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Changes in hashing [message #54110]

Mon, 01 June 2020 15:43

mirek
Messages: 14291
Registered: November 2005

Ultimate Member

Up until now, hash codes in U++ very strictly 32bit dword. It turns out that using 64bit hash codes on 64bit CPUs is actually faster (more bytes can be processed at once), so I have introduced new type, hash_t, which is 32 bit with 32 bit CPU and 64 bit otherwise and changed the code to compute/use 64 bit hashes instead. Results in about 5% improvement in idmap benchmark...

Practical consideration for user types: If type supports hashing by dword GetHashValue() method, it will continue to work just fine, but might be improved by converting that to hash_t. Template specialisation GetHashValue needs to change the return type hash_t (compiler issues error if it is not).

Mirek

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[Message index]

		Changes in hashing By: mirek on Mon, 01 June 2020 15:43
		Re: Changes in hashing By: Oblivion on Fri, 05 June 2020 12:28
		Re: Changes in hashing By: mirek on Fri, 05 June 2020 12:40
		Re: Changes in hashing By: Oblivion on Fri, 05 June 2020 13:02

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