fix(sim): Remove WriteFolder from FairMCApplication::InitGeometry

The function `WriteFolder` (since the introduction of the `MTMode`)
was misused to remove the `TFolder` from `gROOT`
after it was used to create the output tree.
Purely for that reason `WriteFolder` was called in the `InitGeometry()`.
This folder is no longer removed in the sink's `WriteFolder()`.

Introduced a new `FairRootManager::RemoveOutputFolderForMtMode()` function
which removes the `TFolder` from `gROOT`, which is needed in the
MT mode in TGeant4 transport.
Used this function in `FairMCApplicaiton::InitGeometry()`
and in `FairMCApplication::InitFinalizer()`.

Author: karabowi

fairroot/base/sim/FairMCApplication.cxx

@@ -874,7 +874,7 @@ void FairMCApplication::InitGeometry()
     if (fRootManager && !fParent) {
         RegisterOutput();
         if (GetIsMT()) {
-            fRootManager->WriteFolder();
+            fRootManager->RemoveOutputFolderForMtMode();
         }
     }
     fMCEventHeader->SetRunID(runId);
@@ -937,6 +937,7 @@ void FairMCApplication::InitFinalizer()
     {
         std::lock_guard guard(mtx);
         fRootManager->WriteFolder();
+        fRootManager->RemoveOutputFolderForMtMode();
     }
 }
 

fairroot/base/sink/FairRootFileSink.cxx

@@ -245,9 +245,6 @@ void FairRootFileSink::WriteFolder()
         fOutTree = new TTree(FairRootManager::GetTreeName(), Form("/%s", FairRootManager::GetFolderName()), 99);
         TruncateBranchNames();
         CreatePersistentBranchesAny();
-
-        // Delete the folder to make place in the gROOT for fOutFolder created by the Geant4MT threads
-        gROOT->GetRootFolder()->Remove(fOutFolder);
     }
 }
 

fairroot/base/steer/FairRootManager.cxx

@@ -38,6 +38,7 @@
 #include <TNamed.h>
 #include <TObjArray.h>    // for TObjArray
 #include <TObjString.h>   // for TObjString
+#include <TROOT.h>        // for gROOT
 #include <TTree.h>        // for TTree
 #include <algorithm>      // for find
 #include <atomic>
@@ -221,8 +222,8 @@ TClonesArray* FairRootManager::Register(TString branchName, TString className, T
 
 TClonesArray* FairRootManager::GetEmptyTClonesArray(TString branchName)
 {
-    if (fActiveContainer.find(branchName)
-        != fActiveContainer.end()) {               // if a TClonesArray is registered in the active container
+    if (fActiveContainer.find(branchName) != fActiveContainer.end())
+    {                                              // if a TClonesArray is registered in the active container
         if (fActiveContainer[branchName] == 0) {   // the address of the TClonesArray is still valid
             std::cout << "-E- FairRootManager::GetEmptyTClonesArray: Container deleted outside FairRootManager!"
                       << std::endl;
@@ -383,6 +384,12 @@ void FairRootManager::WriteFolder()
     }
 }
 
+void FairRootManager::RemoveOutputFolderForMtMode()
+{
+    auto rootFolder = static_cast<TFolder*>(gROOT->GetRootFolder());
+    rootFolder->Remove(rootFolder->FindObject(GetFolderName()));
+}
+
 Bool_t FairRootManager::SpecifyRunId()
 {
     if (!fSource) {

fairroot/base/steer/FairRootManager.h

@@ -18,12 +18,12 @@
 #include <TRefArray.h>   // for TRefArray
 #include <TString.h>     // for TString, operator<
 #include <fairlogger/Logger.h>
+#include <list>
 #include <map>   // for map, multimap, etc
 #include <memory>
 #include <string>
 #include <type_traits>   // is_pointer, remove_pointer, is_const, remove...
 #include <typeinfo>
-#include <list>
 
 class BinaryFunctor;
 class FairEventHeader;
@@ -218,6 +218,11 @@ class FairRootManager : public TObject
     void WriteFileHeader(FairFileHeader* f);
     /**Write the folder structure used to create the tree to the output file */
     void WriteFolder();
+    /**
+     * \brief Internal: Remove the folder describing the output tree structure from gROOT, called in TGeant4 MT
+     * simulation mode
+     */
+    void RemoveOutputFolderForMtMode();
 
     /**Check the maximum event number we can run to*/
     Int_t CheckMaxEventNo(Int_t EvtEnd = 0);