CityHash for pair of strings

[whalebot...@gmail.com]

I want to use city hash for string pairs. Common recommendation is H((s1,s2))=H(s1)*max(H(S)) + H(s2). Is there some predefinied maxH(S), or how can it be calculated? Some other variants for H((s1,s2))?

[Geoff Pike]

> I want to use city hash for string pairs. Common recommendation is
> H((s1,s2))=H(s1)*max(H(S)) + H(s2). Is there some predefinied maxH(S), or
> how can it be calculated? Some other variants for H((s1,s2))?

For CityHash64 the return values are in [0, 2^64). For CityHash128
they are in [0, 2^128). And so on.

For a hash of two strings, this should work well:
CityHash64WithSeed(str0, size0, CityHash64(str1, size1)).

Geoff

[whalebot...@gmail.com]

Thanks, that help a lot, about 10% of perfomance

[1971 powerChina]

this net might be helpful：
https://sourceforge.net/projects/pwwhashmap/files/?source=navbar