oo/c++ reconstruction model based on geant3

Tuesday, July 16, 2002

Lecce Moun Software Workshop 1

OO/C++ Reconstruction Model OO/C++ Reconstruction Model based on GEANT3based on GEANT3

Yuri Fisyak, Valery Fine,Pavel Nevski, Torre Wenaus

http://www.bnl.gov/


Lecce Moun Software Workshop

2

OutlookOutlook

– Inducement (ATLAS specific) – Motivations– Advantages and limitations of GEANT3 geometry– ``Compact’’ and ``open’’ geometries– Hits/Digits structure– User interface : iterators– Conclusions

http://www.bnl.gov/



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InducementInducement RD event data model which provides interface to AtlSim

Zebra files has to be replaced by DC 1, part 2. AtlSim can provide output for geometry and hits/digits as

ROOT-files. The present ATLAS framework (Athena) does not allow at

least now to use ROOT classes directly. The idea is to use in Athena algorithms iterators over

geometry and hits/digits which don’t depend on ROOT (interfaces).

Concrete implementation of these iterators of cause depends on ROOT classes but this implementation is not seen by Athena algorithms. This talk is devoted to this concrete implementation.

http://www.bnl.gov/



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MotivationsMotivations

– One the main task which has to be solved by a reconstruction is to provide access to geometry and calibration information for a given hit/digit and vise versa.

– A lot of current HENP experiments still have their most detailed geometry in GEANT3. It looks very attractive to be able to access this geometry description from the modern OO/C++ reconstruction.

– As an example, in ATLAS Muon reconstruction access to detailed detector description, including ``dead’’ material information, is mandatory because of very high performance requirements.

http://www.bnl.gov/



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Advantages of the ``compact’’ geometry Advantages of the ``compact’’ geometry modelmodel

An existing experience with GEANT3 allows to formulate so called ``compact’’ detector model.

It provides a model for “ideal” detector : – which accounts symmetries of the detector, and– it is ``compact’’ because it doesn't contain any

duplication of the geometrical nodes,– an example of such type geometry is the ATLAS

detector GEANT3 description which contains ~30M copies of ~7 K different types of volumes.

http://www.bnl.gov/



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ATLAS Detector View With G3ATLAS Detector View With G3

http://www.bnl.gov/



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Limitation of ``compact’’ geometryLimitation of ``compact’’ geometry

However this ``compact’’ model cannot facilitate the real reconstruction needs :

– a subset of geometrical nodes (detector elements) might have their own unique list of parameters:

• calibrations, • alignment, • …

The OO model where each “physical” detector element corresponds to the dedicated object instance we will call "open" geometry.

This “open’’ geometry also is very suitable for detector response (hits, digits) structuring.

http://www.bnl.gov/



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Compact and Open geometryCompact and Open geometry

Even though the "open" structure looks very attractive it is still non realistic to keep it in memory for whole detector.

Thus geometry model for reconstruction has to contain a combination of “compact” geometry for whole detector and

“open” one for its subset.

http://www.bnl.gov/



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Compact & open geometry in ROOTCompact & open geometry in ROOT

A geometry package is being developed within ROOT framework to provide such functionality.

The package uses of ROOT Geometry classes (root/g3d)– TShape (TBRIK, TCONE,…), TMaterial, TMixture,

TRotMatrix The package includes:

– the "compact" model with multiple reuse of geometry objects, providing a C++ detector view "a la GEANT3" (root/table):

• TVolume and TVolumePositon classes;– the “open” model which is created by a request for a subset of

the compact presentation and contains full description, where each detector element is presented by a separate object:

• TVolumeView class

http://www.bnl.gov/



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List of daughter nodes

TVolume and TVolumeView: TVolume and TVolumeView: hierarchical container of containershierarchical container of containers

TVolumeTShapeTShape

TMaterial

TVolume

TVolume

TVolumePosition(relative wrt

parent)

TVolumePosition

TVolumeView

TVolumePosition(position wrt global)

TVolumeView

List of positionsList of nodes

http://www.bnl.gov/



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TVolume and TVolumeView (cont.)TVolume and TVolumeView (cont.)

TVolume:– does not know about its position,– can be positioning in any part of the geometry tree with

respect to ``parent’’ TVolume,– provides only downstream navigation I.e. you can find

children of the given TVolume but you don’t know its parent. TVolumeView:

– does know about its position with respect to any fixed system of coordinates (global, with respect to parent, …),

– Provides navigation both downstream and upstream,– can contain any information (calibrations, …) unique for the

given node.

http://www.bnl.gov/



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Exporting G3 geometryExporting G3 geometry to ROOTto ROOT

Iterator over

developed G3 geometry

as it sees a particle during

propagation

TVolume

TVolumeView

Compact geometry

Open geometry

Mark

``Sensitive’’

volumes

http://www.bnl.gov/



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TVolume/TVolumeView browsingTVolume/TVolumeView browsingFull G3 tree 29’042’213 nodes

TVolume structure

3512 marked nodes

TVolumeView structure

ctorTVolumeTVolume

TVolumePosition

TVolumeView

TVolumePosition

TVolume

http://www.bnl.gov/



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ATLAS muon system in ROOTATLAS muon system in ROOT

http://www.bnl.gov/



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Hits/DigitsHits/Digits

The package also provides a generic hit/digit C++ class together with tools supporting navigation from hits to geometry and vice versa. . TResponseTable: self describing array of c-structs containing hits/digits information.

• TIndexTable: list of indexes in TResponseTable array corresponding a given detector element (TVolumeView) in order to speed up the navigation from geometry to digits/hits structure.

http://www.bnl.gov/



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Response TableResponse TableTResponseTable *mtuiHit = (TResponseTable *) g3->DataSet("Data/Hits/MUCH/MTUI");mtuiHit->Print(0,5) TResponseTable *mtuiDigit = (TResponseTable *) g3->DataSet("Data/Digits/MUCD/MTUI");mtuiDigit->Print(0,5);Muon/.make/AtlSim/.data/Data/Hits/MUCH/MTUI Allocated rows: 36

Table: MTUI [0] : [1] : [2] : [3] : [4]

int TRACK 1 : 1 : 1 : 1 : 1

int ATLS/OUTE/MUCH 2 : 2 : 2 : 2 : 2

int BARI 10 : 10 : 10 : 10 : 10

int BXXI 12 : 12 : 12 : 12 : 12

int BSLI 1 : 1 : 1 : 2 : 2

int BWAI 55 : 109 : 164 : 5 : 6

float X -0.4155 : -0.5245 : -0.6325 : -1.0715 : 1.0635

float Y -0.2635 : -0.3325 : -0.4015 : -0.6805 : 0.6785

float Z 22.309 : 22.398 : 22.487 : 23.008 : 23.056

float TDR 0.4915 : 0.6205 : 0.7495 : 1.2695 : 1.2615

float TOF 0.29778 : 0.29875 : 0.29973 : 0.30544 : 0.30595

float CZ 0.02975 : 0.02975 : 0.02965 : 0.02945 : 0.02945

float CX -0.53645 :-0.53655 : -0.53655 :-0.53685:-0.53685

float CY 0.84345 : 0.84335 : 0.84335 : 0.84315: 0.84315

float STEP 2.7505 : 2.6445 : 2.5075 : 1.4435 : 1.4715

float LGAM 2.485 : 2.485 : 2.485 : 2.485 : 2.485 -

Detector Id, path to detector element

Hit/Digit parameters

Muon/.make/AtlSim/.data/Data/Digits/MUCD/MTUI Allocated rows: 32

Table: MTUI [0] : [1] : [2] : [3] : [4]

int TRACK 1 : 1 : 1 : 1 : 1

int ATLS/OUTE/MUCH 2 : 2 : 2 : 2 : 2

int BARI 10 : 10 : 10 : 10 : 10

int BXXI 12 : 12 : 12 : 12 : 12

int BSLI 1 : 1 : 1 : 2 : 2

int BWAI 55 : 109 : 164 : 5 : 6

float TIME 194.6 : 239.31 : 284.96 : 466.39 : 467.12

float Z 22.309 : 22.398 : 22.487 : 23.008 : 23.056

float TDR 0.4915 : 0.6205 : 0.7495 : 1.2695 : 1.2615

http://www.bnl.gov/



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TIndexTableTIndexTable

TObjectSet

TVolumeView

TIndexTable

TResponseTable

To speed up navigation over hits/digits information from detector elements it has been created hits and digits trees.

The trees structure reflects one for the “open” geometry and contains only nodes with hitted detector elements. These nodes contain indexes (TIndexTable) of hits in Hits/Digits TResponse tables.

http://www.bnl.gov/



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NavigationNavigation

The main goal of the above “compact” and “open” geometries and Hits/Digits trees is to provide straight forward navigation from hits/digits to geometry and from geometry to hits/digits.

Because the ``geometries’’ and hits/digits are containers the way to navigate over them are iterators.

The navigation is provided by two iterators:

TVOLUME::iterator over TVolume and TVolumeView structures and

ADigitIterator / AHitIterator

http://www.bnl.gov/



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Navigation : Navigation : TVOLUME::iterator TVOLUME::iterator void VIter(){ TVolume *oute = (TVolume *) g3->Find(".const/Constants/Geometry/ATLS/OUTE"); // or // TVolumeView *oute = (TVolumeView *) g3->Find(".const/Constants/GeometryTree/ATLS/OUTE"); TVOLUME::iterator Iter(oute); TString BXXI("BXXI"); for (;(long) Iter != 0; Iter++) { TVolumePosition &pos = *Iter; TString Name(pos.GetName()); if (Name != BXXI) continue; pos.Print(); } }… Node: BXXI Position: x=404.401 : y=-976.31 : z=0 OBJ: TRotMatrix 508523 NodeView 1 : 2 : 3 :1. -0.923879 : -0.382684 : -4.37114e-08 : 2. 0.382684 : -0.92388 : -4.37114e-08 : 3. 0 : 0 : 1 :

Muon system

Muon chamber

http://www.bnl.gov/



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ADigitIteratorADigitIterator

TObjectSet *BXXI = (TObjectSet *) g3->GetData("DigitsTree/ATLS/OUTE/MUCH[2]/BARI[10]/BXXI[12]");for (ADigitIterator iter(BXXI); (int)iter != 0; iter++) { ADigit &digi = *iter; digi.Print();}…Digit: TRACK 1 ATLS/OUTE/MUCH[2]/BARI[10]/BXXI[12]/BSLI[2]/BWAI[115] TIME 377.098 Z 23.2315 TDR 1.0015 E 0 Node: BWAI Position: x=1.95198e-06 : y=15.344 : z=-60OBJ: TRotMatrix 520471 NodeView 1: 2 : 3 :1. -4.37114e-08: 4.37114e-08 : -1 : 2. -8.74228e-08: 1 : -8.74228e-08 : 3. 1 : -4.37114e-08 : -8.74228e-08 : …

http://www.bnl.gov/



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Iterator in Athena AlgorithmIterator in Athena AlgorithmAGIterator iter;status = detStore->retrieve( iter, “Geometry" ); // get iterator from StoreGateiter.Reset(“ATLS/OUTE”); // start with Muon SystemIdentifier MuonStation(7); // or whatever defines muon station for (;(long) Iter != 0; Iter++) {

Identifier identifier = iter. Identifier();if (identifier != MuonStation) continue;

// or it can be use a Namestring Name = iter.Name();if (Name != “MuonStation” ) continue; if (iter.GetID() != 5) continue;

….HepTransform3D tras = *iter;

} ===================================The interface has to be discussed and fixed but it clear that it has to provide: transformation with respect to a given reference system (“ATLS/OUTE” in the case); Identifier; shape type and shape parameters; material (may be ?); ….

http://www.bnl.gov/



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ConclusionsConclusions

It has been developed a set of classes which have supported structures and provide parameters description of both ``compact’’ and ``open’’ geometries. This approach naturally accounts for alignment and detector calibration information.

It has been developed structure supporting hits and digits. It has been developed iterators which provide navigation from

hits/digits to geometry and vise versa. These iterators provide the navigation for persistent (ROOT) classes.

Still it is need to discuss what (transient) iterator should be exported into Athena Algorithms.

http://www.bnl.gov/

oo/c++ reconstruction model based on geant3

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