Singularity is a container system developed for the HPC user environment. It is similar to the docker, but it runs on the user-space.

In some cases, setting up the madgraph_aMC@NLO is painful job - to synchronize the system packages. Running the simplest example process works on the vanilla setup but it comes to a problem if you want to run the NLO simulations.

Life gets much easier with the aMC@NLO on the singularity - once you have sif image file then you can re-use the image files keeping the identical setup for each runs.

1. Base image with ROOT: https://hub.docker.com/r/rootproject/root
2. Madgraph install image: https://launchpad.net/mg5amcnlo

# Singularity recipe to run MG5_aMC@NLO
Bootstrap: docker
From: rootproject/root:6.24.06-ubuntu20.04

%post
    export LANG="C"
    export LC_ALL="C"

    ## Install necessary packages
    apt-get update
    apt-get -y install python-six python3-six
    apt-get -y install wget ghostscript bc rsync

    ### Install Madgraph_aMC@NLO
    mkdir -p /sw/install
    cd /sw/install
    wget https://launchpad.net/mg5amcnlo/3.0/3.3.x/+download/MG5_aMC_v3.3.1.tar.gz
    cd /sw
    tar xzf /sw/install/MG5_aMC_v3.3.1.tar.gz
    cd /sw/MG5_aMC_v3_3_1

    ## Install internal subpackages within the Madgraph_aMC@NLO
    ./bin/mg5_aMC <<EOF
install zlib; install boost;
install hepmc; install lhapdf6;
install ninja; install collier; install QCDLoop;
EOF

#    ./bin/mg5_aMC <<EOF
#install looptools
#cuttools install
#iregi install
#EOF
    ./bin/mg5_aMC <<EOF
install pythia8;
install maddm; install maddump; install MadSTR;

EOF
    cat /etc/ld.so.conf

    ./bin/mg5_aMC << EOF
install ExRootAnalysis; install MadAnalysis4
install Delphes

EOF

    ### First launch example process, with QCD at NLO
    ./bin/mg5_aMC << EOF
generate p p > t t~ [QCD]
output /sw/install/out_ttNLO

#launch -m
launch

shower = PYTHIA8    
madspin = ON
0

EOF

    ### Allow generic users to run executables
    chmod go+rx bin/* HEPTools/*/bin/*
    chmod -R go+r .

%environment
    export LC_ALL=C
    export PATH=/usr/games:$PATH

%runscript
    #/usr/local/bin/thisroot.sh
    #export ROOTSYS=/usr
    #export PS1="\[Singularity \e]0;\u@\h: \w\a\]${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]>"
    #python /sw/MG5_aMC_v3_3_1/bin/mg5_aMC

    #/bin/bash
    /sw/MG5_aMC_v3_3_1/bin/mg5_aMC