Re: [ROOT] Trees, own classes and splitting

From: Rene Brun (Rene.Brun@cern.ch)
Date: Wed Dec 05 2001 - 18:01:03 MET


Hi Volker,

Volker Hejny wrote:
> 
> Hi all,
> 
> as far as I know, the basic situation concerning splitting and
> streamers is the following:
> 
> When I run in non-split mode, the Streamer method of a class
> is processed. In split mode this function is never called, because
> all data memebers are branches themselves. Therefore, when I have
> to do some initialisation in the Streamer method of an own class,
> I should never enable splitting for this class.
> 

See Users Guide page 225.
You can instruct Root to not split a data member of a class
by specifying the two caharcters "||" in the comment field.


> If this is correct, then, in principle, whenever I have the need
> to define a custom streamer, splitting in general is a bad idea.
> So, is there any way to disable splitting of a specific class
> by default, e.g. in the LinkDef file, that the user does not need
> to care about that? If not, I think that would be a good idea to
> have that.
> 
> The second question then is following: In accessing the data members,
> e.g. in the Draw() command, the behaviour of split and non-split
> branches are the same. The only difference I see is again the
> behaviour when using the TBrowser. In principle it should be
> possible to generate the branch structure taking the information
> from TStreamerInfo. Are there any plans to do that?
> 

The difference is the time. It will take more time to process the non-split
branch.
Concerning the browser, you are correct. It is possible to browse a non-split
object in principle. However, if we implement this feature, we will get
immediatly complaints that by double clicking on a data member, it takes time
to process the query. On the other hand this could be one way to illustrate
the advantages of the split mode ::)

Rene Brun


> Best regards,
> Volker
> 
> --
> Dr. Volker Hejny                Tel: 02461/616853                      **
> Institut f. Kernphysik          Fax: 02461/613930                     **
> ---------------------------------------------------------------- **  ** ---
> Forschungszentrum Juelich GmbH, D-52425 Juelich                    **



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