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EuroSim FAQs


This FAQ lists common and not-so-common questions which have been raised by existing users. The intention is not to replace or duplicate the User Manual, but to give information about topics which do not fit neatly into the manual for whatever reason.

References to the SUM and OM (EuroSim Software User Manual and Owner's Manual) refer to the latest issues. As well as a hardcopy, you should have installed versions accessible with a Web Browser via $EFOROOT/doc/html/index.html

The FAQs list will be updated regularly, and your suggestions and contributions are welcome! Please send the information to EuroSim Product Support.


  • IRIX as a realtime operating system?
  • Accessing part of a model?
  • An entrypoint with args?
  • Calling functions from mdl?
  • Cannot close PVWAVE window?
  • Cannot open temporary format file?
  • Cannot use python interface on debian?
  • Changing monitor frequency?
  • Changing recorder frequency?
  • Command line building a simulator?
  • Compiler warnings?
  • Condensed vs uncondensed API references?
  • Configuring simulation models?
  • Could not connect?
  • Display settings?
  • EfoList and others not found under Debian?
  • Executing entrypoints from mdl?
  • Ext interrupt handling?
  • Ext sim and debugging?
  • Forking a process?
  • Getting started fast?
  • Hard realtime error in action mgr?
  • Hardware interfaces?
  • Initialising an array?
  • Message repeated x times?
  • Mixed language interface?
  • Nfs and running simulators?
  • No debug information?
  • No suitable servers?
  • No tm tc data received?
  • Reading an init datafile?
  • Reproducibility of a simulation?
  • Samba and running simulators under Windows?
  • Saving and reusing the state vector?
  • Scheduling model?
  • Selecting source editor?
  • Setting file versions?
  • Sharing global variables?
  • Simulation results and disconnecting?
  • Simulation results output directory?
  • Simulator environment?
  • Substitute software by hardware?
  • System calls and async tasks?
  • Typedefs with unnamed field?
  • Use of bitfields?
  • Use of long double type?
  • Use of malloc?
  • Use of pointers?
  • Using events to control recording?
  • Using external datafile as a stimulus?
  • Versioning of binary files?
  • What happened to ei input connector?
  • Which EuroSim version?

    Questions with Answers

    FAQ: IRIX as a realtime operating system?

     How is the real-time performance achieved with IRIX, a Unix OS? 
    As Unix is not preemptable in general, what is the latency time 
    for activation of a process after an interrupt?
    In order to provide a real-time environment, EuroSim uses the SGI IRIX 
    real-time REACT extensions. Because the implementation of POSIX threads
    is in general not sufficient to meet the real-time requirements 
    imposed by simulators based on EuroSim, EuroSim has a proprietary thread 
    implementation that provides a more efficient response. 
    (See also Scheduling model?.)
    The system requirements state that a task should be activated within 0.2
    msec wall-clock time from a hardware interrupt occurring, and within 
    20 msec wall-clock time from an event being raised from model code.

    FAQ: Accessing part of a model?

    I have a large model: is there an easy way to home in on
    a particular section without having to either a) "show all" 
    which can become a bit "crowded"  or b) double-click my way down the 
    required branch which is tedious?
    Try the ModelEditor's Edit | Find Nodes... menu option. You can keep
    repeating the find by clicking the "Find" button again.
    PS. When viewing the API in the Simulation Controller or Schedule Editor
    You can click on it (to give it focus) and then just type the name of the
    part you are interested in.

    FAQ: An entrypoint with args?

    I want to schedule a procedure which has arguments, but
    I can't make an entrypoint from it. 
    When the ApiEditor scans your source code, only those
    procedures which have no return values and no arguments will
    appear in the "list" of those potentially available as
    entrypoints.  The trick to make them accessible is to make a 
    small wrapper that maps those arguments and the return value 
    onto API variables, and allows you to create a void proc(void)
    For example:
    Suppose you have a sub-model A, providing a function TeleCommand:
    	file A.c:
    	int TeleCommand(int a, int b, float c) {
            	blah blah
    This function is not directly schedulable as it does not meet the
    API requirements for entrypoints. But an API compliant wrapper 
    (mainTeleCommand) can be provided in file A.c as follows:
    	file A.c:
    	int TeleCommand(int a, int b, float c) {
            	blah blah
    	static int a;
    	static int b;
    	static float c;
    	static int rTC;
    	void mainTeleCommand(void) {
    	        rTC = TeleCommand(a, b, c);
    This file can then be "APIfied"  so that a, b, c, rTC and 
    mainTeleCommand appear as API variables and an entrypoint 
    respectively in the data dictionary.  This allows the entrypoint 
    to be scheduled, and the values for the arguments to be set via 
    MDL actions or from within the code still.
    The same principle can also be applied to 
    Calling functions from mdl?.

    FAQ: Calling functions from mdl?

    Is it true that I can call model tasks and functions directly
    from MDL?
     Yes, the following examples show how to use the "exec" mdl 
    command in the <Action to be executed:> section of a script
    action definition:
       # Example 1
       # execute a schedule task directly
       exec "task:startApproach"
       # Example 2
       # execute an entrypoint directly
       exec "entry:resetOBSW"
    (See also Executing entrypoints from mdl?.)
    If the procedure that you wish to execute has arguments, then make
    a wrapper for it as described in An entrypoint with args?. Then
    the usual approach is to provide the "arguments" via the appropriate
    API values, followed by a call to the entrypoint, as shown here
    using the example described in An entrypoint with args?:
       # Example 3
       # set TC parameters
       :software:A.c:mainTeleCommand:a = 10
       :software:A.c:mainTeleCommand:b = 20
       :software:A.c:mainTeleCommand:c = 3.14
       # call the function (which uses these values)
       exec "entry:mainTeleCommand"
       # print TC result to log
       print "mdlTC=", :software:A.c:mainTeleCommand:rTC

    FAQ: Cannot close PVWAVE window?

     I can't close the plot windows opened by the PV-WAVE plot backend.
     This is a PV-WAVE "feature". You cannot close PV-WAVE plot windows
    using the methods provided by your favourite window manager. The only way
    to close these windows is by selecting the corresponding plot icon in the
    Test Analyzer and selecting 'Plot | Close Plot(s)...'.

    FAQ: Cannot open temporary format file?

    When I try to build my model I get an error message:
       'Fatal error: Can't open temporary formatfile'
       What is going wrong?
    The current version (Mk3-rev1) of the language parse utilities of
    EuroSim for Windows create a temp file in the root directory of
    the current drive. If you do not have sufficient (write) priviliges,
    then you get this error message. Future versions of the utilities
    will use the TEMP environment variable.

    FAQ: Cannot use python interface on debian?

    An error is reported when using the EuroSim python interface on Debian 3.1
    This is a problem in the Python module that is shipped with the Debian 3.1 release.
    See also
    Revision 1.9 of pystrbase.swg contains the fix.
    You can manually fix it or simply install a more recent Python package.

    FAQ: Changing monitor frequency?

    Can I change the frequency of the data monitors?
    The monitoring frequency is fixed at 2Hz, which is adequate for
    the on-line displays.  If you require a higher sampling rate, then
    the data should be recorded to file (tip: recorder files can be added on
    the "Script Monitors" tabpage in the Simulation Controller).

    FAQ: Changing recorder frequency?

    Changing the frequency of a recorder leads to loss of data?
    When changing the frequency of recorder actions the recorder starts
    recording data from scratch. This means that all previously recorded
    data is lost. This is caused by the way EuroSim processes changes in
    actions. The old action is deleted first and then added back again with
    the new frequency. This means that the new action will open a new
    recorder file overwriting the old one.

    FAQ: Command line building a simulator?

    How can I build a simulator from the command line ?
    Is there a Makefile example ?
    You can build a simulator from the command line by
    calling the EuroSim build commands directly from a
    makefile. The following example shows typical make production
    rules for this:
    # first set the name of your model:
    all: $(MODEL).make
    	$(MAKE) -f $(MODEL).make all
    # Generate a EuroSim makefile $(MODEL).mk from model:
    $(MODEL).make: $(MODEL).model
    	ModelMake $< $@
    	$(MAKE) -f $(MODEL).make clean
    	$(RM) $(MODEL).make
    	$(RM) -r 200?-* core
    # purify targets
    pure: $(MODEL).exe
    	purify $? && mv $?.pure $?

    FAQ: Compiler warnings?

    How can I set compiler flags?
    Any user specific compiler flags can be set in the compile options
    section of the ModelEditor's "Tools | Set Build Options..." form.
    Tip: try using '-xansi -fullwarn' flags in the ANSI-C field in
    order to be SGI extended and ANSI-C compliant.  

    FAQ: Condensed vs uncondensed API references?

    What is the difference between condensed and non-condensed view in the Dict 
    Browsers?  Is there any impact of choosing one over the other?
    An API reference can take one of two forms:
    a) non-condensed
       All variables and entrypoints are visible, as is the full structure of the
       model, as created by the Model Editor.  When a variable or entrypoint is
       selected, it will get the full path as its reference.  This consists of the form:
       	/one_or_more_org_nodes/file_node/entrypoint  or 
      	/one_or_more_org_nodes/file_node/entrypoint/var (for vars with proc scope)
      	/one_or_more_org_nodes/file_node/var            (for vars with file scope)
    b) condensed
       Only variables and organisation nodes are visible, so the Test Conductor is
       not overwhelmed with the model, but can concentrate on the vars which the
       Model Editor has made available for him to manipulate.  The variable gets
       a condensed version of the path as its reference, which consists of the
    In most cases, as a TestConductor, you don't need to know the actual source files
    that the API items were derived from, and can simply use the shorter (condensed)
    references for monitoring, to make recordings from, to alter the values of, etc.
    There are two cases however where the non condensed view is the preferred one:
    1. If the Model Developer has tagged two variables in different files which have 
    the same name then the reference in the condensed view is ambiguous.  By switching
    to the non-condensed view you will get a unique reference for that variable.  
    For example:
    non-condensed		        condensed
    /orgNodeA/file1.c/count         /orgNodeA/count
    /orgNodeA/file2.c/count         /orgNodeA/count
    2. If you wish to activate an entrypoint directly from an action, then you
    need to switch to non condensed view in order to see the names of the entrypoints.
    See Executing entrypoints from mdl?.

    FAQ: Configuring simulation models?

    Can you configure the simulation before each run eg. add or 
    remove sub-models? 
     Changes to the content of the model (ie. to its sub-models 
    (= source code files)) require recompilation of the simulator.  
    However if you wish to keep the same executable each time, then 
    there are two ways of achieving this.  Both require that all possible 
    tasks need to be defined in model development (eg. a task triggering 
    a hifi approach sub-model procedure for a rendezvous and docking 
    simulation, and a low fidelity version).
    1. Both versions of the task are scheduled, but then you use the 
    function of enabling/disabling tasks to alter the runtime 
    configuration.  This can be:
    a) done manually during a run (after initialisation, or during actual
       execution using the Simulation Controller's Schedule tabpage and the
       Debug menu)
    b) controlled via an mdl script (an action in the mission), so that 
       the switch occurs when a particular value is reached, eg. when the 
       spacecraft distance from the target is less than a predetermined 
       # Example mdl script
       <Execution Condition:>
       :some:api:spacecraftDistanceFromTarget < 100.0
       <Action to be executed:>
       deactivate "task:<lowfi task name>"
       activate   "task:<hifi  task name>"
       Note: when a task is disabled, all the tasks which are shown in the
       schedule definition as having a dependency on this task (ie. those
       "downstream" of it) will also no longer be scheduled.
    2. Two schedules are produced, one for each situation; either of these 
    can be used with the executable without having to recompile.  So the 
    configuration of a simulation can be altered by selecting a schedule 
    which only schedules the required tasks (sets of sub-model entrypoints).
    You can easily switch schedules in the Simulation controller by selecting the
    schedule file on the "Input Files" tabpage and choosing "File | Select 

    FAQ: Could not connect?

    When I try to execute a simulation, I get a "could not connect 
    to simulator" error message.  What does this mean? 
     It means that the Simulation Controller has not managed to success-
    fully launch the simulation, and/or to connect itself as client to that
    simulation server.  There are several reasons for this, and you need
    to look in the esim-daemon log to see why the connection has failed.
    The log is by default in /var/adm/esimd.log (IRIX),
    /var/log/esimd.log (Linux) or the Application Event Log 
    (Windows: Start | Administrative Tools | Event Viewer).
    If it's not there, then the output can be found by looking for an esimd
    process in the ps listing for that host (or ask your system manager).
    The startup of a simulator with all its parameters is logged in
    /var/adm/SYSLOG (IRIX), /var/log/messages (Linux) or the Application Event
    Log (Windows). Check the arguments for unexpected values (especially path-
    names). If there are shared library problems you will find them here as well.
    The simulator executable may also be low on locked memory. In that case you
    can specify a global value using the EFO_SHAREDMEMSIZE environment variable.
    You can also set a simulator specific value in the ModelEditor using the
    Tools | Set Build Options menu command. The default value is 4194304 bytes.
    If it looks like a privilege problem then see 
    Nfs and running simulators?.  
    If there's a problem with schedule registration, try going back to the Model-
    Editor, and using Tools | Cleanup, followed by rebuilding with Tools | Build All.

    FAQ: Display settings?

    EuroSim consumes the full colormap of my display and doesn't allow to see
    proper colors in the applications launched after it. How can I change the
    number of colors the EuroSim applications are using?
    EuroSim makes use of the Qt library, which supports the following command
    line options when running the X11 version (i.e. Linux or IRIX). You can
    specify them on the command-line when starting EuroSim:
    -visual TrueColor, forces the application to use a TrueColor visual
     on an 8-bit display. 
    -ncols count, limits the number of colors allocated in the color cube
     on an 8-bit display, if the application is using the QApplication::ManyColor
     color specification. If count is 216 then a 6x6x6 color cube is used (i.e. 6
     levels of red, 6 of green, and 6 of blue); for other values, a cube
     approximately proportional to a 2x3x1 cube is used. 
    -cmap, causes the application to install a private color map on an 8-bit display. 
    Other options that may be of use:
    -display display, sets the X display (default is $DISPLAY). 
    -fn or -font font, defines the application font. The font should 
     be specified using an X logical font description. 
    -bg or -background color, sets the default background color and an
     application palette (light and dark shades are calculated). 
    -fg or -foreground color, sets the default foreground color. 
    -btn or -button color, sets the default button color. 
    -name name, sets the application name. 
    -title title, sets the application title (caption). 
    -style= style, sets the application GUI style. Possible values are motif,
     windows, and platinum.

    FAQ: EfoList and others not found under Debian?

    efoList and others not found under Debian?
    This is because efoList and other EuroSim command line
    utilities are installed in /usr/EuroSim/bin, which is not part of the
    PATH environment variable on a Debian distribution by default. This
    is a Debian policy.
    You can find more information on this subject in /usr/share/doc/base-files/FAQ
    on a Debian system.
    There is a simple work-around: start the EuroSim Project Manager with the
    'esim' command. This utility is installed in /usr/bin and sets the proper
    environment variables. If you then start a new shell from the Project Manager
    with the Tools:Shell command, you have an environment that you can use to
    run the EuroSim command line utilities.
    Alternatively you can add the following two lines to the .bashrc file in
    your home directory:
    export EFOROOT=/usr/EuroSim
    export PATH=$EFOROOT/bin:$PATH

    FAQ: Executing entrypoints from mdl?

    How do I activate an entrypoint directly from mdl?
    By using the following mdl command:
    exec "entry:<entrypoint name>"
    The entrypoint name should be just the name of the actual
    procedure (ie. without path information).  So if you drag&drop
    the name from the dictbrowser, you need to remove the path
    information.  The full name drop is provided because it can be 
    useful eg. for including within a print statement in the same
    action which writes the full path to the log for information.
    See also Calling functions from mdl?.

    FAQ: Ext interrupt handling?

    How does EuroSim support interrupt handling when using
    There are several options (assuming of course that your 
    platform supports external interrupts), depending on what
    the interrupts are to be used for:
    - sub-model code can generate output interrupts to a 
      specified SGI output connector, eg. esimEIPulse
    - sub-model code can request a poll for outstanding interrupts 
      on the /dev/ei device and dequeue one if available
    - you can create an external event handler in the Schedule
      Editor. When using the 'default dispatcher', the editor
      will create a corresponding input connector that can be
      picked from the 'Insert' menu or from the toolbar. Note
      that in Mk3 there no longer is a special EI input connector,
      you have to create an external event handler for it.
    - you can install a user defined handler for incoming
      interrupts for a "direct" response, see 'man esimEH(3)'
    - you can use input interrupts as the (external)  realtime
      clock  of  the  scheduler,  instead  of the default itimer
    Refer to esimEH(3) and esimEI(3) manpages for a more complete
    description of the possibilities and limitations.

    FAQ: Ext sim and debugging?

    My external simulator access isn't working correctly.  Are there
    built-in debug facilities that I can use?
    The following debug flags are available:
    To set one or more of these on, then put the following lines
    in a function to be executed during initialisation, 
    eg. for ext_server_debug_flag:
      extern bool ext_server_debug_flag;
    Note that the client/server flags are only relevant in the
    code on the appropriate "side", whilst the others will activate
    debug feedback in both client and server code.

    FAQ: Forking a process?

    Can I fork a process in my model code?
    First the insurance clauses!
    1. We do not support doing system calls from model code; simply because
    there would be no way to guarantee real-time behaviour of the simulator.
    2. The forked process will not run (hard) real-time.
    3. If (sysv; brrr) semaphores are subsequently used from within the hard 
    real-time model code with the forked process, we cannot assure real-time 
    behaviour and prevention of deadlocks.
    Now the good news!  If you're still convinced that you need to fork a 
    process, it can be done in the following way:
    1. Create a task on your schedule canvas containing an 'entry_point' that 
       will do the fork. Add a 'static int beenhere' to that entry point to 
       assure that the fork is only done once.
       [Never ever exit the parent process]
    2. Connect a STATE_ENTRY input connector to a non-realtime task that gets 
       the name of the newly created task. Do this on the 'initialising' state 

    FAQ: Getting started fast?

    EuroSim is now installed - is there a fast way to get something 
    There are several examples in $EFOROOT/src.  The best ones are:
    - Satellite: which is also the one used in the manual, so you have a
    description and a fallback for checking on what you should be seeing;
    - TmTc+ExtSimModel/SpaceStation: this is part of a simulation used to
    demonstrate connection to another simulator, but can also be used as a
    stand-alone EuroSim simulation.  There's no documentation though (mainly
    because it's the model used for the training course, and people are given
    the documentation then).  But basically, it's a simulation of a 2D array of
    cells, each of which has a heater and a sensor, and an OBSW module which
    monitors the sensed temperatures and turns each of the heaters on and off
    according to the setpoints.
    To be able to access eg. Satellite from EuroSim, try the 
    following steps (it's not as bad as it looks! but the description 
    is detailed so that hopefully it'll work the first time....):
    set up a new (personal) project
    $ mkdir  $HOME/simulations
    Now, copy the model of interest to your simulations directory:
    $ cp -r $EFOROOT/src/Satellite $HOME/simulations
    $ chmod -R +w $HOME/simulations
    Start EuroSim:
    $ esim
    - select File | Add Project
      The Add Project dialog box will appear.
    - Fill in the name (e.g. Satellite) and click the Browse button next to the
      directory field.
      Browse to the copied Satellite directory and press OK.
    - Optionally, fill in a project description in the Description field.
    - Click OK.
    - Choose File | Add Model... browse to the model file and click "Open".
    - Add project files: Choose File | Add Files... and the project files you 
    want. You can select multiple files by keeping the CTRL button pressed while
    clicking on the file names. Click "Add" when done.
    start playing with the project
    The name of your newly created project ("SatelliteDemo") should now
    appear in the top left of the Project Manager window.
    Double click the model file and the Model Editor will start. 

    FAQ: Hard realtime error in action mgr?

    My Action Manager task appears to cause a real-time overrun
    during simulation.
    By default, the Action Manager task (an internal EuroSim task
    which coordinates mission execution, recording, etc) is scheduled
    to execute after completion of all the user tasks (ie. the ones
    defined in your schedule).  This means that the Action Manager 
    task gets "blamed" for any overruns occurring within a particular
    timeslot.  The real culprit is likely to be one of the earlier
    user tasks which needed an excessive amount of execution time, but
    which had no (user defined) limit on its allowed execution time.

    FAQ: Hardware interfaces?

    What libraries are available to support hardware-in-the-loop
    Interface libraries are available to support:
    - RS232/422
    - MIL1553
    - TCP/IP
    - external interrupts
    - External Simulator Access (communicate with an external client via TCP/IP)
    See esimSerial(3), esimMil1553(3), esimEI(3), extClient(3) manpages.
    There is one study using CORBA to access a few parts of EuroSim but
    this use is strictly in the off-line model building/version
    control/traceability area. There is no link with the real-time
    domain. The CORBA support is not available in off-the-shelf
    EuroSim. Contact EuroSim Product Support for more information.
    There has also been a study into DIS extensions, the user of which 
    requires an additional VR-Link license.  Again, this support is not 
    available in the off-the-shelf EuroSim, but can be discussed on

    FAQ: Initialising an array?

    How can I initialise an array variable? 
    There are two ways of doing this:
    1.  Use the Simulation Controller :
        In the Simulation Controller, select the initial conditions file on the 
        "Input Files" tabpage. Choose Edit | Properties and you can enter the
        initial conditions. For large arrays, this can be a bit tedious.
        Using this method, the initial condition file needs to
        be set to active ( Edit | Activate ). The values will then be 
        automatically applied at initialisation time.
    2.  using an MDL action script : 
        this gives more freedom, by allowing individual elements of an 
        array to be set or using for-loops to initialise particular 
        rows/columns of the array, and by allowing absolute values to be
        given or allowing a functional definition.  
        Using this method, you must remember to execute the action; this 
        can be done by:
        a) triggering the action manually before starting the run
        b) triggering the action via a command in another action
           (activate "myInitAction")
        c) adding an appropriate condition to allow automatic execution
           (see Example 3 below)
        Examples of possible action scripts are:   
        # Example 1
        # set an individual element to an absolute value
        <Action to be executed:>
        # Example 2
        # set a row of an array, incrementing the value each time
        # and writing the setting to the log
        <Action to be executed:>
        initValue = 10
        i = 0 
        for (i = 0; i < 10; i = i+1) {
             a[1][i] = initValue
             print "a{1][",i,"] initialised to ", initValue
             initValue = initValue + 1
        # Example 3
        # attributes for action to cause it to be automatically
        # executed when initialising state is reached, and then
        # for it to disable itself
        <Action execution options:>
        Initialising should be checked
        <Execution Condition:>
        <Action to be executed:>
        deactivate "<this action's name>"

    FAQ: Message repeated x times?

    I want to know when my procedure has run, but I get a single message
    to the log ("proc X has completed") followed by "last message repeated 
    10 times".
    The log messages are filtered for duplicates, to prevent the log
    being overrun with duplicate error messages for example.  However, the
    implemented mechanism will also filter out "duplicate" messages 
    which are genuinely required, as described above. 
    If the messages are required to be logged individually, the simplest
    way is to add simtime to the message content to ensure that they 
    "differ" and all appear at the Test Controller interface. An example
    of this for use from within model source code is:
    double sim_time = esimGetSimtime();
    esimMessage("powerInit completed: %s", sim_time);
    A similar trick in an MDL action would be to have the following
    at the end of the action script:
    print "myAction completed: ", time()

    FAQ: Mixed language interface?

    The SUM mentions a constraint when using mixed language code (eg.
    F77 calling C or viceversa). Is this only applicable to the part of 
    code that is directly visible to the Eurosim environment or it is
    applicable to the whole code required by a particular model?
    The constraint is a result of compiler conventions not
    EuroSim tools, and therefore is applicable to all of the code within a
    particular model.  For the Irix compilers on SGI platforms, this means that
    Fortran variables can be referenced within C source by appending an
    underscore to the C variable name.  A more detailed example/explanation of
    its use is given in the SUM (section 4.6).

    FAQ: Nfs and running simulators?

    I'm having problems starting a simulation (messages about permission 
    conflicts), but the files seem to have the correct user/group privileges
    set.  Could it have something to do with the fact that the files are in
    an NFS mounted directory?
    Short explanation: yes, it's a strong possibility!
    Longer explanation: if your directory is NFS mounted, and the NFS server
    did not specify the root option to make you root on the host
    which mounts this file system, and the permissions of the file to be 
    read are set to be not world-readable, then the root uid is mapped to 
    nobody which will result in a denied permission situation.
    To confirm, try mimicking the behaviour of the daemon/simulator to
    find out where exactly the permission is denied. So become superuser, 
    go to the daemon's directory ('ps -ef | grep esimd' will show you where
    it's being run from) and try to read the file.

    FAQ: No debug information?

    I can't set breakpoints or traces and I can't enable/disable tasks!
    Were you running in real-time?  Because this feature is only 
    available when running non real-time.

    FAQ: No suitable servers?

    When I try to execute a simulation, I get the message that 
    my current host cannot be used as a server.  And trying to list
    the available servers, I get a similar message that there appear 
    to be no suitable servers.
     It sounds like the EuroSim server (daemon) running on your 
    machine is no longer active and/or your licence key is invalid.
    The licence key sent with your installation is derived from the
    host details sent with your licence application, and will have
    a limited validity period.  If EuroSim is installed on another 
    machine or if the validity period has expired, then the key will 
    be invalid and it will not be possible to use EuroSim.   To 
    obtain a new licence key, send the outputs of your sysinfo(1) 
    and hostname(1) commands to EuroSim Product Support 
    Alternatively, has the daemon process have been stopped for any 
    reason (eg. maintenance activities)?  You should have a process 
    called $EFOROOT/etc/esimd running on your host.  If not, then it 
    just needs to be restarted.  This is described in the 
    OM (section 4.2); you probably just need to check the config flag 
    and start the daemon as described in steps 4 and 6 (you need 
    root permissions for this btw).

    FAQ: No tm tc data received?

    When I run my simulator (server) and client on different hosts,
    there is no exchange of Tm/Tc data. When I run both on the same
    host, it all works as expected.
    This is probably caused by bad time synchronization of the hosts.
    Check with your system administrator that both hosts use a (the
    same) time synchronization mechanism.

    FAQ: Reading an init datafile?

    How can I read in a data file during initialisation, ie. directly
    in model code rather than via an Initial Condition File?
    The following has been successfully been used in a couple of 
    1. In your model code, you need:
       - to define a subroutine to read the file
       - to tag this subroutine as an entrypoint using the API Editor
       - to signal when the routine is complete by raising an event (from 
         the source code) before returning (eg. use esimRaiseEvent("FileRead") 
         (see esim(3) manpage for details of esimRaiseEvent)).
    2. On your scheduling graph for initialisation, you need to make:
       - a connection from an input connector for "STATE_ENTRY" to a 
         non-realtime task containing your entrypoint 
         (ie. use an arrow to join the two symbols)
       - a connection from an input connector named after your raised event 
         (eg. "FileRead") to either other initialisation tasks or (if no 
         more initialisation is necessary) to an output connector named 
    This means that as soon as initialising begins, the file will be read in as
    a result of the subroutine name being called via the appropriate output
    connector.  When the file read is complete, the raised event will trigger
    the remainder of the initialising graph tasks (or can lead to state exit as

    FAQ: Reproducibility of a simulation?

    The SimulationController says that my simulation is NOT reproducible, 
    while the ModelEditor said that it was!  When I ask the SimulationController
    for Versioning: Check Reproducibility, the given reason is that the
    dict was supposedly generated from a temp model, which it wasn't! 
    The reason for this is that the relevant model file is an 
    old version. When you request that a particular version of 
    mine.model is opened, this is (secretly) checked out under a temporary 
    location.  But when you request one of the build operations, then 
    this temporary file is needed in the normal directory for the makefile, 
    etc., so a temporary modelfile ( is created and referenced for 
    all the build requests. And by definition, has a "not_traceable" 
    status which is inherited by all generated files such as the dict.  So the 
    MissionTool infers that the simulation is non reproducible, whereas the
    ModelEditor (which just checks the source files) knows that it is.
    Solution: if you want derived files to have a "reproducible" state then 
    you need to build them from a "permanent" version of that file on disk - 
    ie. after retrieving the required version of the model file, do a File: 
    SaveAs and then build everything.

    FAQ: Samba and running simulators under Windows?

    When starting a simulator on a Samba share (network drive), I get an
    error: "Not able to connect".
    The simulator is started by the EuroSim daemon, which is implemented as a
    'service' under Windows(NT). Because the current implementation (Mk3Rev0) of
    this service is not running as a specific user, it is possible that it
    cannot read the simulator executable because of insufficient privileges.
    This is also true for ordinary shared drives.
    Windows-NT and Windows-2000:
    You may need to contact your system administrator for this: Add
    sufficient (read+write+execute) privileges to the shared drive for user
    'Everyone'. If you do not want to breach security, you better create a new
    directory (tree) and Samba share for your shared EuroSim project. 
    Redirected drives cannot be shared between processes that are running
    under different user accounts.
    More information in Microsoft article #180362:;en-us;180362&sd=tech
    As an alternative you can open a command shell (Cygwin), stop the
    service with the 'net stop esimd' command and then start the service
    as an ordinary application using the '-n' (no daemon) flag, i.e.:
         $EFOROOT/etc/esimd -n
         %EFOROOT%/etc/esimd -n
    when using 'cmd' as command shell.
    Important Note: because of unpredictable network performance, you should
    always try to run your simulator on a local drive (i.e. a fixed disk) and
    avoid running it on a network drive.
    See also Could not connect? and Nfs and running simulators?

    FAQ: Saving and reusing the state vector?

    Can I save the simulation state vector and use it to 
    restart a simulation the next day? 
     Our snapshot facility records all values of variables which
    you have tagged as "API".  This can be reused in two ways:
    1. As an initial condition
    The snapshot can be referenced as the initial condition for a mission, 
    which means that the values in the file are applied to the global 
    API data after the executable has been loaded and the default values 
    applied, but before any tasks scheduled for the initialising state are 
    2. For applying during a simulation
    The snapshot can be applied during a (paused) simulation, in which
    case the values in the file are applied to the global API data, and
    then the simulation can be resumed, with the new values being used.

    FAQ: Scheduling model?

    What sort of scheduling model does EuroSim use?
    EuroSim uses a scheduling model based on threads, with a thread
    being created for each of the processors (EuroSim is intended for a
    multi-processor platform), and with EuroSim tasks being executed "within"
    each of those threads taking the user's scheduling requirements (fixed/free
    processor allocation, task-dependencies, preemptability, priority) into
    See also IRIX as a realtime operating system?.

    FAQ: Selecting source editor?

    How can I edit source code using my favourite editor? 
     Set the EDITOR environment variable to your favourite editor.
    Eg. to set your favourite editor to vim:
    For bash/sh shells:
      export EDITOR=vim
    For tcsh/csh
      setenv EDITOR vim
    You can add these lines to your .bashrc or .cshrc so you don't 
    have to type them each time you start EuroSim.
    Windows specific note
    For Windows platforms you need to provide the short path notation to
    the editor executable (i.e. the one without spaces). You can use the
    'cygpath' utility for this purpose. Say for example your editor is
    located in:
      C:\Program Files\My Editor\edit.exe
    Then you can set the EDITOR environment variable from your .bashrc as
      export EDITOR=`cygpath -w -s "C:\Program Files\My Editor\edit.exe"`
    Alternatively run the cygpath utility from the command line:
      cygpath -w -s "C:\Program Files\My Editor\edit.exe"
    And place the result in the EDITOR environment variable using the
    Windows system properties dialog. You can decide to add the EDITOR
    environment variable as a system-wide variable (i.e. available to
    all users) or as a user specific variable.

    FAQ: Setting file versions?

    I used "Change version requirement..." and set the version for one 
    of my sources files to 1.2, whilst the latest version is 1.3. I expected
    the node label to be "File.c 1.2 (1.3)" but it's actually "File.c 1.2".
     This is correct.  The figure in the brackets indicates the 
    *disk* version and not the latest version; and the selection of an 
    old version has done a silent retrieve.
    See SUM (section 2.7) for more information on version control.

    FAQ: Sharing global variables?

    I'm trying to integrate two sub-models:
       Model A has global_output variable called 'float VAR_A'  and 
       Model B has global_input variable called 'double VAR_B'
    I wish to use Model A VAR_A output as input for Model B VAR_B. 
    Is this possible or do the variables have to have the same type 
    definition and the same name?
    The API only specifies the interface between the sub-models and EuroSim,
    and is not intended to take care actively of sub-model to sub-model
    interfacing: that has to be accomplished by the normal methods which are 
    supported by the programming language.
    There are three possibilities to solve this problem:
    1. use the Model Description and Parameter Exchange editor to 
       copy the output variable VAR_A to input variable VAR_B.
    2. have sub-models A & B share a variable, which has then to be of 
       the same type
    3. make a function that copies VAR_A into VAR_B and does the type

    FAQ: Simulation results and disconnecting?

    What happens to my simulation results when I disconnect and then
    reconnect to the same simulation?
    When a "disconnect" is requested, the journal file is closed and no
    entries are written for the period when the simulation is running
    "in the background".  However, any active recording actions carry on 
    collecting data regardless.
    Where a "reconnect" to the simulation run is requested, the 
    original directory location is re-used for the timings file (written
    when the simulation run is "stopped") and an additional journal
    file.  In order that the original journal file is not overwritten, 
    the file created on a reconnect will get the name EsimJournal_1 
    (or a similar extension if a user defined name has been provided).

    FAQ: Simulation results output directory?

    I don't seem to be able to find (some of) my simulation results?!
    The simulation results consist of the following files:
       - recording data index (*.tr)
       - recording data files (*.rec)
       - scheduling timings file (timings)
       - log of simulation run (EsimJournal)
    By default, these will appear together in a (new) directory having
    a location such as:
    where the date and timestamps are the time at which the simulation
    was initialised.
    If you have overridden the default directory location (possible via 
    the SimulationController: Tools: Configuration window), then this
    will be used instead as the output directory for that and any
    subsequent simulation runs (or until the value is reset to 
    An additional "feature" occurs if the SimulationController client and 
    the simulation server are on different hosts.  Under these
    circumstances, if an output directory is set to eg. "/tmp", then
    the rec files (made by the server) go to <server>/tmp and the 
    journal file (made locally by the client) goes to <client>/tmp. 
    See also Simulation results and disconnecting?.

    FAQ: Simulator environment?

    Which variables are contained in the environment of a running
    The environment variables are the same as the environment variables
    of the testcontroller, with one exception. The PWD variable is updated
    to match the directory where the simulator is running. This directory
    is defined in the project setup and is equal to the project directory.
    The EuroSim tools add also a number of environment variables for their
    own use. These are present as well.

    FAQ: Substitute software by hardware?

    If I want to substitute a software sub-model by a hardware module,
    how do I have to change the interface?
    It depends on the hardware interface, but you will need to replace
    the calls from other sub-models to this software sub-model with interface
    calls to the required hardware-in-the-loop component.
    We provide certain interface calls as standard within EuroSim
    (see Hardware interfaces?).

    FAQ: System calls and async tasks?

    I understand that that some system calls could cause non 
    deterministic real-time behaviour, but can't I use non-blocking
    calls within EuroSim?
    Our experience with system-calls, advertised non-blocking or 
    not, is that they can, but not necessarily will, introduce non 
    deterministic non-predictable timing delays. The moment you give 
    control to the kernel, you might spend a few milliseconds (!) 
    before returning to your model thread. Moreover, if somebody were 
    to do something simple like a 'chdir' syscall, we'd have serious
    So, the message in the SUM  is not to use them. But of course,
    you can always try to have them in the hard real-time loop. It 
    simply is not advised and we cannot guarantee the timings (nor 
    can Silicon Graphics :).
    The workaround that we give to interface hardware and that has 
    also been used successfully in a couple of projects is to put 
    all system calls in an asynchronous task (ie. create a task from
    model entrypoints, but put it on the scheduler canvas as an 
    output connector with that task name, rather than as a round 
    "normal" task.  This means that when the output connector is
    triggered, the task executes in the non real-time domain, and
    therefore does not compromise the real-time performance.
    Summarising, use of syscalls and real-time performance:
    1. No, no guarantee in the real-time loop. So refrain from using 
       them, but you can always try.
    2. Yes, but again no guarantee, if you're using them in asynchronous
       tasks. This is the advised workaround.
    3. Yes, but with guarantee, if you're using drivers that are provided
       by EuroSim, eg. esimSerial, etc (see Hardware interfaces?).
    See also scheduling_an_output_connector.faq

    FAQ: Typedefs with unnamed field?

    I seem to get a merge conflict when using typedefs with unnamed 
    Yes, it is not (yet) possible to have two files with structures 
    with unnamed sub structures, such as the following, because both
    are allocated the same internal fake type name which generates the
    	file 1: typedef struct
     	     { struct
                 	{ long int Command;
                 	} chaser_command
                 } CHASER_InputType;
    	file2: typedef struct
                 { struct
                 	{ long int target_Command;
                 	} target_command;
                 } TARGET_InputType;
    The solution is to make sure that structs are named!

    FAQ: Use of bitfields?

    My structures contain bitfields. Can I use them with EuroSim ?
    Yes, as long as you remember that the ANSI-C standard only supports
    usage of 'int's as field types, and EuroSim will (currently) always show you
    bitfields on container alignment bounderies, implicitly packing bitfields in
    their container.

    FAQ: Use of long double type?

    I'm having problems integrating some code which has data types of 
    'long double' into EuroSim.  Is this type not supported?
     Although 'long long' (and 'signed' and 'unsigned' friends) and 'long double'
    are in Irix 6.x and Linux, these are *not* an ANSI-C supported types,
    and are therefore outside the reqmts for EuroSim.
    The good news is that EuroSim supports 'long long' and that under IRIX 6.x
    the 'long double' type might even work.

    FAQ: Use of malloc?

    Can I use malloc and other such calls in my model code?
    Yes and no!  The direct use of the malloc (and free, calloc, etc) 
    calls are not possible because this could interfere with the real-time
    performance.  However, there are a set of esim library 
    interface calls (eg. esimMalloc), which are callable from model 
    code and which provide the same function but with real-time 
    performance guaranteed.  
    See esim(3) manpage for a full description of these and other calls.

    FAQ: Use of pointers?

    My pointer type has been given a PARAMETER attribute by the 
    ApiEditor, which leads to errors if the source code tries to 
    assign values to this variable pointer.
    Unfortunately, use of pointers is not supported in EuroSim.

    FAQ: Using events to control recording?

    Can I start and stop data recording upon an event generated
    by a model or a hardware interrupt?
    Yes, there are various ways to start and stop data recording.  Here
    are a couple of ideas:
    1. From within model code, the following library call can be used.  An 
       arg of 0 would stop all recording activities.
       void changeRecState(void) {
    	retVal = esimSetRecordingState(1);
       The proc (technically the task its in) can be scheduled at a fixed 
       frequency, in which case the condition for checking when the state 
       needs to change should be included in the body of the proc.  
       Alternatively, the relevant task can be attached to an input connector
       which represents some raised event which triggers the change of 
       recording state. The event can then be raised:
       a) from the model code via esimRaiseEvent("myEvent"); see esim(3) 
       b) from an mdl script via raise("myEvent")
       c) via a hardware interrupt (a predefined "EI" input connector)
       d) via any of the other predefined input connectors (see SUM 
    2. From within an mdl script, there is no direct call for changing
       all recording states (this can be done from the TestController
       menu option Simulation: Suspend Recording).  A more flexible approach 
       is available, where one action checks the condition for (not) recording 
       and sets a flag accordingly, which all or a subset of the recording 
       actions have in their condition.  
       <Action to be executed:>
            # sets all recording on when spacecraft is close
    	int   recordingCheck = 0
            float thisIsClose    = 100.0
    	if  ( :some:api:spacecraftDistanceFromTarget < thisIsClose ) {
     		recordingCheck = 1
            else {
    		recordingCheck = 0
          	freq(100) && CheckAction:recordingCheck
       <Action to be executed:>
     	record  "someFile.rec" :some:API:variable

    FAQ: Using external datafile as a stimulus?

    I have data from a source other than EuroSim, which I wish to reference in a
    stimulus action, in order to feed data values into an API variable.  Do I have 
    to convert the data first?
    Stimulus data files should have the same format as the recording files which
    EuroSim produces.  This means that there should be an (ascii) header block 
    followed by lines of (binary) data, where each line consists of a value for 
    simulation_time followed by one or more data values.  The values for the 
    simulation_time can be used to synchronise the data input with the simulation 
    time ("compare timestamps") or can be dummy values which are ignored ("ignore 
    timestamps").  This concept is explained in more detail in the SUM 
    (section 9.7.3).
    The first step is to ensure that you have an ascii file which has the data in 
    lines of the format: <simulation_time> <varX_value> <varY_value>, where the 
    values can be space or tab separated. It's important that the first value 
    represents the simulation_time, so even where this value is redundant 
    (eg. file is being fed in at a fixed frequency), it's still necessary to 
    provide a (dummy) value.
    The second step is to add a header to the datafile, which has the following 
    # comment line
    Date recorded: (optional)
    Dict: (optional) eg. ../mymodel/dict
    Number of variables: n
    1{var declarations of the form <name: datatype>}n
    An example of a legal header is:
    # my test file
    Date recorded: 27 Aug 1997
    Number of variables: 3
    /simulation_time: double
    /varX: int
    /varY: int
    The final step is to use the utility a2r(1) (ascii => results) to convert the 
    file to binary and fill in the header with additional information such as 
    record size.  If the dict is not referenced, then use the -D flag to stop the
    check against the dict (see a2r(1) manpage for more details on this and other
    The equivalent r2a(1) converts (results => ascii) allows you to view/edit 
    recording files.

    FAQ: Versioning of binary files?

    I have a FrameMaker file for my model description, but after adding 
    a version to it, it became unreadable by Frame. Why?
    Versioning a non-ASCII file, eg. normal Frame format, is not possible.  
    It is possible to put the MIF version of the file under version control.  

    FAQ: What happened to ei input connector?

    What happened to the EI input connector in Mk2 and later?
    Because all external events can now be configured in
    the 'Tools: External Event' menu of the Schedule Editor,
    it was decided to not have an exception for the EI
    (External Interrupt) on SGI. You can simply create
    an external event handler for 'EI' with the appropriate
    path (i.e. /dev/ei) and set the dispatcher type to 'default'.
    The Schedule Editor then automatically adds an external
    input connector with the name of the event handler to the
    'Insert: External event' menu. You can then use this input
    connector just as the 'EI' input connector in Mk1.

    FAQ: Which EuroSim version?

    Which version of EuroSim am I running?
    There are two ways of finding out the current version:
    1. type in "esimversion" at the Unix command prompt
    2. request Help: About EuroSim from any of the EuroSim
       window menus 

    Last update Tue Dec 13 18:39:04 2011
    Updates, questions, comments, corrections: send mail to EuroSim Product Support Dutch Space BV, Leiden, The Netherlands