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Subject: Re: Hashtables: is larger always better?

Author: Antonio Dieguez

Date: 21:33:04 09/22/01

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On September 23, 2001 at 00:28:03, Antonio Dieguez wrote:

>On September 22, 2001 at 23:42:29, James Swafford wrote:
>
>>On September 22, 2001 at 22:17:06, Uri Blass wrote:
>>
>>>On September 22, 2001 at 19:08:06, Torstein Hall wrote:
>>>
>>>>On September 22, 2001 at 18:29:46, Andreas De Troy wrote:
>>>>
>>
>>>If the hash tables are very big then the probability for hash collision can
>>>increase and if there are enough hash collisions the result can be a bad move.
>>>
>>>Uri
>>
>>Why do you think the size of the table has any bearing on the number
>>of collisions?  The number of collisions is a function of the
>>"uniqueness" of your key, not how many entries are in your table.
>>
>>Maybe my definition of a collision is different than the norm:  I
>>define a collision as a match of the entire key between different
>>positions, not a match of the portion of the key used as a probe into
>>the table.
>
>why not? the probability to have two position differents but seen equal with the
>eyes of the hashtable depends in the portion of bits that are used in the probe.

well, it doesn't matter, sorry.

>Off course more time or speed can cause more colisions, and the thing is that it
>could be that just one hurts the search. I use always 48 bits, nonrandoms
>numbers really, I just hope that doesn't happen.
>
>>Either way, I don't see how making the hash table bigger increases the
>>chance of a collision.  Would you explain?
>
>With the always replace scheme, I don't see neither, at the moment.
>
>>
>>--
>>James



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