Author: chandler yergin
Date: 08:14:09 12/03/05
Go up one level in this thread
On December 03, 2005 at 09:48:12, Matthew Hull wrote: >On December 02, 2005 at 23:27:41, Robert Hyatt wrote: > >>On December 02, 2005 at 17:47:00, Tony Nichols wrote: >> >>>On December 02, 2005 at 17:21:59, Robert Hyatt wrote: >>> >>>>It is time to stop this now. The above is utter nonsense. We don't "search" >>>>hash tables. Larger hash tables do not take longer to search, because we just >>>>don't search them. We randomly probe into them and either hit or miss, so the >>>>size has absolutely no effect other than larger sizes hold more information >>>>without requiring that older data be overwritten sooner. >>>> >>>>You are quoting nonsense... >>> >>> >>>Hello, >>> >>> Is it safe to assume that you can't have too much hash? I mean, as long as you >>>have the ram. >>>Regards >>>Tony >> >> >>pretty much. Beyond some point additional hash will not help. But to see how >>it helps, set it to something like 384K (yes 384 k bytes) and run a position for >>say 10 minutes. Record the highest depth reached and the time to reach that >>depth. Double the hash and re-run. Keep doing this until it doesn't get any >>faster. You just reached the max needed for the 10 minute search time (10 >>minutes was just a number, pick anything you want). You will see significant >>speed improvements at first, but they begin to flatten out and eventually >>doubling the hash doesn't change a thing any further. >> >>If a program clears hash between moves (most do not) then this can be a bigger >>issue with large hashes since they do take time to clear should that be >>needed... > > >Also, a very slight slowdown with a huge hash table can take effect if the >higher memory positions require addressing tricks to reach, which seems to be >especially true on i686 systems. At that point, the diminishing return of a >huge table is overtaken by the extra clock cycles needed for the high-memory >probe, resulting in a slightly perceptible performance hit. Thanks Matt!
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