Frank,
Please send your real code. In your snippet you have
TFile f("subset.root");
this should be
TFile f("subset.root","recreate");
Rene Brun
Frank Winklmeier wrote:
>
> 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