Change of size while cloning TTrees


I found out, that when I am cloning a one specific TTree type without any changes, the compression factor of this TTree increases almost 4 times. I understand that in the process of cloning (CloneTree() without parameters), some processing is done. Can I do similar processing when initially creating this TTree, to have the reduced size from the start?


Besides the requested compression algorithm, the only change I can think of that would be so dramatic might be the change in the basket size (which might be better optimized in the clone). Can you share the file that has this behavior?


I share, but I’ll have to make these files inaccessible some short time after you download. The difference in factors is visible only on the tdataflow TTree, but I left others as the part of the original file.

Original file:!IBJ2EYaJ!EqFsUsegKqsu … 67gR4tnsIk

File after cloning:!kFAkDBaI!Y579MoRzTcR8 … jOrFRgrDf0

The cloning script that I use:!ZRwx3DwA!PVK1ro-r5hc_ … nG35L8hbIA

I have downloaded the files and looking at them.


This is odd … I am not finding the difference yet. Can you provide the producer that lead to the ‘larger’ file?


I think I can. Although it will be a more complicated thing to compile…