Hi Daniel,
What you see seems to be TTree::Draw problems and not I/O problems.
Could you send me (not to the list) a tar file with:
- a copy of an old small file
- a copy of a new small file
Rene Brun
Magestro Daniel wrote:
>
> Rene,
>
> Hi - as a test regarding the use of split level=2 and class def changes, I
> have compiled our code with ROOT v3.01 including a simple change of one
> datamember name (OLD=sector, NEW=sect). When I read in an old DST file that
> was created with the original class def (we used ROOT v2.25), I see the
> original datamember name 'sector' in the TBrowser. However, when I do a
> TTree->Draw(), I get the following error message:
>
> root [2] T->Draw("HMdcCal1.fData.sector")
> Error in <TTreeFormula::DefinedVariable>: sector is not a datamember of
> HMdcCal1
>
> In other words, the old datamember name is not known any longer. Also,
> although the new datamember name doesn't show up in the TBrowser, I *can* do
> a TTree->Draw(), which returns only -1's (sect's initialized value):
>
> root [3] T->Draw("HMdcCal1.fData.sect")
> <TCanvas::MakeDefCanvas>: created default TCanvas with name c1
>
> This seems quite strange to me. The TBrowser shows the old name which cannot
> be drawn, but the new name is not shown but CAN be drawn.
>
> If I do a T->MakeCode() and look at the generated macro, the original
> datamember name is listed as a leaf:
>
> ....
> T->SetBranchAddress("HMdcCal1.fData.sector",HMdcCal1_fData_sector);
> ....
>
> Clearly there is some difficulty in reading old files if the class def has
> changed, even for tree drawing. Do you have any suggestions? Is this due
> to the change in the schema for TBranchClones?
>
> Thanks again for your support, you've been really helpful...
> Dan
>
> | -----Original Message-----
> | From: Rene Brun [mailto:Rene.Brun@cern.ch]
> | Sent: Friday, August 10, 2001 3:12 PM
> | To: Magestro Daniel
> | Cc: 'roottalk@root.cern.ch'
> | Subject: Re: [ROOT] Changing class definition in split level=2
> |
> |
> | Hi Daniel,
> |
> | Trees with TClonesArray in TBranchClones can be read without problem with
> | ROOT version 3, even if the class has evolved. This was one of the
> | advantages of the split mode before we introduced the automatic schema
> | evolution system.
> |
> | I can only suggest that you try to read your files with the version 3.
> |
> | Rene Brun
> |
> |
> | Magestro Daniel wrote:
> | >
> | > Rene,
> | >
> | > Hi - maybe I'm missing the point myself. If a TBranchClones from a
> | > file is read, then don't the individual class definitions in the
> | > loaded libraries have to be the same as in the file? If I change the
> | > name of a data member in a class, and then I use this new class with
> | > the old file, how does the TBranchClones streamer know about this data
> | > member if it's not in the current (loaded) class definition? I don't
> | > see how you can read pre-Root3 files with a different class version
> | > without using a custom streamer for the class (not supported by
> | > pre-Root3 TBranchClones/TClonesArray).
> | >
> | > Also, the old files (files with v2.25/03) were of course created using
> | > the old TBranchClones streamer, not the new one. Maybe this is the
> | > source of our problem?
> | >
> | > I understand that, in the new scheme, the new BypassStreamer()
> | > function of TClonesArray, together with TStreamerInfo, takes care of
> | > class def changes. But this does not explain how old files, with
> | > DIFFERENT class defs from the current ones, can be read properly.
> | > Either (a) they can't be read and we lose some backward compatibility,
> | > (b) they CAN be read but there is another step which is needed that I
> | > don't know, or (c) I'm still missing the point. But if you feel that
> | > there's nothing straightforward that we can do to solve this problem,
> | > then let me know and we'll deal with the consequences.
> | >
> | > Thanks again for taking the time... Dan
> | >
> | > | Hi Daniel,
> | > |
> | > | I do not understand your point. With the old schem, using
> | > | splitlevel=2, TClonesArray Streamer was not used. The TBranchClones
> | > | class split each member of the class into a separate branch.
> | > | TBranchClones can be read without problems with the new scheme.
> | > |
> | > | Rene Brun
> | > |
> | > |
> | > | Magestro Daniel wrote:
> | > | >
> | > | > Rene,
> | > | >
> | > | > Hi - thanks for your response... unfortunately, the page
> | > | reference you sent
> | > | > me (migrating to Root 3) does not relate to the problem I
> | > | have. The problem
> | > | > is that, in our split level = 2 scheme, the data i/o is not
> | > | handled by the
> | > | > individual class streamers but by the TClonesArray
> | > | streamer. Therefore, we
> | > | > cannot simply increment the class version and write a
> | > | custom streamer to
> | > | > read old files because the class's streamer is NOT touched.
> | > | >
> | > | > My fear is that we lose backward compatibility due to our
> | > | dependence on the
> | > | > TClonesArray streamer. Is there a solution for this? As I
> | > | wrote before,
> | > | > migrating to Root 3 doesn't solve the problem for .root
> | > | files which were
> | > | > created for v2.25 with a different class definition because
> | > | the files were
> | > | > created with the TClonesArray streamer...
> | > | >
> | > | > Thanks again,
> | > | > Dan
> | > | >
> | > | > | From: Rene Brun [mailto:Rene.Brun@cern.ch]
> | > | > | Sent: Friday, August 10, 2001 9:23 AM
> | > | > | Subject: Re: [ROOT] Changing class definition in split level=2
> | > | > |
> | > | > | Hi Daniel,
> | > | > |
> | > | > | Please read the discussion on the migration to the new
> | > | scheme at page 204
> | > | > | of the Users Guide.
> | > | > |
> | > | > | Rene Brun
> | > | > |
> | > | > | Magestro Daniel wrote:
> | > | > | >
> | > | > | > Hi all,
> | > | > | >
> | > | > | > I have read old roottalk posts as well as the latest
> | > | Root manuals, but I
> | > | > | > cannot find the solution to a basic problem. (We are
> | > | currently using
> | > | > | > v2.25/03.)
> | > | > | >
> | > | > | > In our analysis, all of our data classes use split
> | > | level = 2. The
> | > | > | > problem is that, if we change a class definition
> | (for example,
> | > | > | > changing the name of a data member), adding a
> | custom streamer to
> | > | > | > that class does not work because the streaming for the
> | > | class is done by
> | > | > | > TClonesArray/TBranchClones. The class streamer is not
> | > | called at all.
> | > | > | >
> | > | > | > ... Is there a way to read our old files created with
> | > | v2.25/03 if we
> | > | > | > now change the class def? We have a large volume of
> | > | files which fit
> | > | > | > this description, and of course we would like to
> | avoid having to
> | > | > | > maintain two versions of our code.
> | > | > | >
> | > | > | > Any ideas would be greatly appreciated... thanks,
> | > | > | >
> | > | > | > Dan
> | > |
> |
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