Hi, I want to select a subset of a tree which is split over several files and save this subset to one new file. Everything works fine but the resulting file size is much bigger than the sum of the input files. I start with: TChain *chain = new TChain("tree"); chain->Add("data-*.root"); // there is data-1 to data-21, each about 13 MB TFile f("subset.root"); TTree *subtree = chain->CopyTree("m0b0>0"); f.Write(); The resuling size of subset.root is about 560 MB !!! But the total size of the (unfiltered) input is only about 270 MB. The compression level is 1 in all the files. The selection criteria "m0b0>0" selects about 50% of all entries. I am using RooT version 3.10-01 on RH9. How is that possible? Why is the compression so much worse for the subset? Thanks, Frank
This archive was generated by hypermail 2b29 : Sun Jan 02 2005 - 05:50:05 MET