[ROOT] object tag too large, sample subset

From: Simon Dean (sdean@pc33.hep.man.ac.uk)
Date: Tue Aug 05 2003 - 18:20:24 MEST 

Dear ROOT experts,

I've been trying to extract a subset of events from a ROOT tree using code 
similar to that shown at the end of this message.

It runs OK (after removing the code in the automatically generated 
TMBTree destructor - otherwise I get a segmentation violation) BUT when I 
then run code over the new TFile, I get this output:

Error in <TBuffer::ReadObject>: object tag too large, I/O buffer corrupted

(...the above line appears 492 times in the real output - there are 374 
branches in the tree...)

 *** Break *** segmentation violation
 Generating stack trace...
 0x401d6cbb in TUnixSystem::StackTrace(void) + 0x25b from 
/home1/sdean/root305/lib/libCore.so
 0x401d5812 in TUnixSystem::DispatchSignals(ESignals) + 0xb2 from 
/home1/sdean/root305/lib/libCore.so
 0x401d49bb in <unknown> from /home1/sdean/root305/lib/libCore.so
 0x401d8585 in <unknown> from /home1/sdean/root305/lib/libCore.so
 0x40f32f75 in <unknown> from /lib/i686/libpthread.so.0
 0x42029188 in <unknown> from ./runTMBTree
 0x4013f447 in TRef::Streamer(TBuffer &) + 0x3f from 
/home1/sdean/root305/lib/libCore.so
 0x401adbb4 in TStreamerInfo::ReadBufferClones(TBuffer &, TClonesArray *, 
int, int, int) + 0x1c9c from /home1/sdean/root305/lib/libCore.so
 0x40d32a52 in TBranchElement::ReadLeaves(TBuffer &) + 0x8ca from 
/home1/sdean/root305/lib/libTree.so
 0x40d2c5dc in TBranch::GetEntry(int, int) + 0x1b4 from 
/home1/sdean/root305/lib/libTree.so
 0x40d31912 in TBranchElement::GetEntry(int, int) + 0x1da from 
/home1/sdean/root305/lib/libTree.so
 0x40d318b5 in TBranchElement::GetEntry(int, int) + 0x17d from 
/home1/sdean/root305/lib/libTree.so
 0x40d4ac90 in TTree::GetEntry(int, int) + 0x98 from 
/home1/sdean/root305/lib/libTree.so
 0x40d36add in TChain::GetEntry(int, int) + 0x49 from 
/home1/sdean/root305/lib/libTree.so
 0x08060908 in TMBTree::Emu(int, int) + 0xf20 from ./runTMBTree
 0x0806694e in main + 0x1aa from ./runTMBTree
 0x42017589 in __libc_start_main + 0x95 from ./runTMBTree
 0x0804a6a1 in __register_frame_info + 0x3d from ./runTMBTree
Aborted

Can anyone halp me fix this?

Thanks a lot,

Simon Dean


(compiled code - TMBTree.cpp and TMBTree.hpp were produced by the 
MakeClass() function)

=====/ runTMBTree.cpp /====

#include "TMBTree.cpp"

int main(){	

  TMBTree data(filename);
  data.SeparateChannels();

  return 0;

}


=====/ TMBTree.cpp /=====

#include "TMBTree.hpp"

void TMBTree::SeparateChannels(){

  if (fChain == 0) return;
  
  int nentries = (nevents)?nevents:int(fChain->GetEntries());

  TFile *newfile = new TFile("SeparateChannels.root","RECREATE");
  TTree *newtree = fChain->CloneTree(0);

  for (int jentry=0; jentry<nentries;jentry++) {

    int ientry = LoadTree(jentry);
    if (ientry < 0) break;
    nb = fChain->GetEntry(jentry);   nbytes += nb;

    if (....) newtree->Fill()

  }

  newtree->Write("",TObject::kOverwrite);
  newfile->Close();

  return;

}

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