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CMS Software & Computing. C. Charlot / LLR-École Polytechnique, CNRS & IN2P3 for the CMS collaboration. The Context. LHC challenges Data Handling & Analysis Analysis environments Requirements & constraints. Challenges: Complexity. Detector:

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CMS Software & Computing


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    1. CMS Software & Computing C. Charlot / LLR-École Polytechnique, CNRS & IN2P3 for the CMS collaboration

    2. The Context LHC challenges Data Handling & Analysis Analysis environments Requirements & constraints

    3. Challenges: Complexity Detector: ~2 orders of magnitude more channels than today Triggers must choose correctly only 1 event in every 400,000 Level 2&3 triggers are software-based (reliability) • Computer resources • will not be available • in a single location ACAT02, 24-28 june 2002, Moscow

    4. Challenges: Geographical Spread 1700 Physicists 150 Institutes 32 Countries CERN state 55 % NMS 45 % ~ 500 physicists analysing data in 20 physics groups • Major challenges associated with: Communication and collaboration at a distance Distribution of existing/future computing resources Remote software development and physics analysis ACAT02, 24-28 june 2002, Moscow

    5. HEP Experiment-Data Analysis Quasi-online Reconstruction Environmental data Detector Control Online Monitoring store Request part of event Store rec-Obj Request part of event Event Filter Object Formatter Request part of event store Persistent Object Store Manager Database Management System Store rec-Obj and calibrations Physics Paper store Request part of event Data Quality Calibrations Group Analysis Simulation User Analysis on demand ACAT02, 24-28 june 2002, Moscow

    6. Data handling baseline CMS data model for computing in year 2007 • typical objects 1KB-1MB • 3 PB of storage space • 10,000 CPUs • Hierarchy of sites: 1 tier0+5 tier1+25 tier2 all over the world • Network bw between sites .6-2.5Gbit/s ACAT02, 24-28 june 2002, Moscow

    7. Data Code Analysis environments Real Time Event Filtering and Monitoring • Data driven pipeline • Emphasis on efficiency (keep up with rate!) and reliability Simulation, Reconstruction and Event Classification • Massive parallel batch-sequential process • Emphasis on automation, bookkeeping, error recovery and rollback mechanisms Interactive Statistical Analysis • Rapid Application Development environment • Efficient visualization and browsing tools • Easy of use for every physicist • Boundaries between environments are fuzzy • e.g. physics analysis algorithms will migrate to the online to make the trigger more selective ACAT02, 24-28 june 2002, Moscow

    8. Architecture Overview Data Browser Generic analysis Tools GRID Distributed Data Store & Computing Infrastructure Analysis job wizards ODBMS tools ORCA COBRA OSCAR FAMOS Detector/Event Display CMS tools Federation wizards Coherent set of basic tools and mechanisms Software development and installation Consistent User Interface ACAT02, 24-28 june 2002, Moscow

    9. TODAY Data production and analysis challenges Transition to Root/IO Ongoing work on baseline software

    10. CMS Production stream ACAT02, 24-28 june 2002, Moscow

    11. Production 2002: the scales ACAT02, 24-28 june 2002, Moscow

    12. 12 MB/s ~60 MB/s client client client client Pile-up server client Pile-up DB Production center setup Most critical task is digitization • 300 KB per pile-up event • 200 pile-up events per signal event  60 MB • 10 s to digitize 1 full event on a 1 GHz CPU • 6 MB / s per CPU (12 MB / s per dual processor client) • Up to ~ 5 clients per pile-up server (~ 60 MB / s on its network card Gigabit) • Fast disk access ~5 clients per server ACAT02, 24-28 june 2002, Moscow

    13. Spring02: production summary 6M CMSIM: 1.2 seconds / event for 4 months requested Nbr of events produced 3.5M requested February 8 May 31 1034 produced High luminosity Digitization: 1.4 seconds / event for 2 months April 19 June 7 ACAT02, 24-28 june 2002, Moscow

    14. Regional Center IMPALA decomposition (Job scripts) “Produce 100000 events dataset mu_MB2mu_pt4” Production manager coordinates tasks distribution to Regional Centers RC farm JOBS Production Interface RC BOSS DB Farm storage Data location through Production DB Production “RefDB” IMPALA monitoring (Job scripts) Request Summary file Production processing ACAT02, 24-28 june 2002, Moscow

    15. RefDB Assignement Interface • Selection of a set of Requests and their Assignment to an RC • the RC contact persons get an automatic email with the assignment ID to be used as argument to IMPALA scripts (“DeclareCMKINJobs.sh -a <id>“) • Re-assignment of a Request to another RC or production site • List and Status of Assignments ACAT02, 24-28 june 2002, Moscow

    16. IMPALA • Data product is a DataSet (typically few 100 jobs) • Impala performs production task decomposition and script generation • Each step in the production chain is split into 3 sub-steps • Each sub-step is factorized into customizable functions JobDeclaration Search for something to do JobCreation Generate jobs from templates JobSubmission Submit jobs to the scheduler ACAT02, 24-28 june 2002, Moscow

    17. Job declaration, creation, submission • Jobs to-do are automatically discovered: • looking for output of previous step at predefined directory for the Fortran Steps • querying the Objectivity/DB federation for Digitization, Event Selection, Analysis • Once the to-dolist is ready, the site manager can actually generate instances of jobs starting from a template • Job execution includes validation of produced data • Thank to the sub-step decomposition into customizable functions site managers can: • Define local actions to be taken to submit the job (local job scheduler specificities, queues, ..) • Define local actions to be taken before and after the start of the job (staging input, staging output from MSS) • Auto-recovery of crashed jobs • Input parameters are automatically changed to restart job at crash point ACAT02, 24-28 june 2002, Moscow

    18. Wrapper farm node farm node BOSS job monitoring • Accepts job submission from users • Stores info about job in a DB • Builds a wrapper around the job (BossExecuter) • Sends the wrapper to the local scheduler • The wrapper sends to the DB info about the job BOSS Local Scheduler boss submit boss query boss kill BOSS DB ACAT02, 24-28 june 2002, Moscow

    19. BossExecuter get job info from DB create & go to workdir run preprocess update DB fork user executable fork monitor wait for user exec. kill monitor run postprocess update DB exit BossMonitor get job info from DB while(user exec is running) run runtimeprocess update DB wait some time exit Getting info from the job • A registered job has scripts associated to it which are able to understand the job output User’s executable ACAT02, 24-28 june 2002, Moscow

    20. CMS transition to ROOT/IO • CMS work up to now with Objectivity • We manage to make it work, at least for production • Painful to operate, a lot of human intervention needed • Now being phased out, to be replaced by LCG software • Hence being in a major transition phase • Prototypes using ROOT+RDBMS layer being worked on • This is done within LCG context (persistency RTAG) • Aim to start testing new system as it becomes available • Target early 2003 for first realistic tests ACAT02, 24-28 june 2002, Moscow

    21. OSCAR: Geant4 simulation • CMS plan is to replace cmsim (G3) by OSCAR (G4) • A lot of work since last year • Many problems from the G4 side have corrected • Now integrated in the analysis chain Generator->OSCAR->ORCA using COBRA persistency • Under geometry & physics validation Overall is rather good • Still more to do before using it in production SimTrack Cmsim 122 OSCAR 1 3 2 pre 03 HitsAssoc ACAT02, 24-28 june 2002, Moscow

    22. OSCAR: Track Finding • Number of rechits/simhits per track vs eta RecHits SimHits ACAT02, 24-28 june 2002, Moscow

    23. Detector Description Database • Several applications (simulation, reconstruction, visualization) needed geometry services • Use a common interface to all services • On the other hand several detector description sources currently in use • Use a unique internal representation derived from the sources • Prototype now existing • co-works with OSCAR • co-works with ORCA (Tracker, Muons) ACAT02, 24-28 june 2002, Moscow

    24. ORCA Visualization • IGUANA framework for visualization • 3D visualization • mutliple views, slices, 2D proj, zoom • Co-works with ORCA • Interactive 3D detector geometry for sensitive volumes • Interactive 3D representations of reconstructed and simulated events, including display of physics quantities • Access event by event or automatically fetching events • Event and run numbers ACAT02, 24-28 june 2002, Moscow

    25. TOMORROW Deployment of a distributed data system Evolve software framework to match with LCG components Ramp up computing systems

    26. Toward ONE Grid • Build a unique CMS-GRID framework (EU+US) • EU and US grids not interoperable today. Need for help from the various Grid projects and middleware experts • Work in parallel in EU and US • Main US activities: • PPDG/GriPhyN grid projects • MOP • Virtual Data System • Interactive Analysis: Clarens system • Main EU activities: • EDG project • Integration of IMPALA with EDG middleware • Batch Analysis: user job submission & analysis farm ACAT02, 24-28 june 2002, Moscow

    27. PPDG MOP system PPDG Developed MOP production System Allows submission of CMS prod. Jobs from a central location, run on remote locations, and returnresults Relies on GDMP for replication Globus GRAM Condor-G and local queuing systems for Job Scheduling IMPALA for Job Specification DAGMAN for management of dependencies between jobs Being deployed in USCMS testbed ACAT02, 24-28 june 2002, Moscow

    28. CMS EU Grid Integration CMS EU developed integration of production tools with EDG middleware Allows submission of CMS production jobs using WP1 JSS from any site that has client part (UI) installed Relies on GDMP for replication WP1 for Job Scheduling IMPALA for Job Specification Being deployed in CMS DataTAG testbed UK, France, INFN, Russia ACAT02, 24-28 june 2002, Moscow

    29. CMSIM ORCA BOSS Query Read from track- ing DB Tracking DB Job specific information Submission Build tracking wrapper Update Write to tracking DB Worker nodes Computing Element Job Submission Service GRAM Resource Broker Finds suitable Location for execution Local Scheduler Condor-G Storage Element Local Objy FDDB Local Storage Information Services LDAP server Resource information CMS EDG Production prototype Reference DB has all information needed by IMPALA to generate a dataset User Interface IMPALA Get request for a production Create location independent jobs ACAT02, 24-28 june 2002, Moscow

    30. GriPhyN/PPDG VDT Prototype = no code = existing = implemented using MOP User Planner Executor Compute Resource Storage Resource Concrete DAG Abstract DAG Concrete Planner/ WP1 BOSS Abstract Planner (IMPALA) MOP/ DAGMan WP1 Local Tracking DB CMKIN Wrap- per Scripts CMSIM Local Grid Storage Etc. ORCA/COBRA Script Catalog Services Replica Mgmt RefDB Virtual Data Catalog Materia-lized Data Catalog Replica Catalog GDMP Objecti-vity Federation Catalog ACAT02, 24-28 june 2002, Moscow

    31. CLARENS: a Portal to the Grid • Grid-enabling environment for remote data analysis • Clarens is a simple way to implement web services on the server • No Globus needed on client side, only certificate • The server will provide a remote API to Grid tools: • Security services provided by the Grid (GSI) • The Virtual Data Toolkit: Object collection access • Data movement between Tier centres using GSI-FTP • Access to CMS analysis software (ORCA/COBRA) ACAT02, 24-28 june 2002, Moscow

    32. Conclusions • CMS has performed large scale distributed production of Monte Carlo events • Baseline software is progressing and this is done now within the new LCG context • Grid is the enabling technology for the deployment of a distributed data analysis • CMS is engaged in testing and integrating grid tools in its computing environment • Much work to be done to be ready for a distributed data analysis at LHC startup ACAT02, 24-28 june 2002, Moscow