Simulation example of MPI-triggered Pythia8

Author: preghenella

MC/config/common/external/trigger/mpi.C

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+// MPI trigger
+//
+//   usage: o2sim --trigger external --configKeyValues 'TriggerExternal.fileName=trigger_mpi.C;TriggerExternal.funcName="trigger_mpi()"'
+//
+
+/// \author R+Preghenella - February 2020
+
+#include "Generators/Trigger.h"
+#include "Pythia8/Pythia.h"
+#include "TPythia6.h"
+#include "FairLogger.h"
+
+o2::eventgen::DeepTrigger
+  trigger_mpi(int mpiMin = 15)
+{
+  return [mpiMin](void* interface, std::string name) -> bool {
+    int nMPI = 0;
+    if (!name.compare("pythia8")) {
+      auto py8 = reinterpret_cast<Pythia8::Pythia*>(interface);
+      nMPI = py8->info.nMPI();
+    } else if (!name.compare("pythia6")) {
+      auto py6 = reinterpret_cast<TPythia6*>(interface);
+      nMPI = py6->GetMSTI(31);
+    } else
+      LOG(FATAL) << "Cannot define MPI for generator interface \'" << name << "\'";
+    return nMPI >= mpiMin;
+  };
+}

MC/config/examples/ini/trigger_mpi.ini

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+### The setup uses an external even generator trigger which is
+### defined in the following file and it is retrieved and configured
+### according to the specified function call
+
+[TriggerExternal]
+fileName=${O2DPG_ROOT}/MC/config/common/external/trigger/trigger_mpi.C
+funcName=trigger_mpi(10)
+
+### This part configures Pythia8
+
+[GeneratorPythia8]
+config = ${O2DPG_ROOT}/MC/config/common/pythia8/generator/pythia8_inel.cfg

MC/run/examples/trigger_mpi.sh

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+#!/usr/bin/env bash
+
+### This script run the simulation of Pythia8 pp INEL events with a trigger on number of MPI.
+### The details of the configuration are defined in the INI config files (--configFile).
+
+set -x
+
+MODULES="PIPE ITS TPC"
+EVENTS=20
+NWORKERS=8
+
+o2-sim -j ${NWORKERS} -n ${EVENTS} -g pythia8 -m ${MODULES} -o sim \
+       --configFile ${O2DPG_ROOT}/MC/config/examples/ini/trigger_mpi.ini \
+       > logsim 2>&1