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The ALICE Offline Framework
F.Carminati, L.Betev, R.Brun, P.Hristov,
A.Morsch, F.Rademakers, K.Safarik
On behalf of the ALICE Computing Project
CHEP’06
February 13-17, 2006
Mumbai, India
ALICE Collaboration


~ 1/2 ATLAS, CMS, ~ 2x LHCb
~1000 people, 30 countries, ~
80 Institutes
Total weight
Overall diameter
Overall length
Magnetic Field
10,000t
16.00m
25m
0.4Tesla
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The history
• Developed since 1998 along a coherent line
• Developed in close collaboration with the
ROOT team
• No separate physics and computing team
– Minimise communication problems
– May lead to “double counting” of people
• Used for the TDR’s of all detectors and
Computing TDR simulations and
reconstructions
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The framework
G3
G4
FLUKA
ISAJET
Virtual MC
AliRoot
AliReconstruction
HIJING
AliSimulation
AliEn + LCG
EVGEN
PYTHIA6
STEER
PMD
STRUCT
EMCAL
CRT
TRD
ITS
START
PHOS
FMD
TOF
MUON
MEVSIM
ZDC
TPC
RICH
RALICE
PDF
HBTP
ESD
HBTAN
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AliAnalysis
ROOT
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JETAN
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The code
•
•
•
•
•
0.5MLOC C++
0.5MLOC “vintage” FORTRAN code
Nightly builds
Strict coding conventions
Subset of C++ (no templates, STL or exceptions!)
– “Simple” C++, fast compilation and link (see R.Brun’s talk)
– No configuration management tools (only cvs)
– aliroot is a single package to install
• Maintained on several systems
– DEC-Tru64, Mac OSX, Linux RH/SLC/Fedora (i32:i64:AMD),
Sun Solaris
• 30% developed at CERN and 70% outside
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The tools
•
•
•
•
•
•
Coding convention checker
Reverse engineering
Smell detection
Branch instrumentation
Genetic testing (in preparation)
Aspect Oriented Programming (in
preparation)
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The Simulation
See A.Morsch’s talk
User
Code
VMC
G3
G3 transport
G4
G4 transport
FLUKA
FLUKA
transport
Reconstruction
Geometrical
Modeller
Visualisation
Generators
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QuickTime™ and a
decompressor
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TGeo modeller
Performance for "Where am I" - physics
case (G3 geometries collected in 2002)
TESLA
BTEV
MINOS_NEAR
CDF
BRAHMS
CMS
ATLAS
ROOT
Gexam 4
G3
Gexam 3
Gexam 1
0
10
20
30
microsec/point
(1 milion
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The reconstruction
See P.Hristov’s talk
• Incremental process
– Forward propagation
towards to the vertex
TPCITS
– Back propagation
ITSTPCTRDTOF
– Refit inward
TOFTRDTPCITS
TOF
TRD
TPC
ITS
• Continuous seeding
– Track segment finding in
all detectors
•
Combinatorial tracking in ITS
–
–
–
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Conflict !
Weighted two-tracks 2 calculated
Effective probability of cluster
sharing
Probability not to cross given layer
for secondary particles
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Best track 1
Best track 2
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Calibration
Physics
data
ECS
files
API
DAQ
API
Trigger
API
DCS
API
DCDB
API
HLT
API
shuttle
calibration
procedures
calibration
files
AliEn+LCG
metadata
file store
From URs:
Source, volume,
granularity, update
frequency, access
pattern, runtime
environment and
dependencies
Calibration
classes
AliRoot
API
API – Application Program Interface
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Alignment
See A.Gheata’s talk
Simulation
Reconstruction
Ideal Geometry
Misalignment
Ideal Geometry
File from
survey
Alignment procedure
Raw data
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Tag architecture
Reconstruction
ev#guid Tag1, tag2, tag3…
ev#guid Tag1, tag2, tag3…
ev#guid Tag1, tag2, tag3…
Index builder
ev#guid Tag1, tag2, tag3…
proof#1
proof#2
proof#3
Bitmap
Index
guid#{ev1…evn}
guid#{ev1…evn}
Selection List of ev#guid’s
guid#{ev1…evn}
…
proof#n
guid#{ev1…evn}
Analysis job
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Visualisation
See M.Tadel’s talk
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QuickTime™ and a
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QuickTime™ and a
TIFF (Uncompressed) decompressor
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QuickTime™ and a
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ALICE Analysis Basic Concepts
•
–
–
–
•
Prompt reco/analysis at T0 using
PROOF infrastructure
Batch Analysis using GRID
infrastructure
Interactive Analysis using
PROOF(+GRID) infrastructure
User Interface
–
•
ALICE User access any GRID
Infrastructure via AliEn or
ROOT/PROOF UIs
AliEn
–
–
Native and “GRID on a GRID”
(LCG/EGEE, ARC, OSG)
integrate as much as possible
common components
•
•
p
Analysis Models
LFC, FTS, WMS, MonALISA ...
PROOF/ROOT
–
–
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single + multitier static and dynamic
PROOF cluster
GRID API class
TGrid(virtual)TAliEn(real)
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ALICE view on the current situation
Exp
Exp specific services
specific
(AliEn’ for ALICE)
services
AliEn
AliEn arch + LCG code
EGEE,
ARC,
OSG…
EGEEEDG
LCG
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ALICE Grid
VO-Box
Submits job
ALICE Job Catalogue
ALICE File Catalogue
Job 1.1
lfn1
lfn
guid
{se’s}
Job 1.2
lfn2
lfn
guid
{se’s}
Job 1.3
lfn3, lfn4
lfn
guid
{se’s}
Job 2.1
lfn1, lfn3
lfn
guid
{se’s}
lfn
guid
{se’s}
Job 2.1
lfn2, lfn4
Job 3.1
lfn1, lfn3
Job 3.2
lfn2
User
Optimizer
Registers
output
User Job
ALICE central
services
ALICE catalogues
Site
packman
Execs
agent
Workload
request
LCG
File access
WN
xrootd
GUID
CE
SRM
SA
Computing
Agent
SURL
LFC
MSS
RB
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Distributed analysis
File Catalogue query
User job (many events)
Data set (ESD’s, AOD’s)
Job output
Job Optimizer
Sub-job 1
Sub-job 2
Job Broker
CE and SE
processing
Output file 1
CE and SE
processing
Output file 2
Sub-job n
Grouped by SE files
location
Submit to CE with
closest SE
CE and SE
processing
processing
Output file n
File merging job
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Data Challenge
• Last (!) exercise
before data taking
• Test of the system
started with
simulation
• Up to 3600 jobs
running in parallel
• Next will be
reconstruction and
analysis
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Mistakes we made
• Planning was very difficult with a really
distributed community
– We found very difficult to set milestones
• Communication stays a real problem in
spite of frequent meetings
• We did not understand that some
essential information was going to
become available (too) late
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Conclusions
• ALICE has followed a single evolution
line since eight years
• Most of the initial choices have been
validated by our experience
• Some parts of the framework still have
to be populated by the sub-detectors
• Wish us good luck!
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