Hello Thomas, Usually the max size of the regular file is 2Gb at most. I wonder if you was able to write 10 % of your data out and then ROOT stuck waiting for the rest 18Gb to come around. It is not slow it is forever. Valeri ----- Dr.Valeri Fine STAR/US Atlas E-mail: fine@bnl.gov Brookhaven National Lab Phone: +1 631 344 7806 Upton, NY 11973-5000 FAX: +1 631 344 4206 USA ----- Original Message ----- From: "Rene Brun" <Rene.Brun@cern.ch> To: "Thomas Bretz" <tbretz@uni-sw.gwdg.de> Cc: <roottalk@pcroot.cern.ch> Sent: Wednesday, October 31, 2001 1:16 PM Subject: Re: [ROOT] How to accelerate root output? > Hi Thomas, > > Difficult to come with a dignostic without looking into your system. > I have no idea of what you mean by "rather slow". > From your class description, I conclude that you have about 20 Kbytes per event. > One million entries will make a file of about 20 GBytes. > Could you send me: > - the result of tree.Print() after filling your Tree. > - if possible your class with a small test that is slow. > > Rene Brun > > Thomas Bretz wrote: > > > > Hello rooters, > > > > I'm writing data like in the following example (using root 3.01/06, with > > a '+' in the pragma statement for MyClass): > > > > { > > MyClass *cls = new MyClass; > > > > TFile file("name", "RECREATE", "title", 0); > > TTree tree("name, "title"); > > tree.Branch("MyClass", "MyClass", &cls, 320000, 0); > > > > for (int i=0; i<1e6; i++) > > { > > FillDataIntoMyClass(&cls); > > tree.Fill(); > > } > > file.Write(); > > delete cls; > > } > > > > Because this is rather slow, I used gprof to find out where the time is > > spend and if I trust its output, only ~15% of all the time (CPU time, > > which should not include I/O) is spend in my part of the program. This > > means about 85% of the CPU-time is spent in root (I/O). In this example > > speed is really critical. Is there a way to accelerate the root output? > > > > I don't think that it is a question of hardware limitation because the > > machine and disks are really powerfull. > > > > Rem: MyClass contains four arrays. Two about 1kB, and two around 8kB. > > (around 18kB in total) > > > > Thanks in advance, > > Thomas. >
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