evolution of cluster design in the instrumented flux return (ifr) of babar

Evolution of cluster Evolution of cluster design in the design in the

Instrumented Flux Instrumented Flux Return (IFR) of BaBarReturn (IFR) of BaBar

Luca ListaINFN, Sezione di Napoli

for the BaBar Computing Group

Luca Lista - CHEP '98Luca Lista - CHEP '98

The Instrumented Flux The Instrumented Flux Return of BaBarReturn of BaBar

• 18-19 layers of Resistive Plate Chambers (RPC)

• 2 layers of cylindrical RPC inside the coil

• Digital strip readout, 2-3cm pitch


Ifr basic reconstruction Ifr basic reconstruction informationinformation

• The Ifr reconstruction provides the following basic information

stripstrip 1D1D clustercluster3D cluster3D cluster


Clustering in the IFRClustering in the IFR• The IFR identifies , and

K0L

• The reconstruction information in the IFR is made of clusters of strips which are “close” in space

• Details of the pattern information give particle ID discriminating power

• Estimate of the impact point provides a determination of the flight direction of the K0

L

clustercluster

clustercluster


2D and 3D Clustering2D and 3D Clustering

• Projective geometry in the planar RPC’s 2D reconstruction in each

projection• 3D association of the two

projections

Ifr2DClusterIfr2DCluster


• The basic class structure

• The initial interface:

Early class designEarly class design

Ifr2DClusternumberOfHits () : intnumberOfStrips () : intfirstLayer () : intlastLayer () : inthitLayer () : int

Ifr3DClustercenterOfGravity () : PointcovMatrix () : BbrError

direction (from : Point) : VectornumberOfHits () : intnumberOfStrips () : intfirstLayer () : intlastLayer () : inthitLayers () : int

21

Ifr1DClusternumberOfStrips( )

1

1..n

Ifr3DCluster Ifr2DCluster21 Ifr1DCluster1 1..n




Ifr3DCompositecenterOfGravity () : PointcovMatrix () : BbrError


1..n

Composite clustersComposite clusters• Cluster segments

associated to the same charged track are combined together


Polimorphic clustersPolimorphic clusters

• The user shouldn’t care about the detail of the cluster substructure:– just use IfrAbs3D

• All clusters implement the same interface.



IfrAbs3DcenterOfGravity () : PointcovMatrix () : BbrError


Ifr3DCompositecenterOfGravity () : PointcovMatrix () : BbrError


1..n


Inner RPC clustersInner RPC clusters• The inner RPC readout layout changed during

software evolution:– stereo readout strips

• 2D clustering is no longer appropriate• Composite clusters can’t be done of

homogeneous elements


Evolution of the Evolution of the cluster modelcluster model

IfrAbs3DIfrAbs3D () : IfrAbs3DIfrAbs3D (a : const IfrAbs3D&) : IfrAbs3Dposition () : HepPoint~IfrAbs3D ()numberOfDigis () : intnumberOfStrips () : intcovMatrix () : BbrErrorpolCovMatrix () : BbrError

$polCovMatrix ( : BbrError&, : HepPoint&) : BbrErrorfirstLayer () : intlastLayer () : inthitLayers () : inthitLayersI () : inthitsInLayer (n : int) : intstripsInLayer (n : int) : intmaxMissed () : int

sectionCode () : Ifr::SectionCodecomponent ( : int = 0) : Ifr3DCluster*numberOfComponents () : intnumberOfComponents ( : Ifr::SectorCode) : intnumberOfComponents ( : Ifr::SectionCode) : intgetComposite () : Ifr3DComposite*hasBarrel () : boolhasEndCap () : boolhasFwdCap () : boolhasBwdCap () : boolhasInner () : booloperator == ( : const IfrAbs3D&) : boolnumber () : unsigned int$resetCounter () : voidsaveGuts ( : RWvostream&) : voidrestoreGuts ( : RWvistream&) : void

Ifr3DComposite Ifr3DCluster1..n

• Cluster information is intrinsically complex

• It is not possible to predict now all the needed functions

• The extension of the class functions requires changing the base class interface

• Extension to new cluster types?


Problems spotted during the Problems spotted during the developmentdevelopment

• The cluster class interface growth rate was more than linear with time

• Code which used deep information of the cluster pattern tended to “understand” which subclass type it was using (dynamic_cast)

• Dependencies on cluster subtypes rather than base class increased

• Problems to effectively evolve the design


Visitor patternVisitor pattern• Each function of the cluster classes is implemented in a

separate class for all cluster types – all inherit from IfrClusterVisitor abstract interface

• Extending the functionality does not require any change to classe interfaces– just add a new visitor class

• Dependency on cluster subclasses is concentrated in the visitor classes

• The design is, according to an OO principle, – open to extensions– closed to class interface changes


Visitor pattern Visitor pattern class diagramclass diagram

Ifr3DClusteraccept (const IfrClusterVisitor<T>& v) : T

Ifr2DClusteraccept (const IfrClusterVisitor<T>& v) : T

IfrAbs3Daccept (IfrClusterVisitor<T>) : T

Ifr3DCompositeaccept (const IfrClusterVisitor<T>& v) : T

T

IfrClusterVisitoroperate (const Ifr3DCluster*) : Toperate (const IfrInner3DCluster*) : Toperate (const Ifr3DComposite*) : Toperate (const Ifr2DCluster*) : T

IfrInner3DClusteraccept (const IfrClusterVisitor<T>& v) : T

{ return v.operate(this);}

1..n

IfrVstCenterOfGravityoperate (const Ifr3DCluster*) : Hep3Vectoroperate (const IfrInner3DCluster*) : Hep3Vectoroperate (const Ifr3DComposite*) : Hep3Vectoroperate (const Ifr2DCluster*) : Hep3Vector

IfrClusterVisitor{Hep3Vector}

2


Visitors featuresVisitors features• New visitors can be added as new subclasses of

IfrClusterVisitor<myType> with no other changes• New cluster types can be added without mayor design

changes (e.g.: Ifr3DFastCluster)– but all the visitors subclasses should be updated to work

on the new cluster subclass• Details can be handled internally:

– calibrations, alignments• The code which uses IfrAbs3D and visitors appears to be

much more robust than before– a couple of unsolved bugs have been understood and fixed

during the migration


Visitors features (cont.)Visitors features (cont.)• Recursive action on Ifr3DComposite

components matches the composite pattern – Ifr3DComposite has n IfrAbs3D’s

• A visitor subclass handles a built-in cache mechanism implemented with a hash dictionary. – a visitor “knows” the cluster he has already “visited” – the cache is invalidated at:

• destruction of every cluster for the deleted cluster• at the end of every event

(to prevent the accumulation of possible memory leaks)


Available VisitorsAvailable Visitors• Visitors are

singleton/multiton

• Some of the available visitors are:

• IfrVstCenterOfGravity• IfrVstCovMatrix• IfrVstFirstLastLayer

– first | last | lastBarrel• IfrVstHasSector

– forward | backward | barrel • IfrVstHitLayers• IfrVstHitsInLayer

– n = 1, ... ,19• IfrVstMaxMissed• IfrVstNumberOfStrips• . . .


Visitors UsageVisitors Usage• How to use visitors:IfrAbs3D* ifr; // get a cluster from somewhere

// compute center of gravityHepPoint c = ifr->accept( IfrVstCenterOfgravity::instance() );

// has hits in the barrel?bool barrel = ifr->accept(IfrVstHasSector::instance (IfrVstHasSector::barrel) ); // get number of hits in each layerint n[19], i;for (i = 0; i < 19; i++) n[i] = ifr->accept( IfrVstHitsInLayer::instance(i+1) );

// compute max. number of missed layersint maxMiss = ifr->accept( IfrVstMaxMissed::instance() );


ReferencesReferences• On-line Ifr documentation:

– http://www1.na.infn.it/wsubnucl/accel/BaBar/Reco/6.7.3/see IfrData and IfrVisitor packages for class diagram and C++ code

• Original proposal document:– http://www1.na.infn.it/wsubnucl/accel/BaBar/Reco/visitors.html

evolution of cluster design in the instrumented flux return (ifr) of babar

Documents

nluca lista chep

pitchluca lista chep

impact point

d reconstruction

ifrthe ifr

evolution of cluster

class functions

base class interface