4 ms·

Looks like djb is giving it a spin: https://twitter.com/hashbreaker/status/1533201734369103872 https://twitter.com/hashbreaker/status/1533201734369103872

janwas 4y ago
Response here because I'm not on Twitter: https://github.com/google/highway/issues/736 https://github.com/google/highway/issues/736 In short, what is being compared is O(1) djbsort sorting network, vs our full quicksort with pivot sampling, partitioning, then sorting network. This is because our sorting network size is 16 * elements_per_vector i.e. 128 in this configuration.
sydthrowaway 4y ago
And he shat all over Google yet again
- aaaaaaaaaaab 4y ago
  But he’s right.
- viraptor 4y ago
  He's just investigating how to reproduce the claimed result. Not sure where you got your take from.
  - jiggawatts 4y ago
    Something to note is that he was testing this on an 11-year old processor: https://ark.intel.com/content/www/us/en/ark/products/52269/intel-xeon-processor-e31220-8m-cache-3-10-ghz.html https://ark.intel.com/content/www/us/en/ark/products/52269/i... The Google sorting algorithm seems to be optimised for the "latest and greatest" AVX-512 capable CPUs.
    - janwas 4y ago
      Oh, thanks for pointing that out. Golly, Sandy Bridge is a bit old, yes - but still the result is surprising. djb reports 8000 cycles for int32 x 256 - this is much slower than we benchmark in bench_sort.cc, even for AVX2 (which he confirms is being reached). Not sure what's going on.
    - wtallis 4y ago
      The Xeon E3-1220 v5 is not the same as the original E3-1220. You want this link: https://ark.intel.com/content/www/us/en/ark/products/88172/intel-xeon-processor-e31220-v5-8m-cache-3-00-ghz.html https://ark.intel.com/content/www/us/en/ark/products/88172/i... The E3 v5 series were part of the generation codenamed Skylake, introduced in 2015. But the Skylake microarchitecture was reused in each subsequent new Intel desktop processor generation through 2019's Comet Lake (due to Intel's 10nm failure). They didn't introduce a new microarchitecture in that product segment until Rocket Lake and Alder Lake, both in 2021. So despite being almost 7 years old, the E3-1220v5 is still representative of most of the installed base for Intel desktops and entry-level workstations, and a large chunk of their mobile installed base. (The original E3-1220 predates AVX2 by two years, so this code wouldn't even run on it.)
      - jiggawatts 4y ago
        Well spotted!

janwas 4y ago

Response here because I'm not on Twitter: https://github.com/google/highway/issues/736 https://github.com/google/highway/issues/736 In short, what is being compared is O(1) djbsort sorting network, vs our full quicksort with pivot sampling, partitioning, then sorting network. This is because our sorting network size is 16 * elements_per_vector i.e. 128 in this configuration.

sydthrowaway 4y ago

And he shat all over Google yet again

aaaaaaaaaaab 4y ago
But he’s right.
viraptor 4y ago
He's just investigating how to reproduce the claimed result. Not sure where you got your take from.
- jiggawatts 4y ago
  Something to note is that he was testing this on an 11-year old processor: https://ark.intel.com/content/www/us/en/ark/products/52269/intel-xeon-processor-e31220-8m-cache-3-10-ghz.html https://ark.intel.com/content/www/us/en/ark/products/52269/i... The Google sorting algorithm seems to be optimised for the "latest and greatest" AVX-512 capable CPUs.
  - janwas 4y ago
    Oh, thanks for pointing that out. Golly, Sandy Bridge is a bit old, yes - but still the result is surprising. djb reports 8000 cycles for int32 x 256 - this is much slower than we benchmark in bench_sort.cc, even for AVX2 (which he confirms is being reached). Not sure what's going on.
  - wtallis 4y ago
    The Xeon E3-1220 v5 is not the same as the original E3-1220. You want this link: https://ark.intel.com/content/www/us/en/ark/products/88172/intel-xeon-processor-e31220-v5-8m-cache-3-00-ghz.html https://ark.intel.com/content/www/us/en/ark/products/88172/i... The E3 v5 series were part of the generation codenamed Skylake, introduced in 2015. But the Skylake microarchitecture was reused in each subsequent new Intel desktop processor generation through 2019's Comet Lake (due to Intel's 10nm failure). They didn't introduce a new microarchitecture in that product segment until Rocket Lake and Alder Lake, both in 2021. So despite being almost 7 years old, the E3-1220v5 is still representative of most of the installed base for Intel desktops and entry-level workstations, and a large chunk of their mobile installed base. (The original E3-1220 predates AVX2 by two years, so this code wouldn't even run on it.)
    - jiggawatts 4y ago
      Well spotted!