Enforce monotonic time invariant in event scheduling#3343
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| raise ValueError( | ||
| f"Cannot schedule event at time {time}, current time is {self.time}" | ||
| ) | ||
| event = Event(time, function, priority=priority) |
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Suggested change
| event = Event(time, function, priority=priority) | |
| raise ValueError( | |
| f"Cannot schedule event in the past. Scheduled time is {time}, but current time is {self.time}" | |
| ) |
quaquel
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| raise ValueError( | ||
| f"Cannot start recurring schedule at time {schedule.start}, " | ||
| f"current time is {self.time}" | ||
| ) |
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| raise ValueError( | |
| f"Cannot start recurring schedule at time {schedule.start}, " | |
| f"current time is {self.time}" | |
| ) | |
| raise ValueError( | |
| f"Cannot start recurring schedule in the past. Start time is {schedule.start}, " | |
| f"current time is {self.time}" | |
| ) |
quaquel
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Looks good to me. Please look at the suggested change to the message and add raises to the docstring.
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Performance benchmarks:
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@quaquel i made the changes you recommended, thanks for the review. |
quaquel
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Summary
This PR enforces a monotonic time invariant in the event scheduling system. It prevents one-off and recurring events from being scheduled at times earlier than the model’s current simulation time. This ensures the model clock cannot move backwards during execution.
Fixes #3342
Bug / Issue
It was previously possible to run the model forward (e.g., to time 10), schedule a new event at an earlier time (e.g., time 3) and then execute that event, causing the model clock to move backward. There is no rollback mechanism in the execution model, so this behavior violates expected time semantics.
Implementation
The fix enforces the invariant at the scheduling boundary:
Model.schedule_event, aValueErroris raised if time <self.timeModel.schedule_recurring, aValueErroris raised ifschedule.startis not None andschedule.start<self.timeThis ensures both one-off and recurring schedules cannot be initialized in the past. This is enforced at the API boundary rather than inside
_advance_time, preventing invalid events from entering the event list in the first place.Testing
Added tests in
tests/test_model.pyfor verification. Normal forward scheduling behavior remains unchanged All time-related tests pass.Additional Notes
This change formalizes time monotonicity as an invariant of the scheduling system. It does not alter normal forward execution behavior. This preserves consistency with the discrete event execution model, which does not support rollback or reversible time progression.