RDataFrame::Snapshot and TDirectory

ROOT
1

Dear RDataFrame experts,

I am using an RDataFrame to create a mini-tree with events my analysis selelection. I create multiple such mini-trees, each corresponding to a different systematic variation. I would like to store each tree in the same file, but a different TDirectory. I am finding that this does not work with MT RDataFrame as demonstrated with the attached example and the output below. It seems that RDF does not check if the TDirectory in each thread and fails to save all of the data. Is this the expected behaviour?

dfsimple.cpp (1.2 KB)

kkrizka@roof ~/tmp $ ./dfsimple 4
Error in ROOT::Experimental::TBufferMergerFile::mkdir: An object with name test exists already
Error in ROOT::Experimental::TBufferMergerFile::mkdir: An object with name test exists already
Error in ROOT::Experimental::TBufferMergerFile::mkdir: An object with name test exists already
Error in ROOT::Experimental::TBufferMergerFile::mkdir: An object with name test exists already
0 34.6941
0 42.2615
test/testTree entries = 50000000
testTree entries = 100000000

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Karol Krizka

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ROOT Version: 6.18/04
Platform: Gentoo Linux
Compiler: 9.1.0-r1

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