(r1) HowToMergeRootFiles < LHCb

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---+!! How Merge root files

%TOC%

---++ Ganga

The easiest way is to let ganga handle it with with the RootMerger()

<verbatim>j=Job(t)
j.merger = RootMerger()
j.merger.files = ['out-file.root']</verbatim>

This worked fine for me for ages until the merging program this calls stayed at 100% forever and the python memory usage consumed everything available. So I had to merge the files manually...

---+++ Merging manually

The program hadd is the one that the root merger calls to merge the files

<verbatim>hadd ~/outputfile.root ~/input1.root ~/input2.root [...]</verbatim>

When running manually this segfaulted on my root file, it turned out to be because I had run SetupProject Ganga at the beginning by starting a new session and doing SetupProject DaVinci the hadd program no longer segfaulted.

-- Main.ThomasBird - 2010-08-04

Topic revision: r1 - 2010-08-04 - ThomasBird