Delphi experience
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DELPHI experience. I left collaboration in 1997 so I won’t talk about data preservation but another costly effort Change of offline compute platform from IBM mainframe  RISC UNIX

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DELPHI experience

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Delphi experience

DELPHI experience

  • I left collaboration in 1997 so I won’t talk about data preservation but another costly effort

    • Change of offline compute platform from IBM mainframe  RISC UNIX

  • Caveat: this recollection covers a period 20 years ago and is reconstructed from my own notes and mails from that period. Any error is entirely mine…


Compute platform

Compute platform

  • Up to ~1992 main computing platform @CERN was the IBM mainframe CERNVM

  • As a physicist one quickly learned about

    • VM/CMS, REXX, XEDIT

  • DAQ and production learned VAX VMS

    • All offline code cross-compiled and certified

      • YPATCHY with CARds and CRAdles to control the versioning and platform differences

      • DELPHI’s own farms in p8 and basement of bat27 was entirely VAX based, at least to begin with

    • But for normal physics analysis there were never enough VAX compute resources to motivate a serious take-up


Delphi offline in numbers

DELPHI offline in numbers

  • 16 sub-detectors

  • ~1Hz trigger rate, average event size 50kB, peak event size 200kB (1990)

  • Yearly total DST (Data Summary Tape) volume

    • 1989: 3x IBM 3480 cartridge

    • 1990: 38x

    • 1991: 146x

  • Source code was pretty FORTRAN 77 formatted for punch-card compatibility

  • Main packages

  • DELSIM: 0.5-1M of SLOC (DELPHI didn’t use Geant3)

  • DELANA: ~>1M SLOC


Migrate to risc unix

Migrate to RISC/UNIX

  • Compute cycles on CERNVM were precious

  • If you wanted run >1hrs job

    • go to offline computing office and give your justification

    • Priority was given to:

      • Higgs search and Z0 resonance precision measurements

    • QCD studies (like mine) were queued behind

       Strong motivation to seek for other resources


Benchmark that convinced me

Benchmark that convinced me

2x60 = 120 CPUs/event

2x38x24x60x60/55’000

119 CPUs/event


Moving to risc unix

Moving to RISC/UNIX

  • Core teams (~1993):

    • DELPHI

      • Alfonso Lopez-Fernandez (CERN) (later Gilbert Grosdidier)

      • D. M. Edsall (Iowa State University Ames HEP Group)

      • Luiz Mundim(LAFEX-CBPF/PUC)

      • O. Bärring (CERN)

    • CN (IT) SHIFT

      • Frédéric Hemmer

      • Christian Boissat

    • CN Public Login (+AFS): Tony Cass

  • Tasks

    • Create an attractive and reliable compute and storage resource

      • More for less ($/IBM cycle  $/Risc cycle)

    • Cross-compile and certify

    • Mirror production and analysis software repos

      • Nightly builds + tests

    • Facilitate migration (REXX sh, csh)

    • Write targeted user guides (UNIX, SHIFT, FATMEN, …)

    • User support, public presentations and publicity

  • Rough cost:

    • Hardware (provided by CN): negligible (probably ~10-2 x IBM)

    • People: DELPHI ~6 person years for the full migration

  • Dedicated efforts completed in ~1995-6. Daily tasks (support etc.) integrated with general offline activities


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