Author: Dann Corbit
Date: 21:50:44 12/09/99
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On December 10, 1999 at 00:06:05, blass uri wrote: >I am interested in this question because I understood that >64 bit signature may be counter productive at correspondence time control >and I would like programs to avoid mistakes even in 24 hours/move. > >How much slower are program if you use 96 or 128 bit signature instead of 64 bit >signature? The problem I see for a big signature is that you will get a smaller number of entries. Let's imagine some extremes. Your hash signature is 1K. You have 4K space for hash entries. That means you have 4 evals you get to store. ;-) Now, if you double your hash signature to 2k, you only store 2. If you double it again you only store 1. So there is a trade off. If you increase the size of your hash it will reduce the number of table entries you can store. If you decrease the size of your hash, it will increase the false matches and increase the probability of error. So do you want to spend a ton of time flushing old cash entries or do you want a lot of bad hits? The solution for bigger hash signature is to get a bigger memory. If you have 512 megs, then you could store a large number of big hash signatures. So if you want to do correspondence chess, get a zobrist hash that does somewhere from 64 to 128 bits on its output. Then, make a hash table with 16,000,000 entries at 128 bits or 32 million at 64 bits and it will consume 256 megs of ram. So it seems (to me) to be a balancing act.
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