Added hybrid trigger example

Author: jackal1-66

run/SimExamples/Hybrid_trigger/README.md

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+<!-- doxy
+\page refrunSimExamplesHybrid Example Hybrid
+/doxy -->
+
+The usage of the Hybrid generator with the o2-sim is presented in this short manual.
+All the other generators are implemented as sub-generators and they can be called thanks to a
+JSON file, fed to o2-sim via the GeneratorHybrid.configFile parameter. The O2sim package needs to be loaded in order to use this example.
+
+The example can be run automatically using the runo2sim.sh script, which contains most of the
+available generators in O2. The JSON template can be generated using the ${O2DPG_ROOT}/MC/bin/o2_hybrid_gen.py script. To use this example the user can simply copy the entire Hybrid example folder and execute the script after giving it execution permissions (`chmod +x runo2sim.sh`).
+
+# Files description
+
+- **runo2sim.sh** &rarr; allows to use the hybrid generator example
+- **hybridconfig.json** &rarr; example JSON file for the hybrid generator configuration
+- **example.optns** &rarr; options file to be used in EPOS4 implemented as subgenerator in this example (the .optns must be available in the current working directory)

run/SimExamples/Hybrid_trigger/hybridconfig.json

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+{
+  "generators": [
+    {
+      "cocktail": [
+        {
+          "name": "pythia8hi",
+          "triggers": {
+            "mode": "or",
+            "specs": [
+              {
+                "macro": "${PWD}/trigger.macro",
+                "function": "trigger_impactb_pythia8(0.,5.)"
+              }
+            ]
+          },
+          "config": ""
+        },
+        {
+          "name": "external",
+          "config": {
+            "fileName": "${O2DPG_MC_CONFIG_ROOT}/MC/config/PWGDQ/external/generator/GeneratorPromptCharmonia.C",
+            "funcName": "GeneratorParamPromptJpsiToElectronEvtGen_pp13TeV()",
+            "iniFile": ""
+          }
+        }
+      ]
+    }
+  ],
+  "fractions": [
+    1
+  ]
+}

run/SimExamples/Hybrid_trigger/runo2sim.sh

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+#!/usr/bin/env bash
+#
+# Hybrid generator simulation example with triggers and cocktail:
+# the simulation is configured using a JSON file (hybridconfig.json in this folder), whose
+# template can be generated using the script ${O2DPG_ROOT}/MC/bin/o2_hybrid_gen.py.
+# Trigger is taken from the trigger.macro and it's a simple impact parameter selection for
+# heavy ion collisions
+set -x
+if [ ! "${O2DPG_ROOT}" ]; then
+    echo "This needs O2DPG loaded; alienv enter ..."
+    exit 1
+fi
+
+[ ! "${O2_ROOT}" ] && echo "Error: This needs O2 loaded" && exit 2
+
+NEV=1
+more=""
+JOBS=2
+
+usage()
+{
+    cat <<EOF
+Usage: $0 [OPTIONS]
+
+Options:
+
+  -m,--more    CONFIG      More configurations ($more)
+  -n,--nevents EVENTS      Number of events ($NEV)
+  -j,--jobs    JOBS        Number of jobs ($JOBS)
+  -h,--help                Print these instructions
+  --                       Rest of command line sent to o2-sim
+
+COMMAND must be quoted if it contains spaces or other special
+characters
+
+Below follows the help output of o2-sim
+
+EOF
+}
+
+if [ "$#" -lt 2 ]; then
+    echo "Running with default values"
+fi
+
+while test $# -gt 0 ; do
+    case $1 in
+        -m|--more)    more="$2" ; shift ;;
+        -n|--nevents) NEV=$2 ; shift ;;
+        -j|--jobs)    JOBS=$2 ; shift ;;
+        -h|--help) usage; o2-sim --help full ; exit 0 ;;
+        --)           shift ; break ;;
+        *) echo "Unknown option '$1', did you forget '--'?" >/dev/stderr
+           exit 3
+           ;;
+    esac
+    shift
+done
+
+# Starting simulation with Hybrid generator
+${O2_ROOT}/bin/o2-sim --noGeant -j $JOBS --field ccdb --vertexMode kCCDB --run 300000 --configKeyValues "MFTBase.buildAlignment=true;GeneratorHybrid.configFile=$PWD/hybridconfig.json;GeneratorHybrid.randomize=false;${more}" -g hybrid -o genevents --timestamp 1546300800000 --seed 836302859 -n $NEV

run/SimExamples/Hybrid_trigger/trigger.macro

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+#include "Generators/Trigger.h"
+#include "TParticle.h"
+#include <iostream>
+
+// a very simple trigger example, examining generated particles
+o2::eventgen::Trigger trigger()
+{
+  //
+  return [](const std::vector<TParticle>& particles) -> bool {
+    std::cout << "Running trigger on event with size " << particles.size() << "\n";
+    if (particles.size() > 10000) {
+      return true;
+    }
+    return false;
+  };
+}
+
+#include "Pythia8/Pythia.h"
+#include "Pythia8/HIInfo.h"
+#include <fairlogger/Logger.h>
+// a deep trigger example, looking into the internal generator state
+o2::eventgen::DeepTrigger
+  trigger_impactb_pythia8(double bmin = 5., double bmax = 10.)
+{
+  return [bmin, bmax](void* interface, std::string name) -> bool {
+    if (!name.compare("pythia8")) {
+      auto py8 = reinterpret_cast<Pythia8::Pythia*>(interface);
+#if PYTHIA_VERSION_INTEGER < 8300
+      auto hiinfo = py8->info.hiinfo;
+#else
+      auto hiinfo = py8->info.hiInfo;
+#endif
+      if (!hiinfo) {
+        LOG(fatal) << "Cannot define impact parameter: is \'pythia8\' running in heavy-ion mode?";
+      }
+      auto b = hiinfo->b();
+      auto selected = (b > bmin && b < bmax);
+      LOG(info) << "Impact parameter = " << b << " fm: " << (selected ? "selected" : "rejected");
+      return selected;
+    } else {
+      LOG(fatal) << "Cannot define impact parameter for generator interface \'" << name << "\'";
+    }
+    return false;
+  };
+}