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Event

Events in Hades are immutable pydantic models including some t value - the time-step in the simulation when the event occurs, and data or identifiers relating to the event.

Events in Hades are static meaning that they are do not contain logic relating to the event as with some other DES frameworks. See design justification for why!

Events should use a consistent tense. Here past is used

It will often be the case that events will need to contain identifying information for processes to identify which entity it relates to within their internal state. In addition it will often be necessary to pass around data.

Another thing which may be useful is some kind of audience identifier, which can help processes distinguish quickly whether to do anything with a give event.

Suggested way to structure this is as follows:

Suppose we have two Event kinds relating to frogs:

  • FrogSpawned
  • FrogTransformed
class FrogLifeCycleStage(Enum):
    SPAWN = 1
    TADPOLE = 2
    FROGLET = 3
    FROG = 4

class FrogSpawned(Event):
    frog_id: str
    audience_pond_id: str

    initial_stage: FrogLifeCycleStage
    frog_genetic_data: GeneticData

class FrogTransformed(Event):
    frog_id: str
    # we dont need the audience here because we might well assume that a frog will spend its whole life in the start pond
    # we also dont need the genetic data because 
    transformed_to: FrogLifeCycleStage

This ensures that processes can cleanly identify whether the event relates to an entity they are interested in and makes a distinction between data (which may be quite sizeable) isn't being unnecessarily passed around.

Event

Bases: BaseModel

base event - event occurrence step t must be included. It is immutable and hashable

Source code in hades/core/event.py 
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class Event(BaseModel):
    """base event - event occurrence step t must be included. It is immutable and hashable"""

    t: int

    @property
    def name(self):
        return self.__class__.__name__

    model_config = ConfigDict(frozen=True)

ProcessUnregistered

Bases: Event

special event for unregistered the process who sent this event. it is unique in that it will be consumed by hades and not broadcast to other processes.

Source code in hades/core/event.py 
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class ProcessUnregistered(Event):
    """
    special event for unregistered the process who sent this event.
    it is unique in that it will be consumed by hades and not broadcast to other processes.
    """

SimulationEnded

Bases: Event

Signals the simulation has ended.

Source code in hades/core/event.py 
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class SimulationEnded(Event):
    """Signals the simulation has ended."""

SimulationStarted

Bases: Event

special event issued by hades to kick off the sim

Source code in hades/core/event.py 
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class SimulationStarted(Event):
    """special event issued by hades to kick off the sim"""

    t: int = 0