Download Data and the Database

OO-Design in PHENIX
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CHEP-2000
PHENIX, a BIG Collaboration
A Liberal Data Model
Simple (and fast) DST I/O
Design Patterns
OO-Database, an example for the abstract extreme
Does it really work?
Ergo. . .
Matthias Messer, BNL
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Under Construction . . .
Software infrastructure
CHEP-2000
Matthias Messer, BNL
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From RAW to DST
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Official Language is C++
FORTRAN legacy now only in simulation (GEANT 3)
200,000 lines of code and still growing fast
Limited manpower and financial resources
– How unusual, what?
– Usage of many free open-source packages
• Linux, automake, Root, Bonsai, CVS, CLHEP (well, sort of)
• many more
– Good experience as compared to commercial software
• Maintenance(!), upgrades, necessary modifications
CHEP-2000
Matthias Messer, BNL
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PHENIXians
• Picture shows
only a third of the
collaboration
• Many developers
– Ideas
– Strong
opinions about
programming
• Software
infrastructure has
to integrate them
all
CHEP-2000
Matthias Messer, BNL
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A Liberal OO Model
• Old OO: Everything is one grand song
– Have a (preferably) complete design before you start coding
– Work done by experienced OO-programmers
– Well . . .
• Liberal OO: Have it your way
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Data-objects with some methods
method-collections (functors) with some data-members
shallow inheritance structures for modularity
Independently designed packages work on one data-structure
• Composite Objects: A node-tree to hold (and share) data
CHEP-2000
Matthias Messer, BNL
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PHOOL, The PHENIX OO Library
• Composite Objects: A node-tree to hold (and share) data
Composite Nodes
Data Node
CHEP-2000
Matthias Messer, BNL
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PHNode
the Data-Classes
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Data node is template
– type-safe
But all inherit from
PHNode
– Navigation class
PHNodeIterator uses
Polymorphism
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PHNodeIterator
– Unix-like navigation
• cd(“ . . .”)
• find(“ . . .”)
– Can use abstract
strategies
• for_each(PHStrategy)
CHEP-2000
Matthias Messer, BNL
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PHModule
the Functor Classes
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Method-container class
– common interface or
entry-point, the event()
function
– Can be used with a
PHModuleManager
– PHDataNode<PHModule>
for implementation of
strategies
CHEP-2000
Matthias Messer, BNL
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Abstract Strategies
• Used in Node tree
– apply a method to
all nodes of a
branch
• Used in Module
Manager
– call event() function
of all Modules in
the collection: the
event-loop
CHEP-2000
Matthias Messer, BNL
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OODBs in PHENIX
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Two autonomous
partitions
– Counting House
– RCF (RHIC Computing
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Facility)
Robust against the
‘bulldozer incident’
The picture shows a
subset
Pdbcal is only one of
many DB applications, but
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The one most of all used
in reconstruction code
The biggest data volume
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CHEP-2000
Matthias Messer, BNL
order of Tbyte/Year
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Pdbcal
• a user-friendly database-application
– small set of wrapped control-classes
• start, end transactions
– easily expandable by the user himself
• provide a storage class (e.g. a hardware-channel)
• gets picked up by code-generators for integration into the DB-package
– you handle only a very abstract (2.5 layers) bank-class
• applications do not depend on later generated code
– transparent low-level activity
• Open a new DB-file when 2 Gbyte limit is reached
• traverse from Tag-DB to calibration-DB
CHEP-2000
Matthias Messer, BNL
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Data-Storage in Objy/Root
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No need for elaborate
design of the base classes
concentrate on functionality
and on ONE application
(objy) for now
add Root I/O later by way
of inheritance
transparent for the user
interface
CHEP-2000
Matthias Messer, BNL
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Useful (and used) Design-Patterns
• singletons
– database application manager
– a classmap hash-table (STL-map)
• abstract base-classes and factories
– change low-level applications without changing interfaces
• Objectivity
Root
– protect the user from implementation details (and vice versa)
• composite objects
– flexible, yet type-safe node-tree
• abstract strategies
– standardized operations on no-tree-data
– great flexibility in choosing analysis methods
CHEP-2000
Matthias Messer, BNL
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The Very Real Life . . .
• . . . of simulated data processing
– MDC: Mock Data Challenge
– two weeks of simultaneous
• data sinking into HPSS
• data mining from HPSS
• parallel data processing using the PHOOL environment
– the new reconstruction software
• is fast:
– 30s / event is factor two faster than with old data-model (STAF)
• is reliable:
– few crashes, none related to memory-management in the reconstruction code
– no memory leaks (non trivial in such a liberal data-model)
CHEP-2000
Matthias Messer, BNL
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In Somma . . .
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The relaxed OO-philosophy (PHOOL)
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• slightly more separation between data and methods
• shallow inheritance trees
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you buy what you want, or
“I don’t want a three-vector that can send me email”
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• integrate many peoples software efforts
• allow flexible usage of outside-packages
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The approach of the abstract extreme (Pdbcal)
– shields user, prevents fear of first contact
– maintains flexibility in usage of low-level software
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Contact
– email: [email protected]
– more info: www.phenix.bnl.gov/~messer
CHEP-2000
Matthias Messer, BNL
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