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Issue #17141: random.vonmisesvariate() no more hangs for large kappas.

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This commit is contained in:
Serhiy Storchaka 2013-02-10 19:29:54 +02:00
commit 06e5e730dd
3 changed files with 40 additions and 10 deletions
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14
Lib/random.py
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@ -432,22 +432,20 @@ 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