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Entry  17 Oct 2007, Randolf Pohl, Forum, Adding MIDAS .root-files 
    Reply  17 Oct 2007, John M O'Donnell, Forum, Adding MIDAS .root-files histoAdd.cxx
Message ID: 412     Entry time: 17 Oct 2007     Reply to this: 415
Author: Randolf Pohl 
Topic: Forum 
Subject: Adding MIDAS .root-files 
Dear MIDAS users,

I want to add several .root-files produced by the MIDAS analyzer, in a fast 
and convenient way. ROOT's hadd fails because it does not know how to treat 
TFolders. I guess this problem is not unique to me, so I hope that somebody of 
you might already have found a solution.

Why don't I just run "analyzer -r 1 10000"?
We have taken lots of runs under (rapidly) varying conditions, so it would be 
lots of "-r". And the analysis is quite involved, so rerunning all data takes 
about one hour on a fast PC making this quite painful.
Therefore, I would like to rerun all data only once, and then add the result 
files depending on different criteria.

Of course, I tried to write a script that does the adding. But somehow it is 
incredibly slow. And I am not the Master Of C++, too.

Is there any deeper reason for MIDAS using TFolders, not TDirectorys? ROOT's 
hadd can treat TDirectory. Can I simply patch "my" MIDAS? Is there general 
interest in a change like this? (Does anyone have experience with the speed of 

Looking forward to comments from the Forum.


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