Re: [ROOT] File with directory structure, memory usage

From: Rene Brun (Rene.Brun@cern.ch)
Date: Mon Sep 23 2002 - 21:41:12 MEST


Hi Amanda,

I do not understand this problem. If you have histograms on a file,
they are loaded in memory only if you explicitly load them in memory
with a call like
   TH1F *h = (TH1F*)f->Get("myhisto").
Could you send me a Root file showing this problem together with
a script (as short as possible) reproducing this problem?

Rene Brun

On Sun, 22 Sep 2002, Amanda Weinstein wrote:

> 
> I'm currently working with a system whereby I want to look at the
> effect of entire set of cuts by creating an output file with a
> nested directory structure:
> 
>   source/
>     /mode1 .. /modeX
>      /cut1 ... /cutX
>        /additional selection1
>        /additional selection2
> 
> and so on.  For the most part it works very nicely, except that for
> any given source, I have to create the output directories and
> book the histograms inside them in advance, and I'm winding up with
> a rather enormous memory usage that scales with the number of
> directories I create.  This starts to create problems with
> performance when the amount of memory used is too large.  I'm guessing
> what is happening is that until the file/directory is closed, the
> histograms inside each directory are loaded into local memory and
> are taking up a substantial amount of space.
> 
> Is this a known problem, and is there any solution other than limiting
> the number of directories that are "open" at one time?
> 
> 					Thanks,
> 			                  Amanda
> 
> 
> 
> 
> 



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