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ALICE Physics Data Challenge’04

P.HristovMarch 19, 2004

CERN

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Goals(http://cern.ch/fca/ALICE-DCs.doc)

■ Determine readiness of the off-line framework for data processing

■ Validate the distributed computing model■ PDC’2004:10% test of the final capacity

■ Complete chain used for trigger studies■ Prototype of the analysis tools■ Comparison with parameterized MC■ Simulated RAW data

■ PDC’04 physics: hard probes (jets, heavy flavours) & pp physics

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Physics Data Challenge'2004

■ Simulation: 10^5 Pb-Pb + 10^7 p-p 102 TB ■ 450 KSI2K (~ tier-1 capacity) x 3 months■ Distributed production, then data are shipped

to CERN■ Reconstruction: 5x10^6 Pb-Pb+10^7 p-p 187 TB

■ Reconstruction is shared between CERN & outside centres according to available resources

■ Data originate from CERN ■ Analysis: 5x10^6 Pb-Pb+10^7 p-p 13 TB ■ See http://aliweb.cern.ch/people/phristov

/PDC04.html

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PDC’04 Strategy■ Part 1: underlying events

■ Distributed simulation, production of summable digits, digitization, clusterization, reconstruction, PID, and generation of ESD

■ Data transfer to CERN: kinematics, track references, summable digits (hits for some detectors)

■ Part 2: signal events & test of CERN as data source■ Distributed simulation, production of summable

digits, merging, digitization, clusterization, reconstruction, PID, generation of ESD

■ Part 3: distributed analysis

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AliRoot Layout

ROOT

AliRoot

STEER

Virtual MC

G3 G4 FLUKA

HIJING

MEVSIM

PYTHIA6

PDF

EVGEN

HBTP

HBTAN

ISAJET

AliE

n

EMCAL ZDCITS PHOSTRD TOF RICH

ESD

AliAnalysis

AliReconstruction

PMD

CRT FMD MUON TPCSTART RALICESTRUCT

AliSimulation

NEW

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Current Status

■ Major changes in the last year■ New multi-file I/O finally in full production■ New coordinate system■ New reconstruction and simulations classes■ First attempt at the ESD and analysis framework■ Improvements in reconstruction and simulation

■ Clearly the system works well, however a lot of changes to come

■ ESD: the philosophy is still evolving■ Introduction of FLUKA and new geometrical modeller■ Development of the analysis framework■ Raw data for all the detectors -- we need them for the

data challenge■ Introduction of the condition database infrastructure

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CERN

Tier2

Tier1

Tier2

Tier1

Production of RAW

Shipment of RAW to CERN

Reconstruction of RAW in all T1’s

Analysis

AliEn job control

Data transfer

PDC’04 Schema

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Signal-free event Merged

signal

Merging

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Alien CE

LCG UIAlien

CEs/SEs

Server

User submits jobs

Catalog

LCG RB

LCG CEs/SEs

LCG LFN

LCG PFN

LCG LFN = AliEn PFN

Catalog

AliEn, Genius & EDG/LCG

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QLCG CPUgood jobs

LCG

CPUavailableLCG ; QAliEn

CPUgood jobsAliEn

CPUavailableAliEn

ALICE PDC04 & LCG

■ All the production is started via AliEn, the analysis will be done via Root/Proof/AliEn

■ LCG-2 is one CE element of AliEn, which integrates seamlessly LCG and non LCG resources

■ If LCG-2 works well, it gets a large amount of jobs, and it is used heavily

■ If LCG-2 does not work well, AliEn will privilege other resources, and it will be less used

■ In all cases we will use LCG-2 as much as possible■ We will not need to take any decision: the performance

of the system will decide for us

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Short History

■ Jan 03: Requirements for ALICE PDC04 presented to PEB

■ End Dec 03: Announcement of LCG-2 by mid February 2004

■ Beg Jan 04: Decision to delay PDC04 by one month waiting for LCG-2

■ Beg Jan 04: LCG announces that there will be no SE in LCG-2

■ Beg Feb 04: The WAN resources allocated by LCG for data storage are insufficient/inadequate

■ Mid Feb 04: Development of an ALICE solution, developed in haste and working against all odds!

■ End Feb 04: IT has also come up with a solution responding to a CMS requirement

■ End Feb 04: Production started, new sites being added

■ End Feb 04: Tape vault flooded -- our tapes have been spared

■ Beg Mar 04: castor nameserver has to be reinstalled (running on Linux 6.2)

■ Beg Mar 04: castor servers have to be reinstalled for security

■ Beg Mar 04: LCG RB works differently on the different centres. ■ e.g. CNAF has to be switched on and off by hand, otherwise it “swallows” all the jobs!

■ Beg Mar 04: we are obtaining now close to 10 TB

■ Mid Mar 04: Files on the IT-provided pool are erased before being copied on tape

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Data Challenge Statistics

Picture from yesterday, 18/03/2004

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Data Challenge Statistics

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Data Challenge Statistics

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Considerations

■ LCG is providing a lot of cycles■ ALICE is the first to use the system for production■ This required continuous efforts and

interventions (ALICE and LCG), particularly due to lousy workload scheduling and lack of stability

■ The lack of an SE will make reconstruction and analysis possible only under AliEn

■ Relations with LCG are in general good■ They are sincerely willing to help■ But the system was not fully prepared for our

PDC’04■ LCG PR / planning can be improved!

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Considerations (cont)

■ Next time we will start six months before!■ LCG needs to be “prompted” for resources and

support■ Some ALICE people did not get well the philosophy

of a DC ■ The period Jan-Feb was well spent

■ Changes in AliRoot improved performance and results

■ AliEn now has a more advanced SE solution■ The Offline members reacted extremely well to

pressure and the exercise is definitely very useful■ We will reach the objectives!

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Period(milestone)

Fraction of the final capacity (%)

Physics Objective

06/01-12/01 1% pp studies, reconstruction of TPC and ITS

06/02-12/02 5%

• First test of the complete chain from simulation to reconstruction for the PPR

• Simple analysis tools• Digits in ROOT format

01/04-06/04 10%

• Complete chain used for trigger studies• Prototype of the analysis tools• Comparison with parameterised

MonteCarlo• Simulated raw data

05/05-07/05 TBD• Refinement of jet studies• Test of new infrastructure and MW• TBD

01/06-06/06 20%• Test of the final system for

reconstruction and analysis

ALICE Physics Data Challenges

NEW NEW