~maddevelopers/mg5amcnlo/GPU

MadGraph/MadEvent 5
By Fabio Maltoni, Tim Stelzer and the CP3 development team

http://madgraph.phys.ucl.ac.be/
http://madgraph.hep.uiuc.edu/
http://madgraph.roma2.infn.it/

Technical Details for Setting Up and Running Gridpacks:
(see http://cp3wks05.fynu.ucl.ac.be/twiki/bin/view/Library/GridDevelopment)

Using the option
   .true.  = gridpack
in the run_card.dat will generate a gridpack.tar.gz. Online, the
results page will have a link to this package.

The gridpackage is meant to be sent over to the cluster or grid
nodes. It's completely frozen, meaning that you cannot change any
parameters or run options, apart from the # of event and the rnd
number.

When you unpack it you get:
run.sh
madevent/
The first is a script which accepts two numbers (the number of events
and the rnd number).

There are two optional packages that can be added to the gridpack:

DECAY is a optional directory that contains a program that decays
final state particles, keeping track of spin correlations at much as
possible. It is of particular use for decays of top quarks.

REPLACE is also an optional directory for lepton replacement. This is
usefull for instance in the case where the generation time of the
diagrams is critical (like for example in the case of (z/gamma>e, mu,
tau)+4 jets including b's).
See below for more details

Basic Use of Gridpacks:

Before you use the gridpack locally or over the grid, you need to
compile the package on a machine compatible with your cluster:
cd madevent
./bin/compile
and after that it is ready to go. There is also an option to compile
madevent with dynamic libraries. Use
./bin/compile dynamic
to compile with dynamic libraries for the madgraph source files. This
will replace all makefiles with makefile_dynamic and compile using
these new makefiles. Using dynamic libraries is greatly encouraged,
because it can make the compiled gridpack significantly smaller.

After a succesful compilation you can run the
./bin/clean4grid
script to remove all source files and reduce the size of the
package. Now you can just repackage and send it to some cpu in india
or run locallly (after chmod +x run.sh)
./run.sh 10000 37

DECAY:

The DECAY directory contains a program to decay final state
particles. It has been designed to keep track of spin correlations as
much as possible and is particularly useful for the decay of (anti)
top quarks E.g. for the decay of top quarks up to 95% of the
correlations are preserved. 
Note that DECAY also needs the HELAS directory to compile.
The DECAY package can be found in the MadGraph 5 developer's kit that
can be downloaded from the MadGraph /MadEvent Downloads webpage or
from Launchpad. To add the package to the gridpack, simply untar the
gridpack to get the ./madevent/ directory and the ./run.sh
script. Move the DECAY and the HELAS directories from the MG 5 developer's kit to the
directory in which you untarred the gridpack, to get here the three
directories and the one script file:
./madevent/                 ./DECAY/         ./HELAS         ./run.sh
The DECAY package is compiled automatically when
./bin/compile
is executed from the ./madevent directory. As input to specify the
decays, files with the names
input_x.in
should be put in the ./DECAY directory. (Where x is a number between 1
and 20.) These files are read automatically, and one file should be
put for each decaying particle. (E.g. for ttbar events 2 files are
necessary: one for the decay of the top and one for the anti-top.) The
first three lines of these files should be
1
../events_in.lhe
../events.lhe
while the fourth line specifies the particle that needs decay, e.g. put
t
for the decay of a top quark. The fifth line is an integer that
specifies the decay mode. This depends on the particle that is going
to be decayed. For top quarks it is:
1 = ' t -> b  w+ '
2 = ' t -> b  ve e+'
3 = ' t -> b  vm mu+'
4 = ' t -> b  vt ta+'
5 = ' t -> b  vl l+    (e+mu)'
6 = ' t -> b  vl l+    (e+mu+ta)'
7 = ' t -> b  j   j    (ud+cs)'
8 = ' t -> b  anything (e+mu+ta+ud+cs)'
and similar for the anti-top.
Hence this file decays all top quarks (ignoring anti-tops!) in the
event file leptonically.

REPLACE

REPLACE is a package that lets the user replace particles in event
files. This is particulary useful to save precious time in the
generation of the diagrams. For example, the generation of Z+4jets, in
which the Z is decay leptonically, will take (at least) three times
longer when the three generations of leptons are specified in the
process. Because we know that, if we assume that all of them are
massless, the decay of Z bosons is unfavored to any specific lepton
flavor, we could as well have generated events with only muons and
then randomly replacing the muons in the event file by electrons or
tau's with 33% probability for each. This is exactly what the REPLACE
script has been designed to do. Note that for MadGraph 5, this is less
of a problem, and in general the full process should be run
(preferentially using sm-no_masses to get as few run directories as
possible).

To add this functionality to the gridpack you'll have to create a
directory 'REPLACE" after you have untarred a gridpack to get the
following:
./madevent/                 ./REPLACE/                 ./run.sh
The replace.pl script from the ./madevent/bin/ directory as well as
the replace_card1.dat from the ./madevent/Cards needs to be copied to
the REPLACE directory by typing:
cp  ./madevent/bin/replace.pl  ./madevent/Cards/replace_card1.dat  ./REPLACE/
(Note the in the latest version of replace, the '1' add the end of the
filename is necessary, and can be any number between 1 and 20, to have
the possibility of more than one replace.) In the replace_card1.dat
the particles that needs to be replaced and the particles in which it
needs to be replaced have to be specified by their corresponding PDG
codes. E.g. adding the lines:
11 : 11 13 15
-11 : -11 -13 -15
will replace all electrons from the event file by electrons (i.e. do
nothing), muons or taus with equal probabilities, and simultaneously
positrons with positrons, anti-muons and anti-taus. The replace card
that can be used in the example above in which only diagrams where the
Z decays in muons were generated and need to be replaced by electrons
and taus can be found here: replace_card1.dat