Conference call notes 20180509 - easybuilders/easybuild GitHub Wiki

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Notes on the 101st EasyBuild conference call, Wednesday May 9th 2018 (5pm - 6pm CEST)

Attendees

Alphabetical list of attendees (7):

  • Damian Alvarez (JSC, Germany)
  • Fotis Georgatos (Illumina, UK)
  • Kenneth Hoste (HPC-UGent, Belgium)
  • Adam Huffman (Big Data Institute, University of Oxford)
  • Bart Oldeman (ComputeCanada)
  • Victor Cameo Ponz (CINES, France)
  • Davide Vanzo (Vanderbilt University)

Agenda

  • outlook to EasyBuild v3.6.1
  • to AVX512 or not to AVX512?
    • discussion on trade-offs for building software using AVX-512 instructions or not on Intel Skylake
  • Q&A

EasyBuild v3.6.1

To AVX-512 or not to AVX-512

  • AVX-512 frequency scaling: https://blog.cloudflare.com/on-the-dangers-of-intels-frequency-scaling/

  • AVX-512 vs FFTW (with a simple benchmark)

  • discussion from GROMACS mailing list:

  • Fotis: we also saw this with GROMACS

    • better performance with FFTW built without AVX...

  • probably early days for AVX-512?

    • only properly tuned in GCC 8.x when relying on -march=native
      • Davide: what else should be used when compiling with GCC 6.x or 7.x on Skylake?
        • Bart: depends on what you're compiling: OK for very vectorizable code
          • for other stuff, may be too heavy use of zmm registers (which may impact clock freq.)
          • recent compilers are less aggressive in that sense
      • should be careful w.r.t. performance
        • compare with installation done with --optarch=march=broadwell or --optarch=march=skylake?
          • skylake (desktop, no AVX512) vs skylake-x (server, AVX512)
    • Bart: similar on Xeon Phi, hard to get very good performance
    • orthogonal to FFTW since that uses assembly

  • should start wiki page or even repository on this?

  • benchmarking AVX512 performance benefits also depends a lot on:

    • which exact processor
    • the system & cooling infrastructure
    • input file used

  • is it really worth to build for AVX-512 currently, or can we get away with AVX2 builds?

    • if there's no clear benefit in performance, why bother building for AVX-512?

Other

  • Davide: {{fosscuda}} toolchain

    • PR for toolchain definition in framework coming up
    • easyconfigs PR for mimicing goolfc/2018a as fosscuda/2018a
    • should also become a common toolchain?

  • some changes to group of EasyBuild maintainers:

    • all 8 current maintainers have been granted admin access to all 4 repositories
    • two additional maintainers will be invited soonish by Kenneth
    • experiment in the next couple of weeks: "EasyBuild maintainer of the week" (MotW)
      • one maintainer (other than Kenneth) who agrees to spend ~1h each (working) day looking at incoming PRs/issues/questions in GitHub repositories + EasyBuild ML
      • best effort, the '~1h' is just a guideline
      • only on voluntary basis, nobody will be forced to
      • plan is to try this in the next couple of weeks to see how it goes
      • some minor concerns were raised w.r.t. being comfortable with framework or easyconfig PRs
        • approach may be revised later to assign different MotW per EasyBuild repository
        • initial setup will be one MotW
      • wiki page will be set up with more info & guidelines