Exercises in Co-simulation timing

A few simple exercises about co-simulation timing

Key Parameters

  • Period: The minimum time resolution a federate will allow.

  • Offset: a shift in the period. Allowed times for federate grants after time 0 are offset+N*period, where N is a non-negative integer.

  • Time_delta: the minimum time between grants, i.e. if a federate is granted time T, the next possible time is T+Time_delta.

Modifier Flags

  • Uninteruptible: a federate can only be granted requested times

  • wait_for_current_time_update: specify that a federate should wait until all federates executing at the current time have finished.

Connectivity Diagram

  1. Federation Setup [A: period=1; B: period=2; C: period=3]

    a. Following time 0, which federate could execute next? ___________________________

    b. If all federates execute at all allowed times, what is the next time Federate B could have access to data from Federate C. __________________

    c. What is the next time all federate will be able to execute simultaneously? __________________

    Key Principle: Federates are interrupted if there is updated data available and allowed time prior to the requested time

  2. Federation Setup [A: period=1,wait_for_current_time_update; B: period=2; C: period=3]

    a. At what time will the data from Federate B published at time 2, be available to Federate A? ______________

    b. Federate A requests time 4: Federate B publishes at time 2. What time is Federate A granted? _____________

    c. Federate A requests time 2: Federate B publishes at time 2. What time does Federate A receive the data? _________________

    e. If A did not have the wait_for_current_time_update flag active, what time would Federate A receive the data? ________________

    Key Principle: Federates are granted the next allowed time after the time specified in a request if they are not interrupted.

  3. Federation Setup [A: period=1; B: period=2,offset=1,time_delta=2; C: period=3]

    a. After time=0 what is the next allowable time for Federate B? _______________

    b. Federate C requested a time of 4, what time is Federate C granted? _______________

  4. Federation Setup [A: period=1; B: period=2,uninterruptible; C: period=3]

    a. Federate C Publishes at time 3, Federate B requests time 6, what time will it be granted?______________

    b. If Federate B were not uninterruptible what time would it be granted? _______________

    Connectivity Diagram

  5. Federation Setup [A: period=1; B: period=2; C: period=3], Federates will send an update when they have received an update from the all other connected federates. Federate A sends an update at time 0, what is the update sequence



For answers see answers