[Halld-offline] Minutes, Offline Software Meeting, March 7, 2012

[Mark M. Ito]

Find the minutes at 
https://halldweb1.jlab.org/wiki/index.php/GlueX_Offline_Meeting,_March_7,_2012#Minutes 
and below as text.
_____

GlueX Offline Meeting, March 7, 2012
Minutes

Present:
* CMU: Will Levine, Paul Mattione, Curtis Meyer
* IU: Kei Moriya, Matt Shepherd
* JLab: Graham Heyes, Mark Ito (chair), David Lawrence, Simon Taylor,
Elliott Wolin, Beni Zihlmann

CLHEP

Mark proposed that we include [32]CLHEP as one of the official GlueX
external packages. As such code that depends on CLHEP would be allowed
as part of the standard build. Reasons for adding it include:
* It is an essential building block of GEANT4. It is therefore common
for experiments to require it. When we start using GEANT4, it will
become a requirement anyway.
* Many of us are using it in current non-standard-build code:
+ Matt uses it in AmpTools.
+ Mark uses it in his least-squared track fitter.
+ Sascha uses it in Monte Carlo studies for eta decays.
* It is a relatively lightweight package, without a lot of
prerequisites itself.

David argued against the proposal:
* We already have a lot of packages that are required. We should
minimize their number.
* Much of the functionality in CLHEP is already present in ROOT and
that is already a required package. So CLHEP is redundant.

Matt remarked that CLHEP has a much smaller code base. Curtis mentioned
that using ROOT classes often incurs some ROOT-ish overhead. Mark did
not disagree fundamentally with David's reasoning, but thought that we
will from time to time find that introduction of a new package is
necessary, that such packages should be considered on a case-by-case
basis, and that this case is compelling.

Matt pointed out that we have some "typedef's" where, for example, a
DVector is used in the code as a proxy for TVector. The idea is that
the underlying code that supports such classes could be changed without
changing GlueX code. He wondered whether we should change the
underlying code library from ROOT to CLHEP, where appropriate. In this
case, we recognized that simply changing typedef statements was
unlikely to work, that full wrapper classes would have to be written.
That would mean that initially we would not have "package purity" but
would depend on a mixture of ROOT and CLHEP classes.

David stated that he would not die if we adopted Mark's proposal. The
Chair then declared that [33]consensus had been reached and the
proposal was adopted.

Offline Software Review Preparations

David reviewed the current situation.
* We still have no information on the committee members or the
charge.
* David has been running weekly meetings on Friday with Matt, Eugene,
Curtis, and Mark.
+ Curtis summarized this effort as understanding among ourselves
where we stand, what has to be done, what manpower it will
take, and where we are thin.
* We are in communication with CLAS12 on their plans.
* Rolf Ent has been leading an effort to get software collaboration
between Halls
+ There is a meeting planned for a week from today, Wednesday,
March 14 at 3:30 pm, to discuss this further.
+ This is a division level meeting, Hall leaders and selected
guests only.
+ Graham will present selected topics dealing with online
systems.
+ We do not intend to focus on the online at present.
+ At the previous meeting, Rolf requested meetings and
discussion of four topic areas: tracking, reconstruction
framework, single event display, and monitoring histograms.
Meetings on the first two have been held. David is organizing
meetings on the others; watch for his announcement.

Reconstruction Subgroup Reports

Calorimeters

Extra Clusters in the FCAL

Will described further work on understanding extra clusters in the
calorimeter. For plots and details see his [34]wiki page. He has put
aside the BCAL for now and is looking at FCAL photons in b1pi events.
* He reviewed the note from Mihajlo Kornicer on FCAL reconstruction.
* He looks separately at photons that convert before the FCAL and
those that don't.
* Reconstruction efficiency for non-converters above 1 GeV is 98.6%.
* There is a big drop off in efficiency below 400 MeV.
* He will check the definition of an unconverted photon: does it
includes photons that convert in the TOF?
* He made two changes that reduce the number of extra clusters:
1. Allow a charged track to veto more than one cluster.
2. Increase the matching radius at between charged tracks and
clusters.
o There is a bug that causes the run-time parameter to be
ignored.
* This more aggressive matching reduces average photons per event, he
thinks it is due to hadronic showers causing multiple clusters over
a wider area.
* Paul volunteered to implement Will's two changes in the default
code.

More Realistic BCAL Hit Generation

David described recent work he has done to output waveform hits from
the BCAL. This is done in mcsmear. It is not the default scheme at
present. One of the goals is to realistically model the inclusion of
dark hits, which seem to have a surprisingly large effect on the timing
of real hits in the default scheme.

The data model changed some time ago to accommodate the new data. The
pulse is built up by histogramming, in time bins, energy deposition in
the BCAL. Updates are weighted by energy and attenuation is taken into
account. The resulting data is then used to extract the threshold
crossing time.

With these additions, mcsmear runs 15 times slower and events are 50%
bigger. Curtis thought that for specialized studies this approach is
valuable but wondered if it was necessary for the standard work. Work
is on-going.

Tracking

Simon described work he had first mentioned at the last tracking
meeting. He is addressing the problem of closely spaced tracks in the
CDC. See his [35]wiki page for plots and details.

He looks at track finding for events with decaying Λ's. The resulting
vee's cause confusion associating hits into segments and extra track
candidates result. He is playing with a simple algorithm, where
segments that share a large fraction of hits are flagged in pairs and
one can be rejected based on the amount of hit sharing and the relative
χ^2 of the segments from a circle fit.

He has also looked at K[S]'s. Mark suggested that crossing tracks would
be another interesting configuration to test.

PID

Paul reminded us of the [36]email he sent yesterday on renaming,
restructuring, and reorganization of some of the reconstruction
classes. The changes have been checked into a separate branch, and
although they compile, the new names break some of the other code, for
example hdview and phys_tree. He solicited help in making the rest of
the tree consistent.

Beni volunteered to look at hdview.

On an unrelated note, Will suggested that we save the co-variance for
neutrals at the shower level, not at particle level. Paul intends to
work on this.

New Sim-Recon Release?

The consensus was that it is time for a new one.

TDR

Curtis raised the issue of what should go into the TDR regarding
offline software. The old TDR had a PWA section and little else. We
decided that a section on the general philosophy with a high-level
summary of the components would be appropriate. David volunteered to
look into this.

New Action Items

1. Fix the renamed-class branch of sim-recon. -> Paul
2. Create a new sim-recon release. -> Mark
3. Look into what might go into a section of offline software in the
TDR. -> David

Retrieved from
"https://halldweb1.jlab.org/wiki/index.php/GlueX_Offline_Meeting,_March_7,_2012"

References

32. http://proj-clhep.web.cern.ch/proj-clhep/
33. http://en.wikipedia.org/wiki/Consensus_decision-making
34. 
https://halldweb1.jlab.org/wiki/index.php/FCAL_Reconstruction_in_b1pi_events_03/06/2012
35. 
https://halldweb1.jlab.org/wiki/index.php/Problems_with_track_finding_in_CDC
36. https://mailman.jlab.org/pipermail/halld-offline/2012-March/000880.html

-- 
Mark M. Ito
Jefferson Lab (www.jlab.org)
(757)269-5295