[ROOT] bug in TChain::Merge?

From: Ken Bloom (kenbloom@umich.edu)
Date: Mon Jan 13 2003 - 16:20:03 MET


Hi,

	I think I've encounted a bug in TChain::Merge.  I've got a large
number of files, each containing an identically-structured tree, and I want to
merge the trees into one file.  As it happens, some of the trees have zero
entries.  (This doesn't bother me; I was running on small chunks of data, and
throwing away events; it's quite possible that I would have zero entries in an
individual tree.)  When I try to do the merge, I don't get the right number of
entries, and it appears that the merge stops at the last file in the chain
with a non-zero number of entries in the tree.

	In looking at the TChain::Merge code, I do see the suspicious line

      if (GetEntry(i) <= 0) break;

but I don't know if that is the cause of the problem, as I'm not quite sure 
what GetEntry does.

	Am I right that there is a bug?  Can it be fixed?  I suppose that for 
now I'll have to comment the empty trees out of my chain.  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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