Fixed

• Sequence-form based equilibrium-finding methods returned incorrect output on games with
  outcomes at non-terminal nodes. (#654)

Added

• Implement IsAbsentMinded() on information sets (C++) and Infoset.is_absent_minded (Python)
  to detect if an information is absent-minded.
• Tests for EFG Nash solvers -- enumpoly_solve, lp_solve, lcp_solve -- in behavior strategies
• In pygambit, Node objects now have a read-only property own_prior_action and Infoset objects
  have a read-only property own_prior_actions to retrieve the last action or the set of last actions
  taken by the player before reaching the node or information set, respectively. (#582)
• In pygambit, Node objects now have a read-only property is_strategy_reachable to determine
  if the node is reachable by at least one pure strategy profile. This proves useful for identifying
  unreachable parts of the game tree in games with absent-mindedness. (#629)

Changed

• Labels for players, outcomes, strategies, and actions are expected to be non-empty and unique within
  the relevant scope (games for players and outcomes, players for strategies, and information sets for
  actions). pygambit now issues a FutureWarning if a label is changed that does not conform to these
  expectations. There is now an optional flag normalize_labels to read_* which will automatically
  fill in non-confirming sets of labels. In version 16.6 these will be enforced; invalid label sets will
  generate an error and files will be normalized automatically on read. (#614)
• Terminology for agent-form calculations on extensive games has been clarified. Mixed behavior profiles
  distinguish "agent" regret and liap values from their strategy-based analogs. Methods which compute
  using the agent-form - specifically enumpure_solve and liap_solve, now clarify this by being named
  differently in pygambit. (#617)
• For clarity, the stop_after and max_depth arguments to lcp_solve are no longer permitted when solving using
  the sequence form. These actually had no effect in previous versions. (#671)
• In the graphical interface, removed option to configure information set link drawing; information sets
  are always drawn and indicators are always drawn if an information set spans multiple levels.
• In pygambit, indexing the children of a node by a string inteprets the string as an action label,
  not a label of a child node. In addition, indexing by an action object is now supported. (#587)
• In pygambit, min_payoff and max_payoff (for both games and players) now refers to payoffs in
  any play of the game; previously this referred only to the set of outcomes. (#498)
• In pygambit, calls to sort_infosets are no longer required to normalise the game representation.
  Iteration ordering of information sets and their members is ensured internally. sort_infosets
  is therefore now a no-op and is deprecated; it will be removed in a future version.

Removed

• Eliminating dominated actions has been removed from the GUI as it was implementing a non-standard
  formulation of dominance. (#612)
• The C++ method for computing subgame perfect equilibria with selected methods has been removed
  (and as a result from the enumpure, lp, and lcp command-line tools); this will be replaced
  with new and more customisable approaches. (#639)

Fixed

• Fixed a regression in which null outcomes in strategic game tables were not handled correctly
  when changing the number of strategies in the game (#571)
• Fixed improper shared pointer handling when writing a .nfg file based on a game in
  extensive form.
• Fixed a regression in the GUI in which unique action labels were not being generated when
  adding a move via drag-and-drop of a player icon (#618)
• Fixed a regression generating null pointer dereference errors when setting the outcome of
  a node to the null outcome (#625, #647)
• Fixed a regression in calculating payoff quantities for mixed strategy profiles derived from
  mixed behavior profiles (#616)

Fixed

• Parsing of output of gambit-logit in the graphical interface did not handle the
  terminal Nash profile correctly. (#172)
• Improved sizing of list of logit profiles computed for normal form games.

Changed

• Removed Ctrl/Cmd-X accelerator for closing program, as this clashes with modern standard
  expectations. (#507)

Removed

• Undo and redo have been removed from the graphical interface. (These were meant to be
  removed previously as they did not work properly and gave unpredictable behaviour.) (#505)

General

• Officially added support for Python 3.13.
• For graphical interface, added support for wxWidgets 3.3; require minimum of wxWidgets 3.2.

Removed

• The deprecated functions Game.read_game, Game.parse_game and Game.write functions have
  been removed as planned. (#357)

Added

• Implement GetPlays() (C++) and get_plays (Python) to compute the set of terminal nodes consistent
  with a node, information set, or action (#517)
• Implement GameStrategyRep::GetAction (C++) and Strategy.action (Python) retrieving the action
  prescribed by a strategy at an information set
• Tests for creation of the reduced strategic form from an extensive-form game (currently only
  for games with perfect recall)
• Implement Nodes collection as a member of GameRep, including a C++ iterator that
  returns nodes in depth-first traversal order (#530)

Changed

• Internally in C++ std::shared_ptr are now used to manage memory allocated for game objects. (#518)
• The iteration order of a player's information sets, and of the members of an information set, now may
  depend on the order of operations to build a game tree. The previous behaviour - ensuring sorting
  by the order encountered in a depth-first traversal of the tree - can now be obtained by calling
  SortInfosets (C++) or sort_infosets (Python) on the game. (#483)

Fixed

• Corrected a regression in which information sets were prematurely invalidated (and therefore
  delete this called on them) when removing the last node from an information set.
• Game.copy_tree and Game.move_tree implementations reversed the roles of the
  src and dest nodes (#499)

Changed

• For graphical interface, added support for wxWidgets 3.3; require minimum of wxWidgets 3.2.

Fixed

• Game.copy_tree and Game.move_tree implementations reversed the roles of the
  src and dest nodes (#499)

Changed

• For graphical interface, added support for wxWidgets 3.3; require minimum of wxWidgets 3.2.

General

• Dropped support for Python 3.8.

Added

• Implemented maximum-likelihood estimation for agent logit QRE, to parallel existing support
  for strategic logit QRE. Strategic logit QRE function names have been modified to provide
  parallel naming. Estimation using the correspondence now supports an option to stop at the
  first interior local maximizer found (if one exists).
• Maximum-likelihood estimation for logit QRE using empirical payoffs has an improved internal
  calculation of log-likelihood, and returns the estimated profile instead of just a list of
  probabilities.
• Reorganized naming conventions in pygambit for functions for computing QRE in both strategic
  and agent versions, and added a corresponding section in the user guide.
• enumpoly_solve has been returned to being fully supported from temporarily being experimental;
  now available in pygambit.
• enumpoly_solve for strategic games now uses the Porter, Nudelman, and Shoham (2004) ordering
  of supports to search.
• to_arrays converts a Game to a list of numpy arrays containing its reduced strategic form.
  (#461)
• Integrated support (in Python) for using PHCpack to solve systems of polynomial equations in
  enumpoly_solve based on an implementation formerly in the contrib section of the
  repository. (#165)
• New format-specific functions pygambit.read_* and pygambit.Game.to_* functions have been
  added to (de-)serialise games. The existing Game.read_game and Game.write functions have
  been deprecated and will be removed in 16.4. (#357)

Changed

• The built-in implementation of lrslib (dating from 2016) has been removed. Instead, access to
  lrsnash is provided as an external tool via the enummixed_solve function, in parallel to
  PHCpack for enumpoly_solve.

Fixed

• When parsing .nfg files, check that the number of outcomes or payoffs is the expected number,
  and raise an exception if not. (#119)

Removed

• Game.write() no longer supports generation of the XML-format files for Game Theory
  Explorer, as GTE no longer reads files in this format.

Fixed

• Corrected an internal implementation error in Game.reveal() in resolving references to
  information sets and players (#453)
• Reading .efg and .nfg game files which did not have whitespace at the end would lead to
  an infinite loop (#457)
• Attempting to call the default constructor on Game objects (rather than one of the factory
  functions) now raises a more informative exception (#463)

Fixed

• gnm_solve/gambit-gnm now correctly handles the degenerate case of a game where all
  payoffs are the same (#405), and checks that the perturbation vector specified has at least
  one non-zero component (#194)
• ipa_solve/gambit-ipa ensures the use of a generic perturbation vector; this resolves a
  problem where the method could return non-Nash output (#406)
• gambit-enumpoly could get stuck in an infinite loop, and/or fail to report some equilibria,
  due to floating-point rounding/tolerance issues; this has been fixed on known cases (#198)
• gambit-logit now uses perturbations to attempt to resolve correspondences that have
  bifurcations, and instead tries always to follow a curve that has the same orientation.
  This should eliminate cases in which tracing gets stuck in a loop or reverses itself
  when encountering bifurcations (#3)

Added

• MixedStrategyProfile and MixedBehaviorProfile objects in pygambit can now be iterated in
  various dict-like ways
• gnm_solve/gambit-gnm now exposes several parameters which control the behavior of the
  path-following procedure
• The MixedBehaviorProfile object can now be initialized on creation by a given distribution.
• append_move/append_infoset now resolves either a singleton node reference or any
  iterable set of node references
• Additional regret-related functions added to MixedBehaviorProfile and MixedStrategyProfile
  in both C++ and Python
• Some caching added to payoff/strategy value calculations in MixedStrategyProfile
• gambit-simpdiv now supports expressing output as floating-point with a specified number of
  digits (#296)
• Parameters first_step and max_accel added to gambit_logit for finer control of
  numerical continuation process

Changed

• Gambit now requires a compiler that supports C++17.
• Functions to compute Nash equilibria now return a NashComputationResult object instead of a bare
  list of profiles (#190)
• liap_solve/gambit-liap has been reimplemented to scale payoffs uniformly across games,
  to always take an explicit starting point (in liap_solve), and to specify a regret-based
  acceptance criterion (#330)
• simpdiv_solve/gambit-simpdiv now accepts a regret-based acceptance criterion (#439)
• simpdiv_solve now takes an explicit starting point (#445)
• Converted test suite for mixed behavior profiles to pytest style; added parametrizations for
  test_realiz_prob; added test_martingale_property_of_node_value (#375)
• Improved test suite for mixed strategy profiles (#374)
• Test suite for pygambit moved from src/pygambit/tests/ to tests/
• Improved repr methods in pygambit for game-related classes
• Further extension of test suite for mixed behavior profiles to cover new indexing and profile
  order consistency for payoff-related calculations
• Overhaul of caching in MixedBehaviorProfile to use maps (std::map)
• Creation of random mixed profiles in pygambit is done with new Game.random_strategy_profile and
  Game.random_behavior_profile methods; these accept numpy.random.Generator objects for
  reproducible state.
  Creation of random mixed profiles in C++ is done with new Game::NewRandomStrategyProfile and
  Game::NewRandomBehaviorProfile methods; these accept STL Generator objects for reproducible state.
  The Python implementation is no longer just a wrapper around the C++ one.
• Graphical interface now uses simplicial subdivision as the recommended method for finding some
  equilibria in games with more than two players, instead of Lyapunov function minimisation

The stable release of version 16.1.1.

Fixed

• In gambit-logit, if there are chance actions with zero probability, information sets may be reached
  with zero probability. In this event, gambit-logit treats beliefs at those information sets as being
  uniform across nodes (#63)
• Corrected outdated code in fit_fixedpoint and fit_empirical, and added extended documentation
  of both methods (#1)
• Fixed bug in gambit-lp which would return non-Nash output on extensive games if the game had chance nodes
  other than the root node (#134)
• In pygambit, fixed indexing in mixed behavior and mixed strategy profiles, which could result
  in strategies or actions belonging to other players or information sets being referenced when
  indexing by string label

Changed

• In pygambit, resolving game objects with ambiguous or duplicated labels results in a ValueError,
  instead of silently returning the first matching object found.