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Re: [ft-devel] To use xxhash for comparision of glyphs
From: |
Werner LEMBERG |
Subject: |
Re: [ft-devel] To use xxhash for comparision of glyphs |
Date: |
Mon, 03 Apr 2017 06:35:39 +0200 (CEST) |
> > Note that generation of MD5 is rather slow. Maybe there are
> > quicker algorithms to generate proper hash values to compare,
> > e.g., `murmur hash 3'.
>
> Sir, I found xxhash by google to be a faster hashing algorithm,
> which is even faster (almost twice) than murmur hash 3. Native
> language of the algorithm is in C.
>
> https://github.com/Cyan4973/xxHash
Thanks for the pointer! I wasn't aware of this algorithm.
> Running the 32 bit version, xxh32sum will be adequate to avoid
> collisions.
Probably, yes. However, for the special purpose of PostScript names
for Variation Fonts, I needed a 128bit version due to the extremely
short imput strings, which xxHash currently doesn't provide. However,
I've found
https://encode.ru/threads/2556-Improving-xxHash
which describes an even faster method than xxHash, and which comes
with a 128bit version...
Note that I decided to use the simplest 128bit version for PS names,
since speed is no issue.
We are digressing :-)
Werner