Class fmipp.RollbackFMU

class RollbackFMU([fmuDirUri, ]modelIdentifier[, loggingOn=False, timeDiffResolution=1e-4, integratorType=integratorBDF])

This class implements an easy way to reset the state of an FMU for Model Exchange to a state corresponding to a previous time step using the methods saveCurrentStateForRollback() and releaseRollbackState().

Assume that at time t0 the method call integrate( t1 ) was issued, i.e., the integration of the associated FMU from time t0 to time t1 > t0. In case there happend no event during the integration, after the method call the internal state of the FMU corresponds to time t1. Now, in order to rollback the FMU to a state corresponding to time t2, with t0 < t2 < t1, the method call integrate( t2 ) is sufficient.

Internally, class RollbackFMU stores a rollback state. No rollbacks corresponding to a time previous to that internally stored rollback state are possible. If not otherwise instructed, the latest stored rollback state is overwritten with the current state, in case the requested integration endpoint is in the future. However, the method saveCurrentStateForRollback() enforces the current state to be stored as rollback state until it is explicitly released with method releaseRollbackState(). This allows to make a rollback over more than one time-consecutive integration cycle.

Note

This class uses objects of type SwigPyObject as inputs and outputs, which are wrappers around C/C++ arrays. Instantiation of and data access to these objects should be done via the corresponding helper functions.

Parameters

  • fmuDirUri (str) – URI to the unzipped FMU

  • modelIdentifier (str) – model identifier of the FMU

  • loggingOn (bool) – enable logger for debugging

  • timeDiffResolution (float) – internal resolution for comparing time differences

  • integratorType (int) – the numerical integration method for solving ODEs (see list of available integrators here)

Methods for interacting with the FMU

instantiate(instanceName)

This functions creates a new internal FMU instance. This function must be called successfully, before any of the following functions can be called.

Parameters

instanceName (str) – a unique identifier for a given FMI component instance, used to identify a component within a co-simulation graph model and for logging messages

Return type

int (statusOK, statusWarning, statusDiscard, statusError or statusFatal)

initialize(toleranceDefined=False, tolerance=1e-05)

Informs the FMU instance that the simulation run starts now.

Parameters

  • toleranceDefined (bool) – if True, the model is called with a numerical integration scheme where the step size is controlled by using tolerance

  • tolerance (float) – relative tolerance for error estimation

Return type

int (statusOK, statusWarning, statusDiscard, statusError or statusFatal)

integrate(tstop[, deltaT=1E-5])

In case there happend no event during the integration, after the method call the internal state of the FMU corresponds to time tstop. To rollback the FMU to a state corresponding to time trollback, the method call integrate( trollback ) is sufficient.

Parameters

  • tend (float) – stop time for the integration

  • deltaT (int) – starting step size to be used by the integrator, smaller values lead to more accuracy

Returns

integration stop time

Return type

float

saveCurrentStateForRollback()

Saves the current state of the FMU as internal rollback state. This rollback state will not be overwritten until releaseRollbackState() is called.

releaseRollbackState()

Realease an internal rollback state, that was previously saved via saveCurrentStateForRollback().

Methods for getting/setting values

getBooleanValue(name)
Parameters

name (str) – variable name

Return type

bool

getIntegerValue(name)
Parameters

name (str) – variable name

Return type

int

getRealValue(name)
Parameters

name (str) – variable name

Return type

float

getStringValue(name)
Parameters

name (str) – variable name

Return type

str

Miscellaneous methods

getTime()
Return type

float

getLastStatus()
Return type

int (statusOK, statusWarning, statusDiscard, statusError or statusFatal)