Author: martin fierz
Date: 07:14:27 04/07/04
Go up one level in this thread
On April 07, 2004 at 10:03:33, Vincent Diepeveen wrote: >On April 07, 2004 at 09:19:13, martin fierz wrote: > >>On April 07, 2004 at 09:14:42, Vincent Diepeveen wrote: >> >>>On April 07, 2004 at 08:27:59, martin fierz wrote: >>> >>>>On April 07, 2004 at 06:49:59, Renze Steenhuisen wrote: >>>> >>>>> >>>>>Hi all, >>>>> >>>>>could someone give me some numbers that are common with hashkey collisions? >>>>>Because I guess my % is little too high... >>>>> >>>>>I'm getting like 0.03% [which is 1 every 3000, if I'm not mistaken] >>>>> >>>>>This is when using TT=32MB (haven't got the exact number of entries) >>>>> >>>>>If you think it is an error, any suggestions on where to start looking? >>>>> >>>>>Thanks! >>>>> >>>>> Renze >>>> >>>>hi renze, >>>> >>>>your number is much too high. a good estimate for the hash collision probability >>>>is 1/sqrt(hashkey_range); which in your case comes out as 2^-32 or about >>>>somewhere around one in a billion... >>> >>>Not at all. It's way less than that with 64 bits Zobrist. >> >>i never took the trouble to measure it, but the math is rather straightforward. >>so i'd say you have an implementation bug too ;-) > >You do not store 64 bits i bet but just like 32 bits or so and use the rest for >index. So effectively having like 60 bits at most. that's not a big difference. 2^-30 is still a very small number :-) cheers martin >Note that i also store the color in a special bit. > >So i had a garantueed 65 bits in DIEP. > >Note that i write i 'had'. > >>cheers >> martin >> >>>I measured it with 460 processors at a supercomputer with a shared hashtable and >>>had major problems to get at 7 million nodes a second stored, some >>>errors/collissions. >>> >>>>make sure you're not doing anything wrong with the hashkey updating like >>>>suggested by others - compare with a computed-from-scratch key. also make sure >>>>that your nullmove doesn't break your hashkey. and just to be sure, check that >>>>you haven't got 32-bit numbers instead of 64 bit numbers by accident... >>>>cheers >>>> martin >>> >>>I'm sure it was some implementation bug with Renze.
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