Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.php > #5689

Re: FYI performance of hash algorithms

Show all headers | View raw

On 4/23/2012 3:42 PM, M. Strobel wrote:
> I am just asking myself which of the many hash algorithms performs best, so I can use
> it to index my translation strings.
>
> So I wrote a test script. It iterates over an array of 3.917.116 strings calculating
> the hash of each.
>
> Here you have the results, with run time, and run time relative to hash length
> (smaller is better).
> Interesting that the tiger hashes seem to perform well.
>
> There were only collisions with adler32 (many), crc32 and crc32b.
>
> /Str.
>

<snip>

Interesting, but only applicable on your system with your libraries and 
your data.  A different system could have different versions of the 
libraries and completely different performance figures.

As for collisions - completely dependent on your data.  While you can 
say some things with certainty (i.e. hashing 2^16+1 values with CRC-16 
is guaranteed to have at least one collision), by picking different 
strings to be hashed your collisions will come out differently.

For instance, it's not really surprising that adler32 had a lot of 
collisions.  It was designed for CRC and works better with binary data; 
it was never meant to be a general purpose hashing algorithm.  Rather it 
was designed for speed.  It's also very short.

The same is true but to a lesser extent with the CRC-32 and CRC-32b 
algorithms, so again I'm not surprised about the collisions.

But the real question here is - how much does it matter if hashing a 
string takes 2 microseconds or 2.5 microseconds?  Unless you're doing 
millions of them at one time, no one is going to notice the difference. 
  Personally, when looking at such things I always elect the fewest 
collisions over the fastest time.

-- 
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex@attglobal.net
==================

Back to comp.lang.php | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

FYI performance of hash algorithms "M. Strobel" <sorry_no_mail_here@nowhere.dee> - 2012-04-23 21:42 +0200
  Re: FYI performance of hash algorithms Jerry Stuckle <jstucklex@attglobal.net> - 2012-04-23 16:16 -0400
    Re: FYI performance of hash algorithms "M. Strobel" <sorry_no_mail_here@nowhere.dee> - 2012-04-23 22:44 +0200

csiph-web