diff options
Diffstat (limited to 'Lib/random.py')
| -rw-r--r-- | Lib/random.py | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/Lib/random.py b/Lib/random.py index 86d562f0b8a..c89cbb755ab 100644 --- a/Lib/random.py +++ b/Lib/random.py @@ -844,8 +844,8 @@ class Random(_random.Random): # BTRS: Transformed rejection with squeeze method by Wolfgang Hörmann # https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.47.8407&rep=rep1&type=pdf assert n*p >= 10.0 and p <= 0.5 - setup_complete = False + setup_complete = False spq = _sqrt(n * p * (1.0 - p)) # Standard deviation of the distribution b = 1.15 + 2.53 * spq a = -0.0873 + 0.0248 * b + 0.01 * p @@ -860,22 +860,23 @@ class Random(_random.Random): k = _floor((2.0 * a / us + b) * u + c) if k < 0 or k > n: continue + v = random() # The early-out "squeeze" test substantially reduces # the number of acceptance condition evaluations. - v = random() if us >= 0.07 and v <= vr: return k - # Acceptance-rejection test. - # Note, the original paper erroneously omits the call to log(v) - # when comparing to the log of the rescaled binomial distribution. if not setup_complete: alpha = (2.83 + 5.1 / b) * spq lpq = _log(p / (1.0 - p)) m = _floor((n + 1) * p) # Mode of the distribution h = _lgamma(m + 1) + _lgamma(n - m + 1) setup_complete = True # Only needs to be done once + + # Acceptance-rejection test. + # Note, the original paper erroneously omits the call to log(v) + # when comparing to the log of the rescaled binomial distribution. v *= alpha / (a / (us * us) + b) if _log(v) <= h - _lgamma(k + 1) - _lgamma(n - k + 1) + (k - m) * lpq: return k |