Author: Robert Hyatt
Date: 10:56:05 06/25/98
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On June 25, 1998 at 13:46:06, Roberto Waldteufel wrote: > >On June 25, 1998 at 12:03:11, Robert Hyatt wrote: > >>On June 25, 1998 at 04:54:02, Roberto Waldteufel wrote: >> >>> >>>Here's another question about Hsu's chess chip. I seem to recall reading some >>>time ago that Hsu was considering a commercial release of his chip. Does anyone >>>know anything more about this? If the chip were to become available, how could I >>>use it in conjunction with a PC? would the fixed depth not be "out of sync" for >>>the speed of, eg a Pentium 333Mhz if it was designed to work with a >>>supercomputer, or can the fixed depth be adjusted to redo the balancing act in >>>the new environment? If it were possible, I would be very interested in >>>experimenting with this sort of hardware coupling. I assume that it would extend >>>the depth to which a program could search by something like 4 extra plies within >>>the same time. This would surely improve the strength of the PC ches programs >>>quite a lot! >>> >>>Roberto >> >>there really isn't a "fixed depth". This is a parameter you set in the chess >>processor when you fire it up. You simply tell it to search to a depth of your >>choosing, although this depth has to be closely matched to the speed of the host >>machine as I mentioned in the past. Since the chess processor has a fixed clock >>speed of 2.4M nodes per second, you have to choose how deep it searches to >>balance that speed against the host machine that has to provide it positions to >>search. Set the depth too high and the host will waste time waiting on the >>chess processor. Set the depth too low, and the host will have to search an >>extra ply deeper to be able to provide the chess hardware positions quickly >>enough to keep it busy. >> >>If you study this, what you find is an interesting phenomonon. If you tell the >>chess processor to search 1 ply deeper, then the host processor has to search >>one ply shallower, or it will provide positions faster than the chess processor >>can search them and return the results. If you tell the chess processor to >>search one ply shallower, then the host processor has to search one ply deeper >>to provide it positions to search fast enough. In short, for a given host, >>there is a very definite max depth you can search. You can do more in the >>hardware, or more in the software. Software is generally better as you can >>change the search, tweak with the extensions, without changing the chess >>processors at all... >> >>Hope that explains what they are doing... > >Thanks for the info. I wonder if the theoretical limit problem could be overcome >in the same way that they did with Deeper Blue, ie many chess processors in >parallel, or would this not be practical for a pentium host? > >Best wishes, > >Roberto if life were only so simple. :) the point is, for any specific host machine, there is an optimal number of chess processors for a host machine. If you get too many chess processors, the host can't keep them busy unless you increase the depth on each chess processor by a ply so that the search on the hardware takes longer. But if you do this, the host can't keep up unless you reduce the depth by 1 ply, so you gain *nothing*. There is a constant ratio between the host processor and the number of chess processors. To go faster, you can double both, or to get cheaper you can divide both by 2, but you can't vary the number of chess processors without varying the number of host processors, *or* (perhaps) getting a single host processor that is twice as fast, which would let you keep 2x the chess processors busy. that's why they used a Scalable SP machine... if they want to double the number of chess processors (to double their NPS) they have to double the host as well. Bob
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