Hi. Is there a simple and fast way of making a TChain chain of .root files, and then saving that chained tree into a single .root file? Right now I have what seems to be a highly inefficient way of doing it:
a) I chain up my .root files; then I open a new TFile file;
b) I then do TTree *newtree = chain->GetTree()->CloneTree(0);
c) after which I individually GetEntry() individual entries from the chain and simulaneously do newtree->Fill();
d) once this is complete I write newtree and close the file.
To do ~7mln entries it takes an hour, on a >2.5GHz core. Methinks that there gotta be a much faster way of doing the same – is there?