Author: Robert Hyatt
Date: 11:16:03 06/28/98
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On June 28, 1998 at 10:44:29, Robert Hyatt wrote: >On June 28, 1998 at 07:02:15, Vincent Diepeveen wrote: > > >I'm going to add my notes here rather than later as this is a long >post with lots of stuff below, (quoted). > >two points: the original 20 ply suggestion for DB was and still is >correct. They can't. And the math I gave below certainly supports >that (since they don't do null-move and must live with a branching >factor of 5.5 or so). > >Second, my math below was based on a branching factor of 3. I am now >doing better than that after the heavy pruning I added in the q-search >a year or so ago. 2.5 vs 3 is a big change when you are cmputing >logarithms. > >My current analysis says that "current crafty" can do a 19 ply search, >if it could search 200M nodes per second exactly as I search now. This >isn't completely possible due to the architecture of deep blue (hash is >not shared across all chess processors, they don't prune in q-search >because they use MVV/LVA and generate one capture (or out of check) move >at a time, etc.) > >So, after reading this old analysis, it is still correct. 20 plies is >still out of reach, although one more hardware redesign, or quadrupuling >the number of processors might bring that within reach. *IF* we could >make the deep blue hardware do all the things I currently do (I do R=2 >null move, their hardware can't do this at all, I prune losers in the >capture search, they can't even estimate whether a move seems to lose >material or not in the current hardware) it would be possible to do 20 >plies. > >*as* the hardware exists, 20 was, and still is, not doable. Maybe that >is a clearer statement, as if you read my most recent post, and the one >vincent quoted, this isn't so clear. My most recent post simply said that >*if* crafty could do 200M, it could hit 19 plies deep. But not on the >current DB hardware due to the above limitations. > >I was a little careless in explaining everything I said, clearly enough so >that it could not be interpreted in a way I didn't intend. > >Bob > > Even that didn't sound too clear. Here's a simpler version... in my original post, I factored everything known about DB and their hardware into the equation, and found that 20 plies was unlikely. In my more recent analysis, I too a "better" branching factor that I am now seeing in most cases (2.5 or so, sometimes better) and re-did the calculations, but with no regard to what their hardware *can't* do. (ie no null-move in the hardware, no pruning captures in the q-search.) So my second set of cal- culations were off by at least a couple of plies, maybe more. *IF* crafty could run 200M+ nodes per second, *in its present form* it could get close to 20 plies. at least 19 there where it does 12 now, 17 there where it does 10 now, and so forth. 200M doesn't seem difficult when Cray Blitz could hit 10M. It seems daunting on a PC of course, unless you factor in a bunch of processors and a parallel search. So, I think my original post was more accurate. My "20 plies is possible" is probably way too optimistic at present. my mistake...
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