1. ATLAS Data Challenges US ATLAS Physics & Computing ANL October 30th 2001 Gilbert Poulard CERN EP-ATC

2. ATLAS Plenary-18 October 2001 2 Outline  ATLAS Data Challenges & “LHC Computing Grid Project”  Goals  Scenarios  Organization

3. ATLAS Plenary-18 October 2001 3 From CERN Computing Review CERN Computing Review (December 1999 - February 2001) Recommendations: organize the computing for the LHC era LHC Grid project Phase 1: Development & prototyping (2001-2004) Phase 2: Installation of the 1st production system (2005-2007) Software & Computing Committee (SC2) Project accepted by the CERN council (20 September) Ask the experiments to validate their Computing model by iterating on a set of Data Challenges of increasing complexity However DC’s were in our plans

4. ATLAS Plenary-18 October 2001 4 LHC Computing GRID project Phase1:  Prototype construction develop Grid middleware acquire experience with high-speed wide-area network develop model for distributed analysis adapt LHC applications deploy a prototype (CERN+Tier1+Tier2)  Software complete the development of the 1st version of the physics application and enable them for the distributed grid model develop & support common libraries, tools & frameworks including simulation, analysis, data management,... in parallel LHC collaborations must develop and deploy the first version of their core software

5. ATLAS Plenary-18 October 2001 5 ATLAS Data challenges  Goal understand and validate: our computing model, our data model and our software our technology choices  How? In iterating on a set of DCs of increasing complexity Start with data which looks like real data Run the filtering and reconstruction chain Store the output data into our database Run the analysis Produce physics results To study Performances issues, database technologies, analysis scenarios,... To identify weaknesses, bottle necks, etc… (but also good points)

6. ATLAS Plenary-18 October 2001 6 ATLAS Data challenges  But: Today we don’t have ‘real data’ Needs to produce ‘simulated data’ first so: Physics Event generation Simulation Pile-up Detector response Plus reconstruction and analysis will be part of the first Data Challenges we need also to “satisfy” the ATLAS communities HLT, Physics groups,...

7. ATLAS Plenary-18 October 2001 7 ATLAS Data Challenges: DC0  DC0 November-December 2001 'continuity' test through the software chain aim is primarily to check the state of readiness for DC1 We plan ~100k Z+jet events, or similar To validate the software: issues to be checked include – G3 simulation running with the ‘latest’ version of the geometry –reconstruction running Re-analyze part of the Physics TDR data “reading from & writing to Objectivity” Would test the “Objy database infrastructure” Complementary to the “continuity test”

8. ATLAS Plenary-18 October 2001 8 ATLAS Data Challenges: DC1  DC1 February-July 2002 reconstruction & analysis on a large scale learn about data model; I/O performances; identify bottle necks … use of GRID as and when possible and appropriate data management Use (evaluate) more than one database technology (Objectivity and ROOT I/O) Learn about distributed analysis should involve CERN & outside-CERN sites site planning is going on, an incomplete list already includes sites from Canada, France, Italy, Japan, UK, US, Russia scale 10 7 events in 10-20 days, O(1000) PC’s data needed by HLT & Physics groups (others?) Study performance of Athena and algorithms for use in HLT simulation & pile-up will play an important role checking of Geant4 versus Geant3

9. ATLAS Plenary-18 October 2001 9 ATLAS Data Challenges: DC1  DC1 will have two distinct phases First, production of events for HLT TDR, where the primary concern is delivery of events to HLT community; Second, testing of software (G4, dBases, detector description,etc.) with delivery of events for physics studies Software will change between these two phases Simulation & pile-up will be of great importance strategy to be defined (I/O rate, number of “event” servers?) As we want to do it ‘world-wide’ we will ‘port’ our software to the GRID environment and use as much as possible the GRID middleware (ATLAS kit to be prepared)

10. ATLAS Plenary-18 October 2001 10 ATLAS Data Challenges: DC2  DC2 Spring-Autumn 2003 Scope will depend on what has and has not been achieved in DC0 & DC1 At this stage the goal includes: Use of ‘TestBed’ which will be built in the context of the Phase 1 of the “LHC Computing Grid Project” Scale at a sample of 10 8 events System at a complexity ~50% of 2006-2007 system Extensive use of the GRID middleware Geant4 should play a major role Physics samples could(should) have ‘hidden’ new physics Calibration and alignment procedures should be tested May be to be synchronized with “Grid” developments

11. ATLAS Plenary-18 October 2001 11 DC scenario  Production Chain: Event generation Detector Simulation Pile-up Detectors responses Reconstruction Analysis These steps should be as independent as possible

12. ATLAS Plenary-18 October 2001 12 Production stream “OO-db” is used for “OO database”, it could be Objectivity, ROOT/IO, …

13. ATLAS Plenary-18 October 2001 13 DC1 Ntuple Pythia, Isajet, Herwig, MyGeneratorModule HepMC Obj., Root ATLFAST OO Ntuple Obj., Root GENZ G3/DICE RD event ? OO-DB ? ATHENA reconstruction Comb. Ntuple Obj., Root Comb. Ntuple G4 Obj. Missing: -- filter, trigger -- Detector description -- HepMC in Root -- Digitisation -- ATLFAST output in Root (TObjects) -- Pile-up -- Link MC truth - ATLFAST -- Reconstruction output in Obj., Root -- EDM (e.g. G3/DICE, G4 input to ATHENA) Ntuple- like ZEBRA

14. ATLAS Plenary-18 October 2001 14 Detector Simulation  Geant3 and Geant4 For HLT & physics studies we will use Geant3 Continuity with past studies ATLAS validation of Geant4 is proceeding well but not completed Detector simulation in Atlsim (Zebra output) Some production with Geant4 too Goals to be defined with G4 and Physics groups It is important to get experience with ‘large production’ as part of G4 validation it is important to use the same geometry input  In the early stage we could decide to use only part of the detector it would also be good to use the same sample of generated events Detector simulation we propose to use the FADS/Goofy framework Output will be ‘Hits collections’ in OO-db  Detector responses (& pileup) has to be worked on in new framework

15. ATLAS Plenary-18 October 2001 15 Reconstruction  Reconstruction we want to use the ‘new reconstruction’ code being run in Athena framework Input should be from OO-db Output in OO-db: ESD (event summary data) AOD (analysis object data) TAG (event tag)

16. ATLAS Plenary-18 October 2001 16 Analysis  We are just starting to work on this but Analysis tools evaluation should be part of the DC It will be a good test of the Event Data Model Performance issues should be evaluated Analysis scenario It is important to know the number of analysis groups, the number of physicists per group, the number of people who want to access the data at the same time It is of ‘first’ importance to ‘design’ the analysis environment to measure the response time to identify the bottle necks for that users’ input is needed

17. ATLAS Plenary-18 October 2001 17 Data management  It is a key issue  Evaluation of more than one technology is part of DC1 Infrastructure has to be put in place: For Objectivity & ROOT I/O Software, hardware, tools to manage the data –creation, replication, distribution discussed in database workshop  Tools are needed to run the production “bookkeeping”, “cataloguing” … Run number, random number allocation, … Working group now set-up Job submission Close collaboration with ATLAS Grid (validation of Release 1)

18. ATLAS Plenary-18 October 2001 18 DC1-HLT - CPU Number of events Time per event sec SI95 Total time Sec SI95 Total time Hours SI95 simulation 10 7 3000 3 * 10 10 10 7 reconstruction 10 7 640 6.4 * 10 9 2 * 10 6

19. ATLAS Plenary-18 October 2001 19 DC1-HLT - data Number of events Event size MB Total size GB Total size TB simulation 10 7 2 20000 20 reconstruction 10 7 0.5 5000 5

20. ATLAS Plenary-18 October 2001 20 DC1-HLT data with pile-up LNumber of events Event size MB Total size GBTotal size TB 2 x 10 33 1.5 x 10 6 (1) 2.6 (2) 4.7 4000 7000 4747 10 34 1.5 x 10 6 (1) 6.5 (2) 17.5 10000 26000 10 26 In addition to ‘simulated’ data, assuming ‘filtering’ after simulation (~14% of the events kept). - (1) keeping only ‘digits’ - (2) keeping ‘digits’ and ‘hits’

21. ATLAS Plenary-18 October 2001 21 Ramp-up scenario @ CERN Week in 2002

22. ATLAS Plenary-18 October 2001 22 What next  This week: Have an updated list of goals & requirements prepared with HLT, Physics communities simulation, reconstruction, database communities people working on ‘infrastructure’ activities bookkeeping, cataloguing,... Have a list of tasks Some Physics oriented But also like testing code, running production, … with ‘established’ responsibilities and priorities And working groups in place You can join

23. ATLAS Plenary-18 October 2001 23 What next  In parallel Define ATLAS validation plan for EU-DataGrid Release 1 ATLAS software for DC0 and DC1 Understand the involvement of Tier centers Insure that we have the necessary resources @ CERN and outside CERN We have already some input and a ‘table’ is being prepared “And turn the key”