Issues with trees with ROOT version > 6.08

ROOT
1

Dear ROOT experts,

Our analysis groups have a specific framework that converts miniAOD to
TTree format. Recently, I’ve launched it in CMSSW_8_0_26_patch1 which is
linked to ROOT 6.06/01. If I open my tree there, I see nearly all
variables in “EventTree” filled with events.

However, if I open this tree with newer version of ROOT, like 6.09 and
6.10 a lot of those variables are shown “Empty”. I tried this on both
MAC and Linux. If I reinstall older versions (tested with 6.06 and 6.08)
it works fine.

Any idea why? You can find a small (~21MB) version of this tree here:
~hdelanno/public/HyperNewsROOT/tree.root

Thanks,

Hugo

NB: This is a duplicate of https://hypernews.cern.ch/HyperNews/CMS/get/root/217.html if you have access to CMS hypernews.

2

I have no problems reading your tree:

epsft-53 ~ $ ls *.root
tree.root
epsft-53 ~ $ root
   -------------------------------------------------------------------
  | Welcome to ROOT 6.11/01                       http://root.cern.ch |
  |                                      (c) 1995-2017, The ROOT Team |
  | Built for linuxx8664gcc                                           |
  | From heads/local@v6-09-02-2966-gc9b7225514, Oct 06 2017, 09:10:40 |
  | Try '.help', '.demo', '.license', '.credits', '.quit'/'.q'        |
   -------------------------------------------------------------------

root [0] TFile f("tree.root", "read");
root [1] f.ls()
TFile**		tree.root	
 TFile*		tree.root	
  KEY: TDirectoryFile	tupel;1	tupel
root [2] TDirectoryFile* d = (TDirectoryFile*) f.Get("tupel"); 
root [3] d->ls()
TDirectoryFile*		tupel	tupel
 KEY: TTree	Header;1	Header
 KEY: TTree	Description;1	Description
 KEY: TTree	BitFields;1	BitFields
 KEY: TTree	BonzaiHeader;1	BonzaiHeader
 KEY: TTree	EventTree;1	 EventTree
root [4] TTree* t = (TTree*) d->Get("EventTree");
root [5] t->ls()
OBJ: TTree	EventTree	 EventTree : 0 at: 0x39daee0
root [6] t->Print()
******************************************************************************
*Tree    :EventTree :  EventTree                                             *
*Entries :     3945 : Total =        44488570 bytes  File  Size =   21935252 *
*        :          : Tree compression factor =   1.36                       *
******************************************************************************
*Br    0 :EvtIsRealData : EvtIsRealData/I                                    *
*Entries :     3945 : Total  Size=      16472 bytes  One basket in memory    *
*Baskets :        0 : Basket Size=      27136 bytes  Compression=   1.00     *
*............................................................................*
*Br    1 :EvtNum    : EvtNum/i                                               *
*Entries :     3945 : Total  Size=      16430 bytes  One basket in memory    *
*Baskets :        0 : Basket Size=      27136 bytes  Compression=   1.00     *
*............................................................................*
*Br    2 :EvtRunNum : EvtRunNum/i                                            *
*Entries :     3945 : Total  Size=      16448 bytes  One basket in memory    *
*Baskets :        0 : Basket Size=      27136 bytes  Compression=   1.00     *
*............................................................................*
*Br    3 :EvtLumiNum : EvtLumiNum/I                                          *
*Entries :     3945 : Total  Size=      16454 bytes  One basket in memory    *
*Baskets :        0 : Basket Size=      27136 bytes  Compression=   1.00     *
*............................................................................*
*Br    4 :EvtBxNum  : EvtBxNum/I                                             *
*Entries :     3945 : Total  Size=      16442 bytes  One basket in memory    *
*Baskets :        0 : Basket Size=      27136 bytes  Compression=   1.00     *
*............................................................................*
<MANY OTHER BRANCHES>
*............................................................................*
root [7]
3

Dear amadio,

Thanks for your test and reply. I realize I forget to precise one important point: I see this issue with the TBrowser.
Indeed if I open the tree like you did, I see everything filled like it should be.
However, if I navigate through the tree thanks to a TBrowser, then I have a lot of “Empty” histograms for ROOT verions 6.09 and 6.10 (didn’t test on 6.11).

Best,

Hugo

4

Hi Hugo,

I’ll investigate and let you know.

Cheers, Bertrand.

5

Hi,

So I tried, and the problem is not related to the TBrowser, but trying to draw some of the branches already fails, For example, this:

root [0] TFile f("tree.root", "read");
root [1] TDirectoryFile* d = (TDirectoryFile*) f.Get("tupel");
root [2] TTree* t = (TTree*) d->Get("EventTree");
root [3] t->Draw("METsigy2")
Info in <TCanvas::MakeDefCanvas>:  created default TCanvas with name c1
root [4]

Gives an “Empty” histogram. Maybe @pcanal or @Axel could help with this issue

Cheers, Bertrand.

6

Hi Bertrand,

Ok, thanks for investigating! Fixing this will be useful for at least 15 people :slight_smile:

Cheers,

Hugo

7

Hi Hugo,

The underlying problem is solved in the master and v6.10 patch branch (i.e. the upcoming 6.12/00 and 6.10/10.

The trigger for this problem is the fact that the TTree (very very oddly) was stored after being put in MakeClass mode; this is odd as TTree is MakeClass mode usually do not work very well for output/writing. [It is even odder as many of the branches, for example those containing a vector, do not work in MakeClass mode …]

Nonetheless the MakeClass-ness of the branch is supposed to be transient (but was not until the fix I made).

To work around the problem do:

t->SetMakeClass(false);

before doing anything with the TTree object.

Cheers,
Philippe.

8

Hi Philippe,

It’s working well with this workaround. Thanks for taking care of this!

Best,

Hugo