Multi agent system (MAS)¶
Univers agent is responsible to execute all agents. Univers is stopped using univers_stop() event.
A session can be stopped using session_stop() event.
Main MAS events:
- project_start(): event received at first step but only for the first session of a project
- session_start(): event received at first step on a session
- session_done(score): event received at the last step of a session
An agent is an object able to send/receive messages to/from other agents. Agents have a limited vision of the whole application: agents do not see them each other. For pratical reasons, they have access to Application, Project and Session objets.
Active or inactive¶
By default, an agent is inactive. It does not receive any event and is not allowed to send messages. Calling activate() method does active then agent and then call init() method. To disable an agent, use deactive() which calls deinit() method.
Sum up of attributes and methods:
- is_active: boolean
- activate(): enable the agent, call init()
- deactivate(): disable the agent, call deinit()
- init(): create objects (eg. open file)
- deinit(): destroy objects (eg. close file)
When an agent is active, it’s live() method is called at each session step. The method have to be fastest as possible, so don’t use any blocking function (eg. select() before read()).
Method related to message handling:
- readMailbox(): read messages and call related agent event handler
- send(event, *arguments): send an event to other agents
You don’t have to call readMailbox(), this job is done by Session.executeObject().
To register to a message, just add a method to your class with the prototype:
def on_EVENT(self, *arguments): ...
Example of method called on session start:
def on_session_start(self): ...
- name (str): Agent name (should be unique in the whole application)
- agent_id (int): Unique identifier in the whole application (integer counter starting at 1)
- logger: Logger object used by methods debug(), info(), ...
- mailbox: Mailbox used to store message until readMailbox() is called
To write string to logger, use methods:
- debug(message): DEBUG level
- info(message): INFO level
- warning(message): WARNING level
- error(message): ERROR level
ProjectAgent and SessionAgent have a method getScore() which return the agent score. Default value is None (agent has no score). An agent has also ‘score_weight’ attribute (default value: 1.0) which is used to compute final agent score:
minmax(-1.0, agent.getScore() * agent.score_weight, 1.0)