Import Geant4 10.2.0 source tree
This commit is contained in:
Gabriele Cosmo
@@ -0,0 +1,145 @@
|
||||
|
||||
-------------------------------------------------------------------
|
||||
|
||||
=========================================================
|
||||
Geant4 - an Object-Oriented Toolkit for Simulation in HEP
|
||||
=========================================================
|
||||
|
||||
Example ThreadsafeScorers
|
||||
----------------------------
|
||||
|
||||
This example demonstrates a very simple application where an energy
|
||||
deposit and # of steps is accounted in thread-local (i.e. one instance per
|
||||
thread) hits maps with underlying types of plain-old data (POD) and global
|
||||
(i.e. one instance) hits maps with underlying types of atomics.
|
||||
The example uses a coarse mesh, extensive physics, and step limiters
|
||||
to ensure that there is a higher degree of conflict between threads
|
||||
when updating the scorers to test the robustness of the atomics
|
||||
classes and maximize the compounding of thread-local round-off error.
|
||||
At the end of the simulation, the scorers are printed to
|
||||
"mfd_<DATA_TYPE>_<SCORER_TYPE>.out", where DATA_TYPE is either
|
||||
"tl" (thread-local) or "tg" (thread-global) and SCORER_TYPE is "EnergyDeposit"
|
||||
or "NumberOfSteps". These values are then compared to a thread-global
|
||||
sum of these scorers that were updated via mutex locking. If round-off
|
||||
errors in thread-local EnergyDeposit are present, they can be viewed
|
||||
in "mfd_diff.out" at the end of the simulation
|
||||
|
||||
1- ATOMICS and the ATOMIC SCORERS
|
||||
|
||||
atomics can ONLY handle plain-old data (POD) types, e.g. int, double, etc.
|
||||
The implementation of atomics in compiler-dependent. At the very worst,
|
||||
the performance of an atomic is the same mutex locking.
|
||||
Atomics, in general, are not copy-constructable. This has to do with
|
||||
thread safety (e.g. making a copy while another thread tries to update)
|
||||
This is why atomics cannot be used in STL containers. The implementation
|
||||
in atomic.hh has limited copy-construction and still cannot be used in
|
||||
STL containers. Use these copy-constructors with extreme caution. See
|
||||
opening comments of G4atomic.hh for more details.
|
||||
|
||||
The newly provided classes in this example (G4atomic, G4TAtomicHitsMap, and
|
||||
G4TAtomicHitsCollection) are intended for applications where memory is a
|
||||
greater concern than performance. While atomics generally perform better than
|
||||
mutex locking, the synchronization is not without a cost. However, since
|
||||
the memory consumed by thread-local hits maps scales roughly linearly
|
||||
with the number of threads, simulations with a large number of scoring
|
||||
volumes can decrease simulation time by increasing the number of threads
|
||||
beyond what was previously allowed due to the increase in memory consumption.
|
||||
***************************************************************************
|
||||
*** These classes are intended to be included in the Geant4 source code ***
|
||||
*** release next year ***
|
||||
***************************************************************************
|
||||
|
||||
The G4TAtomicHitsMap and G4TAtomicHitsCollection work exactly the same way
|
||||
as the standard G4THitsMap and G4THitsCollection, respectively, with the
|
||||
exception(s) that you should only implement one instance and provide a
|
||||
pointer/reference of that instance to the threads instead of having the
|
||||
threads create them. Additionally, there is no need to include them
|
||||
in the G4Run::Merge().
|
||||
|
||||
2- GEOMETRY DEFINITION
|
||||
|
||||
The geometry is constructed in the TSDetectorConstruction class.
|
||||
The setup consists of a box filling the world. The volume is divided into
|
||||
subregions, where the outermost boxes are a different material. The materials
|
||||
by default are water and boron as these have large scattering cross-sections
|
||||
for neutrons (the default particle).
|
||||
|
||||
3- PHYSICS LIST
|
||||
|
||||
The particle's type and the physic processes which will be available
|
||||
in this example are set are built from a variety of physics constructors.
|
||||
The chosen physics lists are extensive, primarily
|
||||
The constructors are:
|
||||
|
||||
G4EmStandardPhysics_option4
|
||||
G4DecayPhysics
|
||||
G4RadioactiveDecayPhysics
|
||||
G4HadronPhysicsQGSP_BERT_HP
|
||||
G4HadronElasticPhysicsHP
|
||||
G4StepLimiterPhysics
|
||||
G4IonElasticPhysics
|
||||
G4IonBinaryCascadePhysics
|
||||
|
||||
4- ACTION INITALIZATION
|
||||
|
||||
TSActionInitialization, instantiates and registers to Geant4 kernel
|
||||
all user action classes.
|
||||
|
||||
While in sequential mode the action classes are instatiated just once,
|
||||
via invoking the method:
|
||||
TSActionInitialization::Build()
|
||||
in multi-threading mode the same method is invoked for each thread worker
|
||||
and so all user action classes are defined thread-local.
|
||||
|
||||
A run action class is instantiated both thread-local
|
||||
and global that's why its instance is created also in the method
|
||||
TSActionInitialization::BuildForMaster()
|
||||
which is invoked only in multi-threading mode.
|
||||
|
||||
5- PRIMARY GENERATOR
|
||||
|
||||
The primary generator is defined in the TSPrimaryGeneratorAction class.
|
||||
The default kinematics is a 1 MeV neutron, randomly distributed in front
|
||||
of the target across 100% of the transverse (X,Y) target size.
|
||||
This default setting can be changed via the Geant4 built-in commands
|
||||
of the G4ParticleGun class.
|
||||
|
||||
6- DETECTOR RESPONSE
|
||||
|
||||
This example demonstrates a scoring implemented
|
||||
in the user action classes and TSRun object.
|
||||
|
||||
The energy deposited is collected per event in the PrimitiveScorer
|
||||
G4PSEnergyDeposit (as part of a MultiFunctionalDetector)
|
||||
and the thread-local version are merged at the end of the run.
|
||||
|
||||
The number of steps is collected per event in the PrimativeScorer
|
||||
G4PSNoOfSteps and the thread-local version are merged at the end of the run.
|
||||
|
||||
When the MFD is recording an event i.e. TSRun::RecordEvent(const G4Event*),
|
||||
the global atomic hits map adds the same hits collections
|
||||
|
||||
In multi-threading mode the energy accumulated in TSRun MFD object per
|
||||
workers is merged to the master in TSRun::Merge().
|
||||
|
||||
7- HOW TO RUN
|
||||
|
||||
- Execute ts_scorers in the 'interactive mode' with visualization:
|
||||
% ./ts_scorers
|
||||
and type in the commands from run.mac line by line:
|
||||
Idle> /control/verbose 2
|
||||
Idle> /tracking/verbose 1
|
||||
Idle> /run/beamOn 10
|
||||
Idle> ...
|
||||
Idle> exit
|
||||
or
|
||||
Idle> /control/execute run.mac
|
||||
....
|
||||
Idle> exit
|
||||
|
||||
- Execute ts_scorers in the 'batch' mode from macro files
|
||||
(without visualization)
|
||||
% ./ts_scorers run.mac
|
||||
% ./ts_scorers run.mac > run.out
|
||||
|
||||
|
||||
Reference in New Issue
Block a user