You first need to append omniweights to the MC file

python addWeightToTree.py

Then you need to install fastjet. I have fastjet-3.4.1

## please check https://fastjet.fr/quickstart.html
curl -O https://fastjet.fr/repo/fastjet-3.4.1.tar.gz
tar zxvf fastjet-3.4.1.tar.gz
cd fastjet-3.4.1/

./configure --prefix=$PWD/../fastjet-install
make
make check
make install
cd ..

To compile:

setupATLAS 
lsetup "root 6.30.02-x86_64-el9-gcc13-opt" 

COMPILER=$(root-config --cxx)
FLAGS=$(root-config --cflags --libs)
echo $COMPILER $FLAGS
$COMPILER $FLAGS -g -O3 -Wall -Wextra -Wpedantic -fopenmp ./doHisto.cc ./MakeOmni.C ./MakeTruth.C  ./DoPlots.cxx ./analysisHelpers.cxx ./jetHelpers.cxx ./AtlasLabels.C ./AtlasStyle.C ./AtlasUtils.C `fastjet-install/bin/fastjet-config --cxxflags --libs --plugins` -I. -o doHisto

To run, it's a 2 step approach (not really needed but well..). First run to get an output root file

./doHisto reco 

then run to get the plots in ATLAS style

./doHisto plots