Re: how to allow a file-split only at very specific times ?

Sebastien Binet <binet_at_cern.ch> writes:

> so... is there a way to specify *when* the split should or should not
> happen ? (in essence, I'd like a way to say that a bunch of
> TTree::Fill should be atomic wrt the file split)

We recently added this feature to Daya Bay offline. To achieve it we handle the rolling to a new output file by hand instead of using some ROOT feature so it maybe doesn't help you.

We have a bit of code to monitor either event count, run time or output file size (depending on how it is configured). When a particular condition is reached the code closes the current file and opens a new one of a +1 higher count (we specify output files to a job like: "myoutput_%02d.root" and then use ROOT's Form() function to set the "%02d" to the file count).

We use internal structure to sync our various trees so also rely on them to be written atomically.

I would also be curious if such functionality is available in ROOT, proper.

-Brett.