Author: David Rasmussen
Date: 15:36:50 12/03/01
Go up one level in this thread
On December 03, 2001 at 18:05:43, Sune Fischer wrote: >On December 03, 2001 at 17:50:15, David Rasmussen wrote: > >>On December 02, 2001 at 23:58:43, Robert Hyatt wrote: >> >>>On December 02, 2001 at 22:38:30, David Rasmussen wrote: >>> >>>>Many people use 32-bit pawn hashkeys. But I've found that 32 bits is not enough >>>>to avoid collisions. 64-bit seems to be enough, and maybe less could do the job. >>>>Why do people use 32-bit keys, when it screws up evaluation this way? >>>> >>>>/David >>> >>> >>>32 is ok for pawns. To see why, figure out how many _different_ positions >>>there are with only pawns on the board. The number is not as large as you >>>might think, which makes collisions unlikely so long as you _only_ hash pawn >>>positions. >> >>Are you saying that if I'm seeing collisions, I have a bug, or are you saying >>that 300 collisions out of 60.000.000 successful probes is not a problem? If the >>latter, then why? How can you be sure? >> >>/David > >I would say so, 300 collisions is way too high, even if you used a 32^2 entry >size table you shouldnt get more than 1 collision per 100 game or so. >Using a smaller table will decrease the probability even further. > >-S. Mmm.. But I use a wellknown good PRNG, the avg. hamming distance of the keys is good, the distribution of the keys is good, and I have no collisions at all using this PRNG for generating my 64-bit keys for the trans/ref table. So how to find my bug... I seriously doubt that there's a bug, but one always does... :) Any ideas of how to find such a bug?
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.