Re: [ROOT] using LoadTree with a TChain

From: Ken Bloom (kenbloom@umich.edu)
Date: Mon Jan 07 2002 - 15:18:38 MET


On Mon, 7 Jan 2002, Rene Brun wrote:

> Hi Ken,
> The code generated by MakeClass is correct.
> The statement:
>      Int_t ientry = LoadTree(jentry);
> is not necessary if you do not need the entry number in the current Tree.
> The statements
>     fChain->GetEntry(jentry)
> and
>     fChain->GetEntry(ientry)
> 
> will give identical results for the first file, but for subsequent
> files, only the first statement will give the correct result.
> 
> I assume that you use the pro version 3.02/06

	I'm afraid that I disagree -- I believe that the "jentry" argument
gives the wrong result after the first file, and the "ientry" argument gives
the right answer for all the files in the chain.  If I use "jentry", I find
that I get the first file just fine, but once jentry becomes sufficiently
large that I have moved past the the first file, then I keep getting the final
event of the first file over and over again.  If it would be useful, I can try
to reproduce this with some small ntuples, although as far as I'm concerned I
have now solved my problem and I would rather move on to other things.  I am
using version 3.01/06, which is the latest that we've got at CDF.  Thanks,
best wishes.

						Ken

------------------------------------------------------------------------------
Ken Bloom, Karma Adjuster                                Department of Physics
734-763-2329 / 734-936-1817 (fax)                       University of Michigan
kenbloom@umich.edu                              http://www.umich.edu/~kenbloom



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