Re: [hash2] Andrey's review

From: Peter Dimov (pdimov_at_[hidden])
Date: 2024-12-10 15:35:31

Andrey Semashev wrote:
> Here's the output on my machine:
> 
> sha1_160 (1024 bytes): 1220.093078 MiB/s
> sha1_160 (1048576 bytes): 1317.424120 MiB/s
> sha1_160 (16777216 bytes): 1318.296514 MiB/s
> sha2_256 (1024 bytes): 406.139530 MiB/s
> sha2_256 (1048576 bytes): 430.141013 MiB/s
> sha2_256 (16777216 bytes): 429.341694 MiB/s
> sha2_512 (1024 bytes): 629.593514 MiB/s
> sha2_512 (1048576 bytes): 712.100583 MiB/s
> sha2_512 (16777216 bytes): 711.549426 MiB/s
> openssl_sha1_160 (1024 bytes): 1531.142208 MiB/s
> openssl_sha1_160 (1048576 bytes): 2759.062140 MiB/s
> openssl_sha1_160 (16777216 bytes): 2738.579482 MiB/s
> openssl_sha2_256 (1024 bytes): 1541.291824 MiB/s
> openssl_sha2_256 (1048576 bytes): 2462.035414 MiB/s
> openssl_sha2_256 (16777216 bytes): 2449.770143 MiB/s
> openssl_sha2_512 (1024 bytes): 781.187505 MiB/s
> openssl_sha2_512 (1048576 bytes): 1086.239840 MiB/s
> openssl_sha2_512 (16777216 bytes): 1082.922782 MiB/s
> 
> So, depending on the input message size, OpenSSL is faster from 1.24x to
> 5.72x. Interestingly, despite what is said in Boost.Hash2 documentation (and
> confirmed by the test), OpenSSL's implementation of SHA2-256 is faster than
> SHA2-512. This could be because of the SHA ISA extensions in my CPU.

These are interesting timings. Originally I assumed that this is
because OpenSSL uses SIMD. But you're right that it might
actually use SHA-NI instead.

https://en.wikipedia.org/wiki/Intel_SHA_extensions

For some reason I thought that SHA-NI only supported SHA1,
but it does support SHA2-256 as well.

Is there an easy way to check what OpenSSL uses? Probably
not because it selects the instruction set at runtime.