Merging root files (not trees)

ROOT
1

Hi,

is there a way to merge several root files into one big file? Note, I don’t mean
merging several trees by using TChain but really merging several root files
independent of what content they have.

Thanks,
Frank

2

hadd result.root file1.root file2.root …filen.root
or with wilcarding
hadd result.root fw*.root

hadd is in $ROOTSYS/bin/hadd

for help about hadd, simply type
hadd

Rene

3

Hello Rene,

thanks for your help. Is there any limitation of what classes hadd can handle?
I have root files with a RooFitResult in them and it crashes with:

Error in TKey::ReadObj: Unknown class RooFitResult

I use root 4.04-02. Is this expected to work in Root 5.x where RooFit is a part
of root?

Thanks,
Frank

4

Frank,

Could you tell me where I can pick one of your files that exhibits this problem? With hadd, you do not need the class in principle.

Rene

5

Hi Rene,

here are two files

slac.stanford.edu/~fwinkl/fit-1.root
slac.stanford.edu/~fwinkl/fit-3.root

Thanks for your help,
Frank

6

Frank,

Your files contain TKey objects of class RooFitResult.
The system does not know what to do with these objects
-There is no dictionary for RooFitResult in the file
-Assuming that a dictionary exists, what would you expect the system
could do with these objects?

If RooFitResult were in a Tree, the system knows what to do (merging Trees)
and by definition the dictionary for RooFitResult would be in the file

Rene

7

Hi Rene,

[quote=“brun”]Frank,

Your files contain TKey objects of class RooFitResult.
The system does not know what to do with these objects
-There is no dictionary for RooFitResult in the file
-Assuming that a dictionary exists, what would you expect the system
could do with these objects?
[/quote]

I would have expected that the objects just get copied into one file so that
the final file contains all the individual TKey objects of the source files. So, I am not expecting that the system is doing anything with the RooFitResult class itself (i.e. merging its content like it is doing for histograms). That said, I realize that other people might have different expectations what a merge in this situation should be doing :wink:

Ah, OK. I’ll see if I can get this to work.

Thanks,
Frank