Things to do:

• Download Pythia.

• Extract everything.

• Configure it to have sharing enabled using: ./configure --enable-shared.

• Compile everything with make.

• Add the following runtime variables to ~/.bashrc.

  export PYTHIA8=/home/aashish/pythia8212

  export PYTHIA8DATA=$PYTHIA8/share/Pythia8/xmldoc

  export LD_LIBRARY_PATH=/home/aashish/pythia8212/lib

• Compile your file with something like the following:

  g -std=c 11 -I$PYTHIA8/include generateEvents.cc -o generateEvents -L$PYTHIA8/lib -lpythia8 -ldl

• Looks like you need ROOT 6 for Delphes. Not that you should be using ROOT 5. The only reason it matters is that, for some werid unexplained reason, the default version in my Ubuntu distro seems to be 5. Just typing in root loads ROOT 5. So to make sure that during Delphes' compilation, classes from ROOT 6 are loaded instead of from ROOT 5, you need to do the whole . bin/thisroot.sh thing. An alternative (and much better) way to do this is remove ROOT 5 and install ROOT 6 in something like /usr/local/ but a superposition of laziness and if it ain't broke, don't fix it is preventing me from doing that. Do that asap.
• ./bin/runDelphes cards/delphes_card_CMS_NoFastJet.tcl data/pythia_output.hepmc.

• Go to the data directory- cd data/.
• Run Herwig read ../cards/herwig_card.in. Note that if you don't change the random number seed in the card file, you get the same set of events.
• Run Herwig run herwig_run.run -d1.

• Go to the data directory- cd data/.
• Sherpa -f../cards/Run.dat.

/usr/bin/ld: cannot find -lPythia can be fixed by adding export LD_LIBRARY_PATH=/home/aashish/pythia8212/lib to your environment variables.

Sometimes adding them to ~/.bashrc~ doesn't work. So enter the following manually: export LD_LIBRARY_PATH=/home/aashish/hepmc/lib:/home/aashish/pythia8212/lib`

dyld: Library not loaded: libpythia8.dylib Referenced from: /Users/aashish/MODMonteCarlo/bin/generateEvents Reason: image not found , in OSX, can be fixed by simply copying libpythia8.dylib from pythia8/lib/ to /usr/local/lib, assuming your pythia installation is in /usr/local/lib/.