Modify default tau value to 25/300 (#61)

* Modify default tau value to 25/300

* Remove note about default tau value

* Add changelog fragment

benchmark/benchmark.py

@@ -5,17 +5,19 @@
 
 import jsonlines
 import trueskill
-from prompt_toolkit import print_formatted_text as print, HTML, prompt
+from prompt_toolkit import HTML
+from prompt_toolkit import print_formatted_text as print
+from prompt_toolkit import prompt
 from prompt_toolkit.completion import WordCompleter
 from prompt_toolkit.shortcuts import ProgressBar
 
 import openskill
 from openskill.models import (
-    ThurstoneMostellerPart,
-    ThurstoneMostellerFull,
     BradleyTerryFull,
     BradleyTerryPart,
     PlackettLuce,
+    ThurstoneMostellerFull,
+    ThurstoneMostellerPart,
 )
 
 # Stores

benchmark/draw_benchmark.py

@@ -6,18 +6,20 @@
 import numpy as np
 import pandas
 import trueskill
-from prompt_toolkit import print_formatted_text as print, HTML, prompt
+from prompt_toolkit import HTML
+from prompt_toolkit import print_formatted_text as print
+from prompt_toolkit import prompt
 from prompt_toolkit.completion import WordCompleter
 from prompt_toolkit.shortcuts import ProgressBar
 from sklearn.model_selection import train_test_split
 
 import openskill
 from openskill.models import (
-    ThurstoneMostellerPart,
-    ThurstoneMostellerFull,
     BradleyTerryFull,
     BradleyTerryPart,
     PlackettLuce,
+    ThurstoneMostellerFull,
+    ThurstoneMostellerPart,
 )
 
 # Stores

benchmark/split_benchmark.py

@@ -6,18 +6,20 @@
 import jsonlines
 import numpy as np
 import trueskill
-from prompt_toolkit import print_formatted_text as print, HTML, prompt
+from prompt_toolkit import HTML
+from prompt_toolkit import print_formatted_text as print
+from prompt_toolkit import prompt
 from prompt_toolkit.completion import WordCompleter
 from prompt_toolkit.shortcuts import ProgressBar
 from sklearn.model_selection import train_test_split
 
 import openskill
 from openskill.models import (
-    ThurstoneMostellerPart,
-    ThurstoneMostellerFull,
     BradleyTerryFull,
     BradleyTerryPart,
     PlackettLuce,
+    ThurstoneMostellerFull,
+    ThurstoneMostellerPart,
 )
 
 # Stores

changes/61.breaking.rst

@@ -0,0 +1 @@
+Modify default ``tau`` value to ``25/300`` #61

docs/conf.py

@@ -48,9 +48,10 @@
     pass
 
 try:
-    import sphinx
     from distutils.version import LooseVersion
 
+    import sphinx
+
     cmd_line_template = (
         "sphinx-apidoc --implicit-namespaces -f -o {outputdir} {moduledir}"
     )

docs/time_decay.py

@@ -1,4 +1,4 @@
-from openskill import Rating, rate, predict_win
+from openskill import Rating, predict_win, rate
 
 x, y = Rating(), Rating()
 

openskill/__init__.py

@@ -1,12 +1,11 @@
-from openskill.rate import ordinal
 from openskill.rate import (
-    rate,
     Rating,
     create_rating,
-    team_rating,
-    predict_win,
+    ordinal,
     predict_draw,
+    predict_win,
+    rate,
+    team_rating,
 )
 
-
 __version__ = "2.5.1"

openskill/constants.py

@@ -40,9 +40,17 @@ def beta_squared(**options) -> float:
         return beta(**options) ** 2
 
 
+def tau(**options) -> float:
+    if "tau" in options:
+        return options["tau"]
+    else:
+        return mu(**options) / 300
+
+
 class Constants:
     def __init__(self, **options):
         self.EPSILON: float = epsilon(**options)
         self.TWO_BETA_SQUARED: float = 2 * beta_squared(**options)
         self.BETA_SQUARED: float = beta_squared(**options)
         self.Z: float = z(**options)
+        self.TAU: float = tau(**options)

openskill/rate.py

@@ -2,13 +2,14 @@
 import itertools
 import math
 from functools import reduce
-from typing import Optional, Union, List
+from typing import List, Optional, Union
 
-from openskill.constants import mu as default_mu, beta, Constants
+from openskill.constants import Constants, beta
+from openskill.constants import mu as default_mu
 from openskill.constants import sigma as default_sigma
 from openskill.models.plackett_luce import PlackettLuce
 from openskill.statistics import phi_major, phi_major_inverse
-from openskill.util import unwind, rankings
+from openskill.util import rankings, unwind
 
 
 class Rating:
@@ -262,13 +263,12 @@ def rate(teams: List[List[Rating]], **options) -> List[List[Rating]]:
     :param prevent_sigma_increase: A :class:`~bool` that prevents sigma from ever increasing.
     :param options: Pass in a set of custom values for constants defined in the Weng-Lin paper.
     :return: Returns a list of :class:`~openskill.rate.Rating` objects.
-
-    .. note::
-       ``tau`` will default to ``25/300`` in the next major version update.
     """
+    constants = Constants(**options)
+    tau = constants.TAU
     original_teams = copy.deepcopy(teams)
     if "tau" in options:
-        tau_squared = options["tau"] * options["tau"]
+        tau_squared = tau * tau
         for team_index, team in enumerate(teams):
             for player_index, player in enumerate(team):
                 teams[team_index][player_index].sigma = math.sqrt(

tests/__init__.py

@@ -1,11 +1,7 @@
 import math
 from abc import ABC, abstractmethod
 from collections import UserString
-from collections.abc import (
-    Mapping,
-    Set,
-    Sequence,
-)
+from collections.abc import Mapping, Sequence, Set
 from decimal import Decimal
 from numbers import Real
 from typing import List

tests/test_constants.py

@@ -1,6 +1,6 @@
 import pytest
 
-from openskill.constants import z, mu, sigma, epsilon, beta, beta_squared
+from openskill.constants import beta, beta_squared, epsilon, mu, sigma, tau, z
 
 
 def test_constants():
@@ -21,3 +21,6 @@ def test_constants():
 
     assert beta_squared(beta_squared=16.2) == 16.2
     assert beta_squared() == pytest.approx(17.361111111111114)
+
+    assert tau(tau=0.3) == 0.3
+    assert tau() == pytest.approx(0.08333333)

tests/test_ordinal.py

@@ -1,6 +1,6 @@
 import pytest
 
-from openskill import ordinal, Rating
+from openskill import Rating, ordinal
 
 
 def test_ordinal():

tests/test_team_rating.py

@@ -1,7 +1,6 @@
 import pytest
 
-from openskill import Rating
-from openskill import team_rating
+from openskill import Rating, team_rating
 
 r = Rating()
 team_1 = [r]