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Forum: Analysis
Re: Question CreateNtuple in multithreaded exMPI03 (Mikhail)
Date: 04 Jan, 2016
From: Ivana Hrivnacova <Ivana Hrivnacova>

In the exMPI03 example, a file is open only before saving histograms, see Analysis::Save() function. If you want to use ntuples, a file has to be open before you fill an ntuple; when you create an ntuple before opening a file, the analysis manager saves the ntuple definition in an "ntuple booking" object and creates the" ntuple" object only when a file is defined in OpenFile() call.

In difference from histograms, the ntuples produced on threads (and the ranks when using MPI) are not merged in a single file, so to use the ntuples with the exMPI03 example, you need to add opening a file with a filename specific per rank in "begin of run action" and remove it from Analysis::Save() function.

Best regards,

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1 None: Re: CreateNtuple in multithreaded exMPI03   (Mikhail - 04 Jan, 2016)
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