Subject: Re: more Q&D results [hash for use in the kernel]
To: matthew green <>
From: David Laight <>
List: tech-kern
Date: 11/29/2001 13:00:33
How good are these hash functions on non-random binary data?
Hashing random data is (should be) trivial.

Say hash a 64 byte buffer containing 1 32bit integer that is incremented
each time (the rest of the data being unchanged random - or zero - bytes).

This is probably nearer to what (NFS certainly) is trying to hash.


----- Original Message ----- 
From: matthew green <>
To: <>
Cc: <>; <>; ozan s. yigit <>
Sent: Wednesday, November 28, 2001 11:58 PM
Subject: re: more Q&D results [hash for use in the kernel] 

>     > i added the "perl" hash function that was posted here; it is a variant
>     > of the bernstein's k=33 hash, and the multiplication can be eliminated.
>    Indeed, GCC does eliminate the multiplication in the targets I checked.
> amusingly, `gcc -mv8' on the sparc generates a call to smul, rather than
> the handful of shift/add's, for the FNV hash.  the perl hash has fewer
> shift/adds IIRC.  i wonder which is actually faster :-)