ExtToHybrid parallel example (#2403)

Author: jackal1-66

MC/config/examples/hybrid/exampleparallel.json

@@ -0,0 +1,47 @@
+{
+  "mode": "parallel",
+  "generators": [
+    {
+        "name": "pythia8pp",
+        "config": ""
+    },
+    {
+        "name": "pythia8pp",
+        "config": ""
+    },
+    {
+        "name": "pythia8pp",
+        "config": ""
+    },
+    {
+        "name": "pythia8pp",
+        "config": ""
+    },
+    {
+        "name": "pythia8pp",
+        "config": ""
+    },
+    {
+        "name": "pythia8pp",
+        "config": ""
+    },
+    {
+        "name": "pythia8pp",
+        "config": ""
+    },
+    {
+        "name": "pythia8pp",
+        "config": ""
+    }
+  ],
+  "fractions": [
+    1,
+    1,
+    1,
+    1,
+    1,
+    1,
+    1,
+    1
+  ]
+}

MC/config/examples/ini/GeneratorExtToHybridParallel.ini

@@ -0,0 +1,4 @@
+[GeneratorHybrid]
+configFile = ${O2DPG_MC_CONFIG_ROOT}/MC/config/examples/hybrid/exampleparallel.json
+switchExtToHybrid = true
+num_workers = 8

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

@@ -0,0 +1,38 @@
+int Hybrid()
+{
+  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;
+  }
+  return 0;
+}