New submission from Stefan Behnel:
Fractions are an excellent way to do exact money calculations and largely beat
Decimal in terms of simplicity, accuracy and safety. Clearly not in terms of
speed, though.
The current implementation does some heavy type checking and dispatching in
__new__() and a simplistic gcd based normalisation. Here is a profiling run
from the benchmark proposed in issue 22458 (which matches more or less the
results with my own code):
6969671 function calls (6969278 primitive calls) in 4.835 seconds
Ordered by: internal time
ncalls tottime percall cumtime percall filename:lineno(function)
519644 1.324 0.000 2.928 0.000 fractions.py:73(__new__)
519632 0.654 0.000 0.654 0.000 fractions.py:17(gcd)
319744 0.637 0.000 2.694 0.000 fractions.py:400(_add)
1039260 0.507 0.000 0.950 0.000 abc.py:178(__instancecheck__)
4 0.459 0.115 4.821 1.205 bm_telco_fractions.py:38(run)
1039300 0.443 0.000 0.443 0.000 _weakrefset.py:70(__contains__)
519616 0.301 0.000 4.329 0.000 fractions.py:373(forward)
199872 0.272 0.000 1.335 0.000 fractions.py:416(_mul)
1598720 0.117 0.000 0.117 0.000 fractions.py:278(denominator)
959232 0.074 0.000 0.074 0.000 fractions.py:274(numerator)
The instantiation itself takes twice as much time as the gcd calculations, and
both dominate the overall runtime of the benchmark by about 60%. Improving the
instantiation time would thus bring a substantial benefit.
----------
components: Library (Lib)
messages: 227284
nosy: scoder
priority: normal
severity: normal
status: open
title: Speed up fractions implementation
versions: Python 3.5
_______________________________________
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue22464>
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