Mantis a framework and toolkit for Geant4 simulation in CMS M. - - PowerPoint PPT Presentation

Mantis

a framework and toolkit for Geant4 simulation in CMS

• M. Stavrianakou

CERN Geant4 Workshop 02.10.2002

• M. Stavrianakou, CMS/CERN

02.10.2002 2

COBRA Mantis OSCAR

• COBRA is the CMS “framework”; it implements the CMS OO architecture
• Mantis is the COBRA interface to Geant4

➨ Mantis as a subsystem of COBRA is ❐a toolkit for building or interfacing to detector geometries and

sensitive volumes, generators, physics, magnetic fields, actions etc

❐a framework for Geant4 simulation applications (interactive or batch)

• relies on COBRA infrastructure and services for core application

steering and control, persistency, histogramming etc

provides run and event management

provides interfaces for loading the specific libraries for geometry, magnetic field, generators, physics, tuning and monitoring actions

• OSCAR is the CMS Geant4 simulation based on Mantis

———————————————————————————————————————————————— Mantis is also:

➨a human able to see the future: from the Greek word for seer, prophet ➨a rather nasty insect ➨a very cute and timid shrimp

• M. Stavrianakou, CMS/CERN

02.10.2002 3

Mantis functionality

Application Steering

• Mantis application (G4Application) is a COBRA SimApplication; it

relies on COBRA for the application main

• Most if not all configurable/tunable aspects of the application (including

persistency) are driven by COBRA “simple configurables” (kind of “datacard”mechanism)

• Persistency, metadata management, histogramming services etc are

available transparently via the underlying COBRA infrastructure

• G4Application instantiates and launches

➨ an event source factory based on a COBRA abstract event “reader”of

simulated events

➨ a run manager

and handles generator, magnetic field and visualisation selection and instantiation

powerful key COBRA features (lazy instantiation, action on demand, etc) and patterns (factories, dispatchers-observers etc) are used extensively (but are probably not yet exploited to their full potential)

• M. Stavrianakou, CMS/CERN

02.10.2002 4

Mantis functionality

Run and Event Management

Run and event management are implemented in order to work around (what we may consider) restrictive Geant4 mechanisms and facilitate synergy with COBRA

➨ Run Manager (inherits from G4RunManager) takes over control for:

❐ geometry initialization

UserInitialization of a G4VUserDetectorConstruction bypassed

❐ generator initialization and Monte Carlo event conversion to G4Event

G4VUserPrimaryGeneratorAction bypassed

❐ physics initialization

UserInitialization of a G4VUserPhysicsList bypassed

➨ Event

❐ is a COBRA SimEvent

analogous to its Geant3 counterpart

❐ manages Monte-Carlo truth

raw event/particles from generator and G4 simulated tracks and vertices

does not directly depend on Geant4, but needs EventAction and Tracking Action to retrieve G4 simulated tracks and vertices

• M. Stavrianakou, CMS/CERN

02.10.2002 5

Mantis functionality

Geometry and Magnetic Field

• Geometry: uses the CMS Detector Description Database (DDD)

➨ Setup selection

❐ full CMS, partial, test beam etc driven by configuration (XML)

➨ Geometry building

❐ automated conversion from DDD to Geant4 solids, materials, volumes

➨ User limits

❐ step and track length, production, tracking and time cuts:

automatic conversion and assignment from DDD to Geant4 work in progress

➨ no code modification, no recompilation, loadable on demand

• Magnetic Field: uses the COBRA infrastructure and several COBRA-

provided types of field, allowing

➨ selection (Uniform, 2D map, 3D map)

➨ interface to G4 with

choice of integrator

tuning options

➨ loadable on demand

• M. Stavrianakou, CMS/CERN

02.10.2002 6

Mantis functionality

Sensitive Detectors and Hits

• Sensitive detectors: creation and assignment to geometrical (logical)

volumes

➨ any number of instances of a given sensitive detector,

assignable to any type and number of logical volumes

➨ loadable on demand

• Hits: COBRA hits and hit collections that handle

➨ creation

❐ using Geant4 ProcessStep

➨ formatting ➨ persistency

hit modelling, numbering scheme, readout choice by CMS detector group experts (OSCAR-side)

hits directly digitizable and usable by the CMS OO reconstruction program ORCA

• M. Stavrianakou, CMS/CERN

02.10.2002 7

Mantis functionality

Generators

• infrastructure based on COBRA mechanisms and the COBRA

GeneratorInterface

➨ to produce a CMS RawHepEvent ❐ converted and passed to Geant4 using the G4HEPEvtInterface ❐ HepMC/HepPDT have been evaluated

will be used following evolution in context of on-going RTAGs

preference/recommendation for physical decoupling from CLHEP

➨ to allow selection and configuration at the application steering level

• implementations

➨ configurable particle gun with choice of vertex generator ➨ CMS HepEvt ntuple ➨ CMS text file with choice of vertex generator ➨ Pythia6 on-the-fly

• loadable on demand

• M. Stavrianakou, CMS/CERN

02.10.2002 8

Mantis functionality

Physics and User Actions

Physics Lists and Cuts infrastructure for

➨ building a concrete physics list ➨ list selection configuration ❐active categories of processes

general, electromagnetic, hadronic, ion …

❐selection of production (range) cuts: default, from file

currently using cuts per material User Actions infrastructure for

➨ tuning ➨ monitoring

quantities of interest (Begin/End Of Run/Event, Step, Pre/Post Track) “dispatched” to potential “observers” using COBRA dispatcher-

• bserver pattern

at present foresee only one CMS “stacking action” possibly emulating level 1 trigger

any number of (combinations of) observers may be present

no need for central “action management”

• M. Stavrianakou, CMS/CERN

02.10.2002 9

Mantis: the framework and its dependencies

The core: G4Application

• M. Stavrianakou, CMS/CERN

02.10.2002 10

Mantis as a toolkit

CMS Geometry example CMS Sensitive Detector and Hits example

• M. Stavrianakou, CMS/CERN

02.10.2002 11

Mantis as a toolkit

CMS Production Physics List User Action Example

• M. Stavrianakou, CMS/CERN

02.10.2002 12

A few last points

Mantis has been inspired by and developed in the context of COBRA

it has also been inspired by and reused ideas from Goofy (ATLAS) and has profited from the pre-existing OSCAR implementation

Interactivity is largely addressed by IGUANA

Mantis relies on basic G4 services/messengers; future versions may exploit emerging G4/Python facilities

Mantis amounts to ~5K lines of code developed by ~1 FTE in ~3 months

Realistic beta-testing by the CMS b/ – Tracker is in progress

vital feedback is contributing to improvements

There are outstanding requirements as well as currently unforeseen ones

Thanks to the underlying COBRA architecture, implementation of most new requirements is straightforward

Several requirements to Geant4 have emerged during the Mantis development

these we sometimes address as Geant4 shortcomings or restrictive mechanisms but this should not be taken as criticism in any negative sense; given the scope and magnitude of LHC experiment simulations, requirement evolution is inevitable

Mantis and the underlying COBRA infrastructure are not CMS-specific