Class: SimpleKit::EventScheduler

Inherits:
Object
  • Object
show all
Defined in:
lib/simplekit.rb

Overview

Class EventScheduler provides the computation engine for a discrete event simulation model. It uses an array-based priority queue implementation for the pending events list.

Users must create a model class which:

  • implements an init method;

  • Instantiates a model and invokes the run method to start execution.

Defined Under Namespace

Classes: EventNotice

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(the_model) ⇒ EventScheduler

Initialize the EventScheduler by remembering the specified model and setting up an empty event list.



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# File 'lib/simplekit.rb', line 42

def initialize(the_model)
  @user_model = the_model
  @event_list = PriorityQueue.new
  @cancel_set = {}
end

Instance Attribute Details

#model_time ⇒ Object (readonly)

Returns the value of attribute model_time.



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# File 'lib/simplekit.rb', line 38

def model_time
  @model_time
end

#user_model ⇒ Object (readonly)

Returns the value of attribute user_model.



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# File 'lib/simplekit.rb', line 38

def user_model
  @user_model
end

Instance Method Details

#cancel(event, args = {}) ⇒ Object

Cancel an individual occurrence of event type event. If no args are provided, the next scheduled occurrence of event is targeted. If a subset of the event’s args is provided, they must all be a match with the corresponding args of the scheduled event in order for the cancellation to apply, but args which are not specified do not affect the target event matching.



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# File 'lib/simplekit.rb', line 68

def cancel(event, args = {})
  @cancel_set[event] ||= Set.new
  # @cancel_set[event].add(args.empty? ? nil : args)
  @cancel_set[event].add(args)
end

#cancel_all(event) ⇒ Object

Cancel all currently scheduled events of type event.



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# File 'lib/simplekit.rb', line 75

def cancel_all(event)
  if event
    PriorityQueue.new.tap do |pq|
      while (event_notice = @event_list.pop)
        pq.push event_notice unless event_notice.event == event
      end
      @event_list = pq
    end
  end
end

#halt ⇒ Object

Clear the event list, which causes termination of the simulation. Never schedule any new events after invoking halt.



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# File 'lib/simplekit.rb', line 107

def halt
  @event_list.clear
end

#run ⇒ Object

Start execution of a model. The simulation model_time is initialized to zero and the model is initialized via the mandatory init method. Then loop while events are pending on the event_list. The event with the smallest time is popped, model_time is updated to the event time, and the event method is invoked with the args, if any, set by schedule.



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# File 'lib/simplekit.rb', line 91

def run
  @model_time = 0.0
  @user_model.init
  while (current_event = @event_list.pop)
    next if should_cancel?(current_event)
    @model_time = current_event.time
    if current_event.args.empty?
      @user_model.send(current_event.event)
    else
      @user_model.send(current_event.event, **current_event.args)
    end
  end
end

#schedule(event, delay, args = {}) ⇒ Object

Add an event to the pending events list.

Arguments

  • event -> the event to be scheduled.

  • delay -> the amount of time which should elapse before the event executes.

  • args -> zero or more named arguments to pass to the event at invocation time. These should be specified with labels, and consequently they can be placed in any order.



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# File 'lib/simplekit.rb', line 57

def schedule(event, delay, args = {})
  raise 'Model scheduled event with negative delay.' if delay < 0
  @event_list.push EventNotice.new(event, @model_time, delay, args)
end