Hi Thomas,
> > I'm writing data like in the following example (using root 3.01/06, with
> > a '+' in the pragma statement for MyClass):
when you use a '+' you use not compiled code for the Streamer.
By my tests, for complicated classes, it is about twice as slower then compiled one.
But "+" provides you an automatic schema evolution.
If you very aware about the speed and not worry about schema evolution at all,
you should not use "+". But then , if you will deside to change your class
you will have a lot of problems.
This slowdown is a payment for the schema evolution. You should choose
what is more important for your application.
But I must say, that often user supposes that his application is temporary,
but at the end it is used years and years.
Victor
Rene Brun wrote:
>
> 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.
--
Victor M. Perevoztchikov perev@bnl.gov perev@vxcern.cern.ch
Brookhaven National Laboratory MS 510A PO Box 5000 Upton NY 11973-5000
tel office : 631-344-7894; fax 631-344-4206; home 631-345-2690
This archive was generated by hypermail 2b29 : Tue Jan 01 2002 - 17:51:05 MET