Report on CHEP ‘06

David Lawrence

Conference had many participants, but was clearly

dominated by LHC

• LHC has 4 major experiments:ALICE, ATLAS, CMS, and LHCb

• Collaboration sizes:~500, ~1000, ~1000, ~2000

LHC Event and Data Rates

Event Size

(bytes)

L1 trigger rate

Data rate

Atlas 1.6 x 106 75 kHz 120 GB/s

CMS 1.0 x 106 100 kHz 100 GB/s

Alice 1.0 x 106 20 kHz 20 GB/s

LHCb 3.5 x 104 1 MHz 3.5 GB/s

PHENIX

• DAQ system used LZO compression to compress raw data after the event builder– Reduced bandwidth requirement– Reduced disk space requirement– Extended time data allowed to linger in

buffer boxes

PHENIX

Buffer boxes: The longer you can buffer data the better you can take advantage of breaks in data flow.

6 reasonably cheap Linux-based buffer boxes (~20k each) allow 40 hours of data taking without tape access.

L3 trigger can be run on disk data so it only needs to keep up with the average event rate, not the peak rate.

PHENIX

Analysis Trains: Improve overall use of resources by limiting random access of data files.

About every 3 weeks a new train is started. Jobs register with train ahead of time.

Tapes are read in tape-order and all jobs run on the data at once.

PHENIX

• 270 TB of data was shipped to computing center in Japan for processing

• This was done by non-experts manning shifts

ROOT• ROOT is now 11 years old and

represents ~500 man-years of effort

ROOTThe 2016 laptop: 32 processors, 16GB RAM,

16TB of disk

Multi-core processors are at the doorstep and better multi-threading support is needed.

PROOFI/O (read-ahead)Fitting/Minimization…

ROOT

• STL and templates take significantly longer to compile.

• Shared libraries become less efficient as the number of packages implemented in them grows

• The new ROOT will be BOOT

GDML

Witold Pokotski of the GDML development team• Repeated structures are now supported• AGDD guys seem to think they have a better

product and are still a bit bitter• I suggested GDML implement the ability to

apply tweaks in a separate file from the default geometry (they’ll think about it)

What do you know, people do develop and run physics

analysis software onMS Windows!

Object Persistence

• Some LHC experiments use POOL which uses Reflex outside of ROOT and then defines TTrees using the Reflex information.

Object Persistence

• ROOT I/O has many new features making it more viable candidate for general use

• ROOT I/O is based on the Reflex project which uses gccxml

IEEE Transactions in Nuclear Physics

• Refereed Journal pushing for publications from CHEP type work (software)

• “Hardware guys are very good at publishing. Software guys need to do better then they are.”

Conclusions• An abstract really, really should have been

submitted for DANA

• We need to publish (e.g. IEEE TNS)

• ROOT is very strongly supported and will continue to be developed over at least the next 6 years

• CHEP 2007 will be in Victoria, BC. I will be there