Re: [ROOT] CopyTree and Single Object Branches

From: Roger Moore (rwmoore@fnal.gov)
Date: Tue Feb 25 2003 - 21:32:50 MET


On Tue, 25 Feb 2003, Rene Brun wrote:

> If you have created your Tree with one single top level branch (eg event), you
> should set the address of this top level branch and not the address of one of
> the sub-branches. I need to see your code to come with a better
> diagnostic.

The tree is definitely not created from a single top level object - it is
created from multiple branches each containing a TClonesArray or a single
object. I can copy the TClonesArray branches successfully - they work
fine. It is only the single object branches that I have trouble with.

The code used to create the branches is:

   if (_Fruits->InheritsFrom("TClonesArray")) {
      tree->Branch(_BranchName.Data(), &_Fruits, buffersize);
   } else {
      tree->Branch(_BranchName.Data(),_Fruits->ClassName(),&_Fruits,buffersize);
   }

However I have no control over this code (it's part of the D0 thumbnail
package). In the case in question _Fruits is a TObject * which points to
an instance of TMBGlob.

The code I have written to access the branch is:

  // Turn on the branch for readout
  tree()->SetBranchStatus(_bname.c_str(),1);
  // Set the branch address to the data object
  tree()->SetBranchAddress(_bname.c_str(),&_ptr);

and this works fine for the original TTree. _ptr points to a valid
instance of TMBGlob which gets filled with the data. I can also email a
tarball of the entire readout code if you need to see it all. I have also
tried turning on branches "Glob.*"  but then I get the error that ROOT
con't find them. One thing that is worth mentioning is that I only provide
addresses for the branches which are turned on. I know this has
implications for the I/O speed but not for the CopyTree method.

> You are mentionning problems with rootcint with the more recent versions of
> ROOT. Did you report these problems to somebody?

I haven't reported these problems yet because I haven't had a chance to
look at them in detail. I had assumed that there were significant changes
to rootcint and that I would need to alter my code to make it work.
However if code that compiles with ROOT 3.03/09 should compile with ROOT
3.04/02 without changes then I'd be happy to send you the error messages I
get along with my code. If there are definite changes that I need to make
then I'd be very happy if you could give me a pointer to them - I didn't
see anything in the release notes that gave me cause for concern.

Roger

> Roger Moore wrote:
> >
> > I have been using the CopyTree method, along with a TEventList, to select
> > a subset of events and branches in a TChain to write out to a TTree. This
> > works absolutely fine for TClonesArray branches. However for the single
> > object branch in the TChain it fails miserably. The entire branch somehow
> > gets converted into a single 'TObject' branch. Shown below is the result
> > of a 'Print' of the original TChain branch:
> >
> > root [5] TMBTree->GetBranch("Glob")->Print("")
> > *Branch  :Glob                                                               *
> > *Entries :    13865 : BranchElement (see below)                              *
> > *............................................................................*
> > *Br    1 :fUniqueID :                                                        *
> > *Entries :    13865 : Total  Size=      68940 bytes  File Size  =       1414 *
> > *Baskets :       14 : Basket Size=       4000 bytes  Compression=  39.59     *
> > *............................................................................*
> > *Br    2 :fBits     :                                                        *
> > *Entries :    13865 : Total  Size=      68860 bytes  File Size  =       1400 *
> > *Baskets :       14 : Basket Size=       4000 bytes  Compression=  39.99     *
> > *............................................................................*
> > *Br    3 :_evtno    :                                                        *
> > *Entries :    13865 : Total  Size=      68880 bytes  File Size  =      49526 *
> > *Baskets :       14 : Basket Size=       4000 bytes  Compression=   1.13     *
> > *............................................................................*
> > *Br    4 :_runno    :                                                        *
> > *Entries :    13865 : Total  Size=      68880 bytes  File Size  =       2602 *
> > *Baskets :       14 : Basket Size=       4000 bytes  Compression=  21.50     *
> > *............................................................................*
> > *Br    5 :_store    :                                                        *
> > *Entries :    13865 : Total  Size=      68880 bytes  File Size  =       2279 *
> > *Baskets :       14 : Basket Size=       4000 bytes  Compression=  24.55     *
> > *............................................................................*
> > *Br    6 :_solpol   :                                                        *
> > *Entries :    13865 : Total  Size=      68900 bytes  File Size  =       1418 *
> > *Baskets :       14 : Basket Size=       4000 bytes  Compression=  39.46     *
> > *............................................................................*
> > *Br    7 :_torpol   :                                                        *
> > *Entries :    13865 : Total  Size=      68900 bytes  File Size  =       1418 *
> > *Baskets :       14 : Basket Size=       4000 bytes  Compression=  39.46     *
> > *............................................................................*
> > *Br    8 :_ticknum  :                                                        *
> > *Entries :    13865 : Total  Size=      68920 bytes  File Size  =      17272 *
> > *Baskets :       14 : Basket Size=       4000 bytes  Compression=   3.24     *
> > *............................................................................*
> > *Br    9 :_lumblk   :                                                        *
> > *Entries :    13865 : Total  Size=      68900 bytes  File Size  =       6973 *
> > *Baskets :       14 : Basket Size=       4000 bytes  Compression=   8.02     *
> > *............................................................................*
> > *Br   10 :_solcur   :                                                        *
> > *Entries :    13865 : Total  Size=      68900 bytes  File Size  =       1980 *
> > *Baskets :       14 : Basket Size=       4000 bytes  Compression=  28.26     *
> > *............................................................................*
> > *Br   11 :_torcur   :                                                        *
> > *Entries :    13865 : Total  Size=      68900 bytes  File Size  =       2299 *
> > *Baskets :       14 : Basket Size=       4000 bytes  Compression=  24.34     *
> > *............................................................................*
> >
> > and after CopyTree has done its work the branch in the output file is now:
> >
> > *Branch  :Glob                                                               *
> > *Entries :      326 : BranchElement (see below)                              *
> > *............................................................................*
> > *Br    0 :TObject   :                                                        *
> > *Entries :      326 : Total  Size=      16976 bytes  File Size  =        526 *
> > *Baskets :        1 : Basket Size=       4000 bytes  Compression=   5.95     *
> > *............................................................................*
> >
> > The original class, TMBGlob, is loaded and ROOT clearly recognises it
> > since with the original branch I can decode and look at all the entries
> > with the class loaded. When I set the branch address I use the command:
> >
> >         SetBranchAddress("Glob",&_ptr);
> >
> > where _ptr is of type "TMBGlob *" and points to a TMBGlob class instance.
> >
> > The version of ROOT I am running is v3.03/09. I have tried compiling the
> > code under both v03.04/02 and v03.05/00. However there are lots of
> > problems with both version from rootcint and, after an initial attempt to
> > fix them, I have come to the conclusiosn that this is several days effort
> > which is time I don't currently have!
> >
> > So is there a fix or workaround which I can use with v03.03/09?
> >
> > Thanks,
> >
> > Roger
>



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