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Gabriele Cosmo
2016-06-09 10:41:53 +02:00
parent 4aea781e80
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examples/extended/biasing/README
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@@ -3,20 +3,21 @@
--------------------------
This directory includes example applications to demonstrate the usage of
different biasing techniques supported in Geant4, or possible from the
user applications.
different variance reduction techniques supported in Geant4, or possible
from the user applications.
General remark to biasing
-------------------------
General remark to variance reduction
------------------------------------
The tools provided for importance sampling (or geometrical splitting and
Russian roulette) require the user to have a good understanding of the
physics in the problem. This is because the user has to decide which
particle types have to be biased, define the regions (physical volumes,
replicas) and assign importances to that regions. If this is not done
properly it can not be expected that the results describe a real
experiment. The examples given here only demonstrate how to use the tools
technically. They don't intend to produce physical correct results.
Russian roulette) and for the weight window technique require the user to
have a good understanding of the physics in the problem. This is because
the user has to decide which particle types have to be biased, define the
cells (physical volumes, replicas) and assign importances or weight
windows to that cells. If this is not done properly it can not be
expected that the results describe a real experiment. The examples given
here only demonstrate how to use the tools technically. They don't intend
to produce physical correct results.
General remark to scoring
-------------------------
@@ -26,24 +27,27 @@ therefore should inherit from the interface G4VScorer.
An example of an implementation of a scorer is G4Scorer
which may be found in source/event.
The scoring in these examples is done with a G4Scorer.
Importance sampling and scoring does not support all options of the
Geant4 geometry. It only supports physical volumes and simple replicas.
The variance reduction techniques and scoring do not support all options
of the Geant4 geometry. It only supports physical volumes and simple
replicas.
To identify a physical volume (or replica) objects of the class
G4GeometryCell are used. Scoring is done according to these
cells and importance values may be assigned to them.
When scoring is done in a "scoring" or in a "importance" geometry
special action has to be taken to prevent counting of
"collisions" with boundaries of the tracking geometry as interactions.
This is differently handled when scoring is done in the tracking geometry.
cells and importance values or the weight windows may be assigned to
them.
When scoring is done in a parallel geometry special action has to be taken
to prevent counting of "collisions" with boundaries of the mass geometry
as interactions. This is differently handled when scoring is done in the
mass geometry.
--> G4GeometryCell must not share boundaries with the world volume! <--
--> G4GeometryCell of the parallel geometry must not share boundaries with
the world volume! <--
Known problems
--------------
In the following scenario it can happen that a particle is not
biased and it's weight is therefore not changed even if it crosses
a boundary where biasing should happen.
The importance sampling creates particles on boundaries
Importance and weight window sampling create particles on boundaries
between volumes. If the GPIL method of a physical process returns
0 as step length for a particle on a boundary and if the PostStepDoIt of
that process changes the direction of the particle to go back in the
@@ -59,9 +63,21 @@ http://dressel.home.cern.ch/dressel/biasscore/Sampling.html
Example B01
===========
The example uses importance sampling and scoring. Importance values are
defined according to the mass geometry. Scoring is also done in according
to the mass geometry.
The example uses importance sampling or the weight window technique
according to an input parameter. It uses scoring in both cases.
Importance values or weight windows are defined according to the mass
geometry. In this example the weight window technique is configured such
that it behaves equivalent to importance sampling: The window is actually
not a window but simply the inverse of the importance value and only
one energy region is used that covers all energies in the problem.
The user may change the weight window configuration by changing the
initialization of the weight window algorithm in example,cc.
Different energy bounds for the weight window technique may be specified
in B01DetectorConstruction.
The executable takes one optional argument: 0 or 1. Without argument or
with argument: 0, the importance sampling is applied with argument: 1,
the weight window technique is applied.
Example B02
@@ -77,26 +93,28 @@ To compile this example you need AIDA 3.0 installed. To link
and run it you need a AIDA compliant analysis package. The
GNUmakefile of this example shows how to use Anaphe as analysis
package.
The following list shows what to do if you are at CERN using rehat61
and gcc-2.95.2:
use the shell /bin/sh
The following list shows what to do if you are at CERN using rehat73
and gcc-3.2 and the tcsh:
1) set the following variables (for example):
ANAPHETOP=/afs/cern.ch/sw/lhcxx
(or if installed in opt: /opt/Anaphe/5.0.1)
AIDA_DIR=/afs/cern.ch/sw/contrib/AIDA/3.0/src/cpp
setenv ANAPHETOP /afs/cern.ch/sw/lhcxx
(or if installed in opt: /opt/Anaphe/5.0.5)
setenv AIDA_DIR /afs/cern.ch/sw/contrib/AIDA/3.0/src/cpp
(or if installed in opt: /opt/AIDA/3.0.0/3.0.0/AIDA/3.0/src/cpp)
export ANAPHETOP AIDA_DIR
2) Source the script:
. $ANAPHETOP/share/LHCXX/5.0.1/scripts/setupAnaphe
source $ANAPHETOP/share/LHCXX/5.0.5/scripts/setupAnaphe.csh
This should set the LD_LIBRARY_PATH and the PATH environment to find the
lizrd executable and Anaphe libraries and header files.
It also sets the environment variable PLATF.
3) and add to lirary path the following directories:
LD_LIBRARY_PATH=${LD_LIBRARY_PATH}:${G4WORKDIR}/lib/${G4SYSTEM}:${G4WORKDIR}/tmp/${G4SYSTEM}/exampleB02
setenv LD_LIBRARY_PATH ${LD_LIBRARY_PATH}:${G4WORKDIR}/lib/${G4SYSTEM}:${G4WORKDIR}/tmp/${G4SYSTEM}/exampleB02
Now you should be able to run gmake and to run exampleB02.
The example stores the plot in the file b02.hbook.
To look at the histogram using lizard you also may use Anaphe 5.0.1
To look at the histogram using lizard you also may use Anaphe 5.0.5
http://anaphe.web.cern.ch/anaphe/index2.html.
Files in B02:
@@ -108,42 +126,53 @@ Example B03
===========
This example uses Geant4 and in particular importance sampling and
scoring through python. It also creates a histogram.
scoring through python. It creates a simple histogram. It's ment
to demonstrate how to use a customized scorer and importance sampling
in combination with a scripting language, python.
Geant4 code is executed from a python session. Therefore, swig is used
to create python shadow classes and to generate the code necessary to
use the Geant4 libraries from a python session.
For simplicity it is recommended to use Anaphe. Anaphe comes with
python and swig installations.
See http://anaphe.web.cern.ch/
Compiling and running
---------------------
To compile and run this example you need a python2.2 installation
see http://www.python.org.
Please set the environment variable "PYTHON_DIR" to your python2.2
installation e.g:
using afs:
to /afs/cern.ch/sw/lhcxx/specific/redhat61/gcc-2.95.2/PublicDomainPackages/2.0.0
or if Anaphe is installed in opt /opt/Anaphe/5.0.1/specific/redhat72/gcc-2.95.2/PublicDomainPackages/2.0.0.
Please add to your environment variables
Building, compiling and running
-------------------------------
Follow similar steps as for example B02. If you already have
the environment set up for example B02 jump to point 3 below:
1) set the following variables (for example):
setenv ANAPHETOP /afs/cern.ch/sw/lhcxx
(or if installed in opt: /opt/Anaphe/5.0.5)
setenv AIDA_DIR /afs/cern.ch/sw/contrib/AIDA/3.0/src/cpp
(or if installed in opt: /opt/AIDA/3.0.0/3.0.0/AIDA/3.0/src/cpp)
2) Source the script:
source $ANAPHETOP/share/LHCXX/5.0.5/scripts/setupAnaphe.csh
3) and add to lirary path the following directories:
setenv LD_LIBRARY_PATH ${LD_LIBRARY_PATH}:${G4WORKDIR}/lib/${G4SYSTEM}:${G4WORKDIR}/tmp/${G4SYSTEM}/exampleB03
and setenv PYTHONPATH $LD_LIBRARY_PATH.
====
setenv PYTHONPATH $LD_LIBRARY_PATH
4) setenv PYTHON_VERSION 2.2
You may run gmake now.
You should be able to execute the file B03RunApplication.py from your
shell now.
If you have Anaphe 5.0.1 installed you may also execute the file
B03RunApplication.py from a lizard session. This will create a
histogram. Therefore you may follow the steps 1 and two
in the above exampleB02.
See http://anaphe.web.cern.ch/anaphe/index2.html.
shell or from a lizard session now.
The histogram is displayed only if the script is beeing ran
from lizard.
Files in B03;
env.csh: Is an example script to set the environment. It should work
if you are at CERN and if you are on a redhat6.1 system.
buildit.sh: You don't need to use this file. Only if you want to
make changes to the python interface defined in B03App.i you may need
to use it.
B03Application.py: Is a example class utilizing importance sampling
and scoring using python.
B03RunApplication.py: Is a python script running the example.
It may be executed from the shell or in a python or lizard
session. In case it is executed from lizard it creates a plot
with a histogram.
B03App.py: Is created by swig using the buildit.sh script.
B03App.py: Is created by swig using swig.