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Minutes of the June 17, 2009 GlueX Offline Meeting
Find them posted at
http://www.jlab.org/Hall-D/software/wiki/index.php/June_17%2C_2009_Software#Minutes
and attached as text. There are some (?)'s in the text; please correct
as you see fit.
June 17, 2009 Software
Minutes
UConn: Richard Jones
JLab: Eugene Chudakov, Mark Ito (chair), David Lawrence, Sascha Somov,
Simon Taylor, Beni Zihlmann
Review of [33]Last Meeting's Minutes
We spent some time discussing Matt's suggestion (from two meetings
ago, actually) of having all random-number related processes, such as
smearing, occur in a stage before reconstruction and having the
results of that stage written to disk. David pointed out that there is
already a program, mcsmear that takes the hdgeant output and produces
smeared hits in HDDM format, suitable for the reconstruction program.
Right now only tracking is smeared but it would be straightforward to
do smearing of the calorimeters as well.
Richard asked if the smearing used the truth information. David told
us that that was done earlier but now the smearing is only applied to
hits (i. e., to detector response information).
Announcements
Special system user account at JLab: gluex
Mark reminded us of the existence of [36]this account. David reminded
us that there are several cron jobs currently running under his
personal account that would should be transferred to the gluex
account.
GPU discussion next time
The often-postponed discussion of using GPU's for data analysis is
tentatively planned for the next Offline Meeting. Sandy Philpott and
Jie Chen of the JLab IT Division, Xipeng Shen of William and Mary, and
Richard plan to participate.
New Magnetic Field Maps
David reviewed the [39]new maps that we received recently from Floyd
Martin. He has written a [40]HOWTO on the procedure to convert Floyd's
Excel files to our field map format. There he also describes how to
produce a ROOT file of the map (Elton has been using these). To use
them, the correct command-line argument needs to be supplied to the
reconstruction program to shift the field by the appropriate amount in
z. David will provide a table for now with the correct values, but in
the future this should not be necessary when all useful maps have the
same coordinate system.
Richard pointed out that the ability to apply a z-offset is provided
in HDDS. This feature is not being exploited in the current code.
Bug Fixes from Richard
Richard reviewed his [42]recent email.
missing CDC and FDC hits
This appears to be an old, well-known feature of GEANT3 when the step
size is made small to account for thin layers of material. Due to an
internal optimization strategy the answer to the question "have I
crossed the boundary" can be answered in two different ways, both are
used in some instances and if the answers conflict, swimming is
halted(?). Richard put in a fix to catch these cases and allow
swimming to continue. The change was made in gtnext(?). Richard
encouraged us to test the code and confirm that the problem has been
solved.
2 GB output file limit in HDGeant
This was fixed by an adjustment in the use of the xdr API. xdr is used
to write machine-independent (endian-independent) binary data. In
addition we need to compile our code with the gcc switch
-D_FILE_OFFSET_BITS=64 thrown whenever we compile. David agreed to
implement this change.
Kalman Filter Update
Simon showed further progress on his fitter. The two most recent
changes are to do a wire-based fit before using drift information and
to change the cut-off angle where he changes from a forward
parametrization to a central parametrization. He showed big
improvements in the formerly problematic areas around 20 to 40 degrees
in polar angle. Resolution is generally slightly better than for the
least-squares fit and in a few regions a lot better. There is still
lots to do (in particular looking at the fitting efficiency) but the
improvements were marked.
Complexity Growth in HDGeant
Richard noted that there have been several changes in HDGeant that
have added dependence on other large packages (such as ROOT) and on
our reconstruction libraries (such as tracking). He thought that if
this could be avoided, it would make maintenance of HDGeant simpler
(the "fewer moving parts" argument). Discussion focused on the the
distance-of-closest approach algorithm in the tracking package. David
introduced the algorithm used in tracking into HDGeant it to get
consistency between Monte Carlo and reconstruction. He was not getting
agreement with the straight-line-while-in-a-cell approximation
formerly used in HDGeant.
We decided that David would back out the change in question and when
he was done, Richard would take track curvature information into
account when creating hits.
Deferred Agenda Items
1. Work disk information
2. Software tag policy
Action Items
We agreed that we should revive our regular review of old items and
listing of new ones. Here are the items generated at this meeting:
1. Introduce calorimeter smearing into mcsmear.
+ Tell Matt about our discussion -> Mark
+ Consult with Matt on how this can be done -> David
2. Add -D_FILE_OFFSET_BITS=64 switch to gcc in makefiles -> David
3. Back out tracking doca algorithm from HDGeant -> David
4. Include "arc correction" in HDGeant straw hit generation ->
Richard
5. Bring back the "Action Items" agenda item in future agendas ->
Mark
_________________________________________________________________
Recorded by [49]Marki 09:35, 19 June 2009 (EDT)
Retrieved from
http://www.jlab.org/Hall-D/software/wiki/index.php/June_17%2C_2009_Software
References
33. http://www.jlab.org/Hall-D/software/wiki/index.php/May_20%2C_2009_Software#Minutes
36. http://www.jlab.org/Hall-D/software/wiki/index.php/Special_system_user_account_at_JLab:_gluex
39. http://www.jlab.org/ccc/mail_archives/HALLD/halld-offline/msg00917.html
40. http://www.jlab.org/Hall-D/software/wiki/index.php/HOWTO_Convert_a_B-field_Map_from_Excel
42. http://www.jlab.org/ccc/mail_archives/HALLD/halld-offline/msg00918.html
49. http://www.jlab.org/Hall-D/software/wiki/index.php/User:Marki