From 6c22b1d7609413f711cb1bcf258ecc13ef15af07 Mon Sep 17 00:00:00 2001 From: Serhiy Storchaka Date: Sun, 10 Feb 2013 19:28:56 +0200 Subject: Issue #17141: random.vonmisesvariate() no more hangs for large kappas. --- Lib/random.py | 14 ++++++-------- Lib/test/test_random.py | 34 ++++++++++++++++++++++++++++++++-- Misc/NEWS | 2 ++ 3 files changed, 40 insertions(+), 10 deletions(-) diff --git a/Lib/random.py b/Lib/random.py index 4cbe9ad..91be5ad 100644 --- a/Lib/random.py +++ b/Lib/random.py @@ -431,22 +431,20 @@ class Random(_random.Random): if kappa <= 1e-6: return TWOPI * random() - a = 1.0 + _sqrt(1.0 + 4.0 * kappa * kappa) - b = (a - _sqrt(2.0 * a))/(2.0 * kappa) - r = (1.0 + b * b)/(2.0 * b) + s = 0.5 / kappa + r = s + _sqrt(1.0 + s * s) while 1: u1 = random() - z = _cos(_pi * u1) - f = (1.0 + r * z)/(r + z) - c = kappa * (r - f) + d = z / (r + z) u2 = random() - - if u2 < c * (2.0 - c) or u2 <= c * _exp(1.0 - c): + if u2 < 1.0 - d * d or u2 <= (1.0 - d) * _exp(d): break + q = 1.0 / r + f = (q + z) / (1.0 + q * z) u3 = random() if u3 > 0.5: theta = (mu + _acos(f)) % TWOPI diff --git a/Lib/test/test_random.py b/Lib/test/test_random.py index 073bed4..97d8098 100644 --- a/Lib/test/test_random.py +++ b/Lib/test/test_random.py @@ -436,6 +436,7 @@ class TestDistributions(unittest.TestCase): g.random = x[:].pop; g.paretovariate(1.0) g.random = x[:].pop; g.expovariate(1.0) g.random = x[:].pop; g.weibullvariate(1.0, 1.0) + g.random = x[:].pop; g.vonmisesvariate(1.0, 1.0) g.random = x[:].pop; g.normalvariate(0.0, 1.0) g.random = x[:].pop; g.gauss(0.0, 1.0) g.random = x[:].pop; g.lognormvariate(0.0, 1.0) @@ -456,6 +457,7 @@ class TestDistributions(unittest.TestCase): (g.uniform, (1.0,10.0), (10.0+1.0)/2, (10.0-1.0)**2/12), (g.triangular, (0.0, 1.0, 1.0/3.0), 4.0/9.0, 7.0/9.0/18.0), (g.expovariate, (1.5,), 1/1.5, 1/1.5**2), + (g.vonmisesvariate, (1.23, 0), pi, pi**2/3), (g.paretovariate, (5.0,), 5.0/(5.0-1), 5.0/((5.0-1)**2*(5.0-2))), (g.weibullvariate, (1.0, 3.0), gamma(1+1/3.0), @@ -472,8 +474,30 @@ class TestDistributions(unittest.TestCase): s1 += e s2 += (e - mu) ** 2 N = len(y) - self.assertAlmostEqual(s1/N, mu, places=2) - self.assertAlmostEqual(s2/(N-1), sigmasqrd, places=2) + self.assertAlmostEqual(s1/N, mu, places=2, + msg='%s%r' % (variate.__name__, args)) + self.assertAlmostEqual(s2/(N-1), sigmasqrd, places=2, + msg='%s%r' % (variate.__name__, args)) + + def test_constant(self): + g = random.Random() + N = 100 + for variate, args, expected in [ + (g.uniform, (10.0, 10.0), 10.0), + (g.triangular, (10.0, 10.0), 10.0), + #(g.triangular, (10.0, 10.0, 10.0), 10.0), + (g.expovariate, (float('inf'),), 0.0), + (g.vonmisesvariate, (3.0, float('inf')), 3.0), + (g.gauss, (10.0, 0.0), 10.0), + (g.lognormvariate, (0.0, 0.0), 1.0), + (g.lognormvariate, (-float('inf'), 0.0), 0.0), + (g.normalvariate, (10.0, 0.0), 10.0), + (g.paretovariate, (float('inf'),), 1.0), + (g.weibullvariate, (10.0, float('inf')), 10.0), + (g.weibullvariate, (0.0, 10.0), 0.0), + ]: + for i in range(N): + self.assertEqual(variate(*args), expected) def test_von_mises_range(self): # Issue 17149: von mises variates were not consistently in the @@ -489,6 +513,12 @@ class TestDistributions(unittest.TestCase): msg=("vonmisesvariate({}, {}) produced a result {} out" " of range [0, 2*pi]").format(mu, kappa, sample)) + def test_von_mises_large_kappa(self): + # Issue #17141: vonmisesvariate() was hang for large kappas + random.vonmisesvariate(0, 1e15) + random.vonmisesvariate(0, 1e100) + + class TestModule(unittest.TestCase): def testMagicConstants(self): self.assertAlmostEqual(random.NV_MAGICCONST, 1.71552776992141) diff --git a/Misc/NEWS b/Misc/NEWS index 6ce6f47..eff2176 100644 --- a/Misc/NEWS +++ b/Misc/NEWS @@ -221,6 +221,8 @@ Core and Builtins Library ------- +- Issue #17141: random.vonmisesvariate() no more hangs for large kappas. + - Issue #17149: Fix random.vonmisesvariate to always return results in [0, 2*math.pi]. -- cgit v0.12