Re: hash question

> Asking for opinions: if I switched from a 32 bit hash value as the 
> record key to using a 64 bit key or even a digest then I could reduce or 
> eliminate the "lossy" nature of the hash format at the expense of a 
> larger data file.
> 
> If I used a 64 bit hash key the record size would increase from 12 to 16 
> bytes (a 33% increase).  Not sure what the loss rate would be with a 64 
> bit hash.
> 
> If I used a digest (128 bit MD5 hash) the record size would double to 24 
> bytes but losses would be virtually eliminated.  Computing an MD5 for 
> each term would probably be significantly slower than either 32 or 64 
> hash as well.

Using a 64 bit hash key sounds reasonable (in relation to the numer of
unhashed keys to store). More important would be the use of a good
hash function which minimizes collisions. Something like taking the
first 64 bits from the MD5, SHA-1 or RIPEMD160 hashs could be a good
choice.


Greetings,
Thomas.


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