On Mon, Feb 18, 2013 at 4:59 PM, Phil Sorber <p...@sorber.net> wrote:
> > On Mon, Feb 18, 2013 at 4:41 PM, Tomasz Kuzemko <tom...@kuzemko.net>wrote: > >> Did not look at the code, but seems like it is part of some general hash >> table implementation. >> >> > It is for a hash table AFAICT. > > >> Good explanation why these are primes: >> >> http://stackoverflow.com/**questions/1145217/why-should-** >> hash-functions-use-a-prime-**number-modulus<http://stackoverflow.com/questions/1145217/why-should-hash-functions-use-a-prime-number-modulus> >> >> > Ah, that is very interesting and makes good sense. I will add a comment. > > Upon further inspection it seems like this is duplicated code in both RamCache implementations. Perhaps this should be abstracted out and added to libts. Or replaced with a libts implementation if it already exists. > Thanks. > > >> Best regards, >> Tomasz Kuzemko >> tom...@kuzemko.net >> >> W dniu 18.02.2013 20:50, Phil Sorber pisze: >> >> In looking through RamCacheCLFUS I came upon this: >>> >>> static const int bucket_sizes[] = { >>> 127, 251, 509, 1021, 2039, 4093, 8191, 16381, 32749, 65521, 131071, >>> 262139, >>> 524287, 1048573, 2097143, 4194301, 8388593, 16777213, 33554393, >>> 67108859, >>> 134217689, 268435399, 536870909, 1073741789, 2147483647 >>> }; >>> >>> Looking through git blame and JIRA it looks like it was part of the >>> initial >>> patch for CLFUS. In talking with James in IRC he pointed out that it >>> looks >>> like the largest prime less than a power of 2. This seems like a very >>> deliberate choice, but I can't figure out why and there are no docs >>> explaining. Can someone, perhaps John, shed some light on it? >>> >>> Thanks. >>> >>> >
