feat(sim): Allow branch registration in `FairGenerator`

[karabowi]

Introduced new function FairMCApplication::InitFinalizer() which initializes event generator, tasks, and triggers FairRootManager::WriteFolder() function. This new function is called from the latter of InitGeometry() and AddIons().

Previously the funcionality of InitFinalizer was split between InitGeometry() and AddIons(), which caused problems because TGeant3 calls AddIons() first, InitGeometry() second, TGeant4 calls InitGeometry() first, AddIons() second.

Current implementation assures that initialization of event generators and tasks come before WriteFolder.

Fixes issues #1183 and #1567.

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Checklist:

• [x] Followed the Contributing Guidelines

[coderabbitai[bot]]

Walkthrough

Walkthrough

The changes enhance the initialization workflow of the FairMCApplication class within Fairroot by introducing the InitFinalizer() method, which consolidates event generator and task initialization. The state management has been refined with the addition of new states and modifications to existing methods like AddIons() and InitGeometry(). Additionally, new methods for folder management have been added to the FairRootManager class to facilitate dynamic folder removal from the ROOT directory.

Changes

File Path	Change Summary
fairroot/base/sim/FairMCApplication.cxx	Restructured initialization; added InitFinalizer(), updated state transitions in InitMC, RunMC, and InitGeometry, modified AddIons()
fairroot/base/sim/FairMCApplication.h	Updated state enum, added InitFinalizer() method, streamlined comments, introduced fIonsAreAdded variable
fairroot/base/steer/FairRootManager.cxx	Added RemoveFolder() and RemoveOutputFolderForMtMode() methods for dynamic folder removal
fairroot/base/steer/FairRootManager.h	Added declarations for RemoveFolder() and RemoveOutputFolderForMtMode() methods; reorganized include statements
fairroot/base/steer/FairRunSim.h	Added documentation comment for SetMCConfig() method to clarify its responsibilities
examples/simulation/rutherford/macros/CMakeLists.txt	Modified command for running run_rutherford.sh to include an additional boolean argument

Possibly related PRs

• #1574: The changes in FairMCApplication.cxx within this PR involve modifications to the FairMCApplication class, which is directly related to the changes made in the main PR regarding state management and method alterations in the same file.
• #1577: This PR involves removing unneeded references to FairRootManager, which is relevant as the main PR also modifies the FairMCApplication class and its interaction with the FairRootManager, indicating a connection in the context of managing application states and resources.

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Recent review details

Configuration used: CodeRabbit UI Review profile: CHILL

Commits

Files that changed from the base of the PR and between d84e17f40c4559515ae8420f8652230107902115 and 63b6d7f02d889cfc79f3d3f8cc5d601fbed85207.

Files selected for processing (7)

• examples/simulation/rutherford/macros/CMakeLists.txt (1 hunks)
• fairroot/base/sim/FairMCApplication.cxx (7 hunks)
• fairroot/base/sim/FairMCApplication.h (6 hunks)
• fairroot/base/sink/FairRootFileSink.cxx (0 hunks)
• fairroot/base/steer/FairRootManager.cxx (3 hunks)
• fairroot/base/steer/FairRootManager.h (2 hunks)
• fairroot/base/steer/FairRunSim.h (1 hunks)

Files not reviewed due to no reviewable changes (1)

• fairroot/base/sink/FairRootFileSink.cxx

Files skipped from review as they are similar to previous changes (6)

• examples/simulation/rutherford/macros/CMakeLists.txt
• fairroot/base/sim/FairMCApplication.cxx
• fairroot/base/sim/FairMCApplication.h
• fairroot/base/steer/FairRootManager.cxx
• fairroot/base/steer/FairRootManager.h
• fairroot/base/steer/FairRunSim.h

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[dennisklein]

Could you please add some documentation of the FairMCApplication state machine? At least on the initialization part? After the FairMCApplication is constructed, e.g. which of the various Init* member functions are supposed to be called in which order to complete a successful initialization? Just for internal code documentation. Thx!

[karabowi]

Could you please add some documentation of the FairMCApplication state machine? At least on the initialization part? After the FairMCApplication is constructed, e.g. which of the various Init* member functions are supposed to be called in which order to complete a successful initialization? Just for internal code documentation. Thx!

It is too hot to work;).

I wish it was that easy. Lets consider three FairMCApplication's functions: ConstructGeometry, InitGeometry and AddIons. They are all called internally from TGeant3 or TGeant4.

FairRunSim runs the simulation initialization in SetMCConfig() function, which:

• runs simulation config (mostly the infamous macros). TGeant4 calls ConstructGeometry in the constructor.
• runs FairMCApplication->InitMC(), which:
  • starts Stack
  • runs fMC->Init(), TGeant4 calls InitGeometry here, while TGeant3 calls AddIons, ConstructGeometry and InitGeometry here.
  • runs fMC->BuildPhysics(), TGeant4 calls AddIons here
• runs postinit config.

What do you think about such a state order: kPreInit -> kConstructGeometry -> kInit -> kInitGeometry -> kPostInit -> kRun? I will implement that and lets see.

[dennisklein]

What do you think about such a state order: kPreInit -> kConstructGeometry -> kInit -> kInitGeometry -> kPostInit -> kRun? I will implement that and lets see.

What do you mean by that? Implement what?

[ChristianTackeGSI]

@karabowi reopned this

If you wanted to rerun the CI due to the errors:

• Please rebase to latest dev. It has a bunch of fixes that affect the CI.
• You should be able to pree some re-run button in jenkins.

[ChristianTackeGSI]

FairRunSim runs the simulation initialization in SetMCConfig() function, which: …

Can we document exactly this somewhere, please?

Maybe on FairRunSim and/or FairMCApplication?

[dennisklein]

What do you think about such a state order: kPreInit -> kConstructGeometry -> kInit -> kInitGeometry -> kPostInit -> kRun? I will implement that and lets see.

What do you mean by that? Implement what?

Now I see the confusion, sry, I was not referring to the fState member variable. I was just using the term "state machine" loosely to refer to the multi-phase initialization design of the FairMCApplication class. What I am looking for is some documentation on each of then Init*-type functions. Basically, what are their pre- and post-conditions.

I now also see that this design is partly coming from VMC and FairRoot attached all kinds of additional state to this class. I give up, nevermind my request for documentation.

[karabowi]

FairRunSim runs the simulation initialization in SetMCConfig() function, which: …

Can we document exactly this somewhere, please?

Maybe on FairRunSim and/or FairMCApplication?

Done.

[ChristianTackeGSI]

Hi @karabowi,

https://github.com/FairRootGroup/FairRoot/blob/6decd1eeb31aba0aa2c196e19b4acafe6f76e854/fairroot/base/sink/FairRootFileSink.cxx#L249-L250

do you want to remove this? Or keep it for backward compatibility?

[karabowi]

Hi @karabowi,

https://github.com/FairRootGroup/FairRoot/blob/6decd1eeb31aba0aa2c196e19b4acafe6f76e854/fairroot/base/sink/FairRootFileSink.cxx#L249-L250

do you want to remove this? Or keep it for backward compatibility?

I have removed this line, or rather moved it to FairMCApplication::InitFinalizer().