1. Experience in ALICE – Analysis Framework and Train
Andreas Morsch
CERN

2. Analysis in ALICE Three main analysis modes
Prompt data processing (calibration, alignment, reconstruction, with PROOF
Analysis with local PROOF clusters
Batch Analysis on the GRID infrastructure

3. Plans for Scheduled Analysis
Most efficient way for many analysis tasks to read and process the full data set.
In particular if resources are sparse.
Optimise CPU/IO ratio
But also
Helps to develop a common well tested framework for analysis.
Develops common knowledge base and terminology.
Helps documenting the analysis procedure and makes results reproducible.

4. Plans for scheduled analysis: Analysis train producing AODs
Acceptance and Efficiency Correction Services
Monte Carlo Truth
ESD/AOD
TASK 1
TASK 2
TASK …
TASK N
AOD

5. What the Analysis Framework does in ALICE
Transparent access to all resources with the same code
Usage: Local, AliEn grid, CAF/PROOF
Transparent access to different inputs
ESD, AOD, Kinematics tree (MC truth)
Allow for „scheduled“ analysis
Common and well tested environment to run several tasks

6. Solutions Transparent access to computing resources
Hide computing scheme dependent code in one Manager Class
Transparent access to data
Make intensive use of interfaces
VEventHandler
VEvent
VTrack

7. AliAnalysis… Framework
Data-oriented model composed of independent tasks
Task execution triggered by data readiness
Tasks are owned and managed by AliAnalysisManager
Parallel execution and event loop done via TSelector functionality
Mandatory for usage with PROOF
AliAnalysisTask
INPUT 0
INPUT 1
OUTPUT 0
CONT 0
CONT 1
CONT 2
N.B.: The analysis framework itself has a
very general design, not bound to ALICE software
A. Gheata

8. AliAnalysisManager and PROOF: The Manager in Disguise
TSelector
Delegates
Creates
AliAnalysisSelector
AliAnalysisManager

9. AliAnalysisManager – PROOF mode
CLIENT
PROOF
AliAnalysisSelector
TSelector
AM->StartAnalysis(“proof”)
MyAnalysis.C
Master O1
Analysis
Manager
task1
task2
task3
taskN
Input chain
Outputs
Input list AM
Output list
Worker
Worker
SlaveBegin() AM
task1
task2
task3
taskN
Inputs
Outputs
Worker
Process()
Worker AM
Worker
SlaveTerminate() O2 O1 On
Terminate() O2 On O

10. TObjArray *fContainers
Tasks and event loop
AliAnalysisManager
TObjArray *fContainers
TObjArray *fTasks
AliAnalysisSelector
Chain->Process()
EVENT LOOP
Top cont
ESD chain
Top level tasks and containers
(“Train”)
task1
task2
output1
output2
POST EVENT LOOP
Task
Fit
task4
result
result

11. (AliAODInputHandler)
Tasks and Common I/O
AliAnalysisManager
AliAODHandler
(Output)
AliAODEvent
AliMCEventHandler
AliVEventHandler
AliMCEvent
AliAnalysisTask
AliMCParticle
AliAODtrack
AliESDEvent
(AliAODEvent)
AliESDtrack
AliESDInputHandler
(AliAODInputHandler)
Tasks
AliVParticle
AliVEvent
Data
I/O via slots

12. AliAnalysisTask ConnectInputData() CreateOutPutObjects()
Define which data is connected to which slot
CreateOutPutObjects()
Create Histograms
Init(),LocalInit()
Optional, e.g. read parameters
Exec()
The event loop
Terminate()
Called at the end, can draw e.g. a histogram

13. Common ESD Access Handling
AliAnalysisManager
AliVirtualEventHandler
AliESDInputHandler
AliESDEvent
AliESDInputHandler* inpHandler = new AliESDInputHandler();
inpHandler->SetInactiveBranches(“ Calo FMD “);
AliAnalysisManager *mgr
= new AliAnalysisManager(‘Analysis Train’, ‘Test’);
mgr->SetInputEventHandler(inpHandler);

14. Common ESD Access Handling
void AliAnalysisTaskXYZ::ConnectInputData(Option_t* option) {
// Connect the input data
AliESDInputHandler* esdH =
(AliAODHandler*) ((AliAnalysisManager::GetAnalysisManager())
->GetInputEventHandler());
fESD = esdH->GetEvent(); }

15. Common AOD Access Handling
AliAnalysisManager
AliVirtualEventHandler
AliAODHandler
AliAODEvent
AliAODHandler* aodHandler = new AliAODHandler();
aodHandler->SetOutputFileName("aod.root");
AliAnalysisManager *mgr
= new AliAnalysisManager(‘Analysis Train’, ‘Test’);
mgr->SetOutputEventHandler(aodHandler);
AliAnalysisDataContainer *coutput1 = mgr->CreateContainer(‘AODTree’, TTree::Class(), AliAnalysisManager::kOutputContainer, "default");

16. User Analysis Code: Output Data
void AliAnalysisTaskXYZ::CreateOutputObjects() {
// Create the output container //
// Default AOD
AliAODHandler* handler = (AliAODHandler*) ((AliAnalysisManager::GetAnalysisManager())
->GetOutputEventHandler());
fAOD = handler->GetAOD(); }

17. AliVirtualEventHandler
AliAnalysisManager
AliVirtualEventHandler
AliVEvent
AliMCEventHandler
AliMCEvent
AliMCEventHandler* mcHandler = new AliMCEventHandler();
AliAnalysisManager *mgr
= new AliAnalysisManager(‘Analysis Train’, ‘Test’);
mgr->SetMCtruthEventHandler(mcHandler);

18. User Analysis Code: MC truth
void AliAnalysisTaskXYZ::Exec(Option_t* option ) {
// During Analysis
AliMCEvent* mc = mgr->GetMCEventHandler()->MCEvent();
Int_t ntrack = mc->GetNumberOfTracks();
for (Int_t i = 0; i < ntrack; i++)
AliVParticle* particle = mc->GetTrack(i);
Double_t pt = particle->Pt(); }

19. (Recommended) Integration of User Analysis Code
AliAnalysisTask
Steers
Delegates
AliAnalysisUserTask
User
AnalysisCode
Implements Interface
Deals with AliAODEvent
Documents selection and
analysis parameters
Factory

20. Example: Gamma Analysis Task
AliAnaGamma
AliAnaGammaDirect
AliAnaGammaCorrelation
AliGammaReader
AliGammaDataReader
AliGammaMCReader
AliGammaMCDataReader
AliAnaGammaParton
AliAnaGammaHadron
AliAnaGammaJetLeadCone
AliAnaGammaJetFinder
AliAnalysisGammaTask

21. CAF Related Issues
We produce large output trees which are currently memory resident on the worker side.
Need urgently the TProofFile/TFileMeger mechanism to handle file resident trees.
Future challenges
Event mixing with nested event loops
Repeating loops (calibration, s. M. Ivanov)

22. Integration of User Tasks
Relatively smooth so far
Needs user support to scrutinize (in particular for CAF/PROOF):
Memory requirements (leaks)
Correct data member initialization
On client and workers

23. Analysis train producing AOD
Tested LOCAL, on GRID and PROOF modes on p-p and Pb-Pb events
Monte Carlo Truth
ESD/AOD
ESD
FILTERING
JET
ANALYSIS
GAMMA
TASK
Others to come …
AOD

24. Summary
ALICE Offline has developed an analysis framework that hides computing scheme dependences from the user. The same user code runs on
Local PC
CAF/PROOF
Grid
Framework manages a list of independent tasks:
Execution triggered by data readiness
Sequential execution of the top level task (train) driven by input chain
Common I/O is managed by event handlers
Run-time configuration of Tasks and Handlers

25. Thanks to … A. Gheata M. Gheata J.-F. Grosse-Oetringhaus
Ch, Klein-Boesing
M. Oldenburg
F. Carminati
Y. Schutz
G. Conesa
and many others