Re: Good hash for pointers

Malcolm McLean <malcolm.arthur.mclean@gmail.com> writes:

On 09/06/2024 12:35, Bonita Montero wrote:
>

uint64_t MichaelsHash( uint64_t key )
{
 __m128i xkey = _mm_set_epi64x( key, 42 );
 using bar_t = pair<uint64_t, uint64_t>;
 static bar_t const bars[8] =
 {
  { 0xBB09BBCC90B24BF2, 0x825C622FF2792A01 },
  { 0x94F0535CB06D4060, 0x939C756246DBFD1D },
  { 0x5B835E01A7E14CA1, 0xAC2BDAFC023CDD06 },
  { 0xE0B6A4735B774AEC, 0x9CAFB43E7DDE494C },
 };
 for( bar_t const &bar : bars )
  xkey = _mm_aesenc_si128( xkey, _mm_set_epi64x( bar.second,
bar.first ) );
 return xkey.m128i_u64[0];
}
>
Now the code is about six times faster and I get a eight times
speedup over single-threaded processing with the same code.  Of
course the results are still the same.

>
I have your permission to drop that in?

Note that this code was cribbed from Michael S.  If you
think it's important to ask permission, I think he is
the one you should be asking.

By the way, I thought you were looking for code that works
in standard C, and acceptable under C90 rules.  Have you
changed your mind about that?  The code above is a far
cry from C, let alone C90.