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Subject: Re: About random numbers and hashing

Author: Sune Fischer

Date: 18:10:53 12/05/01

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On December 05, 2001 at 20:47:56, Sune Fischer wrote:

Oh sorry, my fault you did mention that..

>>This leads to the following criterion for picking a set of hashcodes:
>>A set of vectors in F2^k is a good set of hash codes if each small subset of
>>non-zero vectors is linearly independent.
>>
>>What is not clear here is the meaning of "small", but we want small to be as big
>>as possible. In other words, we consider sets of size up to a certain size as
>>small, and if we can make that size bigger, it is better, since this leads to
>>unique codes deeper in the tree.
>>
>>However what is clear is that this quality criterion does not depend on the base
>>of the vector space. I.e., if we have a good set and multiply each vector by an
>>invertible matrix (in other words, if we rotate the vectors), the obtained set
>>will be just as good, since the rotation does not change the linear
>>independence.

So this is the new problem :)
I wonder if Hamming and PRNG _togther_ don't accomplish exactly this.

-S.



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