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Subject: Re: hash table collisions

Author: Daniel Clausen

Date: 08:38:53 01/15/00

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Hi

On January 15, 2000 at 09:40:51, James Swafford wrote:

[snip]

>If you use 20 bits to probe, why not just store the other 44 bits in the
>table as a checksum?  You already know the other 20 bits match....
>
>I use a "minimum size", so my key is guaranteed to be N bits long.
>My tables only use 64-N bits as the checksum.

This surely will work too. I think most people don't do it because
of one of the following reasons:

1. Most peoples hashentry is 128 bit wide. So if they use 64bit for
   the complete hashkey, they still have 64 bit left. And for most
   people this is more than enough.

2. If you store only the 64-N bits in your hashentry, the size of
   the hashentry changes if you change the hashtable size.

3. If you would keep the hashentry-size constant (eg 128 bit) even
   when you change the hashtable-size, you have a non-contant number
   of bits you can use for storing additional info. It's not easy
   to use this though.

Hope this made some sense.

Kind regards,
 -sargon



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