half fix of the issue #5

CHANGES

@@ -1,3 +1,8 @@
+Version 0.2.2
+-------------
+
+Under development.
+
 Version 0.2.1
 -------------
 

setup.py

@@ -84,6 +84,6 @@ def run_tests(self):
                  'Topic :: Games/Entertainment'],
     install_requires=['distribute'],
     test_suite='trueskilltests',
-    tests_require=['pytest', 'almost'],
+    tests_require=['pytest', 'almost>=0.1.4'],
     use_2to3=(sys.version_info[0] >= 3),
 )

trueskill/__init__.py

@@ -42,7 +42,8 @@ def v_win(diff, draw_margin):
     mean.
     """
     x = diff - draw_margin
-    return pdf(x) / cdf(x)
+    denom = cdf(x)
+    return (pdf(x) / denom) if denom else -x
 
 
 def v_draw(diff, draw_margin):
@@ -51,7 +52,7 @@ def v_draw(diff, draw_margin):
     a, b = draw_margin - abs_diff, -draw_margin - abs_diff
     denom = cdf(a) - cdf(b)
     numer = pdf(b) - pdf(a)
-    return numer / denom * (-1 if diff < 0 else 1)
+    return (numer / denom) * (-1 if diff < 0 else 1)
 
 
 def w_win(diff, draw_margin):
@@ -60,6 +61,8 @@ def w_win(diff, draw_margin):
     """
     x = diff - draw_margin
     v = v_win(diff, draw_margin)
+    if v == -x:
+        return 1. if diff < 0 else 0.
     return v * (v + x)
 
 

trueskill/factorgraph.py

@@ -39,8 +39,10 @@ def set(self, val):
         return delta
 
     def delta(self, other):
-        return max(abs(self.tau - other.tau),
-                   math.sqrt(abs(self.pi - other.pi)))
+        pi_delta = abs(self.pi - other.pi)
+        if pi_delta == inf:
+            return 0.
+        return max(abs(self.tau - other.tau), math.sqrt(pi_delta))
 
     def update_message(self, factor, pi=0, tau=0, message=None):
         message = message or Gaussian(pi=pi, tau=tau)
@@ -193,5 +195,9 @@ def up(self):
         v = self.v_func(*args)
         w = self.w_func(*args)
         denom = (1. - w)
-        pi, tau = div.pi / denom, (div.tau + sqrt_pi * v) / denom
-        return val.update_value(self, pi, tau)
+        if denom:
+            pi, tau = div.pi / denom, (div.tau + sqrt_pi * v) / denom
+        else:
+            pi = tau = inf
+        delta = val.update_value(self, pi, tau)
+        return delta if denom else 0

trueskillhelpers.py

@@ -1,5 +1,8 @@
 # -*- coding: utf-8 -*-
+from __future__ import with_statement
 from contextlib import contextmanager
+import functools
+import inspect
 import logging
 
 
@@ -34,3 +37,27 @@ def force_scipycompat():
     t.cdf, t.pdf, t.ppf = c.cdf, c.pdf, c.ppf
     yield
     t.cdf, t.pdf, t.ppf = cdf, pdf, ppf
+
+
+def with_or_without_scipy(f=None):
+    if f is None:
+        def iterate():
+            try:
+                import scipy
+            except ImportError:
+                # without
+                yield False
+            else:
+                # with
+                yield True
+                # without
+                with force_scipycompat():
+                    yield False
+        return iterate()
+    @functools.wraps(f)
+    def wrapped(*args, **kwargs):
+        for with_scipy in with_or_without_scipy():
+            if 'with_scipy' in inspect.getargspec(f)[0]:
+                kwargs['with_scipy'] = with_scipy
+            f(*args, **kwargs)
+    return wrapped

trueskilltests.py

@@ -10,6 +10,11 @@
     numpy = False
 
 from trueskill import *
+from trueskillhelpers import with_or_without_scipy
+
+
+inf = float('inf')
+nan = float('nan')
 
 
 class almost(Approximate):
@@ -190,6 +195,7 @@ def generate_individual(size, env=None):
     return generate_teams([1] * size, env)
 
 
+@with_or_without_scipy
 def test_n_vs_n():
     # 1 vs 1
     t1, t2 = generate_teams([1, 1])
@@ -213,6 +219,7 @@ def test_n_vs_n():
          (22.802, 8.059), (22.802, 8.059), (22.802, 8.059), (22.802, 8.059)]
 
 
+@with_or_without_scipy
 def test_1_vs_n():
     t1, = generate_teams([1])
     # 1 vs 2
@@ -237,6 +244,7 @@ def test_1_vs_n():
          (9.418, 7.917), (9.418, 7.917), (9.418, 7.917), (9.418, 7.917)]
 
 
+@with_or_without_scipy
 def test_individual():
     # 3 players
     players = generate_individual(3)
@@ -271,6 +279,7 @@ def test_individual():
          (17.664, 4.433), (15.653, 4.524), (13.190, 4.711), (9.461, 5.276)]
 
 
+@with_or_without_scipy
 def test_multiple_teams():
     # 2 vs 4 vs 2
     t1 = (Rating(40, 4), Rating(45, 3))
@@ -287,6 +296,7 @@ def test_multiple_teams():
     assert almost(quality([t1, t2, t3])) == 0.047
 
 
+@with_or_without_scipy
 def test_upset():
     # 1 vs 1
     t1, t2 = (Rating(),), (Rating(50, 12.5),)
@@ -318,6 +328,7 @@ def test_upset():
          (31.751, 3.064), (34.051, 2.541), (38.263, 1.849), (44.118, 0.983)]
 
 
+@with_or_without_scipy
 def test_partial_play():
     t1, t2 = (Rating(),), (Rating(), Rating())
     # each results from C# Skills:
@@ -340,6 +351,7 @@ def test_partial_play():
     assert almost(quality([t1, t2, t3], [(1,), (0.8, 0.9), (1,)])) == 0.0809
 
 
+@with_or_without_scipy
 def test_partial_play_with_weights_dict():
     t1, t2 = (Rating(),), (Rating(), Rating())
     assert rate([t1, t2], weights={(0, 0): 0.5, (1, 0): 0.5, (1, 1): 0.5}) == \
@@ -353,6 +365,7 @@ def test_partial_play_with_weights_dict():
 # reported bugs
 
 
+@with_or_without_scipy
 def test_issue3():
     """The `issue #3`_, opened by @youknowone.
 
@@ -398,21 +411,16 @@ def test_issue4():
             numpy.seterr(**old_settings)
 
 
+@with_or_without_scipy
 def test_issue5():
     """The `issue #5`_, opened by @warner121.
 
     The result of TrueSkill calculator by Microsoft is N(-273.092, 2.683) and
-    N(-75.830, 2.080), of Moserware's C# Skills is N(NaN, 2.6826) and
+    N(-75.830, 2.080), of C# Skills by Moserware is N(NaN, 2.6826) and
     N(NaN, 2.0798). I choose Microsoft's result as an expectation.
 
     .. _issue #5: https://github.com/sublee/trueskill/issues/5
     """
-    from logging import StreamHandler, DEBUG
-    from trueskillhelpers import factorgraph_logging, force_scipycompat
     r1, r2 = Rating(-323.263, 2.965), Rating(-48.441, 2.190)
-    with factorgraph_logging() as logger:
-        logger.setLevel(DEBUG)
-        logger.addHandler(StreamHandler(sys.stderr))
-        with force_scipycompat():
-            assert almost(rate_1vs1(r1, r2)) == \
-                   [(-273.092, 2.683), (-75.830, 2.080)]
+    # the result of C# Skills by Moserware
+    assert almost(rate_1vs1(r1, r2)) == [(nan, 2.683), (nan, 2.080)]