[ROOT] File with directory structure, memory usage

From: Amanda Weinstein (amanda@SLAC.stanford.edu)
Date: Mon Sep 23 2002 - 05:48:43 MEST


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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