Mercurial > cpython-lru_cache-weakref

annotate Lib/test/double_const.py @ 87690:66c1c9f32567 default tip

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Add use_weakref option to functools.lru_cache The use_weakref option makes lru_cache create weak references to the function arguments when creating the cache key, which prevents them from staying in the memory forever even after all other references to them are gone. This is a proof of concept for http://bugs.python.org/issue19859
author Radomir Dopieralski <devel@sheep.art.pl>
date Tue, 03 Dec 2013 16:02:48 +0100
parents 9c930a32cebb
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
47201
9c930a32cebb #2621 rename test.test_support to test.support
Benjamin Peterson <benjamin@python.org>
parents: 24442
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1 from test.support import TestFailed
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2
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3 # A test for SF bug 422177: manifest float constants varied way too much in
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4 # precision depending on whether Python was loading a module for the first
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5 # time, or reloading it from a precompiled .pyc. The "expected" failure
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Tim Peters <tim.peters@gmail.com>
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6 # mode is that when test_import imports this after all .pyc files have been
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7 # erased, it passes, but when test_import imports this from
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8 # double_const.pyc, it fails. This indicates a woeful loss of precision in
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9 # the marshal format for doubles. It's also possible that repr() doesn't
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10 # produce enough digits to get reasonable precision for this box.
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11
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12 PI = 3.14159265358979324
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13 TWOPI = 6.28318530717958648
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14
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15 PI_str = "3.14159265358979324"
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16 TWOPI_str = "6.28318530717958648"
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17
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18 # Verify that the double x is within a few bits of eval(x_str).
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19 def check_ok(x, x_str):
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20 assert x > 0.0
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21 x2 = eval(x_str)
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22 assert x2 > 0.0
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23 diff = abs(x - x2)
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24 # If diff is no larger than 3 ULP (wrt x2), then diff/8 is no larger
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25 # than 0.375 ULP, so adding diff/8 to x2 should have no effect.
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26 if x2 + (diff / 8.) != x2:
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27 raise TestFailed("Manifest const %s lost too much precision " % x_str)
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28
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29 check_ok(PI, PI_str)
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30 check_ok(TWOPI, TWOPI_str)