Reading and writing ttrees

Newbie
1

I have a program that reads a tree from a file and writes the tree to another file based on a selection. The initialization takes place in one routine, selection and fill in another, and writing in a third. The problem is this: if I look at the tree after CloneTree(0) at initialization I see all the branches of the tree. If I look at the tree in the selection routine, I see the header, but not the branches. Clearly, there is something I am missing. Code and output follow.

The initialization of the write tree looks like this:

  if(writeTreeEvent==0){
    std::cout << "writeTreeEvent not found - creating" << std::endl;
    fsel->cd();
    writeTreeEvent=new TTree("myEvent","Selected Events");
    writeTreeEvent=myEvent->CloneTree(0);
    writeTreeEvent->Write();
    writeTreeEvent->Print("all");
    std::cout << "writeTreeEvent - created" << std::endl;
  }

and the write after the selection looks like this:

    if(deltaT>100.e-9){
      //                                                                                                                                
      // Write selected event                                                                                                           
      //                                                                                                                                
      std::cout << "Fill selected event" << std::endl;
      TTree* writeTreeEvent=(TTree*) cB->fsel->Get("myEvent");
      cB->fsel->cd();
      writeTreeEvent->Print("all");
      writeTreeEvent->Fill();
}

the final write looks like this

  TFile* fsel=cB->fsel;
  fsel->cd();
  TTree* wt=(TTree*) fsel->Get("myEvent");
  std::cout << "wt " << wt->GetEntries() << std::endl;
  wt->Write();

Print"all") of the tree at initialization,

writeTreeEvent not found - creating
******************************************************************************
*Tree    :myEvent   : event data                                             *
*Entries :        1 : Total =          165104 bytes  File  Size =      35137 *
*        :          : Tree compression factor =   4.69                       *
******************************************************************************
*Br    0 :nChan     : nChan/I                                                *
*Entries :        1 : Total  Size=        561 bytes  File Size  =         79 *
*Baskets :        1 : Basket Size=      51200 bytes  Compression=   1.00     *
*............................................................................*
*Br    1 :trace1V   : trace1V[nChan]/F                                       *
*Entries :        1 : Total  Size=      40678 bytes  File Size  =      10030 *
*Baskets :        1 : Basket Size=    6394368 bytes  Compression=   4.00     *
*............................................................................*
*Br    2 :trace2V   : trace2V[nChan]/F                                       *
*Entries :        1 : Total  Size=      40678 bytes  File Size  =       8280 *
*Baskets :        1 : Basket Size=    6394368 bytes  Compression=   4.84     *
*............................................................................*
*Br    3 :trace3V   : trace3V[nChan]/F                                       *
*Entries :        1 : Total  Size=      40678 bytes  File Size  =       8023 *
*Baskets :        1 : Basket Size=    6394368 bytes  Compression=   5.00     *
*............................................................................*
*Br    4 :trace4V   : trace4V[nChan]/F                                       *
*Entries :        1 : Total  Size=      40678 bytes  File Size  =       7569 *
*Baskets :        1 : Basket Size=    6394368 bytes  Compression=   5.30     *
*............................................................................*
*Br    5 :eventNumber : eventNumber/I                                        *
*Entries :        1 : Total  Size=        591 bytes  File Size  =         85 *
*Baskets :        1 : Basket Size=      51200 bytes  Compression=   1.00     *
*............................................................................*
*Br    6 :eventTime : eventTime/I                                            *
*Entries :        1 : Total  Size=        581 bytes  File Size  =         83 *
*Baskets :        1 : Basket Size=      51200 bytes  Compression=   1.00     *
*............................................................................*
*Br    7 :eventDate : eventDate/I                                            *
*Entries :        1 : Total  Size=        581 bytes  File Size  =         83 *
*Baskets :        1 : Basket Size=      51200 bytes  Compression=   1.00     *
*............................................................................*

In selection reoutine,

Fill selected event
******************************************************************************
*Tree    :myEvent   : Selected Events                                        *
*Entries :        0 : Total =             329 bytes  File  Size =        905 *
*        :          : Tree compression factor =   1.00                       *
******************************************************************************

Peter

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ROOT Version: Not Provided
Platform: Linux, Devuan GNU/Linux, ascii/ceres \n \l
Compiler: gcc version 7.2.0 (Debian 7.2.0-11)

2

Hi @fisherp,
sorry for the late reply, @pcanal can probably help here.
It’s not clear to me how the different routines interact. Could you put together a simple ROOT macro/C++ program that reproduces the issue, and specify what is the output you would expect from it?

Cheers,
Enrico

3

Were you able to resolve this problem?

From your description it is unclear why you ‘re-read’ the output TTree rather than re-using the pointer value that was returned by CloneTree. From the code snippet, I also can not tell whether the output TTree get attached to the proper/intended (output) TFile.