Author: martin fierz
Date: 17:11:34 12/04/01
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On December 04, 2001 at 09:16:22, Severi Salminen wrote: >Hi! > >What is the definition of "hamming distance"? What characteristics should I test >when testing my random numbers' suitability for zobrist keys? What alternatives >there are for random number generators besides the rand() in C? > >Severi aloha! my experience is from a checkers program, but it shouldnt really matter. i am using 32-bit random numbers generated by calling rand() twice, because rand() only returns a 16-bit value on my compiler. i used to use these numbers and read some posts here about hamming distance, so i decided to check: i produced myself a set of random numbers x_i with the condition hammingdistance(x_i,x_j) >=10 instead of the numbers the random generator was generating. in my test suite i run a depth 19 search on 80 positions and can compare two different versions - result: no difference. while i did have small changes like 101% or 99% in some test positions, it was never much and on average just zero. i don't know if my condition above is stupid or if it doesnt really matter. i think the condition is stupid, because you will only have a real problem if x_i XOR x_j equals some other x_k. or if x_i XOR x_j XOR x_k equals x_l XOR x_m etc. looks like these conditions are kind of hard to check... i also think it doesnt matter: another thing i did was to initialize rand() with different seeds and see what happens. result: again zero. i'd like to see someone come up with hard numbers showing that rand() is really bad for generating zobrist keys. i don't believe it is. cheers martin
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