/*******************************************************************************************/
/*                                                                                         */
/* This macro allows to merge .root files with total size larger than 100 GB.              */
/* Please check the limit here:   TTree::SetMaxTreeSize (...)                              */
/*                                                                                         */
/* Runset range    : [run1 ... run2]                                                       */
/*                                                                                         */
/* Input file names: The assumed naming is: [InNamePrefix][RunNumber].root                 */
/*                                                                                         */
/* Output file name: [OutNamePrefix].root , Default is MergedFile.root . Change if needed. */
/*                                                                                         */
/* For TFileMerger reference see:   root.cern.ch/doc/master/classTFileMerger.html          */
/*                                                                                         */
/*******************************************************************************************/

int ttree_merger (int run1 = 1, int run2 = 2,
                  char* InNamePrefix = "test",
                  char* OutNamePrefix = "MergedFile" )
{
  TTree::SetMaxTreeSize (1LL*1024*1024*1024*1024);  // Set the size limit to 1 TB. Change if needed.

  TFileMerger merger (kFALSE, kFALSE); // hadd style
  merger.OutputFile ( Form("%s.root", OutNamePrefix) );

  cout << endl;

  for (Int_t irun = run1; irun <= (Int_t) run2; ++irun) 
  {
    TString name = Form ("%s%i.root", InNamePrefix, irun);
    cout << "| Adding " << name << endl;

    if ( !merger.AddFile ( name ) ) 
      return false;
  }

  cout << "|\n";
  gSystem->Exec ("echo '| Date: ' `date`");
  cout << "|\n+--> Merging files into: " << Form ("%s.root",outFile) << endl;

  merger.Merge();

  cout << "|\n";
  gSystem->Exec ("echo '+ Date: ' `date`");
  cout << endl;

  return 0;
}