10-14 October 2016
San Francisco Marriott Marquis
America/Los_Angeles timezone

How To Review 4 Million Lines of ATLAS Code

11 Oct 2016, 11:30
GG A+B (San Francisco Mariott Marquis)


San Francisco Mariott Marquis

Oral Track 5: Software Development Track 5: Software Development


Graeme Stewart (University of Glasgow (GB))


As the ATLAS Experiment prepares to move to a multi-threaded framework
(AthenaMT) for Run3, we are faced with the problem of how to migrate 4
million lines of C++ source code. This code has been written over the
past 15 years and has often been adapted, re-written or extended to
the changing requirements and circumstances of LHC data taking. The
code was developed by different authors, many of whom are no longer
active, and under the deep assumption that processing ATLAS data would
be done in a serial fashion.

In order to understand the scale of the problem faced by the ATLAS
software community, and to plan appropriately the significant efforts
posed by the new AthenaMT framework, ATLAS embarked on a wide ranging
review of our offline code, covering all areas of activity: event
generation, simulation, trigger, reconstruction. We discuss the
difficulties in even logistically organising such reviews in an
already busy community, how to examine areas in sufficient depth to
learn key areas in need of upgrade, yet also to finish the reviews in
a timely fashion.

We show how the reviews were organised and how the ouptuts were
captured in a way that the sub-system communities could then tackle
the problems uncovered on a realistic timeline. Further, we discuss
how the review influenced overall planning for the ATLAS Run3 use of
AthenaMT and report on how progress is being made towards realistic
framework prototypes.

Primary Keyword (Mandatory) Parallelization
Tertiary Keyword (Optional) Software development process and tools
Secondary Keyword (Optional) Algorithms

Primary author

Graeme Stewart (University of Glasgow (GB))


Walter Lampl (University of Arizona (US))

Presentation Materials