7/16/2015 ACAT'2002 Workshop 1 OO/C++ Reconstruction Model based on GEANT3 Yuri Fisyak, Valery Fine, Pavel Nevski, Torre Wenaus

7/16/2015 ACAT'2002 Workshop 2 Outlook –Motivations –Advantages and limitations of GEANT3 geometry –``Compact’’ and ``open’’ geometries –Hits/Digits structure –User interface : iterators –Conclusions

7/16/2015 ACAT'2002 Workshop 3 Motivations –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.

7/16/2015 ACAT'2002 Workshop 4 Advantages of the ``compact’’ geometry model 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.

7/16/2015 ACAT'2002 Workshop 5 ATLAS Detector View With G3

7/16/2015 ACAT'2002 Workshop 6 Limitation 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.

7/16/2015 ACAT'2002 Workshop 7 Compact 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.

7/16/2015 ACAT'2002 Workshop 8 Compact & 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

7/16/2015 ACAT'2002 Workshop 9 List of daughter nodes TVolume and TVolumeView: hierarchical container of containers TVolume TShape TMaterial TVolume TVolumePosition (relative wrt parent) TVolumePosition TVolumeView TVolumePosition (position wrt global) TVolumeView List of positions List of nodes

7/16/2015 ACAT'2002 Workshop 10 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.

7/16/2015 ACAT'2002 Workshop 11 Exporting G3 geometry to ROOT Iterator over developed G3 geometry as it sees a particle during propagation TVolume TVolumeView Compact geometry Open geometry Mark ``Sensitive’’ volumes

7/16/2015 ACAT'2002 Workshop 12 TVolume/TVolumeView browsing Full G3 tree 29’042’213 nodes TVolume structure 3512 marked nodes TVolumeView structure ctor TVolume TVolumePosition TVolumeView TVolumePosition TVolume

7/16/2015 ACAT'2002 Workshop 13 ATLAS muon system in ROOT

7/16/2015 ACAT'2002 Workshop 14 Hits/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.

7/16/2015 ACAT'2002 Workshop 15 Response Table TResponseTable *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 : : : : float Y : : : : float Z : : : : float TDR : : : : float TOF : : : : float CZ : : : : float CX : : : : float CY : : : : float STEP : : : : float LGAM : : : : 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 : : : : float Z : : : : float TDR : : : :

7/16/2015 ACAT'2002 Workshop 16 TIndexTable 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.

7/16/2015 ACAT'2002 Workshop 17 Navigation 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

7/16/2015 ACAT'2002 Workshop 18 Navigation : 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= : y= : z=0 OBJ: TRotMatrix NodeView 1 : 2 : 3 : : : e-08 : : : e-08 : 3. 0 : 0 : 1 : Muon system Muon chamber

7/16/2015 ACAT'2002 Workshop 19 ADigitIterator 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 Z TDR E 0 Node: BWAI Position: x= e-06 : y= : z=-60 OBJ: TRotMatrix NodeView 1: 2 : 3 : e-08: e-08 : -1 : e-08: 1 : e-08 : 3. 1 : e-08 : e-08 : …

7/16/2015 ACAT'2002 Workshop 20 Conclusions 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. This model is used in development of ATLAS muon reconstruction. But this model itself does not use any ATLAS specific features and can be applied for any reconstruction.