occasion it >will run out to 15 or 16 in certain types of tactically obvious positions... From their own publication, 'Deep Blue', June 2001 Example of search depths over one position r1r1q1k1/6p1/3b1p1p/1p1PpP2/1Pp5/2P4P/R1B2QP1/R5K1 w from DB-Kasparow game 2 from 1997, before move 37 When chips were set to minimum fullwith 4 plys: A.Iteration B.Minimum software depth C.Maximum software depth D.Maximum Estimated combined depth A B C D ---------------- 6 2 5 11-21 7 3 6 12-22 8 4 11 17-27 9 5 15 21-31 10 6 17 23-33 11 7 20 26-36 12 8 23 29-39 So iteration is clearly the sum of minimum software depth (B) and hardware depth (4 plys here). -Andrew-
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