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Accessing Event Data

Accessing Event Data. Event Data Reside In Data Store. Tree - similar to file system Identification by path ”/Event/MC/Particles” LHCb::MCParticleLocation::Default Objects or Containers of objects KeyedContainer<Type>. Containers: e.g. KeyedContainer. Templated class

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Accessing Event Data

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  1. Accessing Event Data

  2. Event Data Reside In Data Store • Tree - similar to file system • Identification by path”/Event/MC/Particles”LHCb::MCParticleLocation::Default • Objects or • Containers of objectsKeyedContainer<Type>

  3. Containers: e.g. KeyedContainer • Templated class • Usually hidden to end-user code by typedefs in header file • Iteration like any STL vector • //note LHCb:: namespace • LHCb::MCParticle::Container* parts = … ; • LHCb::MCParticle::Container::const_iterator i;for( i=parts->begin(); i != parts->end(); i++ ) • { info() << (*i)->particleID().pid() << endmsg;}

  4. Data Service Algorithm (3) Request load (1) get<class>(location) PersistencyService Request dispatcherSICB, ROOT,.. (5) Register Conversion Service (4) Request creation Converter Converter Converter Converter Understanding Data Stores: Loading Unsuccessful ifrequested object is not present (2) Search in Store Try to accessan object data Data Store

  5. Caveats • Consider Objects on the store asREAD-ONLY • Do not modify existing objects! • Do not destroy existing objects! • Never, never delete an object which is registered to the store • It’s not yours! • It will only screw up others!

  6. Data Access In GaudiAlgorithm • const LHCb::MCHeader* evt = • get<LHCb::MCHeader>( LHCb::MCHeaderLocation::Default ); • // No need to test a return code, this method throws • // an exception if data is not found

  7. Conventions • For Event Model objects of type TYPE: • The actual type stored in TES • LHCb::<TYPE>::Container • Vector of pointers [ std::vector<TYPE*> ] • LHCb::<TYPE>::Vector • Vector of “pointers-to-const” [ std::vector<const TYPE*> ] • LHCb::<TYPE>::ConstVector • “default” location in TES : • LHCb::<TYPE>Location::Default

  8. Specify Event Data Input EventSelector.Input = { “DATAFILE=‘a_filename’ [Spec]” [,“DATAFILE=‘another_filename’ [Spec]”] }; • Event data input is specified in the job options • [Spec] is an array of qualified strings:KEY1=‘VALUE1’ … KEYn=‘VALUEn’ • Several files can be specified, separated by a comma

  9. Specify POOL Event Input • EventSelector.Input = {"DATAFILE='PFN:castor:/castor/cern.ch/grid/lhcb/production/DC06/v1-lumi2/00001284/SIM/00001284_00000001_1.sim' TYP='POOL_ROOTTREE' OPT='READ'"} • PFN: keyword tells POOL this is a physical file name • castor: keyword selects data transfer protocol (rootd in this case)omit for a disk file • OPT=‘READ’ is read only file

  10. Specify POOL Event Input • For simple file on disk • EventSelector.Input ={ • "DATAFILE=‘/software/lhcb/BenderData/Bs2PsiPhi/00001395_00000005_5.dst' TYP='POOL_ROOTTREE' OPT='READ'"}

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