GlueX Offline Meeting, December 15, 2010
GlueX Offline Software Meeting
Wednesday, December 15, 2010
1:30 pm EST
JLab: CEBAF Center F326/7
- Review of minutes from the last meeting: all
- Tagger hall geometry/simulation: Sascha
- Calibration Database Update: Dmitry
- Random number seed policy: Richard
- Solenoid text file conversion approach
- Action Item Review: all
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- Review of recent repository activity: all
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- IU: Kei Moriya, Matt Shepherd
- JLab: Craig Bookwalter, Mark Ito (chair), David Lawrence, Lubomir Pentchev, Dmitry Romanov, Sascha Somov, Simon Taylor, Beni Zihlmann
- Simon announced that he has added time and energy smearing to the start counter in mcsmear.
Review of minutes from previous meeting
We went over the minutes from the December 1st meeting.
- David mentioned yet another issue with using GEANT3 for our simulation. There are some CERNLIB routines that we have imported to the GlueX repository because of bug fixes. These can sometimes cause problems with include files.
Tagger hall geometry/simulation
Sascha led us through some recent work he has done, documented in a recent GlueX Note. The main conclusion is that we expect that dark rates in SiPM's used in the microscope could increase by a factor of five in about 2.5 months. This estimate includes shielding with polyethylene which reduces the exposure by about a factor of 7. See his note for details.
The geometry configurations that were used have not been released for public consumption yet. See Sascha if you have a need for them.
Calibration Database Update
Dmitry gave us a review of the scheme for the calibration database and reported on the current status. See his slides for details. Status is as follows:
- File specification is done
- File upload to DB in progress
- “Field” C++ API in progress
- Core C++ API done
- User C++ API mostly done
- Python wrapping--mostly done
- Console utils--first working prototype is done
- Web interface--prototype is done
There was some discussion during and after the talk:
- Security: We had a lot of discussion about what level of security was necessary or appropriate. Too little and unauthorized changes can be made to sensitive calibration sets. Too much and making modifications is made difficult and the central collaboration copy might not get all important changes; those changes may languish in private version.
- Access outside JLab firewall: Richard asked about how the constants would be accessed outside JLab.
- David has implemented a web service to deliver constants. This was some time ago and needs to be revisited.
- The database can be replicated at other sites and access granted to the replicas as needed. This is useful for the console tools, for example.
- The system will export files that can be used to supply constants from a local filesystem. For example, this could be used on a laptop without a network connection.
- [added in press] There will be a web application that will allow any user with a web browser to access the contents of the database.
Random number seed policy
Richard reviewed the options he outlined in his email to the offline list. He recalled for us that the issue was raised by Kei getting indentical results from separate runs of genr8 when they were started within a second of each other.
We formed a consensus around using /dev/urandom, at least initially. We commissioned Richard to write an appropriate python script that would produce a seed on standard output as an initial stab at a more robust random seed strategy.
David noted that we should add better random seed management to mcsmear.
New Action Items
- Write a python script that uses /dev/urandom to produce pretty darn random numbers.
- Random seed management for mcsmear.
- You have to be a member of the "halld" Unix group to do this.