# 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.

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? _______________

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

Time

Federate(s)