Cloning trees with TChain: drastic performance loss

Hi,

I am using a slightly modified version of some standard ROOT example code from

http://root.cern.ch/root/html/tutorials/tree/copytree3.C.html

to skim TTrees. The main difference is that I am using TChain instead of TTree, and therefore I am using

     Long64_t ientry = collChain->LoadTree(jentry);
     collChain->GetEntry(ientry);

This works fine, but after ~500 events (which is probably all from the first file in the TChain) the speed abruptly decreases from about 27 events/s to 0.05 events/s, spent in equal parts in LoadTree and GetEntry as it seems.

Is there something I can do about this?

cu,
Alexander Received on Mon May 16 2011 - 17:41:05 CEST