Ciw

A discrete event simulation library for queueing networks

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Ciw is a discrete event simulation library for open queueing networks. It’s core features include the capability to simulate networks of queues, multiple customer classes, and implementation of Type I blocking for restricted networks.

• Read the documentation <https://ciw.readthedocs.io>_
• Contribution guidelines <https://github.com/CiwPython/Ciw/blob/master/CONTRIBUTING.rst>_
• Our great contributors <https://github.com/CiwPython/Ciw/blob/master/AUTHORS.rst>_

Install with :code:pip install ciw.

Current supported version of Python:

• Python 3.6
• Python 3.7
• Python 3.8
• Python 3.9

Usage

Import Ciw::

>>> import ciw

To define an M/M/3 queue, with λ = 0.2 and μ = 0.1::

>>> N = ciw.create_network(
...     arrival_distributions=[ciw.dists.Exponential(rate=0.2)],
...     service_distributions=[ciw.dists.Exponential(rate=0.1)],
...     number_of_servers=[3]
... )

Now set a seed, create a Simulation object, and simulate for 1440 time units::

>>> ciw.seed(1)
>>> Q = ciw.Simulation(N)
>>> Q.simulate_until_max_time(1440)

Collect results::

>>> recs = Q.get_all_records()

Manipulate results to get useful statistics, e.g. average waiting time::

>>> waits = [r.waiting_time for r in recs]
>>> sum(waits) / len(waits)
4.2305...

Features

A number of other features are also implemented, including:

• Type I blocking <https://ciw.readthedocs.io/en/latest/Tutorial-II/tutorial_vi.html>_
• A large range of sampling distributions <https://ciw.readthedocs.io/en/latest/Reference/distributions.html>_
• Phase-Type distributions <https://ciw.readthedocs.io/en/latest/Guides/phasetype.html>_
• Time-dependent and state-dependent distributions <https://ciw.readthedocs.io/en/latest/Guides/time_dependent.html>_
• Batch arrivals <https://ciw.readthedocs.io/en/latest/Guides/batching.html>_
• Baulking customers <https://ciw.readthedocs.io/en/latest/Guides/baulking.html>_
• Reneging customers <https://ciw.readthedocs.io/en/latest/Guides/reneging.html>_
• Processor sharing <https://ciw.readthedocs.io/en/latest/Guides/processor-sharing.html>_
• Multiple customer classes <https://ciw.readthedocs.io/en/latest/Tutorial-II/tutorial_vii.html>_
• Priorities <https://ciw.readthedocs.io/en/latest/Guides/priority.html>_
• Server priorities <https://ciw.readthedocs.io/en/latest/Guides/server_priority.html>_
• Customers changing classes <https://ciw.readthedocs.io/en/latest/Guides/dynamic_customerclasses.html>_
• Server schedules <https://ciw.readthedocs.io/en/latest/Guides/server_schedule.html>_
• State tracking <https://ciw.readthedocs.io/en/latest/Guides/state_trackers.html>_
• Stopping the simulation after a certain amount of customers <https://ciw.readthedocs.io/en/latest/Guides/sim_numcusts.html>_
• Process-based routing <https://ciw.readthedocs.io/en/latest/Guides/process_based.html>_
• Deadlock detection <https://ciw.readthedocs.io/en/latest/Guides/deadlock.html>_