Created EPOS4 external example generator (#1789)

* Created EPOS4 external example generator

* Updated center-of-mass energy of EPOS4 example

* Implemented GeneratorEPOS4 test

* Testing fix for EPOS4 external

* Revert "Implemented GeneratorEPOS4 test"

This reverts commit e0b88b1.

* Reapply "Implemented GeneratorEPOS4 test"

This reverts commit 53671e8.

* Revert "Testing fix for EPOS4 external"

This reverts commit 920cf42.

* Check for LIBDIR

* Added EPO4 as env variable in external script

* Explicit definition of EPOS4 version

* Reorganised and improved fix for CI

MC/config/examples/epos4/epos.sh

@@ -0,0 +1,41 @@
+#!/bin/sh
+# Script based on CRMC example
+# EPOS4 option files must contain ihepmc set to 2 to print HepMC
+# data on stdout. -hepmc flag is not needed anymore, but -hepstd is fundamental
+# in order not to print useless information on stdout (a z-*optns*.mtr file will be created)
+
+optns="example"
+seed=$RANDOM
+
+while test $# -gt 0 ; do
+    case $1 in
+        -i|--input)   optns=$2 ; shift ;;
+        -s|--seed)    seed=$2 ; shift ;;
+        -h|--help) usage; exit 0 ;;
+    esac
+    shift
+done
+
+if [ ! -f $optns.optns ]; then
+    echo "Error: Options file $optns.optns not found"
+    exit 1
+fi
+
+if [ $seed -eq 0 ]; then
+    echo "Seed can't be 0, random number will be used"
+    seed=$RANDOM
+fi
+
+# Check if the environment variable EPO4 is set (mandatory with o2dpg-sim-tests on CI machines)
+# If not, set all the EPOS4 related variables, most likely they are unset as well.
+if [ -z "${EPO4}" ]; then
+    export EPO4=$EPOS4_ROOT/epos4/
+    export LIBDIR=$EPOS4_ROOT/epos4/bin
+    export EPO4VSN=4.0.0
+    export OPT=./
+    export HTO=./
+    export CHK=./
+fi
+
+# Or filters the stdout with only HepMC2 useful data
+$EPOS4_ROOT/epos4/scripts/epos -hepstd -s $seed $optns | sed -n 's/^\(HepMC::\|[EAUWVP] \)/\1/p'

MC/config/examples/epos4/generator/example.optns

@@ -0,0 +1,32 @@
+!--------------------------------------------------------------------
+!           proton-proton collision no hydro no hadronic cascade
+!--------------------------------------------------------------------
+
+!---------------------------------------
+!            Define run
+!---------------------------------------
+
+application hadron !hadron-hadron, hadron-nucleus, or nucleus-nucleus
+set laproj 1 !projectile atomic number
+set maproj 1 !projectile mass number
+set latarg 1 !target atomic number
+set matarg 1 !target mass number
+set ecms 13600 !sqrt(s)_pp
+set istmax 25 !max status considered for storage
+
+ftime on     !string formation time non-zero
+!suppressed decays:
+nodecays
+ 110 20 2130 -2130 2230 -2230 1130 -1130 1330 -1330 2330 -2330 3331 -3331
+end
+
+set ninicon 1            !number of initial conditions used for hydro evolution
+core off                 !core/corona not activated
+hydro off                !hydro not activated
+eos off                  !eos not activated
+hacas off                !hadronic cascade not activated
+set nfreeze 1            !number of freeze out events per hydro event
+set modsho 1             !printout every modsho events
+set centrality 0         !0=min bias
+set ihepmc 2             !HepMC output enabled on stdout
+set nfull 10

MC/config/examples/epos4/generator_EPOS4.C

@@ -0,0 +1,61 @@
+#include <iostream>
+#include <fstream>
+#include <filesystem>
+#include <fairlogger/Logger.h>
+
+class GeneratorEPOS4 : public o2::eventgen::GeneratorHepMC
+{
+    public:
+        GeneratorEPOS4() = default;
+        ~GeneratorEPOS4() = default;
+
+};
+
+// Next function takes the optns file as argument and edits the maximum number of events to be generated.
+// When used as an external generator it is important that the events passed with the -n flag are the same
+// or lower of the events set in the optns file, otherwise the generation will crash. That is why the .ini
+// example file contains the maximum integer available, assuming less events than that are generated in a real
+// life scenario. Unfortunately a larger number cannot be used at the moment since EPOS4 has a signed integer
+// type for the nfull parameter. Might be changed in the future.
+// When running locally, or on the GRID (not in hyperloop), the default parameters provided in the .ini file of the
+// external generation can be overwritten using the confKeyValues option (or similar depending on the tool used).
+FairGenerator* generateEPOS4(const std::string &name, const int& nEvents)
+{
+    // check if the file exists
+    auto filename = gSystem->ExpandPathName(name.c_str());
+    if (!std::filesystem::exists(filename))
+    {
+        LOG(fatal) << "Options file " << filename << " does not exist!";
+        exit(1);
+    }
+    // cache all the lines of the optns file and replace the number of events
+    std::ifstream file(filename);
+    std::string line;
+    bool found = false;
+    std::stringstream buffer;
+    while (std::getline(file, line))
+    {
+        if (line.find("nfull") != std::string::npos){
+            // replace the number of events
+            found = true;
+            line = "set nfull " + std::to_string(nEvents);
+        }
+        buffer << line << "\n";
+    }
+    file.close();
+    // Write the updated content back to a file in the current directory
+    std::ofstream outFile("cfg.optns");
+    outFile << buffer.str();
+    if (!found)
+    {
+        outFile << "set nfull " + std::to_string(nEvents);
+    }
+    outFile.close();
+    auto gen = new GeneratorEPOS4();
+    auto& param0 = o2::eventgen::GeneratorFileOrCmdParam::Instance();
+    auto& param = o2::eventgen::GeneratorHepMCParam::Instance();
+    auto& conf = o2::conf::SimConfig::Instance();
+    // setup the HepMC generator to run with automatic FIFOs
+    gen->setup(param0, param, conf);
+    return gen;
+}

MC/config/examples/ini/GeneratorEPOS4.ini

@@ -0,0 +1,10 @@
+[GeneratorExternal]
+fileName=${O2DPG_MC_CONFIG_ROOT}/MC/config/examples/epos4/generator_EPOS4.C
+funcName=generateEPOS4("${O2DPG_MC_CONFIG_ROOT}/MC/config/examples/epos4/generator/example.optns", 2147483647)
+
+[GeneratorFileOrCmd]
+cmd=${O2DPG_MC_CONFIG_ROOT}/MC/config/examples/epos4/epos.sh -i cfg
+bMaxSwitch=none
+
+[HepMC]
+version=2

MC/config/examples/ini/tests/GeneratorEPOS4.C

@@ -0,0 +1,64 @@
+int External()
+{
+  std::string path{"o2sim_Kine.root"};
+  // Check that file exists, can be opened and has the correct tree
+  TFile file(path.c_str(), "READ");
+  if (file.IsZombie())
+  {
+    std::cerr << "Cannot open ROOT file " << path << "\n";
+    return 1;
+  }
+  auto tree = (TTree *)file.Get("o2sim");
+  if (!tree)
+  {
+    std::cerr << "Cannot find tree o2sim in file " << path << "\n";
+    return 1;
+  }
+  std::vector<o2::MCTrack> *tracks{};
+  tree->SetBranchAddress("MCTrack", &tracks);
+
+  // Check if all events are filled
+  auto nEvents = tree->GetEntries();  
+  for (Long64_t i = 0; i < nEvents; ++i)
+  {
+    tree->GetEntry(i);
+    if (tracks->empty())
+    {
+      std::cerr << "Empty entry found at event " << i << "\n";
+      return 1;
+    }
+  }
+  // Check if there are 100 events, as simulated in the o2dpg-test
+  if (nEvents != 100)
+  {
+    std::cerr << "Expected 100 events, got " << nEvents << "\n";
+    return 1;
+  }
+  // check if each event has two protons with 6800 GeV of energy
+  // exits if the particle is not a proton 
+  for (int i = 0; i < nEvents; i++)
+  {
+    auto check = tree->GetEntry(i);
+    int count = 0;
+    for (int idxMCTrack = 0; idxMCTrack < tracks->size(); ++idxMCTrack)
+    {
+      auto track = tracks->at(idxMCTrack);
+      double energy = track.GetEnergy();
+      // Check if track energy is approximately equal to 6800 GeV (a tolerance of 65 keV is considered, straight equality does not work due to floating point precision)
+      if (std::abs(energy - 6800) < 1e-4) 
+      {
+        if (track.GetPdgCode() != 2212){
+          std::cerr << "Found 6800 GeV particle with pdgID " << track.GetPdgCode() << "\n";
+          return 1;
+        }         
+        count++;  
+      }
+    }
+    if (count < 2)
+    {
+      std::cerr << "Event " << i << " has less than 2 protons at 6800 GeV\n";
+      return 1;
+    }
+  }
+  return 0;
+}