Populating Event Logs

Event types

Four event types are supported in the model:

• ‘arrival_departure’
• ‘resource_use’
• ‘resource_use_end’
• ‘queue’.

As a minimum, you will require the use of ‘arrival_departure’ events and one of

• ‘resource_use’ / ‘resource_use_end’
• OR ‘queue’

You can also use both ‘resource_use’ and ‘queue’ within the same model very effectively (see ex_1_simplest_case and ex_2_branching_and_optional_paths, among others).

arrival_departure

Within this, two ‘arrival_departure’ events per entity are mandatory - arrival and depart, both with an event_type of arrival_departure, as shown below.

Arrivals

Important

Arrivals must use

‘event_type’: ‘arrival_departure’

‘event’: ‘arrival’

event_log.append(
      {'patient': unique_entity_identifier,
      'pathway': 'Revision',
      'event_type': 'arrival_departure',
      'event': 'arrival',
      'time': env.now}
  )

Departures

Important

Departures must use

‘event_type’: ‘arrival_departure’

‘event’: ‘depart’

event_log.append(
      {'patient': unique_entity_identifier,
      'pathway': 'Revision',
      'event_type': 'arrival_departure',
      'event': 'depart',
      'time': env.now}
  )

Warning

These are critical as they are used to determine when patients should first and last appear in the model.

Important

Forgetting to include a departure step for all types of patients can lead to slow model and animation performance as the size of the event logs for individual moments will continue to increase indefinitely.

queue

Queues are key steps in the model.

It is possible to solely use queues and never make use of a simpy resource.

By tracking each important step in the process as a ‘queue’ step, the movement of patients can be accurately tracked.

Patients will be ordered by the point at which they are added to the queue, with the first entries appearing at the front (bottom-right) of the queue.

Record the time the entity begins queueing for a resource with an event_type of ‘queue’.

You may use whatever string you wish to for the event name.

event_log.append(
            {'patient': unique_entity_identifier,
             'pathway': 'High intensity',
             'event_type': 'queue',
             'event': 'appointment_booked_waiting',
             'time': self.env.now
             }
        )

While the keys shown above are mandatory, you can add as many additional keys to a step’s log as desired. This can allow you to flexibly make use of the event log for other purposes as well as the animation.

resource_use and resource_use_end

Resource use is more complex to include but comes with two key benefits over the queue: - it becomes easier to monitor the length of time a resource is in use by a single entity as users won’t ‘move through’ the resource use stage (which can also prove confusing to less experienced viewers) - it becomes possible to show the total number of resources that are available, making it easier to understand how well resources are being utilised at different stages

In addition to the other fields, this also requires you to pass a resource_id argument. If you have set up your simpy store using the populate_store function from the utils module of the vidigi package, then your resources will have an ID attribute you can access in the way shown below after you have requested the resource with .get()

Record the time the resource begins use with an event_type of ‘resource_use’.

You may use whatever string you wish to for the event name.

# request the resource
my_resource = yield my_resource_store.get()

event_log.append( 
    {'patient': unique_entity_identifier, 
     'pathway': 'My Pathway Name', 
     'event_type': 'resource_use', 
     'event': 'triage_begins', 
     'time': env.now, 
     'resource_id': triage_resource.id_attribute 
    } 
) 

When the resource is no longer in use, record the time with an event_type of ‘resource_use_end’.

Again, you may use whatever string you wish to for the event name.

Once again, you must record the ID of the resource that is being freed up.

You can do this before or after putting the resource back in the store.

event_log.append( 
            {'patient': unique_entity_identifier, 
             'pathway': 'My Pathway Name', 
             'event_type': 'resource_use_end', 
             'event': 'triage_complete', 
             'time': env.now, 
             'resource_id': triage_resource.id_attribute} 
        ) 

# Resource is no longer in use, so put it back in the store
my_resource_store.put(my_resource)