Hi Roger, Could you move to version 3.03/09 and tell me if this symptom persists? If it does, please send me the result of tree.Print(); for your old and new Trees Rene Brun On Fri, 27 Sep 2002, Roger Moore wrote: > Converting some analysis code from using a ROOT-tuple to using a ROOT Tree > (i.e. from individual variables in arrays to real objects) I've noted some > very strange behaviour with the readout speed. > > With the old ROOT-tuple I could vastly increase the speed of the code by > turning off all branches and then just turning back on the branches that I > was interested in looking at. > > However with the shift to the ROOT-Tree whose branches consist of > TClonesArray the exact reverse is true! When I turn off all the branches > except the one I am interested in the GetEntry() method of the tree takes > 50-60ms to execute. However when I to not turn the branches off the time > taken for GetEntry() drops to ~3ms/event. > > Does anyone understand what is going on here? I don't see how not > unpacking a branch can possibly slow the code down! > > I'm using ROOT 3.03/07 and in both cases I only do SetBranchAddress (to a > TClonesArray) for the branches I am interested in reading out. > > Roger >
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