# 6. OMSimulatorPython

This is a shared library that provides a Python interface for the OMSimulatorLib library.

Installation using `pip` is recommended:

    > pip3 install OMSimulator --upgrade

## 6.1. Examples

    from OMSimulator import OMSimulator

    oms = OMSimulator()
    oms.setTempDirectory("./temp/")
    oms.newModel("model")
    oms.addSystem("model.root", oms.system_sc)

    # instantiate FMUs
    oms.addSubModel("model.root.system1", "FMUs/System1.fmu")
    oms.addSubModel("model.root.system2", "FMUs/System2.fmu")

    # add connections
    oms.addConnection("model.root.system1.y", "model.root.system2.u")
    oms.addConnection("model.root.system2.y", "model.root.system1.u")

    # simulation settings
    oms.setResultFile("model", "results.mat")
    oms.setStopTime("model", 0.1)
    oms.setFixedStepSize("model.root", 1e-4)

    oms.instantiate("model")
    oms.setReal("model.root.system1.x_start", 2.5)

    oms.initialize("model")
    oms.simulate("model")
    oms.terminate("model")
    oms.delete("model")

The python package also provides a more object oriented API. The following example is equivalent to the previous one:

    import OMSimulator as oms

    oms.setTempDirectory('./temp/')
    model = oms.newModel("model")
    root = model.addSystem('root', oms.Types.System.SC)

    # instantiate FMUs
    root.addSubModel('system1', 'FMUs/System1.fmu')
    root.addSubModel('system2', 'FMUs/System2.fmu')

    # add connections
    root.addConnection('system1.y', 'system2.u')
    root.addConnection('system2.y', 'system1.u')

    # simulation settings
    model.resultFile = 'results.mat'
    model.stopTime = 0.1
    model.fixedStepSize = 1e-4

    model.instantiate()
    model.setReal('root.system1.x_start', 2.5)
    #or system.setReal('system1.x_start', 2.5)

    model.initialize()
    model.simulate()
    model.terminate()
    model.delete()

## 6.2. Python Scripting Commands

## 6.3. activateVariant

This API provides support to activate a multi-variant modelling from an ssp file [(e.g). SystemStructure.ssd, VarA.ssd, VarB.ssd ] from a ssp file. By default when importing a ssp file the default variant will be “SystemStructure.ssd”. The users can be able to switch between other variants by using this API and make changes to that particular variant and simulate them.

    status = oms.activateVariant(crefA, crefB)

> An example of activating the number of available variants in a ssp file

> oms_newModel(“model”) oms_addSystem(“model.root”, “system_wc”) oms_addSubModel(“model.root.A”, “A.fmu”) oms_duplicateVariant(“model”, “varA”) // varA will be the current variant oms_duplicateVariant(“varA”, “varB”) // varB will be the current variant oms_activateVariant(“varB”, “varA”) // Reactivate the variant varB to varA oms_activateVariant(“varA”, “model”) // Reactivate the variant varA to model

## 6.4. addBus

Adds a bus to a given component.

    status = oms.addBus(cref)

## 6.5. addConnection

Adds a new connection between connectors A and B. The connectors need to be specified as fully qualified component references, e.g., “model.system.component.signal”.

    status = oms.addConnection(crefA, crefB, suppressUnitConversion)

The two arguments crefA and crefB get swapped automatically if necessary. The third argument suppressUnitConversion is optional and the default value is false which allows automatic unit conversion between connections, if set to true then automatic unit conversion will be disabled.

## 6.6. addConnector

Adds a connector to a given component.

    status = oms.addConnector(cref, causality, type)

    The second argument "causality", should be any of the following,

    oms.input
    oms.output
    oms.parameter
    oms.bidir
    oms.undefined

    The third argument "type", should be any of the following,

    oms.signal_type_real
    oms.signal_type_integer
    oms.signal_type_boolean
    oms.signal_type_string
    oms.signal_type_enum
    oms.signal_type_bus

## 6.7. addConnectorToBus

Adds a connector to a bus.

    status = oms.addConnectorToBus(busCref, connectorCref)

## 6.8. addResources

Adds an external resources to an existing SSP. The external resources should be a “.ssv” or “.ssm” file

    status = oms.addResources(cref, path)

    ## Example
    from OMSimulator import OMSimulator
    oms = OMSimulator()
    oms.importFile("addExternalResources1.ssp")
    ## add list of external resources from filesystem to ssp
    oms.addResources("addExternalResources", "../../resources/externalRoot.ssv")
    oms.addResources("addExternalResources:externalSystem.ssv", "../../resources/externalSystem1.ssv")
    oms.addResources("addExternalResources", "../../resources/externalGain.ssv")
    ## export the ssp with new resources
    oms_export("addExternalResources", "addExternalResources1.ssp")

## 6.9. addSignalsToResults

Add all variables that match the given regex to the result file.

    status = oms.addSignalsToResults(cref, regex)

The second argument, i.e. regex, is considered as a regular expression (C++11). “.*” and “(.)*” can be used to hit all variables.

## 6.10. addSubModel

Adds a component to a system.

    status = oms.addSubModel(cref, fmuPath)

## 6.11. addSystem

Adds a (sub-)system to a model or system.

    status = oms.addSystem(cref, type)

## 6.12. compareSimulationResults

This function compares a given signal of two result files within absolute and relative tolerances.

    oms.compareSimulationResults(filenameA, filenameB, var, relTol, absTol)

The following table describes the input values:

Input | Type | Description
--- | --- | ---
filenameA | String | Name of first result file to compare.
filenameB | String | Name of second result file to compare.
var | String | Name of signal to compare.
relTol | Number | Relative tolerance.
absTol | Number | Absolute tolerance.

The following table describes the return values:

Type | Description
--- | ---
Integer | 1 if the signal is considered as equal, 0 otherwise

## 6.13. copySystem

Copies a system.

    status = oms.copySystem(source, target)

## 6.14. delete

Deletes a connector, component, system, or model object.

    status = oms.delete(cref)

## 6.15. deleteConnection

Deletes the connection between connectors crefA and crefB.

    status = oms.deleteConnection(crefA, crefB)

The two arguments crefA and crefB get swapped automatically if necessary.

## 6.16. deleteConnectorFromBus

Deletes a connector from a given bus.

    status = oms.deleteConnectorFromBus(busCref, connectorCref)

## 6.17. deleteResources

Deletes the reference and resource file in a SSP. Deletion of “.ssv” and “.ssm” files are currently supported. The API can be used in two ways.

1. deleting only the reference file in “.ssd”.

2. deleting both reference and resource files in “.ssp”.

To delete only the reference file in ssd, the user should provide the full qualified cref of the “.ssv” file associated with a system or subsystem or component (e.g) “model.root:root1.ssv”.

To delete both the reference and resource file in ssp, it is enough to provide only the model cref of the “.ssv” file (e.g) “model:root1.ssv”.

When deleting only the references of a “.ssv” file, if a parameter mapping file “.ssm” is binded to a “.ssv” file then the “.ssm” file will also be deleted. It is not possible to delete the references of “.ssm” seperately as the ssm file is binded to a ssv file.

The filename of the reference or resource file is provided by the users using colon suffix at the end of cref. (e.g) “:root.ssv”

    status = oms.deleteResources(cref))

    ## Example
    from OMSimulator import OMSimulator
    oms = OMSimulator()
    oms.importFile("deleteResources1.ssp")
    ## delete only the references in ".ssd" file
    oms.deleteResources("deleteResources.root:root.ssv")
    ## delete both references and resources
    oms.deleteResources("deleteResources:root.ssv")
    oms.export("deleteResources1.ssp")

## 6.18. doStep

Simulates a macro step of the given composite model. The step size will be determined by the master algorithm and is limited by the definied minimal and maximal step sizes.

    status = oms.doStep(cref)

## 6.19. duplicateVariant

This API provides support to develop a multi-variant modelling in OMSimulator [(e.g). SystemStructure.ssd, VarA.ssd, VarB.ssd ]. When duplicating a variant, the new variant becomes the current variant and all the changes made by the users are applied to the new variants only, and all the ssv and ssm resources associated with the new variant will be given new name based on the variant name provided by the user. This allows the bundling of multiple variants of a system structure definition referencing a similar set of packaged resources as a single SSP. However there must still be one SSD file named SystemStructure.ssd at the root of the ZIP archive which will be considered as default variant.

    status = oms.duplicateVariant(crefA, crefB)

An example of creating a multi-variant modelling is presented below

    oms_newModel("model")
    oms_addSystem("model.root", "system_wc")
    oms_addSubModel("model.root.A", "A.fmu")
    oms_setReal("model.root.A.param1", "10")
    oms_duplicateVariant("model", "varB")
    oms_addSubModel("varB.root.B" ,"B.fmu")
    oms_setReal("varB.root.A.param2", "20")
    oms_export("varB", "variant.ssp")

The variant.ssp file will have the following structure

    Variant.ssp
        SystemStructure.ssd
        varB.ssd
        resources\
            A.fmu
            B.fmu

## 6.20. export

Exports a composite model to a SPP file.

    status = oms.export(cref, filename)

## 6.21. exportDependencyGraphs

Export the dependency graphs of a given model to dot files.

    status = oms.exportDependencyGraphs(cref, initialization, event, simulation)

## 6.22. exportSSMTemplate

Exports all signals that have start values of one or multiple FMUs to a SSM file that are read from modelDescription.xml with a mapping entry. The mapping entry specifies a single mapping between a parameter in the source and a parameter of the system or component being parameterized. The mapping entry contains two attributes namely source and target. The source attribute will be empty and needs to be manually mapped by the users associated with the parameter name defined in the SSV file, the target contains the name of parameter in the system or component to be parameterized. The function can be called for a top level model or a certain FMU component. If called for a top level model, start values of all FMUs are exported to the SSM file. If called for a component, start values of just this FMU are exported to the SSM file.

    status = oms.exportSSMTemplate(cref, filename)

## 6.23. exportSSVTemplate

Exports all signals that have start values of one or multiple FMUs to a SSV file that are read from modelDescription.xml. The function can be called for a top level model or a certain FMU component. If called for a top level model, start values of all FMUs are exported to the SSV file. If called for a component, start values of just this FMU are exported to the SSV file.

    status = oms.exportSSVTemplate(cref, filename)

## 6.24. exportSnapshot

Lists the SSD representation of a given model, system, or component.

Memory is allocated for contents. The caller is responsible to free it using the C-API. The Lua and Python bindings take care of the memory and the caller doesn’t need to call free.

    contents, status = oms.exportSnapshot(cref)

## 6.25. freeMemory

Free the memory allocated by some other API. Pass the object for which memory is allocated.

    oms.freeMemory(obj)

## 6.26. getBoolean

Get boolean value of given signal.

    value, status = oms.getBoolean(cref)

## 6.27. getDirectionalDerivative

This function computes the directional derivatives of an FMU.

    value, status = oms.getDirectionalDerivative(cref)

## 6.28. getFixedStepSize

Gets the fixed step size. Can be used for the communication step size of co-simulation systems and also for the integrator step size in model exchange systems.

    stepSize, status = oms.getFixedStepSize(cref)

## 6.29. getInteger

Get integer value of given signal.

    value, status = oms.getInteger(cref)

## 6.30. getReal

Get real value.

    value, status = oms.getReal(cref)

## 6.31. getResultFile

Gets the result filename and buffer size of the given model cref.

    filename, bufferSize, status = oms.getResultFile(cref)

## 6.32. getSolver

Gets the selected solver method of the given system.

    solver, status = oms.getSolver(cref)

## 6.33. getStartTime

Get the start time from the model.

    startTime, status = oms.getStartTime(cref)

## 6.34. getStopTime

Get the stop time from the model.

    stopTime, status = oms.getStopTime(cref)

## 6.35. getString

Get string value.

Memory is allocated for value. The caller is responsible to free it using the C-API. The Lua and Python bindings take care of the memory and the caller doesn’t need to call free.

    value, status = oms.getString(cref)

## 6.36. getSubModelPath

Returns the path of a given component.

    path, status = oms.getSubModelPath(cref)

## 6.37. getSystemType

Gets the type of the given system.

    type, status = oms.getSystemType(cref)

## 6.38. getTime

Get the current simulation time from the model.

    time, status = oms.getTime(cref)

## 6.39. getTolerance

Gets the tolerance of a given system or component.

    relativeTolerance, status = oms.getTolerance(cref)

## 6.40. getVariableStepSize

Gets the step size parameters.

    initialStepSize, minimumStepSize, maximumStepSize, status = oms.getVariableStepSize(cref)

## 6.41. getVersion

Returns the library’s version string.

    oms = OMSimulator()
    oms.getVersion()

## 6.42. importFile

Imports a composite model from a SSP file.

    cref, status = oms.importFile(filename)

## 6.43. importSnapshot

Loads a snapshot to restore a previous model state. The model must be in virgin model state, which means it must not be instantiated.

    newCref, status = oms.importSnapshot(cref, snapshot)

## 6.44. initialize

Initializes a composite model.

    status = oms.initialize(cref)

## 6.45. instantiate

Instantiates a given composite model.

    status = oms.instantiate(cref)

## 6.46. list

Lists the SSD representation of a given model, system, or component.

Memory is allocated for contents. The caller is responsible to free it using the C-API. The Lua and Python bindings take care of the memory and the caller doesn’t need to call free.

    contents, status = oms.list(cref)

## 6.47. listUnconnectedConnectors

Lists all unconnected connectors of a given system.

Memory is allocated for contents. The caller is responsible to free it using the C-API. The Lua and Python bindings take care of the memory and the caller doesn’t need to call free.

    contents, status = oms.listUnconnectedConnectors(cref)

## 6.48. listVariants

This API shows the number of variants available [(e.g). SystemStructure.ssd, VarA.ssd, VarB.ssd ] from a ssp file.

    status = oms.listVariants(cref)

An example for finding the number of available variants in a ssp file

    oms_newModel("model")
    oms_addSystem("model.root", "system_wc")
    oms_addSubModel("model.root.A", "A.fmu")
    oms_duplicateVariant("model", "varA")
    oms_duplicateVariant("varA", "varB")

    oms_listVariants("varB")

The API will list the available variants like below

    <oms:Variants>
      <oms:variant name="model" />
      <oms:variant name="varB" />
      <oms:variant name="varA" />
    </oms:Variants>

## 6.49. loadSnapshot

Loads a snapshot to restore a previous model state. The model must be in virgin model state, which means it must not be instantiated.

    newCref, status = oms.loadSnapshot(cref, snapshot)

## 6.50. newModel

Creates a new and yet empty composite model.

    status = oms.newModel(cref)

## 6.51. newResources

Adds a new empty resources to the SSP. The resource file is a “.ssv” file where the parameter values set by the users using “oms_setReal()”, “oms_setInteger()” and “oms_setReal()” are writtern to the file. Currently only “.ssv” files can be created.

The filename of the resource file is provided by the users using colon suffix at the end of cref. (e.g) “:root.ssv”

    status = oms.newResources(cref)

    ## Example
    from OMSimulator import OMSimulator
    oms = OMSimulator()
    oms.newModel("newResources")

    oms.addSystem("newResources.root", oms_system_wc)
    oms.addConnector("newResources.root.Input1", oms.input, oms_signal_type_real)
    oms.addConnector("newResources.root.Input2", oms.input, oms_signal_type_real)

    ## add Top level resources, the filename is provided using the colon suffix ":root.ssv"
    oms.newResources("newResources.root:root.ssv")
    oms.setReal("newResources.root.Input1", 10)
    ## export the ssp with new resources
    oms.export("newResources", "newResources.ssp")

## 6.52. referenceResources

Switches the references of “.ssv” and “.ssm” in a SSP file. Referencing of “.ssv” and “.ssm” files are currently supported. The API can be used in two ways.

1. Referencing only the “.ssv” file.

2. Referencing both the “.ssv” along with the “.ssm” file.

This API should be used in combination with “oms_deleteResources”.To switch with a new reference, the old reference must be deleted first using “oms_deleteResources” and then reference with new resources.

When deleting only the references of a “.ssv” file, if a parameter mapping file “.ssm” is binded to a “.ssv” file, then the reference of “.ssm” file will also be deleted. It is not possible to delete the references of “.ssm” seperately as the ssm file is binded to a ssv file. Hence it is not possible to switch the reference of “.ssm” file alone. So inorder to switch the reference of “.ssm” file, the users need to bind the reference of “.ssm” file along with the “.ssv”.

The filename of the reference or resource file is provided by the users using colon suffix at the end of cref (e.g) “:root.ssv”, and the “.ssm” file is optional and is provided by the user as the second argument to the API.

    status = oms.referenceResources(cref, ssmFile)

    ## Example
    from OMSimulator import OMSimulator
    oms = OMSimulator()
    oms.importFile("referenceResources1.ssp")
    ## delete only the references in ".ssd" file
    oms.deleteResources("referenceResources1.root:root.ssv")
    ## usage-1 switch with new references, only ssv file
    oms.referenceResources("referenceResources1.root:Config1.ssv")
    ## usage-2 switch with new references, both ssv and ssm file
    oms.referenceResources("referenceResources1.root:Config1.ssv", "Config1.ssm")

## 6.53. removeSignalsFromResults

Removes all variables that match the given regex to the result file.

    status = oms.removeSignalsFromResults(cref, regex)

The second argument, i.e. regex, is considered as a regular expression (C++11). “.*” and “(.)*” can be used to hit all variables.

## 6.54. rename

Renames a model, system, or component.

    status = oms.rename(cref, newCref)

## 6.55. replaceSubModel

Replaces an existing fmu component, with a new component provided by the user, When replacing the fmu checks are made in all ssp concepts like in ssd, ssv and ssm, so that connections and parameter settings are not lost. It is possible that the namings of inputs and parameters match, but the start values might have been changed, in such cases new start values will be applied in ssd, ssv and ssm. In case if the Types of inputs and outputs and parameters differed, then the variables are updated according to the new changes and the connections will be removed with warning messages to user. In case when replacing a fmu, if the fmu contains parameter mapping associated with the ssv file, then only the ssm file entries are updated and the start values in the ssv files will not be changed.

    status = oms.replaceSubModel(cref, fmuPath)

> It is possible to import an partially developed fmu (i.e contains only modeldescription.xml without any binaries) in OMSimulator, and later can be replaced with a fully develped fmu. An example to use the API, oms_addSubModel(“model.root.A”, “../resources/replaceA.fmu”) oms_export(“model”, “test.ssp”) oms_import(“test.ssp”) oms_replaceSubModel(“model.root.A”, “../resources/replaceA_extended.fmu”)

## 6.56. reset

Reset the composite model after a simulation run.

The FMUs go into the same state as after instantiation.

    status = oms.reset(cref)

## 6.57. setBoolean

Sets the value of a given boolean signal.

    status = oms.setBoolean(cref, value)

## 6.58. setCommandLineOption

Sets special flags.

    status = oms.setCommandLineOption(cmd)

Available flags:

    info:    Usage: OMSimulator [Options] [Lua script] [FMU] [SSP file]
             Options:
               --addParametersToCSV=<bool>      false              Export parameters to a .csv file
               --algLoopSolver=<arg>            "kinsol"           Specifies the loop solver method (fixedpoint, kinsol) used for algebraic loops spanning multiple components.
               --clearAllOptions                                   Reset all flags to their default values
               --CVODEMaxErrTestFails=<int>     100                Maximum number of error test failures for CVODE
               --CVODEMaxNLSFailures=<int>      100                Maximum number of nonlinear convergence failures for CVODE
               --CVODEMaxNLSIterations=<int>    5                  Maximum number of nonlinear solver iterations for CVODE
               --CVODEMaxSteps=<int>            1000               Maximum number of steps for CVODE
               --deleteTempFiles=<bool>         true               Delete temporary files as soon as they are no longer needed
               --directionalDerivatives=<bool>  true               Use directional derivatives to calculate the Jacobian for algebraic loops
               --dumpAlgLoops=<bool>            false              Dump information for algebraic loops
               --emitEvents=<bool>              true               Emit events during simulation
               --help [-h]                                         Display the help text
               --ignoreInitialUnknowns=<bool>   false              Ignore initial unknowns from the modelDescription.xml
               --initialStepSize=<double>       1e-6               Specify the initial step size
               --inputExtrapolation=<bool>      false              Enable input extrapolation using derivative information
               --intervals=<int> [-i]           500                Specify the number of communication points (arg > 1)
               --logFile=<arg> [-l]             ""                 Specify the log file (stdout is used if no log file is specified)
               --logLevel=<int>                 0                  Set the log level (0: default, 1: debug, 2: debug+trace)
               --master=<arg>                   "ma"               Specify the master algorithm (ma)
               --maxEventIteration=<int>        100                Specify the maximum number of iterations for handling a single event
               --maxLoopIteration=<int>         10                 Specify the maximum number of iterations for solving algebraic loops between system-level components. Internal algebraic loops of components are not affected.
               --minimumStepSize=<double>       1e-12              Specify the minimum step size
               --mode=<arg> [-m]                "me"               Force a certain FMI mode if the FMU provides both cs and me (cs, me)
               --numProcs=<int> [-n]            1                  Specify the maximum number of processors to use (0=auto, 1=default)
               --progressBar=<bool>             false              Show a progress bar for the simulation progress in the terminal
               --realTime=<bool>                false              Enable experimental feature for (soft) real-time co-simulation
               --resultFile=<arg> [-r]          "<default>"        Specify the name of the output result file
               --skipCSVHeader=<bool>           true               Skip exporting the CSV delimiter in the header
               --solver=<arg>                   "cvode"            Specify the integration method (euler, cvode)
               --solverStats=<bool>             false              Add solver stats to the result file, e.g., step size; not supported for all solvers
               --startTime=<double> [-s]        0                  Specify the start time
               --stepSize=<double>              1e-3               Specify the (maximum) step size
               --stopTime=<double> [-t]         1                  Specify the stop time
               --stripRoot=<bool>               false              Remove the root system prefix from all exported signals
               --suppressPath=<bool>            false              Suppress path information in info messages; especially useful for testing
               --tempDir=<arg>                  "."                Specify the temporary directory
               --timeout=<int>                  0                  Specify the maximum allowed time in seconds for running a simulation (0 disables)
               --tolerance=<double>             1e-4               Specify the relative tolerance
               --version [-v]                                      Display version information
               --wallTime=<bool>                false              Add wall time information to the result file
               --workingDir=<arg>               "."                Specify the working directory
               --zeroNominal=<bool>             false              Accept FMUs with invalid nominal values and replace the invalid nominal values with 1.0

## 6.59. setFixedStepSize

Sets the fixed step size. Can be used for the communication step size of co-simulation systems and also for the integrator step size in model exchange systems.

    status = oms.setFixedStepSize(cref, stepSize)

## 6.60. setInteger

Sets the value of a given integer signal.

    status = oms.setInteger(cref, value)

## 6.61. setLogFile

Redirects logging output to file or std streams. The warning/error counters are reset.

filename=”” to redirect to std streams and proper filename to redirect to file.

    status = oms.setLogFile(filename)

## 6.62. setLoggingInterval

Set the logging interval of the simulation.

    status = oms.setLoggingInterval(cref, loggingInterval)

## 6.63. setLoggingLevel

Enables/Disables debug logging (logDebug and logTrace).

0 default, 1 default+debug, 2 default+debug+trace

    oms.setLoggingLevel(logLevel)

## 6.64. setMaxLogFileSize

Sets maximum log file size in MB. If the file exceeds this limit, the logging will continue on stdout.

    oms.setMaxLogFileSize(size)

## 6.65. setReal

Sets the value of a given real signal.

    status = oms.setReal(cref, value)

This function can be called in different model states:

- Before instantiation: setReal can be used to set start values or to define initial unknowns (e.g. parameters, states). The values are not immediately applied to the simulation unit, since it isn’t actually instantiated.

- After instantiation and before initialization: Same as before instantiation, but the values are applied immediately to the simulation unit.

- After initialization: Can be used to force external inputs, which might cause discrete changes of continuous signals.

## 6.66. setRealInputDerivative

Sets the first order derivative of a real input signal.

This can only be used for CS-FMU real input signals.

    status = oms.setRealInputDerivative(cref, value)

## 6.67. setResultFile

Set the result file of the simulation.

    status = oms.setResultFile(cref, filename)
    status = oms.setResultFile(cref, filename, bufferSize)

The creation of a result file is omitted if the filename is an empty string.

## 6.68. setSolver

Sets the solver method for the given system.

    status = oms.setSolver(cref, solver)

solver | Type | Description
--- | --- | ---
oms.solver_sc_explicit_euler | sc-system | Explicit euler with fixed step size
oms.solver_sc_cvode | sc-system | CVODE with adaptive stepsize
oms.solver_wc_ma | wc-system | default master algorithm with fixed step size
oms.solver_wc_mav | wc-system | master algorithm with adaptive stepsize
oms.solver_wc_mav2 | wc-system | master algorithm with adaptive stepsize (double-step)

## 6.69. setStartTime

Set the start time of the simulation.

    status = oms.setStartTime(cref, startTime)

## 6.70. setStopTime

Set the stop time of the simulation.

    status = oms.setStopTime(cref, stopTime)

## 6.71. setString

Sets the value of a given string signal.

    status = oms.setString(cref, value)

## 6.72. setTempDirectory

Set new temp directory.

    status = oms.setTempDirectory(newTempDir)

## 6.73. setTolerance

Sets the tolerance for a given model or system.

    status = oms.setTolerance(const char* cref,  double relativeTolerance)

Default values are 1e-4 for both relative and absolute tolerances.

A tolerance specified for a model is automatically applied to its root system, i.e. both calls do exactly the same:

    oms_setTolerance("model", relativeTolerance);
    oms_setTolerance("model.root", relativeTolerance);

Component, e.g. FMUs, pick up the tolerances from there system. That means it is not possible to define different tolerances for FMUs in the same system right now.

In a strongly coupled system (oms_system_sc), the relative tolerance is used for CVODE and the absolute tolerance is used to solve algebraic loops.

In a weakly coupled system (oms_system_wc), both the relative and absolute tolerances are used for the adaptive step master algorithms and the absolute tolerance is used to solve algebraic loops.

## 6.74. setUnit

Sets the unit of a given signal.

    status = oms.setUnit(cref, value)

## 6.75. setVariableStepSize

Sets the step size parameters for methods with stepsize control.

    status = oms.getVariableStepSize(cref, initialStepSize, minimumStepSize, maximumStepSize)

## 6.76. setWorkingDirectory

Set a new working directory.

    status = oms.setWorkingDirectory(newWorkingDir)

## 6.77. simulate

Simulates a composite model.

    status = oms.simulate(cref)

## 6.78. stepUntil

Simulates a composite model until a given time value.

    status = oms.stepUntil(cref, stopTime)

## 6.79. terminate

Terminates a given composite model.

    status = oms.terminate(cref)

### 6.79.1. Example: Pi

This example uses a simple Modelica model and FMI-based batch simulation to approximate the value of pi.

A Modelica model is used to calculate two uniform distributed pseudo-random numbers between 0 and 1 based on a seed value and evaluates if the resulting coordinate is inside the unit circle or not.

    model Circle
      parameter Integer globalSeed = 30020 "global seed to initialize random number generator";
      parameter Integer localSeed = 614657 "local seed to initialize random number generator";
      Real x;
      Real y;
      Boolean inside = x*x + y*y < 1.0;
    protected
      Integer state128[4];
    algorithm
      when initial() then
        state128 := Modelica.Math.Random.Generators.Xorshift128plus.initialState(localSeed, globalSeed);
        (x, state128) := Modelica.Math.Random.Generators.Xorshift128plus.random(state128);
        (y, state128) := Modelica.Math.Random.Generators.Xorshift128plus.random(state128);
      end when;
      annotation(uses(Modelica(version="4.0.0")));
    end Circle;

The model is then exported using the FMI interface and the generated FMU can then be used to run a million simulations in just a few seconds.

Batch simulation of the simple Cirlce model with different seed values. All OMSimulator-related comands are highlighted for convenience.

     1import math
     2import matplotlib.pyplot as plt
     3import OMSimulator as oms
     4
     5# redirect logging to file and limit the file size to 65MB
     6oms.setLogFile('pi.log', 65)
     7
     8model = oms.newModel('pi')
     9root = model.addSystem('root', oms.Types.System.SC)
    10root.addSubModel('circle', 'Circle.fmu')
    11
    12model.resultFile = '' # no result file
    13model.instantiate()
    14
    15results = list()
    16inside = 0
    17
    18MIN = 100
    19MAX = 1000000
    20for i in range(0, MAX+1):
    21  if i > 0:
    22    model.reset()
    23  model.setInteger('root.circle.globalSeed', i)
    24  model.initialize()
    25  if model.getBoolean("root.circle.inside"):
    26    inside = inside + 1
    27  if i >= MIN:
    28    results.append(4.0*inside/i)
    29model.terminate()
    30model.delete()
    31
    32plt.plot([MIN, MAX], [math.pi, math.pi], 'r--', range(MIN, MAX+1), results)
    33plt.xscale('log')
    34plt.ylabel('Approximation of pi')
    35plt.savefig('pi.png')

The following figure shows the approximation of pi in relation to the number of samples.

Results of the above batch simulation which approximates the value of pi