Reading a tree containing vector<TLorentzVector>

ROOT
1

Dear all,

I was given a tree filled with vector’s and tried to read it with TSelector, but failed because of the following name clashes (C-style comments added by me, C++ comments by MakeSelector):

/* (…) */
//TLorentzVector lep_l;
/ UInt_t fUniqueID; /
/ UInt_t fBits; /
/ UInt_t fP_fUniqueID; /
/ UInt_t fP_fBits; /
/ Double_t fP_fX; /
/ Double_t fP_fY; /
/ Double_t fP_fZ; /
/ Double_t fE; /
/ (…) */
//TLorentzVector lep_nl;
/ UInt_t fUniqueID; /
/ UInt_t fBits; /
/ UInt_t fP_fUniqueID; /
/ UInt_t fP_fBits; /
/ Double_t fP_fX; /
/ Double_t fP_fY; /
/ Double_t fP_fZ; /
/ Double_t fE; /
/ (…) */

Now, one of the branches is supposed to contain TLorentzVector’s representing jets. I tried to change the .h file this way (commenting away everything written by MakeSelector):

std::vector* jetVec;
TBranch* b_jetVec;

and later

fChain->SetBranchAddress(“jet”, &jetVec, &b_jetVec);

Then, inside Process(), I wrote few simple lines:

b_RunNumber->GetEntry(entry);
b_EventNumber->GetEntry(entry);
cerr << "event " << EventNumber << " from run " << RunNumber << “:” << endl;

b_jetVec->GetEntry(entry);
cerr << " b_jetVec " << b_jetVec << endl;

cerr << " jetVec " << jetVec << endl;

unsigned nJets = jetVec->size();
cerr << " nJets " << nJets << endl;

The jetVec->size() statement makes a crash, as it is shown by this output:

event 27702 from run 116830:
b_jetVec 0x7fbc4a53def0
jetVec 0x7fbc00000002

*** Break *** segmentation violation

Thread 3 (process 45022):
#0 0x00007fff8d854192 in __workq_kernreturn ()
#1 0x00007fff8d678594 in _pthread_wqthread ()
#2 0x00007fff8d679b85 in start_wqthread ()

Thread 2 (process 45022):
#0 0x00007fff8d8547e6 in kevent ()
#1 0x00007fff8b3315be in _dispatch_mgr_invoke ()
#2 0x00007fff8b33014e in _dispatch_mgr_thread ()

Thread 1 (process 45022):
#0 0x00007fff8d854168 in wait4 ()
#1 0x00007fff8d62c5f5 in system ()
#2 0x000000010bf8a98a in TUnixSystem::StackTrace ()
#3 0x0000004100000111 in ?? ()

It seems that jetVec is a valid pointer (at least, it’s not null), but cannot use it.

Do you have any suggestion?

Thanks a lot,
Diego

2

See [url]Event class containing variable length array and https://root.cern.ch/root/html534/TTree.html#TTree:Branch@2

3

Thanks for checking. The problem is in my first statement “I was given a tree”, which means that I cannot change the way the tree was created. The tree is there and cannot change it :frowning:

I’d like to know if I can read it via TSelector (well, also MakeClass had troubles, just for information).

Thanks,
Diego

4

Return that tree to the one who sold it to you. It’s broken. If they don’t honor the warranty, find a good lawyer. :mrgreen:

5

Hi,

The constructions of the TTree makes it difficult/impossible to use the automatic tools. You would need to replace the calls to SetBranchAddress to introduce the fully specified branch name … and if this does not work you would need to do a recursive search for the correct branch and call SetAddress on it. (And of course you need to manually update the name of the data member generated by MakeSelector).

Cheers,
Philippe.

6

Hi,

I am the one who made and sold the tree. Since I cannot give warranty I would like to know how (and if) it would be possible to go around this problem (that is giving warranty, in a way :slight_smile: ).
I need to have some “list” of TLorentzVector in my tree, and I used a std::vector since I use an hand-made code to read it.
But how can I make it more “universal” ? Replace the std::vector with a TClonesArray would help ? Is it the only correction I have to apply or do I need something else ?

Thanks,
Francesco

7

See the links that I posted in my previous post(s) and search for “dot” inside (in short … when you define / create your TTree, append a “dot” to the name of your branches which contain class objects that create duplicate names afterwards).

8

Hi Francesco,

One important question is whether those vector are semantically independent or are they part of a collection (for example whether they represent the values for a series of particles or whether they represent values for things that would never be mixed together (one for the dectector, one for a particle, for something else).

If it comes from a collection, they I would stored them together as part of either a TClonesArray or a std::vector but in a single (possibly split) branch. Otherwise, it does not matter much what container you use, the important thing is that you name the individual branches distinctly (and with a trailing dot a the end of the name for the name to be carryed into the sub-branches). [This might mean that you need to carry in the collection both the TLorentzVector and its ‘name’].

Cheers,
Philippe.