TTree::SetBranchStatus and TLorentzVector

ROOT
1

Hi everyone,

I’m working with TTree and TBranch and I am having some troubles enabling and disabling branches status. Everything is ok if you are working with primitive types or std::vector in a ROOT file, each branch could be enabled or disabled anytime and works correctly, but I have experimented some cases where branches containing TLorentzVector objects are not re-enabled successfully.

I have created a quick script that shows this behaviour. The first case, it is the simplest workflow, it opens a tree and test if at entry 0 of “value” branch (Type: TLorentzVector) has a “1” as a value of its Y component. The case 2, shows that if you disables and re-enables the branches without get an entry, it also works. And finally, the third case, it is similar to case 2 but after disable all branches, it get an entry. In this last case, I have not been able to get the TLorentzVector after the first GetEntry.

I have attached the macro described (TLorentzTree.C) and a ROOT file (Tree_TLorentz.root). I am using ROOT 5.34.30.

Here it is also the macro:

void PrintTLorentz(TTree* tree)
{
	TLeaf* leaf = tree->GetLeaf("value");
	TLorentzVector* lorentz = (*(TLorentzVector**)leaf->GetBranch()->GetAddress());

	if (lorentz->Y() == 1)
	{
		std::cout << "Alright." << std::endl;
	}
	else
	{
		std::cout << "Wrong, TLorentzVector is not loaded." << std::endl;
	}
}

void Case1()
{
	TFile file("Tree_TLorentz.root");
	TTree* tree = (TTree*)file.Get("tree");
	tree->GetEntry(0);
	PrintTLorentz(tree);
}

void Case2()
{
	TFile file("Tree_TLorentz.root");
	TTree* tree = (TTree*)file.Get("tree");
	tree->SetBranchStatus("*", kFALSE);
	tree->SetBranchStatus("*", kTRUE);
	tree->GetEntry(0);
	PrintTLorentz(tree);
}

void Case3()
{
	TFile file("Tree_TLorentz.root");
	TTree* tree = (TTree*)file.Get("tree");
	tree->SetBranchStatus("*", kFALSE);
	tree->GetEntry(0);
	tree->SetBranchStatus("*", kTRUE);
	tree->GetEntry(0);
	PrintTLorentz(tree);
}

void TLorentzTree()
{
	Case1();
	Case2();
	Case3();
}

Greetings and thanks in advance,
Javier Delgado.
TLorentzTree.C (937 Bytes)
Tree_TLorentz.root (7.9 KB)

2

Hi,

There is indeed a problem of inconsistency of the default setting of the branch addresses.
You can work around the problem by either calling:tree->SetBranchAddress("value",0);before the first disabling or by calling:tree->ResetBranchAddresses();after the re-enabling.

Cheers,
Philippe.