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31 lines
1.2 KiB
Python
31 lines
1.2 KiB
Python
3 weeks ago
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from test.support import TestFailed
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# A test for SF bug 422177: manifest float constants varied way too much in
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# precision depending on whether Python was loading a module for the first
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# time, or reloading it from a precompiled .pyc. The "expected" failure
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# mode is that when test_import imports this after all .pyc files have been
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# erased, it passes, but when test_import imports this from
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# double_const.pyc, it fails. This indicates a woeful loss of precision in
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# the marshal format for doubles. It's also possible that repr() doesn't
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# produce enough digits to get reasonable precision for this box.
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PI = 3.14159265358979324
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TWOPI = 6.28318530717958648
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PI_str = "3.14159265358979324"
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TWOPI_str = "6.28318530717958648"
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# Verify that the double x is within a few bits of eval(x_str).
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def check_ok(x, x_str):
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assert x > 0.0
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x2 = eval(x_str)
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assert x2 > 0.0
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diff = abs(x - x2)
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# If diff is no larger than 3 ULP (wrt x2), then diff/8 is no larger
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# than 0.375 ULP, so adding diff/8 to x2 should have no effect.
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if x2 + (diff / 8.) != x2:
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raise TestFailed("Manifest const %s lost too much precision " % x_str)
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check_ok(PI, PI_str)
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check_ok(TWOPI, TWOPI_str)
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