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For LCLS, we will pre-compute the optics from the lattice, so each modeling application doesn't have to track a lattice for itself before starting. The online modeling "tracker" will be that in XAL (primarily in the gov.sns.xal.model package). The output of this phase will be the Courant-Snyder (Twiss) parameters of each element of the beamline. A second probe can calculate the transfer matrices (R-matrices). The Twiss param outputs will be captured in a series of second XAL files. There is presently no file-handling code in XAL for statically recording the R-matrices or global parameters (path length, energy, betamax), so new output files will be designed for that (either extending the XAL syntax, or creating some other XML file).
One can track an XAL beamline in either of 2 "modes", i) "design" or ii) "from EPICS PV" - which is to say using settings for each lattice element found either in the XAL input file ("design") or by accessing the EPICS Process Variables of optical components themselves at runtime. The latter produces a model of the optics of the extant machine. We should have file management capability to store a single recognized "design" lattice file, plus a "gold" lattice (the inputs "from PV" that produced good optics To Add), plus at least one experimental lattice file. This capability to switch easily between a lattice of the extant machine and an ad-hoc lattice was badly missed in the SLC modeling environment.
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The results of tracking (Twiss, R-matrices, global machine params, k-values of optical components) for each of these beamlines for each of the choices of model (design, gold, experimental) for each source of input data (design, PV), will have to be stored. We should put them in CVS.
The input source combinations lead to a number of such outputs, calling for careful filenaming. Additionally, if it's sufficient to do tracking in the initialization stage of each modeling program's startup, whcih recall involves getting extant PV values and tracking the lattice, we can do that. But if that proves too slow then we'll need to persist the outputs into the Oracle DB and programs will go to the db to get optical parameters. See figure 2.
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Tool | Function |
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x86 Linux RH, KDE/GTK-2 window system | (Native) Desktop O/S for applications. Note, Windows is NOT listed. As described in the architecture Windows clients will go through X11 See X11. x86 and GTK-2 specification is important so performance can be tuned. |
Matlab | Ad-hoc analysis: acquiring data through aida, jca and XAL, performing computation and implementing results. Acquire hist data through Aida. |
XAL | 1) Modelling components (tracking); 2) OO device control, 3) Application framework, 4) Existing XAL applications. |
Eclipse RPC | Integrated application launching. Rich Client Platform (RPC) for integrated applications shared with "EPICS Office" and gumtree. |
Eclipse SWT/Jface | High performance Interactive Applications |
XAL (JCA), AIDA (CORBA), JCA/CAJ | Data Interoperability. Getting and setting device data. Aida can also get history and model data to unix apps from the SLC control system. |
Jcmlog, cmlog, Err | Error handling, logging and browsing. See error handling. |
Cvs, make |
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Source repository |
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and building. Distribution by simple "install" to an AFS or mounted NFS directory. See Filesystem. Note not ANT | |
Oracle | Enterprise RDB. Stores the XAL geometry, and in architecture described here also the optics. Applications acquire optics from the db rather by tracking an XAL lattice at runtime. |
OC4J |
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or Jboss |
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or Apache jakarta | Choose an Application Server. We're making heavy use of Oracle and XML, so displays based on contents of those datasources will go through an App server (AS). |
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Pick one. | |
Java | Programming Language |
Linux, Solaris | Server Hosts O/S |
NFS | Production Host Filesystem? See Filesystem |
AFS | Development Host Filesystem |
Integrated Development Environments
Not a good idea to prescribe these for everyone. Three good open source choices for our technology stack are emacs+jdee, Netbeans (including matisse) and the Eclipse IDE. All three include CVS integration.
RED FLAGS
Some important choices or questions.
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Windows filesystem.
If we do require native execution on Windows that decision should be made clearly and early, and resources assigned to implement the common executable and configuration file distribution so that Unix and Windows running applications are in sync and see the same configuration files. Java Web Start and Eclipse update site technology may be places to find solutions.
XAL Plane Coupled modeling.
The existing XAL probes for calculating R-matrices, run on either the X-plane or Y-plane and returns only a 2x2 matrix for each element. That is, it's uncoupled. This is reflected in the fact that only the Twiss parameters can be stored into an XAL file - it only contains uncoupled optics. So, if plane coupled orbit correction is important for us, we need to add at least 4x4 and probably 6x6 tracking.
XAL Modelled acceleration and solenoid. XAL does not model acceleration (required for ???) nor solenoid field (required for ???). These have to be added.
Archiver. Which one?
REQUIRED ADDITIONS TO SLC CONTROL SYSTEM
An LCLS model beamline, associated sectors and db additions in support of it, must be added.
Pulse-id acquisition by Correlation Plots. Presently broken needs to be fixed.
REQUIRED SOLUTIONS
This section lists functional components of the LCLS modeling applications architecture which for which we need to decide on a vendor:
- Numerical Analysis package, for matrix manipulation and linear algebra. Some classes of XAL extend JAMA 4, this may be sufficient.
- J2EE compliant Application Server. Application Servers include technology for accessing databases (eg oracle) and displaying information to the web. This will be useful for displaying static control data, model information and other slow control configs etc, to the web and to the Integrated Control Program. Suggest Apache Jakarta, plus PHP, Xerces, Xalan, etc.
JOB LIST
Lists some jobs that might otherwise be forgotten.
SQL script and other munging to get from Oracle db description of geometry and devices to a lattice description in an XAL input file.
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jcmlog. jcmlog is a sophisticated error log viewer for CMLOG developed at SLAC recently for LCLS. It is in general much faster and smother than the nominal CMLOG viewer from Jlab and includes facilities for handling the particular requirements of Err (above) such as horizontal scroll for long messages.
NAMES
Light relief - what are we going to call this system?
LIPS LCLS integrated physics system
SIPS SLAC integrated/interactive physics system
iSCP Integrated SLAC Control System
SOMA SLAC online modeling applications.
TECHNOLOGY GLOSSARY
#Oracle: The enterprise db contains static data on devices and their beamline geometry.
#XAL: Existing software which contains a lattice tracker, java bean classes for programs to deal with accelerator devices in an object oriented way, and code for building GUI applications based on Swing.
#XML (see references): A computer language for writing files containing structured data. XML is used by XAL as the language of its input model files. Data in XML is trivially transformed via XSL into other forms, such as HTML for easy display on the web, or other XML files suitable for other programs or putting into a db.
#AIDA (Accelerator Independent Data Access), a Java API to EPICS Channel Access, SLC database device data, BPM and magnet data and control, EPICS and SLC history data, SLC modeling data.
- Err - a platform and language independent (java & c++) error handling framework for creating and logging error messages.
#global message: error or warning text message typically going to some log like cmlog, and viewed by a user through a browser like cmlog browser. A global message is on generated by a front-end computer or an application that thinks it's worth telling the world about. compare to local message
#local message: a message generated by an application that is intended only for viewing by the application's user at that time. Eg "0 is not a permitted number of iterations to average bpm readings".
REFERENCES
- XAL http://www.sns.gov/APGroup/appProg/xal/xal.htm
- XML entry in Wikipedia http://en.wikipedia.org/wiki/XML
- LCLS lattice files
- JAMA http://math.nist.gov/javanumerics/jama/
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