glast large area telescope: lat science analysis software’s use of gaudi & root heather kelly

GLAST ADASS 2005 Oct 4

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GLAST Large Area Telescope:GLAST Large Area Telescope:

LAT Science Analysis Software’s Use of Gaudi & ROOT

Heather KellyNASA Goddard Space Flight CenterScience Systems and Applications Inc.For the GLAST LAT Collaboration [email protected]

Gamma-ray Large Gamma-ray Large Area Space Area Space TelescopeTelescope

http://www-glast.slac.stanford.edu/software


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GLAST MissionGLAST Mission

GLAST measures the direction, energy and arrival time of celestial gamma rays

-LAT measures gamma-rays in the energy range ~20 MeV - >300 GeV

- There is no telescope now covering this range!!

- GBM provides correlative observations of transient events in the energy range ~20 keV – 20 MeV

Launch: August 2007 Florida

Orbit: 565 km, 28.5o inclination

Lifetime: 5 years (minimum; 10 yrs goal)


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GLAST ParticipationGLAST Participation

NASA - DoE Partnership on LAT

LAT is being built by an international teamStanford University (SLAC & HEPL, Physics)Goddard Space Flight CenterNaval Research LaboratoryUniversity of California, Santa CruzUniversity of WashingtonOhio State UniversityCEA/Saclay & IN2P3 (France)INFN & ASI (Italy)Hiroshima University, ISAS, RIKEN (Japan)Royal Inst. of Technology & Stockholm Univ. (Sweden)

GBM is being built by US and GermanyMPE, Garching (Germany)Marshall Space Flight Center

Spacecraft and integration - Spectrum Astro

France Germany Italy Japan Sweden USA

LAT managed by SLACPI – Peter Michelson


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0.01 GeV 0.1 GeV 1 GeV 10 GeV 100 GeV 1 TeV0.01 GeV 0.1 GeV 1 GeV 10 GeV 100 GeV 1 TeV

Gamma Ray Bursts

Unidentified sources Cosmic ray

acceleration

Active Galactic Nuclei

Dark matter

GLAST science - the sky above 20 MeV

Pulsars

Solar flares


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GLAST Large Area Telescope (LAT)GLAST Large Area Telescope (LAT)

e+ e–

Si Tracker Towerpitch = 228 µm5.52 104 channels12 layers × 3% X0

+ 4 layers × 18% X0

+ 2 layers

Grid (& Thermal Radiators)

3000 kg, 650 W (allocation)

1.8 m 1.8 m 1.0 m

20 MeV – 300 GeV

CsI CalorimeterHodoscopic array8.4 X0 8 × 12 bars

2.0 × 2.7 × 33.6 cm cosmic-ray rejection shower leakage correction

ACDSegmented scintillator tiles0.9997 efficiency

minimize self-veto

Data acquisition

16 identical towers300 Hz average downlink

Single Photon Angular Resolution3.5o @ 100 MeV0.15o @ 10 GeV

Good Energy ResolutionE/E ~ 10%; 100 MeV – 10 GeV ~ < 20%; 10 GeV – 300 GeV


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GLAST Concept

• Low profile for wide f.o.v.

• Segmented anti-detector to minimize self-veto at high E.

• Finely segmented calorimeter for enhanced background rejection and shower leakage correction.

• High-efficiency, precise track detectors located close to the conversions foils to minimize multiple-scattering errors.

• Modular, redundant design.

• No consumables.

• Low power consumption (650 W)

Calorimeter (energy measurement)

Particle tracking detectors

Conversion foils (W)

Charged particle anticoincidence shield

e+ e-

Pair production is the dominant photon interaction in our energy range

detection – pair conversion telescope


7/21

A Special NoteA Special Note

• This talk discusses the LAT data format and software.• FITS and FTOOLs will be delivered to the user community.

• Science End-Users view GLAST data as photon lists, tend to be taken in aggregate.

• LAT team looks at data on an event by event basis.– Upon triggering GLAST freezes its detectors and writes out

its buffers.– Once on the ground, the game is to separate gammas from

background. (1000:1)• Determine best estimate for direction and energy.

– Part of the LAT collaboration’s job is to provide the highest quality photon lists to the science user community.


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Some BackgroundSome Background

• ~25 developers distributed across 9 time zones– VRVS (www.vrvs.org) and Instant Messaging (ICQ/Gaim)– Face-to-Face meetings twice a year– Close-knit team

• Support Windows, Red Hat Linux, (perhaps Mac OS X)– Why Windows??? Visual Studio Development Environment

• Currently ~35 MB of source code for:– Detailed Monte Carlo Simulation– Reconstruction and Calibration algorithms– I/O infrastructure

• GLAST LAT software is open and available to anyone who wants it.– Brookhaven group - KOPIO

• C++ was adopted for coding efforts – early on

• By 1999, we had detailed Monte Carlo simulation and prototype reconstruction code.– This was before the proposal!!!


9/21

Why Use a Framework?Why Use a Framework?

• By 1999, we had plenty of code – but it was unmaintainable.• Our MC generator was custom built, planned move to Geant4

– Looked to re-use existing code as much as possible• HEP offered a number of packages: CLHEP, Geant4

• Small team, of distributed programmers, with varying amounts of OO C++ programming experience.

• Provide one code system for simulation, test data analysis, and flight operations.

• Needed organization and clear lines of division between the components of our code.

• Flexible• Extensible


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Gaudi FrameworkGaudi Framework

• An Object Oriented C++ Framework– “The implementation of an architecture which defines a structure

flexible enough to support all types of physics data processing needs..from simulation to analysis to visualization.”

• http://proj-gaudi.web.cern.ch/proj-gaudi/welcome.html• Promotes the creation of small maintainable components which can

be loaded at runtime – Components = algorithms, services, I/O, etc

• Standard Gaudi interface for each type of component• Embraces the division of data from algorithms• Gaudi provides a number of basic services such as:

– Event Data Service (TDS) – a fancy OO common block!– Messaging and Logging Services– Infrastructure for I/O where various output formats may be

supported• Provides standard event loop• Job parameters are handled via an input ASCII file• Optional Python interface


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Example of Using Gaudi ToolsExample of Using Gaudi Tools

IEnergyCorr* m_lastLayerTool; sc = toolSvc()->retrieveTool(m_lastLayerToolName, m_lastLayerTool);

m_lastLayerTool->setTrackSlope(slope); m_lastLayerTool->doEnergyCorr((*it)->getEnergySum(),(*it));

Retrieve tool by name via base class

Refer to base class functions. Does not know which concrete tool it is.

Concrete classes that customize behaviour

Tools id’ed by name in ascii config file (“jobOptions”)


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Data flow in the Gaudi frameworkData flow in the Gaudi framework

TransientDataStore

Ntuple

Level 1

SimulationAlgorithms

Level 0

ReconstructionAlgorithms

NtupleService

PersistencyAlgorithms

G4

ACD, TKR, CAL

DigitizationAlgorithms

SourceGenerators

Root

ACD, TKR, CAL,Trigger

Raw data

Ready for astronomy

MC

Real Data

User-DefinedAlgorithms


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Gaudi Interface to Geant4Gaudi Interface to Geant4

http://www-glast.slac.stanford.edu/software/core/documentation/reviews/G4Generator/g4greview.pdf

Usurp this!


14/21

FRED: Our Event DisplayFRED: Our Event Display


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What is ROOT?What is ROOT?

• http://root.cern.ch (circa 1995)• A floor wax and a dessert topping

– Machine independent file format– An analysis toolkit written in C++– Created to address the needs of large scale data analysis

• Object I/O• Self-describing files• Utilizes gzip algorithm for compression (user controlled)• Typically store event data in trees• C/C++ interpreter for command line analysis• PyROOT – python interface


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Pretty PicturesPretty Pictures


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Why ROOT?Why ROOT?

• As of 1999, our output was tab-delimited ASCII ntuples• GLAST code is Object-Oriented C++• A OO friendly file format seemed better suited for our needs

– Store our objects “as is” in ROOT• Either read them back into our sim/analysis framework• Or use ROOT/JAS or any ROOT capable analysis toolkit

to perform analysis.• Open-source, widely used within the HEP community• Well supported and good user documentation• Pledged backward compatibility• Development is actively extending and improving the system

– Planning support for multi-core – Adding context-sensitive help


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Persistent ROOT OutputPersistent ROOT Output

• Four types of ROOT files: MC, Digitization, Reconstruction and ntuple.

• Two Levels of Output at end of Reconstruction:– Root Trees

• Basically, all the output of all steps of reconstruction• Enough information to read back in and continue

reconstruction from that point• Detailed offline analysis for reconstruction algorithm

improvements• Main component of System Tests

– Output Ntuple• A detailed branch which contains enough information

for checking of reconstruction performance• The analysis data which is ultimately FITisfied.


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Advantages and DisadvantagesAdvantages and Disadvantages

• Provides standardized structure• Free, source code available• Pick and Choose Components• Python Interface• OO

• Not well documented• Steep learning curve• Slow start up during loading• Requires use of DataObject

interface

• Open-source

• Strong user support and documentation

• OO

• Python interface

• Extending capabilities

ADVANTAGES DISADVANTAGES

GAUDI

ROOT

• Steep Learning Curve for users unfamiliar with OO

• C/C++ interpreter can be flaky

• Up to now, has required use of TObject interface


21/21

Have you seen these men?Have you seen these men?

Richard Dubois P.7Overview of SAS

Dan Flath P.35Data processing

Pipeline

Navid Golpayegani P.13Release Manager

Tony Johnson P.24JAS3

Tom Stephens P.61SSC Data Server

Max Turri P.26Scientific plotting

glast large area telescope: lat science analysis software’s use of gaudi & root heather kelly

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