Internal pub/sub for brain subsystem communication using pg.

This module provides a thin wrapper around OTP's pg (process groups) for communication between brain subsystems. It uses pg's built-in group management with brain-specific naming conventions.

Design Philosophy

Brain subsystems communicate through events rather than direct calls: - Publishers don't know about subscribers - Subscribers don't know about publishers - New subsystems can be added without modifying existing code - Events form a clear contract between subsystems

Event Types

| Event | Publisher | Description | |-------|-----------|-------------| | evaluated | brain | After each forward propagation | | reward_received | brain_system | When reward signal arrives | | weights_updated | brain_learner | After plasticity applied | | learning_toggled | brain_system | Learning enabled/disabled |

Usage

Initialize pubsub for a brain (typically in brain_sup): brain_pubsub:init(BrainId)

Subscribe to events: brain_pubsub:subscribe(BrainId, evaluated) brain_pubsub:subscribe(BrainId, [evaluated, reward_received])

Publish events: brain_pubsub:publish(BrainId, evaluated, #{activations => Acts})

Receive events in subscriber: receive {brain_event, evaluated, Data} -> %% Handle evaluation event ... end

Implementation

Uses OTP pg (process groups) with group names of the form: {brain_pubsub, BrainId, Topic}

This allows multiple brain instances to have independent pubsub.