Import examples from O2 into O2DPG

Author: preghenella

MC/config/common/external/generator/hijing.C

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+// configures a AliGenHijing class from AliRoot
+//   usage: o2sim -g external --configKeyValues 'GeneratorExternal.fileName=hijing.C;GeneratorExternal.funcName="hijing(5020., 0., 20.)"'
+
+/// \author R+Preghenella - October 2018
+
+R__LOAD_LIBRARY(libTHijing)
+
+FairGenerator*
+  hijing(double energy = 5020., double bMin = 0., double bMax = 20.)
+{
+  // instance and configure Hijing
+  auto hij = new AliGenHijing(-1);
+  hij->SetEnergyCMS(energy);
+  hij->SetImpactParameterRange(bMin, bMax);
+  hij->SetReferenceFrame("CMS");
+  hij->SetProjectile("A", 208, 82);
+  hij->SetTarget("A", 208, 82);
+  hij->SetSpectators(0);
+  hij->KeepFullEvent();
+  hij->SetJetQuenching(0);
+  hij->SetShadowing(1);
+  hij->SetDecaysOff(1);
+  hij->SetSelectAll(0);
+  hij->SetPtHardMin(2.9);
+  hij->Init();
+
+  // instance and configure TGenerator interface
+  auto tgen = new o2::eventgen::GeneratorTGenerator();
+  tgen->setMomentumUnit(1.);        // [GeV/c]
+  tgen->setEnergyUnit(1.);          // [GeV/c]
+  tgen->setPositionUnit(0.1);       // [cm]
+  tgen->setTimeUnit(3.3356410e-12); // [s]
+  tgen->setTGenerator(hij->GetMC());
+  return tgen;
+}

MC/config/common/external/generator/pythia6.C

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+// configures a TPythia6 class
+//   usage: o2sim -g external --configKeyValues 'GeneratorExternal.fileName=pythia6.C;GeneratorExternal.funcName="pythia6(14000., "pythia.settings")"'
+
+/// \author R+Preghenella - October 2018
+
+#if !defined(__CLING__) || defined(__ROOTCLING__)
+#include "TPythia6.h"
+#include "FairGenerator.h"
+#include "Generators/GeneratorTGenerator.h"
+#include <fstream>
+#include <iostream>
+#endif
+
+R__LOAD_LIBRARY(libpythia6)
+
+void configure(TPythia6* py6, const char* params);
+
+FairGenerator*
+  pythia6(double energy = 14000., const char* params = nullptr)
+{
+  // instance and configure Pythia6
+  auto py6 = TPythia6::Instance();
+  if (params)
+    configure(py6, params);
+  py6->Initialize("CMS", "p", "p", energy);
+
+  // instance and configure TGenerator interface
+  auto tgen = new o2::eventgen::GeneratorTGenerator();
+  tgen->setMomentumUnit(1.);        // [GeV/c]
+  tgen->setEnergyUnit(1.);          // [GeV/c]
+  tgen->setPositionUnit(0.1);       // [cm]
+  tgen->setTimeUnit(3.3356410e-12); // [s]
+  tgen->setTGenerator(py6);
+  return tgen;
+}
+
+void configure(TPythia6* py6, const char* params)
+{
+  std::ifstream file(params);
+  if (!file.is_open()) {
+    std::cerr << "Cannot open configuration file: " << params << std::endl;
+    return;
+  };
+  std::string line, command;
+  while (std::getline(file, line)) {
+    /** remove comments **/
+    command = line.substr(0, line.find_first_of("#"));
+    if (command.length() == 0)
+      continue;
+    py6->Pygive(command.c_str());
+  }
+  file.close();
+}