Skip to content

Change Log

  • Unreleased
  • Added the healthcare-oriented service discipline hciw.disciplines.wait_time_over_benchmark, which serves the customer furthest past their customer class's target waiting time. Targets are set with the new customer_class_benchmarks argument to create_network, and are stored on each CustomerClass as benchmark. Covered by tests/test_disciplines.py and documented in the service-disciplines guide.
  • Broadened the Ruff configuration to select = ["ALL"], enabling every stable lint rule (including the D docstring family with the Google convention) and excluding only rules that conflict with the formatter, another rule, or a documented project convention. Fixed the resulting violations across hciw/, tests/ and doctests.py; no runtime behaviour changed.
  • Fixed exact-arithmetic (exact=<precision>) runs failing at wrap-up with TypeError: unsupported operand type(s) for +=: 'float' and 'decimal.Decimal'. A Server now initialises its busy_time and total_time to zeros of the same numeric type as its start_date, so Decimal arithmetic is used throughout in exact mode. This also fixes TypeError when a node computes its utilisation with a server that was never used. Covered by tests/test_server.py.

  • Reoriented the documentation toward academic and industry audiences. The README and landing page now state the model, the algorithm, and the intended users; a new docs/Background/overview.md page covers the queueing-network model (Kendall notation, Little's law, stability, Jackson and BCMP networks), the discrete-event simulation algorithm, and applications in healthcare, call centres, telecommunications, and manufacturing, with citations. The bibliography was expanded with the cited sources.

  • 4.0.0 (2026-10-12)

  • First release of HCiw, a fork of the Ciw queueing network simulation library, taken from the Ciw 3.2.7 codebase.
  • Breaking: the importable package is renamed from ciw to hciw, and the distribution from Ciw to HCiw; existing import ciw code must be updated. This is a new major version because the public identifier changed.
  • Packaging migrated from setup.py/requirements\*.txt to pyproject.toml with uv and a committed uv.lock; Python restricted to \>=3.12,\<3.13.
  • Added ROADMAP.md documenting the fork's direction; the previous healthcare-oriented HCiw wrapper is archived under old/.
  • Added warm starts: hciw.waitlist.create_existing_customers_from_list seeds a simulation with a backlog of pre-existing individuals, preserving their historical arrival dates so waiting times include time before the simulation begins. The same backlog can be passed to the Simulation constructor via the new initial_individuals argument.

  • The release history below records the upstream Ciw releases the fork inherits.

  • 3.2.7 (2025-12-05)

  • All distribution objects have attributes corresponding to their summary stats: mean, median, variance, standard deviation, upper and lower limits.

  • 3.2.6 (2025-06-13)

  • Add the include_incomplete keyword tot he get_all_records method to allow for collection of incomplete data records.

  • 3.2.5 (2025-03-25)

  • Fixes bug in PoissonIntervals distribution where if the last rate is zero or so small there is no samples, the cycle begins again too early.

  • 3.2.4 (2024-12-04)

  • Adds a new method for the simulate_until_max_customers: "Complete" simulates until a specific number of completed customer journeys; while "Finish" simulates until a specific number of customers have reached the exit node (through bailking or reneging).

  • 3.2.3 (2024-10-15)

  • Allow some numerical imprecision in the PMF probability sums. This allows for very large arrays of probabilities and use of Pandas and Numpy to define probabilities.

  • 3.2.2 (2024-07-05)

  • Allow custom exit node classes.

  • 3.2.1 (2024-06-19)

  • Remove reneging_destinations, move to a jockeying routing option within the routing objects.

  • 3.2.0 (2024-05-07)

  • System capacity implemented.
  • Server schedules objects now take numbers_of_servers and shift_end_dates keywards, instead of schedule.
  • Server schedules and slotted services can be offset.
  • Added a GroupedNodePopulation tracker.
  • Restructures documentation, adds more guides, and updates reference pages.
  • Routing objects implemented: TransitionMatrix object, ProcessBased object, FlexibleProcessBased object, NetworkRouting object, Direct object, Leave object, Probabilistic object, JoinShortestQueue object, LoadBalancing object

  • Added reroute as an option for interrupted preemptive services.

  • 3.1.4 (2024-04-09)

  • Fix bug where Individual's server isn't reset after a slotted service.

  • 3.1.3 (2024-04-08)

  • Allows class methods as generator functions for process-based routing.

  • 3.1.2 (2024-04-08)

  • Fix bug when using Mixture distribution.

  • 3.1.1 (2024-04-04)

  • Add a MixtureDistrubution that probabilistically chooses from a number of other distributions to sample from.
  • Baulking functions now take the simulation, current node, and current individual.
  • Service disciplines now take the current time.
  • Service disciplines now called when a customer arrives (allowing for lingering customers).
  • Distributions have parameters in their reprs.

  • Adding type hints and better doctrings.

  • v3.1.0 (2023-12-03)

  • Server schedules now defined with objects.
  • Slotted services feature added, with capacitated and non-capacitated slots, and pre-emption options.
  • Rename 'continue' pre-emption option to 'resume'.
  • Allows simultaneous renegeing customers.

  • Internal refactoring.

  • v3.0.2 (2023-11-14)

  • Fix bug where simulation errors if fist event of a node is a shift change.
  • Minor docstring and documentation changes.

  • Default statetracker is now None.

  • v3.0.1 (2023-10-31)

  • Fix bug where class change individual not reset after preemption.

  • v3.0.0 (2023-08-22)

  • Adds service disciplines - FIFO, LIFO, SIRO and ability for custom disciplines.
  • Removes baulking and rejection dictionaries, these are recorded as DataRecords.
  • Adds an optional filter to Q.get_all_records to filter only records of given types.
  • Removes ciw.dists.NoArrivals, can just use None.
  • Removes ability to write to file and read from file.
  • Allows any string to represent customer classes.
  • Api changes to class_change_matrices and class_change_distributions
  • ciw.trackers.NodeClassMatrix now required a class_ordering keyword to ordet the arbitrary customer class string names.

  • Performance improvements.

  • v2.3.7 (2023-04-06)

  • Adds Poisson, Geometric, and Binomial distributions for batching.

  • v2.3.6 (2023-02-16)

  • Writes a data record for interrupted services caused by server schedules.

  • Raises an error when an inconsistant number of custom node classes are used.

  • v2.3.5 (2023-02-07)

  • Fixes bug caused when implementing preemptive priority classes and server schedules that take all servers off duty.

  • v2.3.4 (2022-12-07)

  • PoissonIntervals distribution now allows rates of zero

  • v2.3.2 (2022-10-07)

  • Add PoissonIntervals distribution
  • Add numpy random generator, ciw.seed now also creates new random generator
  • Documentation on parallelising trials

  • Remove support for Python 3.6

  • v2.3.1 (2022-07-25)

  • Fixes bug where blocked customers were candidates for finish_service when more than one customer finishes service simultaneously
  • Correctly writes csv's in Windows

  • Support for Python 3.9 by updating tqdm requirement

  • v2.3.0 (2022-05-10)

  • Reneging customers implemented
  • Customer class changes while waiting implemented
  • Preemptive interruption options implemented

  • New record_type field added to DataRecords

  • v2.2.4 (2022-03-02)

  • Improve docs on pausing simulations and server priorities
  • Record server ID in the DataRecords

  • Move CI to GitHub Actions

  • v2.2.3 (2022-01-27)

  • Server priority functions implemented.

  • v2.2.2 (2021-12-17)

  • State trackers now take objects not indices
  • Servers are attached to individuals before sampling service times
  • Docs on sever-dependant distributions

  • Docs on DES+SD hybrid simulations

  • v2.2.1 (2021-11-04)

  • PhaseType distributions implemented

  • Classes for specific PhaseType distributions: Erlang, HyperExponential, HyperErlang, and Coxian

  • v2.2.0 (2021-07-22)

  • Processor sharing implemented (limited and capacitated)
  • Ability to use a different node_class per node of the network
  • State tracking now works with simulate_until_max_customers

  • Remove testing on Python 3.5

  • v2.1.3 (2020-10-06)

  • Small refactor to Node adding new servers, and to Individuals receiving the Simulation object.
  • Add a library of custom behaviour to docs

  • Support Python 3.8, update hypothesis

  • v2.1.2 (2020-09-26)

  • Ability to incorporate customer behaviour Server and Individual classes.

  • v2.1.1 (2020-05-27)

  • State Trackers slightly more efficent, they do not record any state changes that result in the same state as before.
  • Add the NodePopulationSubset tracker.

  • Distribution objects can now see the Simulation object, for true state dependent distributions.

  • v2.1.0 (2020-04-23)

  • State Trackers now track history
  • State Trackers give state probabilities
  • A number of performance improvements
  • Fix some documentation

  • Test on PyPy3.6 and Python 3.7 too

  • v2.0.1 (2019-07-17)

  • setup.py now finds packages to fix pip install bug

  • v2.0.0 (2019-07-10)

  • Large refactor:
  • Drop support for Python 2.7, Python 3.4.
  • Update networkx and pyyaml requirements.
  • Refactor time so that Simulation has current_time attribute.
  • Change Transition_matrices keyword to routing.
  • routing can take a process-based routing function.
  • Refactor distributions to be objects: ['Exponential', 0.5] -> ciw.dists.Exponential(0.5).
  • Distribution objects can be manipulated with +, -, * and /.
  • All keywords lower case to conform to Pep8.
  • deadlock_detector keyword takes object, not string.
  • tracker keyword takes object, not string.
  • Add tests and docs to show how objects can be used for state-dependent distributions.
  • All user facing api now takes float('inf') not 'Inf', expect for .yml files.
  • Reference Ciw paper in docs.

  • Add AUTHORS.rst to docs.

  • v1.1.6 (2018-10-22)

  • Fixed bug in which preemptively iterrupted individuals remained blocked once service resampled.
  • Fixed bug in which interrupted individuals not removed from interrupted list when restarting service.
  • Some performance improvements.

  • Improve deadlock detection to check for knots less often.

  • v1.1.5 (2018-01-11)

  • Fixed bug calculating the utilisation of servers.

  • v1.1.4 (2017-12-12)

  • Time dependent batching distributions

  • Hard pin requirements versions

  • v1.1.3 (2017-08-18)

  • Replace DataRecord object with namedtuple.

  • Number of minor tweaks for speed improvements.

  • v1.1.2 (2017-07-05)

  • Batch arrivals.

  • v1.1.1 (2017-06-23)

  • Server utilisation & overtime.
  • Small fixes to docs.

  • Testing on Python 3.6.

  • v1.1.0 (2017-04-26)

  • Replace kwargs with actual keyword arguments in ciw.create_network.

  • Refactor server schedule inputs (schedules placed inside Number_of_servers instead of as their own keyword).

  • v1.0.0 (2017-04-04)

  • ciw.create_network takes in kwargs, not dictionary.
  • Add Sequential distribution.
  • Add truncated Normal distribution.
  • Refactor inputs for custom PDF.
  • Refactor inputs for server schedules.
  • Transition matrix now optional for 1 node networks.
  • Overhaul of documentation.
  • Add CONTRIBUTING.rst.

  • Slight improvement of ciw.random_choice.

  • v0.2.11 (2017-03-13)

  • Add ability to simulate until max number of customers have passed arrived/been accepted/passed through the system.

  • v0.2.10 (2017-03-10)

  • Performance improvements.

  • Drop dependency on numpy.

  • v0.2.9 (2017-02-24)

  • Allow zero servers.

  • v0.2.8 (2016-11-10)

  • Add option for time dependent distributions.

  • v0.2.7 (2016-10-26)

  • Run tests on Appveyor.
  • Check docs build and pip installable on Travis.

  • Remove hypothesis cache.

  • v0.2.6 (2016-10-17)

  • Add AUTHORS.rst.

  • Add progress bar option.

  • v0.2.5 (2016-10-06)

  • Fix bug that didn't include .rst files in MANIFEST.in.

  • v0.2.4 (2016-09-27)

  • Fixed bug in which priority classes and dynamic classes didn't work together.

  • New feature: preemptive interruptions for server schedules.

  • v0.2.3 (2016-07-27)

  • Ability to set seed. More docs. Fixes to tests.

  • v0.2.2 (2016-07-06)

  • Baulking implemented, and minor fixes to order of unblocking.

  • v0.2.1 (2016-06-29)

  • Priority classes implemented.

  • v0.2.0 (2016-06-20)

  • Python 3.4 and 3.5 compatible along with 2.7.

  • Data records now kept in list.

  • v0.1.1 (2016-06-06)

  • Ability to incorporate behaviour nodes.

  • Data records are now named tuples.

  • v0.1.0 (2016-04-25)

  • Re-factor inputs.
  • Simulation takes in a Network object.
  • Helper functions to import yml and dictionary to a Network object.
  • Simulation object takes optional arguments: deadlock_detector, exact, tracker.

  • simulate_until_max_time() takes argument max_simulation_time.

  • v0.0.6 (2016-04-04)

  • Exactness implemented.
  • Restructure some features e.g. times_to_deadlock.

  • Custom simulation names.

  • v0.0.5 (2016-03-18)

  • State space tracker plug-and-playable.

  • Add rejection dictionary.

  • v0.0.4 (2016-02-20)

  • Empirical and UserDefined distributions added.

  • Tidy ups.

  • v0.0.3 (2016-02-09)

  • Arrival distributions.
  • MMC options removed.

  • Fix server schedule bugs.

  • v0.0.2 (2016-01-06)

  • Some kwargs optional.
  • Hypothesis tests.

  • Minor enhancements.

  • v0.0.1 (2015-12-14)

  • Initial release.

  • v0.0.1dev (2015-12-14)

  • Initial release (dev).