Source(env, id, in_edges=None, out_edges=None, item_length=1, flow_item_type='item', inter_arrival_time=0, blocking=False, out_edge_selection='FIRST_AVAILABLE')

Bases: Node

Parameters:
  • state (str) –

    Current state of the source node. One of :

    • SETUP_STATE: Initial setup phase before item generation starts.
    • GENERATING_STATE: Actively generating and dispatching items.
    • BLOCKED_STATE: Waiting to transfer item when edge is full (in blocking mode).
  • inter_arrival_time (None, int, float, generator, or callable, default: 0 ) –

    Time between item generations. Can be:

    • None: Used when the setup time depends on parameters of the node object (like current state of the object) or environment.
    • int or float: Used as a constant delay.
    • Callable: A function that returns a delay (int or float).
    • Generator: A generator function yielding delay values over time.
  • flow_item_type (str, default: 'item' ) –

    Type of item to be generated. Default is "item". Can be

    • "item" : Smallest unit of discrete item and it cannot hold other items inside.
    • "pallet" : Entities that can store multiple smaller units of items
  • blocking (bool, default: False ) –

    If True, the source waits until it can put an item into the out edge.

  • out_edge_selection (None or str or callable, default: 'FIRST_AVAILABLE' ) –

    Criterion or function for selecting the out edge. Options include "RANDOM", "FIRST", "LAST", "ROUND_ROBIN", "FIRST_AVAILABLE".

    • None: Used when out edge selection depends on parameters of the node object (like current state of the object) or environment.
    • str: A string that specifies the selection method.
      • "RANDOM": Selects a random out edge.
      • "ROUND_ROBIN": Selects out edges in a round-robin manner.
      • "FIRST_AVAILABLE": Selects the first out edge that can accept an item.
    • callable: A function that returns an edge index.

Behavior:

The Source node is responsible for generating items that flow in the simulation model. It operates in two modes: blocking and non-blocking.

when blocking=True: - After each inter_arrival_time, the source generates an item. - If the selected out edge is full, the source waits until space is available. - Once space is available, the item is transferred to the selected edge. - inter_arrival_time must not be None.

when blocking=False: - After each inter_arrival_time, the source generates an item. - If the selected out edge is full, the item is discarded immediately. - If space is available, the item is transferred without waiting. - inter_arrival_time must not be 0.

Raises:
  • ValueError –

    If inter_arrival_time is 0 in non-blocking mode or if out_edge_selection is not a valid type.

  • ValueError –

    If out_edge_selection is not a string or callable.

  • ValueError –

    If out_edges is not provided or has less than one edge.

  • ValueError –

    If in_edges is provided, as Source nodes should not have input edges.

  • ValueError –

    If out_edges already has an edge when trying to add a new one.

Output performance metrics: The key performance metrics of the Source node is captured in stats attribute (dict) during a simulation run. 

last_state_change_time    : Time when the state was last changed.
num_item_generated        : Total number of items generated.
num_item_discarded        : Total number of items discarded due to lack of space in out edge.
total_time_spent_in_states: Dictionary with total time spent in each state.

add_out_edges(edge)

Adds an out_edge to the source node. Raises an error if the source already has an out_edge or if the edge already exists in the out_edges list.

Parameters:
  • edge (Edge Object) –

    The edge to be added as an out_edge.

update_state(new_state, current_time)

Update node state and track the time spent in the previous state.

Parameters:
  • i (int) –

    The index of the worker thread to update the state for.

  • new_state (str) –

    The new state to transition to. Must be one of "SETUP_STATE", "GENERATING_STATE", "BLOCKED_STATE".

  • current_time (float) –

    The current simulation time.