1. GEANT4 performance studies
Pedro Arce
(CERN/CIEMAT)
GEANT4 Workshop 02
GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)

2. GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)
Outline
GEANT3 vs GEANT4 performance for full events
Where time is spent
Tracking speed
Tuning GEANT4 tracking in field parameters
GEANT4 Workshop 02
GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)

3. GEANT4 vs GEANT3 Time Performance
- Full events in full CMS: H / tte / Z
- Cuts in primary particles: Pt : 1 GeV, || < 2.4 (3.0)
- Full CMS geometry
- 3D TOSCA magnetic field
- Production and tracking cuts as in CMSIM (GEANT3)
- GEANT4 voxel navigation
- GEANT ref02
- Pentium III 850 Mhz
- Checked that they are really the same events (see next)
GEANT4 Workshop 02
GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)

4. GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)
G3-G4 events detailed comparison
H in all CMS (10 Events)
Initial track energy
No Tracks
MeV
Track length
No Tracks mm
GEANT4 Workshop 02
GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)

5. GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)
G3-G4 events: detailed comparison
Origin of secondary tracks: R vs Z
R (mm)
CMSIM
( tracks)
Z (mm)
R (mm)
OSCAR
( tracks)
Z (mm)
GEANT4 Workshop 02
GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)

6. GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)
Time performance
- H (10 events)
CMSIM: 439k tracks sec/evt
OSCAR: 400k tracks sec/evt (1.83)
- tte (10 events)
CMSIM: 1809k tracks sec/evt
OSCAR: 1159k tracks sec/evt (2.31)
- Z (10 events)
CMSIM: 1105k tracks sec/evt
OSCAR: 941k tracks sec/evt (2.58)
GEANT4 Workshop 02
GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)

7. GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)
Where time is spent?
Profile (´gprof´)10 full pp events in full CMS (GEANT4.3.2.ref02)
(numbers are accumulated: spent in the method itself or those invoked)
100% main
1,8% G4RunManager::RunInitialization
0.8% G4SteppingManager::SetInitialStep
0.3% G4ProcessManager::EndTracking
0.2% G4ProcessManager::StartTracking
95,7% G4TrackingManager::ProcessOneTrack
95,7% G4SteppingManager::Stepping
41% G4SteppingManager::DefinePhysicalStepLength
22% G4VProcess::AlongStepGPIL
17% G4VProcess::PostStepGPIL
26% G4SteppingManager::InvokeAlongStepDoItProcs
20% G4SteppingManager::InvokePostStepDoItProcs
GEANT4 Workshop 02
GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)

8. GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)
Where time is spent?
41% G4SteppingManager::DefinePhysicalStepLength
22% G4VProcess::AlongStepGPIL
18% G4Transportation::AlongStepGetPhysicalInteractionLength
4% G4MultipleScattering::AlongStepGetPhysicalInteractionLength
17% G4VProcess::PostStepGPIL
14% G4VContinuousDiscreteProcess::PostStepGetPhysicalInterac-tionLength
1% G4VDiscreteProcess::PostStepGetPhysicalInteractionLength
1% G4VRestDiscreteProcess::PostStepGetPhysicalInteraction-Length
GEANT4 Workshop 02
GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)

9. GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)
Where time is spent?
26% G4SteppingManager::InvokeAlongStepDoItProcs
5% G4ParticleChangeForTransport::UpdateStepForAlongStep
5% G4ParticleChange::UpdateStepForAlongStep
3% G4VeEnergyLoss::AlongStepDoIt
3% G4Transportation::AlongStepDoIt
1% G4MultipleScattering::AlongStepDoIt
1% G4VhEnergyLoss::AlongStepDoIt
20% G4SteppingManager::InvokePostStepDoItProcs
5% G4MultipleScattering::PostStepDoIt
4% G4Step::UpdateTrack
4% G4Transportation::PostStepDoIt
2% G4ParticleChangeForMSC::UpdateStepForPostStep
GEANT4 Workshop 02
GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)

10. GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)
Where time is spent?
25% TRANSPORTATION:
18% G4Transportation::AlongStepGetPhysicalInteractionLength
14% G4PropagatorInField::ComputeStep
8% G4ChordFinder::AdvanceChordLimited
3% G4Transportation::AlongStepDoIt
4% G4Transportation::PostStepDoIt
4.2% LOCATE IN GEOMETRY TREE
1.0% G4PropagatorInField::LocateIntersectionPoint
0.8% G4Navigator::LocateGlobalPointWithinVolume
1.5% G4Navigator::LocateGlobalPointAndUpdateTouchableHandle
1.0% G4Navigator::LocateGlobalPointAndSetup
GEANT4 Workshop 02
GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)

11. GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)
Tracking speed: G3 vs G4
Track charged geantinos in CMS (muon w/o physics as there are no charged geantinos in GEANT3)
1000 tracks at random eta and phi
Magnetic field OFF
GEANT4 magnetic field is more precise...
... Can we make it less precise and get as fast as GEANT3?
... Or maybe GEANT3 is too unprecise for our needs?
Magnetic field ON
GEANT3
GEANT4
P=10000 GeV
13.7s
12.62s
P=50 GeV
P=5 GeV
12.57s
GEANT3
GEANT4
P=10000 GeV
24.7s
88.2s
P=50 GeV
26.0s
131.2s
P=5 GeV
28.2s
174.3s
GEANT4 Workshop 02
GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)

12. Tracking in field parameters
GEANT4 gives you a big freedom to optimise magnetic field tracking.
User can select:
IntegratorStepper class
G4FieldManager::SetDeltaChord(value)
G4FieldManager::SetDeltaOneStep(value)
G4FieldManager::SetDeltaIntersection(value)
G4PropagatorInField::SetMinimumEpsilonStep(value)
G4PropagatorInField()::SetMaximumEpsilonStep(value)
G4IntegrationDriver()->SetHmin( value )
Select a default and Change systematically one parameter each time
1000 tracks of 50 GeV (same effects observed for 5 Gev & GeV)
Integrator Stepper
delta Chord
delta
OneStep
delta Intersection
minEpsilon
maxEpsilon
driverHmin
G4ClassicalRK4
0.1 mm
0.25 mm
0.001 mm
1.E-5
0.05
0.01
GEANT4 Workshop 02
GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)

13. Tracking in field parameters
deltaChord (mm):
deltaOneStep (mm):
deltaIntersection (mm):
minEpsilon
1.E-5
1.E-4
1.E-3
1.E-2
0.1 1.
10.
281.2
151.7
131.2
164.7
320.8
641.6
1710.9
0.001
0.01
0.1
0.25 1.
10.
100.
321.1
321.4
320.8
321.0
316.5
170.8
0.001
0.01
0.1 1.
10.
320.8
306.5
293.7
294.7
295.3
1.E-3
1E-4
1E-5
1E-6
1E-7
134.7
172.7
320.8
630.9
799.9
GEANT4 Workshop 02
GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)

14. Tracking in field parameters
maxEpsilon:
driverHmin:
Select some good parameters:
and change integrator stepper: 1.
1E-1
0.05
1E-2
1E-3
1E-4
321.2
320.8
321.5
321.1
320.4
0.0001
0.001
0.01
0.1 1.
10.
295.5
295.6
296.4
296.1
291.8
delta Chord
delta
OneStep
delta Intersection
minEpsilon
maxEpsilon
driverHmin
0.01 mm
0.25 mm
0.001 mm
1.E-4
0.05
0.1
ClassicalRK4
CashKarpRKF45
HelixExplicitEuler
HelixImplicitEuler
HelixSimpleRunge
SimpleHeum
SimpleRunge
125.2
110.9
55.2
92.4
57.9
99.0
72.0
GEANT4 Workshop 02
GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)

15. Tracking in field parameters
Push it to the limit (although not clear how much the optimal value of a parameter depends on others):
We can play with the parameters, but first we have to understand
How much we can change the parameters without affecting the physics results?
What are ´good physics results´ (is GEANT3 precision enough?)
Long way to go...
Integrator Stepper
delta Chord
delta
OneStep
delta Intersection
minEpsilon
maxEpsilon
driverHmin
HelixExplicitEuler
0.001 mm
100. mm
1.E-3
0.05
0.01
GEANT3
GEANT4
GEANT4 (opti?)
P=10000 GeV
24.7s
88.2s
41.5s
P=50 GeV
26.0s
131.2s
48.9s
P=5 GeV
28.2s
174.3s
65.2s
GEANT4 Workshop 02
GEANT4 preformance studies Pedro Arce (CERN/CIEMAT)