[RF] RooDataSet conversion to TTree fails for large datasets (bytecount too large)

[vlisovsk]

Describe the bug

I have a RooDataSet with (say) 100 million events.
I try to do

RooDataSet::setDefaultStorageType(RooAbsData::Tree);
const TTree* tree8 = mydataw_z.GetClonedTree();

This works well for smaller datasets, but for my huge dataset I get the following error:

Error in <TBufferFile::WriteByteCount>: bytecount too large (more than 1073741822)
Error in <TBufferFile::WriteByteCount>: bytecount too large (more than 1073741822)
Error in <TBufferFile::CheckByteCount>: object of class TObjArray read too many bytes: 1600049012 instead of 526307188
Warning in <TBufferFile::CheckByteCount>: TObjArray::Streamer() not in sync with data, fix Streamer()
Warning in <TBufferFile::CheckObject>: reference to object of unavailable class TList, offset=4216542 pointer will be 0
Error in <TExMap::Remove>: key 2005325560 not found at 371
Warning in <TBufferFile::CheckObject>: reference to object of unavailable class TObject, offset=2005325560 pointer will be 0
Error in <TExMap::Remove>: key 364036325 not found at 135
Warning in <TBufferFile::CheckObject>: reference to object of unavailable class TList, offset=364036325 pointer will be 0
Error in <TExMap::Remove>: key 1061746196 not found at 217
Warning in <TBufferFile::CheckObject>: reference to an unavailable class, pointers of that type will be 0
Warning in <TBufferFile::CheckObject>: reference to object of unavailable class TObject, offset=1171537962 pointer will be 0
Error in <TExMap::Remove>: key 586225820 not found at 447
Warning in <TBufferFile::CheckObject>: reference to object of unavailable class TObject, offset=586225820 pointer will be 0
Error in <TExMap::Remove>: key 423978783 not found at 84
Warning in <TBufferFile::CheckObject>: reference to object of unavailable class TList, offset=423978783 pointer will be 0
Warning in <TBufferFile::CheckObject>: reference to object of unavailable class TObject, offset=4207193 pointer will be 0
Error in <TExMap::Remove>: key 839042239 not found at 12
Warning in <TBufferFile::CheckObject>: reference to object of unavailable class TBranchRef, offset=839042239 pointer will be 0
Error in <TBufferFile::CheckByteCount>: object of class TTree read too many bytes: 883788679 instead of 526307551
Warning in <TBufferFile::CheckByteCount>: TTree::Streamer() not in sync with data, fix Streamer()

 *** Break *** segmentation violation
root.exe(60607,0x102138580) malloc: Incorrect checksum for freed object 0x15c1e1a00: probably modified after being freed.
Corrupt value: 0x0
root.exe(60607,0x102138580) malloc: *** set a breakpoint in malloc_error_break to debug

Expected behavior

The tree should be written to file without failures.

To Reproduce

I have prepared a rather minimal example: https://cernbox.cern.ch/s/jhiOyKZJN89I3Hq
It is based on the RooFit example because my actual use case is saving the result of the sPlot into a TTree, but the sPlot is not the issue here.

Setup

1. ROOT version: 6.28/02
2. Operating system: MacOS (but the same happens on lxplus)
3. How you obtained ROOT: macports (but the same happens on lxplus).

Additional context

I would be glad to learn if there is a more efficient way of saving RooDataSet into a TTree. I tried to find if there is a RooDataSet conversion to RDataFrame but found only the inverse operation.

[guitargeek]

Thanks for reporting this!

It will take some time to get a useful answer, because this seems to be quite a fundamental problem that was already discussed here with no solution:
https://sft.its.cern.ch/jira/browse/ROOT-10686

Thanks for setting up a reproducer. This will help me to figure out what can be done.

[dpiparo]

I believe this is another incarnation of the same limitation encountered here https://its.cern.ch/jira/projects/ROOT/issues/ROOT-10450

[ferdymercury]

maybe related: https://root-forum.cern.ch/t/crash-when-writing-canvas-to-tfile/58010/7

and #6734

[dpiparo]

This is the reference issue in GH #6734