sPHENIX discussion of software

[pinkenburg <pinkenburg AT bnl.gov>]

Hi folks,

if you are not too interested in the technical explanation, here is what 
you need to know:

if you have problems reading old file, please let me know immediately 
(mentioning what file and what you are doing). If you create new files, 
you probably will not be able to read them with old (ana) builds.

and here the details:
Our node tree is mapped onto the root TTrees in the output file by using 
the TTree branch names to store the node names. This is just one string 
and so we need to have some unused character to separate the 
subdirectories in those names and we have been using "." so far after 
"/" turned out to collide with the root parser when doing a 
TTree->Draw() (DST/HCALIN/G4HIT_HCALIN --> DST.HCALIN.G4HIT_HCALIN). In 
root 6.18 using "." tickled a bug (you might remember that we had to 
revert to root 6.16 because our stored hepmc records crashed root on 
readback). The bug is fixed but the "." still confuses the parser. I 
switched this to "#" which is not interpreted, so using TTree->Draw() 
(or drawing from the TBrowser) works fine as does the saving/readback 
into fun4all. It is backward compatible ("." is still recognized as 
separating character when reading files).

This would enable us to move to root 6.18 but we still have files from 
previous production which cannot be read, so we will wait for 6.20 for 
the root upgrade (which will save us some memory which was the original 
motivation to go to root 6.18)

That's a pretty intrusive change (which you shouldn't notice). If you 
encounter problems, please let me know.

Chris

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Christopher H. Pinkenburg       ;    pinkenburg AT bnl.gov
                                ;    http://www.phenix.bnl.gov/~pinkenbu

Brookhaven National Laboratory  ;    phone: (631) 344-5692
Physics Department Bldg 510 C   ;    fax:   (631) 344-3253
Upton, NY 11973-5000

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