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Current Monte Carlo calculation activities in ATLAS (ATLAS Data Challenges )

Current Monte Carlo calculation activities in ATLAS (ATLAS Data Challenges ). Oxana Smirnova LCG/ATLAS, Lund University SWEGRID Seminar (April 9, 2003, Uppsala). ATLAS: preparing for data taking. Currently @ Data Challenge 1 (DC1). Event generation completed during DC0 Main goals of DC1:

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Current Monte Carlo calculation activities in ATLAS (ATLAS Data Challenges )

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  1. Current Monte Carlo calculation activities in ATLAS(ATLAS Data Challenges) Oxana SmirnovaLCG/ATLAS, Lund UniversitySWEGRID Seminar (April 9, 2003, Uppsala)

  2. ATLAS: preparing for data taking oxana.smirnova@hep.lu.se

  3. Currently @ Data Challenge 1 (DC1) • Event generation completed during DC0 • Main goals of DC1: • Need to produce simulated data for High Level Trigger & Physics Groups • Reconstruction & analysis on a large scale • learn about data model; I/O performances; identify bottlenecks etc • Data management • Use/evaluate persistency technology • Learn about distributed analysis • Involvement of sitesoutside CERN • Use of Grid as and when possible and appropriate oxana.smirnova@hep.lu.se

  4. DC1, Phase 1: Task Flow • Example: one sample of di-jet events • PYTHIA event generation: 1.5 x 107 events split into partitions (read: ROOT files) • Detector simulation: 20 jobs per partition, ZEBRA output Athena-Root I/O Zebra Hits/ Digits MCTruth Atlsim/Geant3 + Filter Di-jet HepMC (~450 evts) (5000 evts) 105 events Pythia6 Atlsim/Geant3 + Filter Hits/ Digits MCTruth HepMC Atlsim/Geant3 + Filter Hits/ Digits MCtruth HepMC Detector Simulation Event generation oxana.smirnova@hep.lu.se

  5. Piling up events oxana.smirnova@hep.lu.se

  6. Future: DC2-3-4-… • DC2: • Originally Q3/2003 – Q2/2004 • Will be delayed • Goals • Full deployment of Event Data Model & Detector Description • Transition to the new generation of software tools and utilities • Test the calibration and alignment procedures • Perform large scale physics analysis • Further tests of the computing model • Scale • As for DC1: ~ 107 fully simulated events • DC3: Q3/2004 – Q2/2005 • Goals to be defined; Scale: 5 x DC2 • DC4: Q3/2005 – Q2/2006 • Goals to be defined; Scale: 2 X DC3 Sweden can try to provide ca 3-5% contribution (?) oxana.smirnova@hep.lu.se

  7. DC requirements so far • Integrated DC1 numbers: • 50+ institutes in 20+ countries • Sweden enter with other Nordic countries via the NorduGrid • 3500 “normalized CPUs” (80000CPU-days) • Nordic share: equivalent of 320 “normalized CPUs” (ca. 80 in real life) • 5 × 107 events generated • No Nordic participation • 1 × 107 events simulated • Nordic: ca. 3× 105 • 100 TB produced (135 000 files of output) • Nordic: ca. 2 TB, 4600 files • More precise quantification is VERY difficult because of orders of magnitude complexity differences between different physics channels and processing steps • CPU time consumption: largely unpredictable, VERY irregular • OS: GNU/Linux, 32 bit architecture • Inter-processor communication: never been a concern so far (no MPI needed) • Memory consumption: depends on the processing step/data set, so far 512 MB have been enough • Data volumes: vary from KB to GB per job • Data access pattern: mostly unpredictable, irregular • Data bases: each worker node is expected to be able to access a remote database • Software is under constant development, will certainly exceed 1 GB, includes multiple dependencies on HEP-specific software, sometimes licensed oxana.smirnova@hep.lu.se

  8. And a bit about Grid • ATLAS DC ran on Grid since summer 2002 (NorduGrid, US Grid) • Future DCs will be to large extent (if not entirely) gridified • Allocated computing facilities must have all the necessary Grid middleware (but ATLAS will not provide support) • Grids that we tried: • NorduGrid – a Globus-based solution developed in Nordic countries, provides stable and reliable facility, executes all the Nordic share of DCs • US Grid (iVDGL) – basically, Globus tools, hence missing high-level services, but still serves ATLAS well, executing ca 10% of US DC share • EU DataGrid (EDG) – way more complex solution (but Globus-based, too), still in development, not yet suitable for production, but can perform simple tasks. Did not contribute to DCs • Grids that are coming: • LCG: will be initially strongly based on EDG, hence may not be reliable before 2004 • EGEE: another continuation of EDG, still in the proposal preparation state • Globus moves towards Grid Services architecture – may imply major changes both in existing solutions, and in planning oxana.smirnova@hep.lu.se

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