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Hoist the float conversion out of the inner loop. (GH-10430)

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Currently, the *n* and *total* variables get converted to floats each time they are multiplied by random().  This minor tweak does the conversion just once and gets a small speedup (approx 3%).
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Raymond Hettinger 2018-11-09 02:39:50 -08:00 • committed by Miss Islington (bot)
parent cf5863faab
commit 0a18e0510a
1 changed files with 2 additions and 1 deletions
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3
Lib/random.py
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@ -375,6 +375,7 @@ class Random(_random.Random):
if cum_weights is None: if cum_weights is None:
if weights is None: if weights is None:
_int = int _int = int
n += 0.0 # convert to float for a small speed improvement
return [population[_int(random() * n)] for i in range(k)] return [population[_int(random() * n)] for i in range(k)]
cum_weights = list(_itertools.accumulate(weights)) cum_weights = list(_itertools.accumulate(weights))
elif weights is not None: elif weights is not None:
@ -382,7 +383,7 @@ class Random(_random.Random):
if len(cum_weights) != n: if len(cum_weights) != n:
raise ValueError('The number of weights does not match the population') raise ValueError('The number of weights does not match the population')
bisect = _bisect.bisect bisect = _bisect.bisect
total = cum_weights[-1] total = cum_weights[-1] + 0.0 # convert to float
hi = n - 1 hi = n - 1
return [population[bisect(cum_weights, random() * total, 0, hi)] return [population[bisect(cum_weights, random() * total, 0, hi)]
for i in range(k)] for i in range(k)]