CFEL - ASG Software Suite  2.5.0
CFEL - ASG Software Suite Documentation

Table of Contents

CASS stands for (C)Fel-(A)SG (S)oftware (S)uite. It is a program designed to analyze and visualize data taken at Free-electron-lasers (FELs). To be easily adaptable to the various different types of experiments, it is based on a highly modular design. The analysis part of CASS allows the user to set up an analysis chain that can be tailored for each experimental need. The section general layout describes the details of CASS.

Please find below the links to most important parts of the description


See for short installation instructions.

Getting CASS source code

Downloading a tarball

You can download a recent tarball version of CASS from the following location

Older versions of CASS are also available for download from:

Note that versions without a numeric version name were created when CASS was still developed in svn and are therefore outdated. They are only available for historical reasons.

Retrieving the version controlled source code (git)

CASS is being developed using the distributed version control system 'git'. One can clone a copy from the server using the following command

git clone

This requires that you have set up a ssh key pair and sent Lutz Foucar your public key.

The recent stable version is contained in the 'master' branch.

Anonymous retrieval via GitHub

An anonymous clone of the latest master branch of the repository is accessible via GitHub

Building CASS

See the file for the prerequisites. Once you have cloned / downloaded the version you want to compile you need to do the following steps:

cd /path/to/cass/directory/
copy cass_defaultconfig.pri to cass_myconfig.pri

Now modify the cass_myconfig.pri file to include what you need and whether you want to use the offline and/or online version of CASS. Make sure that you have set up all the paths correctly. Once you are done with this type:


If you want to install the binaries later on in a directory other than "/usr/local" you need to type:

qmake PREFIX=/path/to/desired/location

Once you have done this you can type:

make [-j5]

After it is done with compiling you have the choice to either leave the binary in the ./bin folder and start CASS from there or you might want to install it into the location that you requested with the optional PREFIX parameter by typing:

make install

Now CASS is ready to run. Please see the Using CASS section of the documentation to see how to configure and run CASS. Parameters for the program start can be found here: CASS Commandline Parameters.

By enabling the corresponding options in the cass_myconfig.pri file one can enable CASS to compile the additional viewers that ship with CASS.


The Software Suite is documented using doxygen. One can create a html version of the documentation by running doxygen in the "doc" sub directory of the CASS directory. For this please install doxygen on your computer (see for details). Then cd into the doc directory and use doxygen there e.g. if you are in the CASS base directory do:

cd doc
make doc

This will create a subdirectory of the doc directory called doxygen/html. Within this directory you will find the html version of the documentation. Open index.html with your favorite browser to view the documentation.

An online version of the documentation that shows the latest stable version in the master branch is located at

Using CASS

CASS multiple input modes allow running online (get the data from a live data stream) and offline (get the data from the written files). Depending on the settings in cass_myconfig.pri one can compile CASS for either online or offline mode. Please see Install instructions for CASS for details.

A complete list of all available command-line parameters for the compiled mode can be found by starting CASS with the help switch:

cass --help
cass -h

To quit CASS in either online or offline mode one can use

crtl + \

Killing the program with

crtl + c

has various implications. Please refer to the following sections for details.

Running Online at LCLS

To run CASS online at LCLS you need shared memory access to the data provided by LCLS. This access is only available on selected dedicated computers. For the AMO-Hutch these are


Please ask the LCLS DAQ people on which machine you will have access to the online data stream.

When starting the online CASS program you need to determine where to find the shared memory that has been preset by the DAQ people. Doing

ls /dev/shm

gives a list which shared memory tags have been set up. The shared memory tag can be passed to the program with the

-p <partition tag>

parameter. If more than one person is running on the same machine trying to get the data from the online stream it is possible to pass an id to each one with the

-c <client id>


With the

-s <server port>

parameter you tell the program on which port the CASS results are provided to the viewers. See The Viewers for details on how to use this parameter in the viewer.


-f <path/to/.inifile>

parameter lets you choose which .ini file to use. Please see How to set up the .ini file for details of the contents of the .ini file. If this parameter is not set CASS will by default load CASS.ini that resides in the UserScope path. On Unix or Mac OS X this is $HOME/.config or $HOME/Settings ie.


A typical program start command looks like this:

./cass_online -p 0_1_cass_AMO -c 0 -f "inifilename"

For your convenience the most recent CASS binary compiled by an expert is located here:


In this location you will also find some convenient startup scripts, as well as binaries of older versions of CASS.

To end the program you should use:

crtl + \

Killing the program with crtl + c had the potential to consume communication buffers for the interface to the shared memory communication with LCLS. This should be under control but be advised that one might use up all the available buffer, such that one has to restart the shared memory server in order to be able to retrieve live data again.

Using the offline version

The offline version of CASS will process the data files that are provided to one of the offline input modules of CASS. All files that need to be processed need to be put into a text file. Then provide the name of the text file to CASS with the

-i <filename containing filenames of xtcfiles to process>


Usually CASS will not quit after it has finishes processing all the files. It will keep all results in memory to be accessible via the viewers. If you would like CASS to quit after it has processed all provided files you have to pass the


parameter to CASS at the program start.

Sometimes you don't want to have the rate displayed, e.g. when you run the program in a batched way on a cluster. You can suppress the output with


Results of Processors can optionally be saved to either a root, cbf or a hdf5 file. One has to enable these options in cass_myconfiq.pri. Please refer to Install instructions for CASS for more details. The filename has to be given in the Processor setup in the ini file.

If you want to quit the program before the file has been fully analyzed but still want to dump everything that has been processed so far to the file you can quit the program with

crtl + \

Using crtl + c will result in immediate stop of the program without the data being written to file.

The Viewers

There are two options to look at the results that are created and filled by CASS, Jocassview and Lucassview. Both viewers need to be told where to find the CASS server and on which port it will listen for requests.


This viewer is based on QWT, a library for scientific widgets that are based on QT.

At LCLS, one can also use the convenient startup script to start the viewer.


This viewer is based on ROOT which was developed by CERN. Please visit for details.

In order to run properly one has to provide a startup script to lucassview'er which is called lucassStartup.C. Apart from the declaration of the appropriate server and port, there are several options such as an automatic update.

All options in the script can also be typed in the root console manually. A template of the startup script is located in the lucassview folder of the repository you have downloaded:


In order to increase the usability of root there are a collection of macros available, which need to be loaded to root.

One of such a collection of macros is available at LCLS and can be found at


How to set up the .ini file

CASS consists of a lot of processing modules that one can put together to process the data as you want it. These modules are called "Processors". For better understanding of this concept, here is a short overview of the program flow:

for each event:

The .ini file exist of basically three parts:

One part that describes how the data is retrieved using the different available input modules, one part that describes all general available CASS parameters, such as the log output and the processing part.

The processing part is the most advanced part. List of Processors gives an overview of all available Processors. The parenthesis refers to the Processor to look up in the parameter list .ini Parameter List to find out which parameters it takes. In this reference you will also find all available parameters that one can give in the .ini file. There are some examples given in Examples as a starting point for your own custom made .ini file.

The special detector Parameters. Currently there are Acqiris-detectors that need such special parameters. The need for the pixel detectors to use these special parameters has been loaded off the more specialized Processors that allow to output results of an analysis into tables. There are Processors that allow manipulation of the table outputs.

The special Acqiris Detector Parameters

If you want to use the Processors that deal with the AcqirisDetectors you need to set up the AcqirisDetectors first. Basically there are two types of Acqiris Detectors:

Where the Delayline detectors are Time of Flight detectors with additional spatial information. Everything that a Time of Flight detector can do, a information. So everything that a Time of Flight detector can do, also a Delayline detector will do, but more. Basically the concept behind these detectors is that a ToF detector has a cass::ACQIRIS::SignalProducer which is called MCP.

The SignalProducer contains a SignalExtractor object that knows where to find the signals in the data and how to extract them from there. The parameter SignalExtractionMethod lets you choose what kind of SignalExtractor should be used to extract the signals from the data. Please refer to the specific SignalExtractor for its available parameters.

Next to an MCP SignalProducer the delay line detector (DLD) has also cass::ACQIRIS::AnodeLayer which contain wireends which themselves are again cass::ACQIRIS::SignalProducer. So one can set up how to extract the produced signals from the wireends as described for the MCP SignalProducer.

To be able to convert or resort the Signals produced by the MCP and the wireends of a DLD to actual hits on the detector the DLD also contains a DetectorAnalyzer object. There are several ways to sort the signals into detector hits. You can choose which one of these methods you want to use with the AnalysisMethod parameter. Please refer to the description of the specific DetectorAnalyzer to see what parameters are available.

Once you have set up the DLD to identify hits, these hits can be assigned to certain particles. There are several ways of identifying which hit belongs to which particle. You can choose which one to use with the ConditionType parameter of the particle to define which method to use. For the other parameters available for a particle please refer to the documentation of cass::ACQIRIS::Particle.

In order to calculate the momenta and energy of the particles each particle contains a CASS cass::ACQIRIS::Spectrometer object. You need to set up this object for each particle individually. The particles momentum will be calculated based upon the parameters you provide. To calculate the momentum, the raw values of the detectorhit are taken and corrected using a cass::ACQIRIS::HitCorrector object. Please refer to the documentation of cass::ACQIRIS::HitCorrector to see which parameters are available.

CASS developer notes

Coding Rules

These are some guidelines for the CASS software development.

Software repository rules

General program layout Information

There are two versions of CASS available, the online and offline version. Both differ in the choice of input modules that one can choose from and how the ringbuffer behaves.

Each version of CASS has two basic parts, an input module and the analyze module. The responsibility of the input module is to fetch the "raw" data from whichever source is available and adapt it to CASS conventions. The data is then put into a cass::CASSEvent.

The purpose of the analysis module is to process the data according to the processing chain that the user provides with the help of the .ini file. There are multiple processing units, where each will analyze one of the data in the CASSEvents.

The linkage between the input threads and the analysis thread is done by cass::RingBuffer. This is a buffer that contains the amount of cass::CASSEvent elements that can be chosen by setting cass::RingBufferSize. It allows to retrieve elements that should be filled with new data and elements whose contents should be analyzed. The difference of the cass::RingBuffer between the online and offline version of CASS is that the online version allows for elements that haven't been processed yet to be filled with new data. The offline version ensures that only elements of the cass::RingBuffer that have been processed by the analysis module can be filled with new data by the input module.

Available input modules in CASS

The input modules will do the following tasks after they have retrieved the data from whichever source that they get the data from:

  1. get fillable (empty) cass::CASSEvent element from cass::RingBuffer
  2. convert retrieved data to cass::CASSEvent data and fill them with the data.
  3. put cass::CASSEvent back into cass::RingBuffer

Offline input modules of CASS

The following input modules are available in the offline version:

General File input

The input part that will read the data from one of the supported binary or ASCII file types is handled by the class cass::FileInput. This just parses the input file containing the file names to analyze, put them into string list and then goes through that list. Please refer to cass::FileInput for all options that this input module provides.

This input can read data files within the following file types:

Multi-File input

The multi-file input allows to combine information that is distributed among several files of the types that the general file input can read. Please refer to cass::MultiFileInput to get an overview of all the parameters the user can choose from.

HDF5 File input

As the HDF5 files are not ordinary binary files where the data is just concatenated and one can parse them by serially reading the contents, a dedicated input module had to be written to read hdf5 files. It is highly recommended that one adds all the data related to the experiment into a single HDF5 file, since it is not currently possible to combine information from other sources with the data read in this input module.

The layout of the data within the HDF5 file should be such, that data from all detectors for one event is bundled into a group. This input module will determine all "root" groups and assumes that each root groups contains all the information for one event. For more details and all available users options, refer to cass::HDF5FileInput

SACLA offline input

At SACLA the data is not stored in files, but in a database. One can use one of their tools to retrieve the data and let it be written into the HDF5 file or one can use a provided API to access all data. This input modules makes use of the provided API and allows the user to access the data directly, hence speeding up the offline analysis chain. One has to provide this input with all data that one is interested in. For details please refer to cass::SACLAOfflineInput and cass::SACLAConverter, where the latter will provide information about how to extract the user requested data.

Online input modules of CASS

The following input modules are available in the online version:

LCLS shared memory input

This input module will read the xtc like data from the LCLS shared memory. The corresponding class is cass::SharedMemoryInput. It derives from the Pds::XtcMonitorClient class provided by LCLS. This class will do all the communication between the shared memory and CASS. Once new data is available it will call the overwritten cass::SharedMemoryInput::processDgram() member, where all the necessary steps for an input module will be performed. Parsing of the xtc like data will be done with the same class that also parses the data in offline mode cass::FormatConverter. For further details please refer to the documentation of this class.

General TCP input

This class connects to a tcp server on port 9090. It will then retrieve data from this server and parse it. The data packets need to have the following layout: The first 32 bits should contain the size of the following data packet. The following data packet then needs to be deserialized according to the rules of the program that serves the data. Please refer to cass::TCPInput for more details and user choosable parameters.

Two types of data sources are currently supported:

SACLA online input

At SACLA a specialized API is provided that allows access to the live detector data. This means that as the data is acquired it is also provided to the user via the API. Other data, that is typically stored in the database, is made available via the offline API, which is quite slow, thus it is currently not recommended to retrieve additional data about the experiment. However, it is possible to do so using this input module of CASS. One can retrieve the latest data, within which it is described what event id the latest data has. Using the event id, all additional information about the experiment is retrieved. Please refer to cass::SACLAOnlineInput for all user parameters and details.

Analysis part of CASS

The analysis part is done by multiple threads. One can set the number of analysis threads by modifying the cass::NbrOfWorkers variable. Each analysis thread is a cass::Worker object, which are handled by the cass::Workers singleton. Each one of the cass::Worker objects will do the following until it is told to quit:

  1. Retrieve an analyzable cass::CASSEvent element from cass::RingBuffer
  2. Analyze the cass::CASSEvent element using the user set analysis chain build by individual cass::Processors.
  3. Put the event back to the Ringbuffer to be refilled again.

For further details on how to select what Processors should run please see section How to set up the .ini file .

Communicating with CASS

CASS is using SOAP to communicate with the viewers. The class that handles these communication is cass::SoapServer. There are several commands that are understood by the CASS implementation of the server:

The Processors

All Processors are managed by the cass::ProcessorManager singleton. This manager will parse the ini file and set up the requested Processors and put them in an internal list. Once all requested Processors have been created they will be ordered correctly such that all dependencies will be processed before the Processors that require the information from the Processors they depend upon.

When processing the events the event data contained in cass::CASSEvent will be passed to the individual Processors in that order. After the event has been passed to all Processors by the manager, the manager instructs all Processors that the event with the given id can be released and can be overwritten by the result of a different event.

Each regular Processor stores a list of pointers to results to cache the events it has processed so far. The list is implemented by cass::CachedList. This is to ensure that each event is only evaluated once. It allows for a client that uses the TCP-server to visualize the result of an evaluation to pull results of events that already have been analyzed a while ago.

When told to process an event a regular Processor will check if the condition for the requested event is true. If this is the case it will get a new event from the internal list and lock the contents for writing. It will then call the cass::Processor::process function that should have been overwritten by the individual Processor type. Once the event is fully analyzed by the Processor, the result will be marked as the latest event into the list. It will be also be locked until the analysis chain has completed processing this event. When all Processors have analyzed the event, the result in the list unlocked and can thus be overwritten with the outcome of another event.

Some of the Processors do not have a separate result for each event, i.e. the summing up and averaging Processors. These types of Processors are based upon the cass::AccumulatingProcessor base class. Unlike the regular Processors, this only holds one result. Thus when told to process an event it will also check if the condition is true and if so it will lock the single result for writing before calling the overwritten cass::Processor::process member of the cass::Processor base class of this accumulating Processor class.

Adding new functionality to CASS

How to add a new Processor

A new "normal" Processor needs to inherit from cass::Processor. The most important functions that need to be overwritten are:

cass::Processor::loadSettings() and cass::Processor::process().

In cass::Processor::loadSettings() you need to load all user information, setup the dependencies you are relying on, and most importantly, the result. With cass::Processor::setupCondition() you set up that your Processor has a condition.

cass::Processor::setupGeneral() will setup all the default parameters that are available for Processors. Optionally you can use the function member cass::Processor::setupDependency() to set up the dependencies that it relies on.

To initialize the list of cached results you need to call the cass::Processor::createHistList() member. This member needs to have a shared pointer to the result that will work as a template to generate the cached list of the results.

Most Processors rely on the fact that a results shape or size will not be changed during the processing step. (An exception to this rule are the table like Processors.) Therefore one needs to ensure that the result will have the right size or shape during the load settings step.

The result is write locked before calling the cass::Processor::process() function. There is no need to lock it again in definition of your Processor. However the result of the Processor you depend on is not locked. Therefore one needs to readlock it before trying to read contents from it to ensure its contents are not changed during the time one reads them. It is recommended to use the locker facility that Qt provides, e.g.:

// retrieve the result for this event from the dependency (_input)
const result_t& input(_input->result(;

// lock the result for read access
QReadLocker lock(&(input.lock));

When you are done coding your Processor you need to make it available to the user. To do this you need to complete the following steps:

Please document what your processor does so that other people can understand its function. When documenting please use doxygen style since your documentation will then be available on the Web server. Documenting the parameters in cass.ini can be done using the custom doxygen tag cassttng.

How to add a new LCLS Converter

Your converter has to inherit from cass::ConversionBackend and it should be a singleton. This means that it should have a static member function called instance that will return a cass::ConversionBackend::converterPtr_t object that contains the singleton pointer.

In the constructor of the class you need to fill the cass::ConversionBackend::_pdsTypeList with the type id's from the LCLS that you want the converter to react on.

You need to overwrite cass::ConversionBackend::operator()() with the code that extracts the desired data from the datagram and put it into the cass::CASSEvent. Once you have set up your converter, you need to modify cass::ConversionBackend::instance() and add an else-if-statement that returns converter. Please document in cass/format_converter.h which string will return your the singleton of your converter.

Update the LCLS library

The LCLS library is needed if one wants to parse the xtc files or the xtc file stream. This library get updated very often by LCLS. Historically this library was provided as a regular shared or static library that was generated from c++ source code.

Updating it was just a matter of finding out which files have been changed and then copy them into the local copy of the LCLS library. Unfortunately in the beginning of 2013 a decision was made to provide the library in a metalanguage that allows exporting it to different computer languages. The c++ version of parts of the library is completely different to what was used before and it would require extensive effort to rewrite CASS to work with this new implementation. Luckily however, if one wants to only update the already existing parts, it can be done fairly easy, as the whole xtc part of the library has not been converted to the new metalanguage.

Find out which files have changed

The LCLS library is kept within a svn repository. One can get the latest version of the library as described here Once one has a checkout version of the library one can see whether there have been any changes by doing run the svn up command.

How to update the files

Typically files that have changed in the xtc sub directory can just be copied. The same is true for the XtcMonitorClient/Server/Msg files. The tricky part is the BLD. Here one has to update the file


by comparing the contents with the contents of


In the latter everything is implemented completely in the header, so one has to extract the essentials of a new class from this file and add it to the files in the LCLS library.

How to add a feature to cass using git

The master branch should be linear, to be able to create a changelog from the commit history at some point. Optimally all feature branches should be rebased to a few single commits that would explain in the changelog what was done. For now we just keep merging every commit to the master branch.

On your local repository ensure that everything is up to date:

git pull origin

Make sure that the feature branch and the master branch are up to date. One might have to checkout both branches and then redo the pull command. Make sure that branch can be fast forward merged into master by rebasing it to master.

git checkout %feature branch name%
git rebase master (only if cannot be fast forwarded)

Now merge the feature branch into master

git checkout master
git merge %feature branch name%

Give the new master branch head a new annotated tag following the Tagging rules

git tag -a major.minor.bugfix -m”version major.minor.bugfix”

Push the tags to the repository server before pushing the changes in master. Otherwise the tag number will not appear in the automatically generated documentation.

git push origin --tags
git push origin

The last command might take a while, because when the master branch has changed a hook script will automatically create the new documentation and the new binaries.

Then remove the feature branch from all the repositories (locals and remote)

git push origin --delete %feature branch name%
git branch -D %feature branch name%

Make sure that you update the other repositories that you might work on in different places by doing a git pull (–rebase) git remote prune origin


The tags should follow the versioning scheme


^ ^ ^
| | |
| | +--- Build number
| +----- Minor version number
+------- Major version number

Try to use the RubyGems Rational Versioning policy in which:

When releasing a version (pushing a commit in the master branch to the repository) you need to give a tag according to the version number described above first.


Lutz Foucar

Nicola Coppola

Uwe Hoppe

Stephan Kassemeyer

Nils Kimmel

Jochen Küpper

Mirko Scholz

Thomas White


CASS is developed under the terms of the GNU General Public License, version 3 as of 29 June 2007. See LICENCE for details.

If you use this software for publishable work, please cite and acknowledge the authors and the CASS collaboration in your publication. The paper describing CASS is published in 'Computer Physics Communication'. Please cite it as:

Lutz Foucar; Barty, A.; Coppola, N.; Hartmann, R.; Holl, P.; Hoppe, U.; Kassemeyer, S.; Kimmel, N.; Küpper, J.; Scholz, M.; Techert, S.; White, T. A.; Strüder, L. & Ullrich, J CASS—CFEL-ASG software suite Computer Physics Communications, 2012, 183, 2207 - 2213